記述言語：その他   掲載種別：研究論文（学術雑誌）  

A double-stranded spiroborate helicate bearing a bisporphyrin unit in the middle forms an inclusion complex with electron-deficient aromatic guests that are sandwiched between the porphyrins. In the present study, we systematically investigated the effects of size, electron density, and substituents of a series of aromatic guests on inclusion complex formations within the bisporphyrin. The thermodynamic and kinetic behaviors during the guest-encapsulation process were also investigated in detail. The guest-encapsulation abilities in the helicate increased with the increasing core sizes of the electron-deficient aromatic guests and decreased with the increasing bulkiness and number of substituents of the guests. Among the naphthalenediimide derivatives, those with bulky N-substituents at both ends hardly formed an inclusion complex. Instead, they formed a [2]rotaxane-like inclusion complex through the water-mediated dynamic B-O bond cleavage/reformation of the spiroborate groups of the helicate, which enhanced the conformational flexibility of the helicate to enlarge the bisporphyrin cavity and form an inclusion complex. Based on the X-ray crystal structure of a unique pacman-like 1:1 inclusion complex between the helicate and an ammonium cation as well as the molecular dynamics simulation results, a plausible mechanism for the inclusion of a planar aromatic guest within the helicate is also proposed.

DOI： 10.1021/acs.joc.1c01155

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A stimuli-responsible reversible structural transformation is of key importance in biological systems. We now report a unique water-mediated reversible transformation among three discrete double-stranded dinuclear titanium(IV) achiral meso- and chiral rac-helicates linked by a mono(mu-oxo) or a bis(mu-hydroxo) bridge between the titanium ions through hydration/dehydration or its combination with a water-mediated dynamic cleavage/re-formation of the titanium-phenoxide (Ti-OPh) bonds. The bis(mu-hydroxo) bridged titanium(IV) meso-helicate prepared from two tetraphenol strands with titanium(IV) oxide was readily dehydrated in CD 3 CN containing a small amount of water upon heating, accompanied by Ti-OPh bond deavage/re-formation catalyzed by water, resulting in the formation of the mono(mu-oxo)-bridged rac-helicate, which reverted back to the original bis(mu-hydroxo)- bridged meso-helicate upon hydration in aqueous CD3CN. These reversible transformations between the meso- and rac-helicates were also promoted in the presence of a catalytic amount of an acid, which remarkably accelerated the reactions at lower temperature. Interestingly, in anhydrous CD3CN, the bis(mu-hydroxo)-bridged meso-helicate was further slowly converted to a different helicate, while its meso-helicate framework was maintained, namely the mono(mu-oxo)-bridged meso-helicate, through dehydration upon heating and its meso to meso transformation was significantly accelerated in the presence of cryptand[2.2.1], which contributes to removing Na+ ions coordinated to the helicate. Upon cooling, the backward mew to meso transformation took place via hydration. Hence, three different, discrete double-stranded chiral rac- and achiral meso-titanium(IV) helicates linked by a mono(mu-oxo) or a bis(mu-hydroxo) bridge were successfully generated in a controllable manner by a change in the water content of the reaction media.

DOI： 10.1021/jacs.0c13351

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Sequence-controlled synthetic polymers have received increasing interest because of their great potential to develop next-generation functional materials. Here, we report a facile synthesis of a symmetric spiro bis(six-membered cyclic carbonate), 2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-dione (1), its reactivity, and a one-pot, nonisocyanate synthesis of sequence-controlled poly(hydroxy urethane)s (PHUs) from 1 with two different symmetric diamines. The second-order rate constant for the ring-opening addition reaction of one of the two cyclic carbonates of 1 with 1-hexylamine is two orders of magnitude larger than that of the remaining one of the resulting intermediate due to a remarkable difference between their ring strain energies. This difference in the reactivity enables the selective formation of a diurethane-linked bis(six-membered cyclic carbonate) from the reaction of 1 with a diamine (0.5 equiv). The subsequent addition of a different diamine (0.5 equiv) to the same pot affords sequence-controlled PHUs with an ABAC sequence.

DOI： 10.1021/acs.macromol.1c00045

記述言語：英語  

A wide variety of synthetic molecular machines has been designed and synthesized to construct nanometer-scale assemblies whose molecular motions can be precisely controlled by external stimuli. A helical structure is one of the most intriguing structural motifs to realize such molecular machines, because of its unique spring-like shape that enables reversible extension and contraction motions. This short review highlights the recent progress in the synthesis, structures, and functions of synthetic molecular springs based on single- and multi-stranded helical structures.

DOI： 10.1246/cl.200737

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We report a highly enantio- and helix-sense-selective encapsulation of helical poly(lactic acid)s (PLAs) through a unique "helix-in-helix" superstructure formation within the helical cavity of syndiotactic poly(methyl methacrylate) (st-PMMA) with a one-handed helicity memory, which enables the separation of the enantiomeric helices of the left (M)- and right (P)-handed-PLAs. The M- and P-helical PLAs with different molar masses and a narrow molar mass distribution were prepared by the ring-opening living polymerization of the optically pure L- and D-lactides, respectively, followed by end-capping of the terminal residues of the PLAs with a 4-halobenzoate and then a C-60 unit, giving the C-60-free and C-60-bound M- and P-PLAs. The C-60-free and C-60-bound M- and P-PLAs formed crystalline inclusion complexes with achiral st-PMMA accompanied by a preferred-handed helix induction in the st-PMMA backbone, thereby producing helix-in-helix superstructures with the same-handedness to each other. The induced helical st-PMMAs were retained after replacement with the achiral C-60, indicating the memory of the induced helicity of the st-PMMAs. Both the C-60-free and C-60-bound helical PLAs were enantio- and helix-sense selectively encapsulated into the helical hollow space of the optically active M- and P-st-PMMAs with the helicity memory prepared using chiral amines. The M- and P-PLAs are preferentially encapsulated within the M- and P-st-PMMA helical cavity with the same-handedness to each other, respectively, independent of the terminal units. The C-60-bound PLAs were more efficiently and enantioselectively trapped in the st-PMMA compared to the C-60-free PLAs. The enantioselectivities were highly dependent on the molar mass of the C-60-bound and C-60-free PLAs and significantly increased as the molar mass of the PLAs increased.

DOI： 10.1021/jacs.0c11204

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Photodimerization of a novel 2-substituted anthracene linked to a right-handed 3(10)-helical nonapeptide induced by long-range chiral information transfer from the remote chiral l-Val residue through a chiral domino effect proceeded in a highly regio- and diastereo-differentiating manner to produce the chiral head-to-head anti-photodimer in 90% relative yield with up to 97% diastereomeric excess.

DOI： 10.1039/d0cc06164f

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The deracemization reaction of a racemic double-stranded spiroborate helicate containing a bisporphyrin unit in the middle assisted by optically-active guests efficiently proceeded even below room temperature in the presence of a catalytic amount of strong acids that triggered the partial B-0 bond cleavage/ reformation of the spiroborate groups, affording an optically-active helicate with a high enantioselectivity up to 93% ee.

DOI： 10.1246/cl.200352

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/anie.202004586

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/ange.201916103

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A novel 2,6-anthrylene-linked bis(m-terphenylcarboxylic acid) strand (1) self-associates into a racemic double-helix. In the presence of chiral mono- and diamines, either a right- or left-handed double-helix was predominantly induced by chiral amines sandwiched between the carboxylic acid strands with accompanying stacking of the two prochiral anthracene linker units in an enantiotopic face-selective way, as revealed by circular dichroism and NMR spectral analyses. The photoirradiation of the optically active double helices complexed with chiral amines proceeded in a diastereo- (anti or syn) and enantiodifferentiating way to afford the chiral anti-photodimer with up to 98 % enantiomeric excess when (R)-phenylethylamine was used as a chiral double-helix inducer. The resulting optically active anti-photodimer can recognize the chirality of amines and diastereoselectively complex with chiral amines.

DOI： 10.1002/anie.201916103

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/ange.202004586

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Two novel chiral dimer and trimer strands composed of m-terphenyl groups linked through p-diethynylbenzene units with the chiral amidine group and achiral piperazine group introduced at the terminus or center of the strands, respectively, and its complementary achiral carboxylic acid dimer and trimer were synthesized. The complementary chiral/achiral strands form an excess-handed double-helical structure as supported by intense split-type Cotton effects in the absorption regions of the conjugated backbones biased by the chiral amidinium-carboxylate salt bridges. The double-helical trimer was found to catalyze the direct aldol reaction of cyclohexanone with 4-nitrobenzaldehyde and produce the products with a moderate enantioselectivity despite the fact that the catalytically active bifunctional piperazine/carboxylic acid pair introduced in the middle is achiral, indicating the key role of the one-handed double-helical framework for supramolecular bifunctional organocatalysis.

DOI： 10.1002/chir.23169

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A novel double-stranded spiroborate helicate bearing terminal pyrene residues exhibited reversible fluorescence color changes (green and blue colors) due to the unique unidirectional springlike motions of the helicate triggered by catch and release of alkali metal ions.

DOI： 10.1039/c9cc06126f

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Deracemization is a powerful method by which a racemic mixture can be transformed into an excess of one enantiomer with the aid of chiral auxiliaries, but has been applied only to small chiral molecular systems. Here we report a deracemization of a racemic double-stranded spiroborate helicate containing a bisporphyrin unit upon encapsulation of chiral aromatic guests between the bisporphyrin. The chiral guest-included helicate is kinetically stable, existing as a mixture of right- and left-handed double helices, which eventually undergo an inversion of the helicity triggered by water resulting from the water-mediated reversible diastereoselective B-O bond cleavage/reformation of the spiroborate groups, thus producing an optically-active helicate with a high enantioselectivity. Quantum chemical calculations suggest that the stereospecific CH-pi interactions between the porphyrin hydrogen atoms of the helicate and an aromatic pendant group of the chiral guest play a key role in the enhancement of the helical handedness of the helicate.

DOI： 10.1038/s41467-019-09443-z

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A one-handed double-stranded spiroborate helicate exhibits a unique reversible extension-contraction motion coupled with a twisting motion in one direction triggered by binding and release of a Na+ ion while retaining its handedness. Here we report that an extended meso-helicate was also produced together with the racemo-helicate, and the meso-helicate was readily converted to the racemo-helicate assisted by a Na+ ion as a template in the presence of water. The thermodynamic analyses of the ion-triggered springlike motion of the racemo-helicate using a series of monovalent cations with different sizes revealed that the association constants of the extended racemo-helicate decreased in the following order: Li+ > Na+ > NH4+ > Ag+ >= Cs+ > Rb+, which roughly agrees with the reverse order of their ionic radii except for the NH4+ ion due to the more elongated contracted helicates when complexed with larger cations as supported by the crystal and DFT calculated structures. The one-handed contracted helicates showed characteristic CD spectra depending on the cation species due to the differences in their contracted helical structures, and its absolute handedness of the spiroborate helicate was determined by X-ray crystallography. The kinetic studies of the springlike motions of the racemo-helicate showed that the exchange rate between the extended and contracted helicates tend to increase in the following order: Li+ < Na+ < K+ <= NH4+ < Rb+ < Cs+ < Ag+ as anticipated from the association constants, being in good agreement with the order of the cation sizes except for Ag+.

DOI： 10.1021/jacs.8b08268

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A one-handed double-stranded spiroborate helicate exhibits a unique reversible extension-contraction motion coupled with a twisting motion in one direction triggered by binding and release of a Na+ ion while retaining its handedness. Here we report that an extended meso-helicate was also produced together with the racemo-helicate, and the meso-helicate was readily converted to the racemo-helicate assisted by a Na+ ion as a template in the presence of water. The thermodynamic analyses of the ion-triggered springlike motion of the racemo-helicate using a series of monovalent cations with different sizes revealed that the association constants of the extended racemo-helicate decreased in the following order: Li+ > Na+ > NH4+ > Ag+ >= Cs+ > Rb+, which roughly agrees with the reverse order of their ionic radii except for the NH4+ ion due to the more elongated contracted helicates when complexed with larger cations as supported by the crystal and DFT calculated structures. The one-handed contracted helicates showed characteristic CD spectra depending on the cation species due to the differences in their contracted helical structures, and its absolute handedness of the spiroborate helicate was determined by X-ray crystallography. The kinetic studies of the springlike motions of the racemo-helicate showed that the exchange rate between the extended and contracted helicates tend to increase in the following order: Li+ < Na+ < K+ <= NH4+ < Rb+ < Cs+ < Ag+ as anticipated from the association constants, being in good agreement with the order of the cation sizes except for Ag+.

DOI： 10.1021/jacs.8b08268

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The dynamic axial chirality of oligopeptide-bound 2,2 '-bipyridine (bpy) residues can be remote-controlled and diastereoselectively locked. A right-handed (P)-3(10)-helix is first induced in the dynamic helical oligopeptide by an l-valine (l-Val) far from the bpy moiety and the induced axial bpy chirality is diastereoselectively dioxidized. The resulting l-Val-containing linear oligopeptides at the 3,3 '-positions retain their (P)-3(10)-helices independent of the axial chirality (aR or aS) of the N-terminal N,N '-dioxide-bpy unit, while a lactam-bridged dynamic helical oligopeptide exhibits a unique solvent-induced helix-helix transition as a result of competitive helix-inducing biases between the l-Val and (aR) or (aS)-N,N '-dioxide-bpy residues remote from each other along the entire oligopeptide chain in a tug-of-war like manner.

DOI： 10.1002/asia.201801111

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The dynamic axial chirality of oligopeptide-bound 2,2 '-bipyridine (bpy) residues can be remote-controlled and diastereoselectively locked. A right-handed (P)-3(10)-helix is first induced in the dynamic helical oligopeptide by an l-valine (l-Val) far from the bpy moiety and the induced axial bpy chirality is diastereoselectively dioxidized. The resulting l-Val-containing linear oligopeptides at the 3,3 '-positions retain their (P)-3(10)-helices independent of the axial chirality (aR or aS) of the N-terminal N,N '-dioxide-bpy unit, while a lactam-bridged dynamic helical oligopeptide exhibits a unique solvent-induced helix-helix transition as a result of competitive helix-inducing biases between the l-Val and (aR) or (aS)-N,N '-dioxide-bpy residues remote from each other along the entire oligopeptide chain in a tug-of-war like manner.

DOI： 10.1002/asia.201801111

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A helical foldamer possessing conformationally switchable metal-binding linkers underwent supramolecular polymerization to form a helical nanofiber. A reversible helix-to-helix transition of the helical nanofiber took place upon cooperative binding and release of Ag(I) ions via a metal-coordination-driven W-to-U-shape conformational change of the linkers in a positive allosteric manner.

DOI： 10.1039/c8cc00728d

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Here, we show the induced chirality of an achiral chromophoric dye as a joint of polylactide-containing chiral block copolymers (BCPs*) driven by self-assembly, giving the achiral dyes preferentially arranged in a one-handed helical array at the microphase-separated interface. This helical arrangement of the achiral dyes can be "memorized" after hydrolysis of the polylactides in the BCPs* and serves as a chiral template for further chirality induction of different achiral dyes, probably through attractive aromatic pi-pi interactions at the interface, producing nanostructured chiral materials with tunable circular dichroism signals at desired wavelengths.

DOI： 10.1021/acsmacrolett.7b00493

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Here, we show the induced chirality of an achiral chromophoric dye as a joint of polylactide-containing chiral block copolymers (BCPs*) driven by self-assembly, giving the achiral dyes preferentially arranged in a one-handed helical array at the microphase-separated interface. This helical arrangement of the achiral dyes can be "memorized" after hydrolysis of the polylactides in the BCPs* and serves as a chiral template for further chirality induction of different achiral dyes, probably through attractive aromatic pi-pi interactions at the interface, producing nanostructured chiral materials with tunable circular dichroism signals at desired wavelengths.

DOI： 10.1021/acsmacrolett.7b00493

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Threading of a poly(ethylene glycol) (PEG) chain linked to a perylenediimide unit at one end with a bulky stopper at the other end through an inner cavity of a bisporphyrin-based double-stranded spiroborate helicate was remarkably accelerated in a specific solvent, in which the PEG chain enfolded sodium cations coordinating to the negatively charged spiroborate helicate, thus forming a 1: 1 inclusion complex with the perylenediimide sandwiched between the bisporphyrin unit.

DOI： 10.1246/cl.170271

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Threading of a poly(ethylene glycol) (PEG) chain linked to a perylenediimide unit at one end with a bulky stopper at the other end through an inner cavity of a bisporphyrin-based double-stranded spiroborate helicate was remarkably accelerated in a specific solvent, in which the PEG chain enfolded sodium cations coordinating to the negatively charged spiroborate helicate, thus forming a 1: 1 inclusion complex with the perylenediimide sandwiched between the bisporphyrin unit.

DOI： 10.1246/cl.170271

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Since the pioneering work by Stoddart, Sauvage, and Feringa on the design and synthesis of molecular machines, to whom the 2016 Nobel Prize in Chemistry was awarded, various kinds of synthetic molecular machines have been developed. A helical structure, one of the essential structural motifs in biological systems, has the potential as a versatile structural component for constructing such a molecular machine, because of its spring-like shape that enables extension and contraction motions. We report here the recent progress in the synthesis, structures, and functions of artificial molecular springs based on single-or double-stranded helical oligomers and polymers that undergo an intriguing stimuli-responsive extension-contraction motion with maintaining their helical structures but with a change in the helical pitch. In particular, double stranded spiroborate helicates with a one-handed helical sense exhibit a unique reversible elastic motion accompanied by a unidirectional twisting motion, thereby enabling a chiral molecular motion.

DOI： 10.5059/yukigoseikyokaishi.75.466

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A series of optically active amidine dimers composed of m-terphenyl backbones joined by a variety of linkers, such as achiral and chiral p-phenylene and chiral amide linkers, were synthesized and used as templates for the regio- (head-to-tail (HT) or head-to-head (HH)), diastereo- (anti or syn), and enantioselective [4 + 4] photocyclodimerization of an achiral m-terphenyl-based carboxylic acid monomer bearing a prochiral 2-substituted anthracene at one end (1) through complementary amidiniumcarboxylate salt bridges. The amidine dimers linked by p-phenylene linkages almost exclusively afforded the chiral syn-HT and anti-HH dimers at 25 degrees C, while those joined by amide linkers produced all four dimers. The p-phenylene-linked templates tended to enhance the syn-HT-photodimer formation at high temperatures with no significant changes in the product enantiomeric excess (ee), while the anti-HH-photodimer formation remarkably increased with the decreasing temperature accompanied by a significant enhancement of the product ee up to -86&#37; at -50 degrees C. Temperature-dependent inversion of the chirality of the anti-HH dimer was observed when the chiral phenylene-linked amidine dimer was used and the product ee was changed from 22&#37; at 50 degrees C to -86&#37; at -50 degrees C. A similar enhancement of the enantioselectivity of the anti-HH dimer was also observed for the chiral amide-linked template, producing the anti-HH dimer with up to -88&#37; ee at -50 degrees C. The observed difference in the regio-, diastereo-, and enantioselectivities due to the difference in the linker structures of the amidine dimers during the template-directed photodimerization of 1 was discussed on the basis of a reversible conformational change in the amidine dimers complexed with 1.

DOI： 10.1021/jacs.7b03317

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Since the pioneering work by Stoddart, Sauvage, and Feringa on the design and synthesis of molecular machines, to whom the 2016 Nobel Prize in Chemistry was awarded, various kinds of synthetic molecular machines have been developed. A helical structure, one of the essential structural motifs in biological systems, has the potential as a versatile structural component for constructing such a molecular machine, because of its spring-like shape that enables extension and contraction motions. We report here the recent progress in the synthesis, structures, and functions of artificial molecular springs based on single-or double-stranded helical oligomers and polymers that undergo an intriguing stimuli-responsive extension-contraction motion with maintaining their helical structures but with a change in the helical pitch. In particular, double stranded spiroborate helicates with a one-handed helical sense exhibit a unique reversible elastic motion accompanied by a unidirectional twisting motion, thereby enabling a chiral molecular motion.

DOI： 10.5059/yukigoseikyokaishi.75.466

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A series of optically active amidine dimers composed of m-terphenyl backbones joined by a variety of linkers, such as achiral and chiral p-phenylene and chiral amide linkers, were synthesized and used as templates for the regio- (head-to-tail (HT) or head-to-head (HH)), diastereo- (anti or syn), and enantioselective [4 + 4] photocyclodimerization of an achiral m-terphenyl-based carboxylic acid monomer bearing a prochiral 2-substituted anthracene at one end (1) through complementary amidiniumcarboxylate salt bridges. The amidine dimers linked by p-phenylene linkages almost exclusively afforded the chiral syn-HT and anti-HH dimers at 25 degrees C, while those joined by amide linkers produced all four dimers. The p-phenylene-linked templates tended to enhance the syn-HT-photodimer formation at high temperatures with no significant changes in the product enantiomeric excess (ee), while the anti-HH-photodimer formation remarkably increased with the decreasing temperature accompanied by a significant enhancement of the product ee up to -86&#37; at -50 degrees C. Temperature-dependent inversion of the chirality of the anti-HH dimer was observed when the chiral phenylene-linked amidine dimer was used and the product ee was changed from 22&#37; at 50 degrees C to -86&#37; at -50 degrees C. A similar enhancement of the enantioselectivity of the anti-HH dimer was also observed for the chiral amide-linked template, producing the anti-HH dimer with up to -88&#37; ee at -50 degrees C. The observed difference in the regio-, diastereo-, and enantioselectivities due to the difference in the linker structures of the amidine dimers during the template-directed photodimerization of 1 was discussed on the basis of a reversible conformational change in the amidine dimers complexed with 1.

DOI： 10.1021/jacs.7b03317

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Novel double helices covalently bridged by cyclic boronate esters were synthesized from complementary dimers with an m-terphenyl backbone joined by a chiral or achiral phenylene linker bearing diethyl boronates and diols, respectively. The X-ray crystallographic analysis and variable-temperature NMR and circular dichroism measurements, along with theoretical calculations, revealed that the double helices function as a molecular rotor in which the cyclic boronate ester units rotate, yielding two stable rotamers at low temperatures. Moreover, our data indicates that the covalently bonded double helices can undergo a unique helix-inversion simultaneously with a rotational motion of the boronate esters.

DOI： 10.1002/asia.201700162

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Novel double helices covalently bridged by cyclic boronate esters were synthesized from complementary dimers with an m-terphenyl backbone joined by a chiral or achiral phenylene linker bearing diethyl boronates and diols, respectively. The X-ray crystallographic analysis and variable-temperature NMR and circular dichroism measurements, along with theoretical calculations, revealed that the double helices function as a molecular rotor in which the cyclic boronate ester units rotate, yielding two stable rotamers at low temperatures. Moreover, our data indicates that the covalently bonded double helices can undergo a unique helix-inversion simultaneously with a rotational motion of the boronate esters.

DOI： 10.1002/asia.201700162

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A one-handed 3(10)-helical hexapeptide is efficiently encapsulated within the helical cavity of st-PMMA when a fullerene (C-60) derivative is introduced at the C-terminal end of the peptide. The encapsulation is accompanied by induction of a preferred-handed helical conformation in the st-PMMA backbone with the same-handedness as that of the hexapeptide to form a crystalline st-PMMA/peptide-C-60 inclusion complex with a unique optically active helix-in-helix structure. Although the st-PMMA is unable to encapsulate the 3(10)-helical peptide without the terminal C-60 unit, the helical hollow space of the st-PMMA is almost filled by the C-60-bound peptides. This result suggests that the C-60 moiety can serve as a versatile molecular carrier of specific molecules and polymers in the helical cavity of the st-PMMA for the formation of an inclusion complex, thus producing unique supramolecular soft materials that cannot be prepared by other methods.

DOI： 10.1002/anie.201611349

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A one-handed 3(10)-helical hexapeptide is efficiently encapsulated within the helical cavity of st-PMMA when a fullerene (C-60) derivative is introduced at the C-terminal end of the peptide. The encapsulation is accompanied by induction of a preferred-handed helical conformation in the st-PMMA backbone with the same-handedness as that of the hexapeptide to form a crystalline st-PMMA/peptide-C-60 inclusion complex with a unique optically active helix-in-helix structure. Although the st-PMMA is unable to encapsulate the 3(10)-helical peptide without the terminal C-60 unit, the helical hollow space of the st-PMMA is almost filled by the C-60-bound peptides. This result suggests that the C-60 moiety can serve as a versatile molecular carrier of specific molecules and polymers in the helical cavity of the st-PMMA for the formation of an inclusion complex, thus producing unique supramolecular soft materials that cannot be prepared by other methods.

DOI： 10.1002/anie.201611349

記述言語：英語  

In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

DOI： 10.1021/acs.chemrev.6b00354

記述言語：英語  

In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

DOI： 10.1021/acs.chemrev.6b00354

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Organic nanotubes (ONTs) are tubular nanostructures composed of small molecules or macromolecules that have found various applications including ion sensor/channels, gas absorption, and photovoltaics. While most ONTs are constructed by self-assembly processes based on weak noncovalent interactions, this unique property gives rise to the inherent instability of their tubular structures. Herein, we report a simple "helix-to-tube" strategy to construct robust, covalent ONTs from easily accessible poly(m-phenylene diethynylene)s (poly-PDEs) possessing chiral amide side chains that can adopt a helical conformation through hydrogen-bonding interactions. The helically folded poly-PDEs subsequently undergo light-induced cross-linking at longitudinally aligned 1,3-butadiyne moieties across the whole helix to form covalent tubes (ONTs) both in solution and solid phases. The structures of poly-PDEs and covalent ONTs were characterized by spectroscopic analyses, diffraction analysis, and microscopic analyses. We envisage that this simple yet powerful "helix-to-tube" strategy will generate a range of ONT-based materials by introducing functional moieties into a monomer.

DOI： 10.1021/jacs.6b05582

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Organic nanotubes (ONTs) are tubular nanostructures composed of small molecules or macromolecules that have found various applications including ion sensor/channels, gas absorption, and photovoltaics. While most ONTs are constructed by self-assembly processes based on weak noncovalent interactions, this unique property gives rise to the inherent instability of their tubular structures. Herein, we report a simple "helix-to-tube" strategy to construct robust, covalent ONTs from easily accessible poly(m-phenylene diethynylene)s (poly-PDEs) possessing chiral amide side chains that can adopt a helical conformation through hydrogen-bonding interactions. The helically folded poly-PDEs subsequently undergo light-induced cross-linking at longitudinally aligned 1,3-butadiyne moieties across the whole helix to form covalent tubes (ONTs) both in solution and solid phases. The structures of poly-PDEs and covalent ONTs were characterized by spectroscopic analyses, diffraction analysis, and microscopic analyses. We envisage that this simple yet powerful "helix-to-tube" strategy will generate a range of ONT-based materials by introducing functional moieties into a monomer.

DOI： 10.1021/jacs.6b05582

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Double-helical, bimetallic chiral Co(II)-salen complexes stabilized by chiral amidinium-carboxylate salt bridges efficiently catalyzed the asymmetric nitro-aldol (Henry) reaction, producing products with up to an 89&#37; enantiomeric excess (ee); the reactivity and enantioselectivity were higher than those catalyzed by the corresponding single strands. The key role of the chiral double-helical framework for the supramolecular bimetallic catalysis has been revealed by a double-helical catalyst carrying achiral Co(II)-salen units that promoted the Henry reaction, yielding the product with a 50&#37;-45&#37; ee, while the corresponding single strands showed poor or no enantioselectivity.

DOI： 10.1021/acscatal.6b01627

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Double-helical, bimetallic chiral Co(II)-salen complexes stabilized by chiral amidinium-carboxylate salt bridges efficiently catalyzed the asymmetric nitro-aldol (Henry) reaction, producing products with up to an 89&#37; enantiomeric excess (ee); the reactivity and enantioselectivity were higher than those catalyzed by the corresponding single strands. The key role of the chiral double-helical framework for the supramolecular bimetallic catalysis has been revealed by a double-helical catalyst carrying achiral Co(II)-salen units that promoted the Henry reaction, yielding the product with a 50&#37;-45&#37; ee, while the corresponding single strands showed poor or no enantioselectivity.

DOI： 10.1021/acscatal.6b01627

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We report the unprecedented allosteric regulation of the extension and contraction motions of double stranded spiroborate helicates composed of 4,4'-linked 2,2'-bipyridine (bpy) and its N,N'-dioxide units in the middle of ortho-linked tetraphenol strands. NMR and circular dichroism measurements and an X-ray crystallographic analysis along with theoretical calculations revealed that enantiomeric helicates contract and extend upon the binding and release of protons and/or metal ions at the covalently linked two binding bpy or N,N'-dioxide moieties without racemization, respectively, regulated by a cooperative anti-syn conformational change of the two bpy or N,N'-dioxide moieties. These anti-syn conformational changes that occurred at the linkages are amplified into a large-scale molecular motion of the helicates leading to reversible spring-like motions coupled with twisting in one direction in a highly homotropic allosteric fashion.

DOI： 10.1021/jacs.6b00787

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We report the unprecedented allosteric regulation of the extension and contraction motions of double stranded spiroborate helicates composed of 4,4'-linked 2,2'-bipyridine (bpy) and its N,N'-dioxide units in the middle of ortho-linked tetraphenol strands. NMR and circular dichroism measurements and an X-ray crystallographic analysis along with theoretical calculations revealed that enantiomeric helicates contract and extend upon the binding and release of protons and/or metal ions at the covalently linked two binding bpy or N,N'-dioxide moieties without racemization, respectively, regulated by a cooperative anti-syn conformational change of the two bpy or N,N'-dioxide moieties. These anti-syn conformational changes that occurred at the linkages are amplified into a large-scale molecular motion of the helicates leading to reversible spring-like motions coupled with twisting in one direction in a highly homotropic allosteric fashion.

DOI： 10.1021/jacs.6b00787

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Nonplanar conformations of pyrazine-fused Zn-II diporphyrins could be controlled by the choice of the meso-aryl substituents and an axial ligand on the central metals. Zn-II diporphyrins bearing sterically demanding meso-aryl groups with ortho-substituents led to a twisted chiral D-2 conformation, while an achiral C-2h form was preferred in the case of aryl groups without ortho-substituents. Helical chirality induction on Zn-II diporphyrins in the twisted conformation was achieved by controlling their handedness of the molecular twist through coordination of optically active 1-phenethylamine.

DOI： 10.1002/asia.201600105

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Nonplanar conformations of pyrazine-fused Zn-II diporphyrins could be controlled by the choice of the meso-aryl substituents and an axial ligand on the central metals. Zn-II diporphyrins bearing sterically demanding meso-aryl groups with ortho-substituents led to a twisted chiral D-2 conformation, while an achiral C-2h form was preferred in the case of aryl groups without ortho-substituents. Helical chirality induction on Zn-II diporphyrins in the twisted conformation was achieved by controlling their handedness of the molecular twist through coordination of optically active 1-phenethylamine.

DOI： 10.1002/asia.201600105

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The dynamic planar chirality in a peptide-bound Ni-II-salphen-based macrocycle can be remotely controlled. First, a right-handed (P)-3(10)-helix is induced in the dynamic helical oligopeptides by a chiral amino acid residue far from the macrocyclic framework. The induced planar chirality remains dynamic in chloroform and acetonitrile, but is almost completely locked in fluoroalcohols as a result of the solvent-induced transition of the peptide chains from a 3(10)-helix to a wider a-helix, which freezes the rotation of the pendant peptide units around the macrocycle.

DOI： 10.1002/anie.201507918

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The dynamic planar chirality in a peptide-bound Ni-II-salphen-based macrocycle can be remotely controlled. First, a right-handed (P)-3(10)-helix is induced in the dynamic helical oligopeptides by a chiral amino acid residue far from the macrocyclic framework. The induced planar chirality remains dynamic in chloroform and acetonitrile, but is almost completely locked in fluoroalcohols as a result of the solvent-induced transition of the peptide chains from a 3(10)-helix to a wider a-helix, which freezes the rotation of the pendant peptide units around the macrocycle.

DOI： 10.1002/anie.201507918

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Self-recognition and self-discrimination within complex mixtures are of fundamental importance in biological systems, which entirely rely on the preprogrammed monomer sequences and homochirality of biological macromolecules. Here we report artificial chirality- and sequence-selective successive self-sorting of chiral dimeric strands bearing carboxylic acid or amidine groups joined by chiral amide linkers with different sequences through homo-and complementary-duplex formations. A mixture of carboxylic acid dimers linked by racemic-1,2-cyclohexane bis-amides with different amide sequences (NHCO or CONH) self-associate to form homoduplexes in a completely sequence-selective way, the structures of which are different from each other depending on the linker amide sequences. The further addition of an enantiopure amide-linked amidine dimer to a mixture of the racemic carboxylic acid dimers resulted in the formation of a single optically pure complementary duplex with a 100&#37; diastereoselectivity and complete sequence specificity stabilized by the amidinium-carboxylate salt bridges, leading to the perfect chirality- and sequence-selective duplex formation.

DOI： 10.1038/ncomms8236

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Self-recognition and self-discrimination within complex mixtures are of fundamental importance in biological systems, which entirely rely on the preprogrammed monomer sequences and homochirality of biological macromolecules. Here we report artificial chirality- and sequence-selective successive self-sorting of chiral dimeric strands bearing carboxylic acid or amidine groups joined by chiral amide linkers with different sequences through homo-and complementary-duplex formations. A mixture of carboxylic acid dimers linked by racemic-1,2-cyclohexane bis-amides with different amide sequences (NHCO or CONH) self-associate to form homoduplexes in a completely sequence-selective way, the structures of which are different from each other depending on the linker amide sequences. The further addition of an enantiopure amide-linked amidine dimer to a mixture of the racemic carboxylic acid dimers resulted in the formation of a single optically pure complementary duplex with a 100&#37; diastereoselectivity and complete sequence specificity stabilized by the amidinium-carboxylate salt bridges, leading to the perfect chirality- and sequence-selective duplex formation.

DOI： 10.1038/ncomms8236

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Two foldamer strands, which possess chiral amide pendants but imperfect helical handedness, were linked by an achiral (metallo)salen tether, leading to a remarkable enhancement of helical stability and helix-sense excess as a result of the intramolecular hydrogen-bond networks along the entire dimeric foldamer strand; the Mn-II salen complexes catalyzed an asymmetric epoxidation reaction.

DOI： 10.1246/cl.131168

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Two foldamer strands, which possess chiral amide pendants but imperfect helical handedness, were linked by an achiral (metallo)salen tether, leading to a remarkable enhancement of helical stability and helix-sense excess as a result of the intramolecular hydrogen-bond networks along the entire dimeric foldamer strand; the Mn-II salen complexes catalyzed an asymmetric epoxidation reaction.

DOI： 10.1246/cl.131168

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A new class of (Fe4L4)-L-II capsules, based upon a tritopic trialdehyde subcomponent, is reported. One such capsule was prepared diastereoselectively through the incorporation of a chiral amine residue. This amine was displaced by an achiral one, while maintaining the stereochemistry of the cage framework (99&#37; ee); this cage retained its stereochemistry even after 4 days at 90 degrees C. Mechanistic studies indicate the memory displayed by this capsule to be the result of effective stereochemical communication between the metal centers mediated by the rigid 3-fold-symmetric faces, in combination with a stepwise substitution mechanism.

DOI： 10.1021/ja410117q

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A new class of (Fe4L4)-L-II capsules, based upon a tritopic trialdehyde subcomponent, is reported. One such capsule was prepared diastereoselectively through the incorporation of a chiral amine residue. This amine was displaced by an achiral one, while maintaining the stereochemistry of the cage framework (99&#37; ee); this cage retained its stereochemistry even after 4 days at 90 degrees C. Mechanistic studies indicate the memory displayed by this capsule to be the result of effective stereochemical communication between the metal centers mediated by the rigid 3-fold-symmetric faces, in combination with a stepwise substitution mechanism.

DOI： 10.1021/ja410117q

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/chem.201300361

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/chem.201300361

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A series of large, optically active Fe4L6 cages was prepared from linear 5,5'-bis(2-formylpyridines) incorporating varying numbers (n = 0-3) of oligo-p-xylene spacers, chiral amines, and Fe-II. When a cage was constructed from the ligand bridged by one p-xylene spacer (n = 1) and a bulky chiral amine, both a homochiral Fe2L3 helicate and Fe4L6 cage were observed to coexist in solution due to a delicate balance between steric factors. In contrast, when a less bulky chiral amine was used, only the Fe4L6 cage was observed. In the case of larger cages (n = 2, 3), long-range (>2 nm) stereochemical coupling between metal centers was observed, which was minimally diminished as the ligands were lengthened. This communication was mediated by the ligands' geometries and rigidity, as opposed to gearing effects between xylene methyl groups: the metal-centered stereochemistry was not observed to affect the axial stereochemistry of the ligands.

DOI： 10.1021/ja306615d

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A series of large, optically active Fe4L6 cages was prepared from linear 5,5'-bis(2-formylpyridines) incorporating varying numbers (n = 0-3) of oligo-p-xylene spacers, chiral amines, and Fe-II. When a cage was constructed from the ligand bridged by one p-xylene spacer (n = 1) and a bulky chiral amine, both a homochiral Fe2L3 helicate and Fe4L6 cage were observed to coexist in solution due to a delicate balance between steric factors. In contrast, when a less bulky chiral amine was used, only the Fe4L6 cage was observed. In the case of larger cages (n = 2, 3), long-range (>2 nm) stereochemical coupling between metal centers was observed, which was minimally diminished as the ligands were lengthened. This communication was mediated by the ligands' geometries and rigidity, as opposed to gearing effects between xylene methyl groups: the metal-centered stereochemistry was not observed to affect the axial stereochemistry of the ligands.

DOI： 10.1021/ja306615d

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Long-range communication of stereochemical information is common in biological systems, particularly in enzyme-catalysed reactions. Here, we report the remote control of the dynamic chirality of metal centres, coordinated by 2,2'-bipyridine ligands bearing dynamic helical oligopeptides. The helical chirality of the oligopeptides is controlled by a stereocentre remote from the metal. We show that when a mixture of chiral and achiral peptide ligands is used, both the chirality of the metal centre and that of the achiral oligopeptide helices are significantly amplified. The amplification mechanism relies on several steps of chirality induction, first from a single chiral peptide to the helicity of an oligopeptide through the induction of propeller chirality at the metal centre, then on to induction of helical chirality in an achiral oligopeptide.

DOI： 10.1038/NCHEM.1146

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Long-range communication of stereochemical information is common in biological systems, particularly in enzyme-catalysed reactions. Here, we report the remote control of the dynamic chirality of metal centres, coordinated by 2,2'-bipyridine ligands bearing dynamic helical oligopeptides. The helical chirality of the oligopeptides is controlled by a stereocentre remote from the metal. We show that when a mixture of chiral and achiral peptide ligands is used, both the chirality of the metal centre and that of the achiral oligopeptide helices are significantly amplified. The amplification mechanism relies on several steps of chirality induction, first from a single chiral peptide to the helicity of an oligopeptide through the induction of propeller chirality at the metal centre, then on to induction of helical chirality in an achiral oligopeptide.

DOI： 10.1038/NCHEM.1146

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A single intramolecular cross-linking between the chiral side chains at the i and i + 3 positions induces only a one-handed helix in a 3(10)-helical peptide of which the main chain lacks a chiral center and, thus, transforms the "dynamic" helix to a "static" one.

DOI： 10.1021/ja8091714

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A single intramolecular cross-linking between the chiral side chains at the i and i + 3 positions induces only a one-handed helix in a 3(10)-helical peptide of which the main chain lacks a chiral center and, thus, transforms the "dynamic" helix to a "static" one.

DOI： 10.1021/ja8091714

記述言語：英語  

This study aims at demonstrating end-to-end transfer of noncovalent chiral information along a peptide chain. The domino-type induction of helical sense is proven by using achiral peptides 1-m of bis-chromophoric sequence with different chain lengths: H-(Aib-Delta(Z)Phe)(m)-(Aib-Delta(Z)Bip)(2)-Aib-OCH3 [m = 2, 4, and 6; Aib = alpha-aminoisobutyric acid; Delta(Z)Phe = (Z)-alpha,beta-didehydrophenylalanine; Delta(Z)Bip = (Z)-beta-(4,4'-biphenyl)-alpha,beta-didehydroalanine]. They all showed the tendency to adopt a 3(10)-helix. Whereas peptide 1-m originally shows no circular dichroism (CD) signals, marked CD signals were induced at around 270-320 nm based on both the beta-aryl didehydroresi dues by chiral Boc-proline (Boc = tert-butoxycarbonyl). The observed CD spectra were interpreted on the basis of the exciton chirality method and theoretical CD simulation of several helical conformations that were energy-minimized. The experimental and theoretical CD analysis reveals that Boc-L-proline induces the preference for a right-handed helicity in the whole chain of 1-m. Such noncovalent chiral induction was not observed in the corresponding N-terminally protected 1-m. Obviously, helicity induction in I-in originates from the binding of Boc-proline to the N-terminal site. In the 17-mer (1-6), the information of helix sense reaches the 16th residue from the N-terminus. We have monitored precise transfer of noncovalent chiral stimulus along a helical peptide chain. The present study also proposes a primitive allosteric model of a single protein-mimicking backbone. Here chiral molecule binding the N-terminal site of 1-6 controls the chiroptical signals and helical sense of the C-terminal site about 30 angstrom away.

DOI： 10.1021/jo801686m

記述言語：英語  

This study aims at demonstrating end-to-end transfer of noncovalent chiral information along a peptide chain. The domino-type induction of helical sense is proven by using achiral peptides 1-m of bis-chromophoric sequence with different chain lengths: H-(Aib-Delta(Z)Phe)(m)-(Aib-Delta(Z)Bip)(2)-Aib-OCH3 [m = 2, 4, and 6; Aib = alpha-aminoisobutyric acid; Delta(Z)Phe = (Z)-alpha,beta-didehydrophenylalanine; Delta(Z)Bip = (Z)-beta-(4,4'-biphenyl)-alpha,beta-didehydroalanine]. They all showed the tendency to adopt a 3(10)-helix. Whereas peptide 1-m originally shows no circular dichroism (CD) signals, marked CD signals were induced at around 270-320 nm based on both the beta-aryl didehydroresi dues by chiral Boc-proline (Boc = tert-butoxycarbonyl). The observed CD spectra were interpreted on the basis of the exciton chirality method and theoretical CD simulation of several helical conformations that were energy-minimized. The experimental and theoretical CD analysis reveals that Boc-L-proline induces the preference for a right-handed helicity in the whole chain of 1-m. Such noncovalent chiral induction was not observed in the corresponding N-terminally protected 1-m. Obviously, helicity induction in I-in originates from the binding of Boc-proline to the N-terminal site. In the 17-mer (1-6), the information of helix sense reaches the 16th residue from the N-terminus. We have monitored precise transfer of noncovalent chiral stimulus along a helical peptide chain. The present study also proposes a primitive allosteric model of a single protein-mimicking backbone. Here chiral molecule binding the N-terminal site of 1-6 controls the chiroptical signals and helical sense of the C-terminal site about 30 angstrom away.

DOI： 10.1021/jo801686m

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A new optically inactive 3(10)-helical peptide with a side-chain cross-linking was found to exhibit chiral memory stored in the peptide backbone, whose chirality was induced by a noncovalent interaction of a chiral molecule at the N-terminal end of the peptide.

DOI： 10.1021/ja805647k

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A new optically inactive 3(10)-helical peptide with a side-chain cross-linking was found to exhibit chiral memory stored in the peptide backbone, whose chirality was induced by a noncovalent interaction of a chiral molecule at the N-terminal end of the peptide.

DOI： 10.1021/ja805647k

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Cooperative structural stabilization and the deceleration of chirality interconversion of an octapeptide helix are achieved by a single intramolecular side-chain crosslinking, as revealed by X-ray crystallography, H-1 NMR spectroscopy, and computational analyses. The helical inversion is slow on the NMR time scale even at 80 degrees C. This is the first case of decelerated chirality inversion for helices based on the biological backbone, and the sequence -Api-Alb(2)-Api- bridged with p-phenylenediacetic acid may serve as a key structural unit for the design of optically active peptides composed of only achiral building blocks and/or a variety of peptides with enhanced structural rigidity.

DOI： 10.1021/ja077857h

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Cooperative structural stabilization and the deceleration of chirality interconversion of an octapeptide helix are achieved by a single intramolecular side-chain crosslinking, as revealed by X-ray crystallography, H-1 NMR spectroscopy, and computational analyses. The helical inversion is slow on the NMR time scale even at 80 degrees C. This is the first case of decelerated chirality inversion for helices based on the biological backbone, and the sequence -Api-Alb(2)-Api- bridged with p-phenylenediacetic acid may serve as a key structural unit for the design of optically active peptides composed of only achiral building blocks and/or a variety of peptides with enhanced structural rigidity.

DOI： 10.1021/ja077857h

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja063873n

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja063873n

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Noncovalent chiral domino effect (NCDE) has been proposed as terminal-specific interaction upon a 3(10)-helical peptide chain, of which the helix sense is manipulated by an external chiral stimulus (mainly amino acid derivatives) operating on the N-terminus (Inai, Y., et al. J Am Chem Soc 2000, 122, 11731-11732; ibid., 2002, 124, 2466-2473; ibid., 2003, 125, 8151-8162). We have investigated here a helix-sense induction in an optically inactive N-terminal-free nonapeptide (1) through the screening of several peptide species that differ in chiral sequence, chain length, and C-terminal group. Helix-sense induction in peptide I depends largely on both the C-terminal chirality and carboxyl group in the external peptide, in which N-carbonyl-blocked amino acids, "monopeptide acids," should be the minimum requirement for effective induction. N-Protected mono- to tetrapeptides of L-Leu residue commonly induce a right-handed helix. NMR study and theoretical computation reveal that the N-terminal segment of peptide 1 binds the N-protected dipeptide molecule through multipoint coordination to induce a right-handed helix preferentially. The present findings not only will improve our understanding of the chiral roles in peptide or protein helical termini, but also might demonstrate potential applications to chirality-responsive materials based on peptide helical fragments. (c) 2006 Wiley Periodicals, Inc.

DOI： 10.1002/bip.20491

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Noncovalent chiral domino effect (NCDE) has been proposed as terminal-specific interaction upon a 3(10)-helical peptide chain, of which the helix sense is manipulated by an external chiral stimulus (mainly amino acid derivatives) operating on the N-terminus (Inai, Y., et al. J Am Chem Soc 2000, 122, 11731-11732; ibid., 2002, 124, 2466-2473; ibid., 2003, 125, 8151-8162). We have investigated here a helix-sense induction in an optically inactive N-terminal-free nonapeptide (1) through the screening of several peptide species that differ in chiral sequence, chain length, and C-terminal group. Helix-sense induction in peptide I depends largely on both the C-terminal chirality and carboxyl group in the external peptide, in which N-carbonyl-blocked amino acids, "monopeptide acids," should be the minimum requirement for effective induction. N-Protected mono- to tetrapeptides of L-Leu residue commonly induce a right-handed helix. NMR study and theoretical computation reveal that the N-terminal segment of peptide 1 binds the N-protected dipeptide molecule through multipoint coordination to induce a right-handed helix preferentially. The present findings not only will improve our understanding of the chiral roles in peptide or protein helical termini, but also might demonstrate potential applications to chirality-responsive materials based on peptide helical fragments. (c) 2006 Wiley Periodicals, Inc.

DOI： 10.1002/bip.20491

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja035040s

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja035040s