|矢崎 亮（やざき りよう）||データ更新日：2020.02.21|
助教 ／ 薬学研究院 創薬科学部門 生命薬学
|1.||Seiya Taninokuchi, Ryo Yazaki, Takashi Ohshima, Mechanistic insight into catalytic aerobic chemoselective α-oxidation of acylpyrazoles, Heterocycles, 10.3987/COM-18-S(F)58, 99, 2, 906-918, 2019.01, [URL], Mechanistic studies on catalytic aerobic chemoselective α-oxidation of acylpyrazoles, including control experiments, kinetic isotope effect experiments, and radical clock experiments, are described. The key to promoting the reaction was the in-situ generation of a copper(II) peroxo complex, which serves as a Lewis acid/Brønsted base cooperative catalyst for efficient enolization. The present catalysis was applicable to late-stage α-oxidation of functionalized acylpyrazoles. A preliminary diastereoselective reaction using readily available chiral acylpyrazoles demonstrated that the present catalysis provided access to optically active α-hydroxy acid derivatives..|
|2.||Ryo Yazaki, Takashi Ohshima, Recent strategic advances for the activation of benzylic C–H bonds for the formation of C–C bonds, Tetrahedron Letters, 10.1016/j.tetlet.2019.151225, 60, 45, 2019.11, [URL], Alkylarenes, obtained from abundant hydrocarbon feedstock sources, are an attractive starting material for the formation of complex molecular architectures. Conventional activation strategies of the relatively inert sp3-hybridized benzylic C–H bonds usually require relatively harsh conditions and are difficult to apply to the synthesis of fine chemicals. The present review describes recent strategic advances for the activation of benzylic C–H bonds for the catalytic formation of C–C bonds. In particular, two activation methods, i.e., strategies that generate benzylic radicals or benzyl anions, are discussed..|
|3.||Takafumi Tanaka, Tsukushi Tanaka, Taro Tsuji, Ryo Yazaki, Takashi Ohshima, Strategy for Catalytic Chemoselective Cross-Enolate Coupling Reaction via a Transient Homocoupling Dimer, Organic Letters, 10.1021/acs.orglett.8b01313, 20, 12, 3541-3544, 2018.06, [URL], A new strategy, a transient homocoupling dimer strategy, for direct catalytic oxidative cross-enolate coupling reactions is developed. Cross-enolate coupling products bearing a (contiguous) tetrasubstituted carbon center were obtained chemoselectively without the need for stoichiometric amounts of strong bases/metal oxidants, and thus, the present catalysis provides a general method for the synthesis of unnatural α,α-disubstituted amino acid motifs. The distinct transformation of azlactone and 2-acylimidazole units highlighted the synthetic utility of the present catalysis..|
|4.||Hao Luo, Kensuke Nishi, Shuhei Ishikura, Anthony Swain, Naoyuki Morishige, Ryo Yazaki, Takashi Ohshima, Senji Shirasawa, Toshiyuki Tsunoda, Growth suppression of human colorectal cancer cells with mutated KRAS by 3-deaza-cytarabine in 3d floating culture, Anticancer research, 10.21873/anticanres.12721, 38, 7, 4247-4256, 2018.07, [URL], Background/Aim: During screening for compounds that selectively suppress growth of human colorectal cancer (CRC) spheroids with mutant (mt) KRAS, the uridine analogue, 5-bromouridine (BrUrd) was identified and its derivatives were explored. Materials and Methods: DNA incorporation in two-dimensional (2D) and three-dimensional floating (3DF) cultures was examined with the uridine analogue, 5-ethynyl-2'-deoxyuridine (EdU). The area of HKe3 CRC spheroids expressing wild type (wt) KRAS (HKe3-wtKRAS) and mtKRAS (HKe3-mtKRAS) were measured in 3DF culture with 11 BrUrd derivatives. Results: EdU was strongly incorporated into newly-synthesized DNA from HKe3-mtKRAS cells compared to HKe3-wtKRAS in 2D and 3DF culture. 3-Deaza-cytarabine, which has properties of BrUrd and cytidine, was the most effective inhibitor of HKe3-mtKRAS spheroids with the least toxicity to HKe3-wtKRAS. Growth suppression of 3-deaza-cytarabine was stronger than cytarabine in 2D culture, and toxicity was lower than gemcitabine in long-term 3DF culture. Conclusion: 3-Deaza-cytarabine exhibits properties useful for the treatment of CRC patients with mtKRAS..|
|5.||Tsukushi Tanaka, Kayoko Hashiguchi, Takafumi Tanaka, Ryo Yazaki, Takashi Ohshima, Chemoselective Catalytic Dehydrogenative Cross-Coupling of 2-Acylimidazoles
Mechanistic Investigations and Synthetic Scope, ACS Catalysis, 10.1021/acscatal.8b02361, 8, 9, 8430-8440, 2018.09, [URL], Chemoselective iron-catalyzed dehydrogenative cross-coupling using 2-acylimidazoles is described. The addition of a phosphine oxide ligand substantially facilitated the generation of tert-butoxy radicals from di-tert-butyl peroxide, allowing for efficient benzylic C-H bond cleavage under mild conditions. Extensive mechanistic studies revealed that the enolization of 2-acylimidazole proceeded through dual iron catalyst activation, followed by subsequent chemoselective cross-coupling with a benzyl radical over an undesired benzyl radical-derived homocoupling dimer that inevitably formed in earlier reported conditions. A variety of alkylarenes, aliphatic alkane, and functionalized 2-acylimidazoles were applicable, demonstrating the synthetic utility of the present catalysis. Contiguous all-carbon quaternary carbons were constructed through dehydrogenative cross-coupling. The catalytic chemoselective activation of 2-acylimidazole over bidentate coordinative and much more acidic malonate diester was particular noteworthy. Catalytic oxidative cross-enolate coupling of two distinct carboxylic acid equivalents was also achieved using acetonitrile as a coupling partner..
|6.||Yohei Matsumoto, Taro Tsuji, Daiki Nakatake, Ryo Yazaki, Takashi Ohshima, Thionoesters as 1,2-Dipolarophiles for [4+2] Cycloaddition with Cyclobutanones, Asian Journal of Organic Chemistry, 10.1002/ajoc.201900156, 2019.01, [URL], The utility of thionoester as a 1,2-dipolarophile for [4+2] cycloaddition with cyclobutanones is described. The [4+2] cycloaddition reaction provided tetrahydrothiopyran, which is found in biologically active natural products, in high yield with high diastereoselectivity by using readily available TiCl
. This synthetic method was applicable to a wide range of thionoesters and cyclobutanones. The ketone and S,O-ketal functionalities of the product could be reduced with excellent diastereoselectivity. Furthermore, the C−O bond was transformed into a C−C bond, affording contiguous tetrasubstituted carbon centers..
|7.||Yohei Matsumoto, Daiki Nakatake, Ryo Yazaki, Takashi Ohshima, An Expeditious Route to trans-Configured Tetrahydrothiophenes Enabled by Fe(OTf)3-Catalyzed [3+2] Cycloaddition of Donor–Acceptor Cyclopropanes with Thionoesters, Chemistry - A European Journal, 10.1002/chem.201800957, 24, 23, 6062-6066, 2018.04, [URL], A synthetic route to trans-configured tetrahydrothiophenes (THTs) through Fe(OTf)3-promoted [3+2] cycloaddition of donor–acceptor cyclopropanes with thionoesters was developed. The cycloaddition proceeded in high yield with high diastereoselectivity, affording transient α-alkoxy THTs. Not only aromatic and aliphatic thionoesters, but also thionolactone were applicable to the present iron catalysis. Further transformation of the S,O-ketal functionality of the product was achieved in a highly trans diastereoselective manner. Moreover, the utility of our methodology was clearly demonstrated by the synthesis of enantioenriched trans-configured THTs..|
|8.||Seiya Taninokuchi, Ryo Yazaki, Takashi Ohshima, Catalytic Aerobic Chemoselective α-Oxidation of Acylpyrazoles en Route to α-Hydroxy Acid Derivatives, Organic Letters, 10.1021/acs.orglett.7b01293, 19, 12, 3187-3190, 2017.06, [URL], Catalytic aerobic chemoselective α-oxidation of acylpyrazoles is described. Acylpyrazoles, carboxylic acid oxidation state substrates, were efficiently oxidized under aerobic conditions using TEMPO as an oxygenating agent. The mild catalytic conditions of the present catalysis were amenable to late-stage α-oxidation of various pharmaceutical agents and natural products, leading to previously unreported α-hydroxy acid derivatives in short steps. Preliminary mechanistic studies revealed that in situ generated copper(II) peroxo species served as a Lewis acid/Brønsted base cooperative catalyst..|
|9.||Zhao Li, Masamichi Tamura, Ryo Yazaki, Takashi Ohshima, Catalytic chemoselective conjugate addition of amino alcohols to α,β-unsaturated ester
Hydroxy group over amino group and conjugate addition over transesterification, Chemical and Pharmaceutical Bulletin, 10.1248/cpb.c16-00333, 65, 1, 19-21, 2017, [URL], A highly chemoselective conjugate addition of amino alcohols to α,β-unsaturated ester using a soft Lewis acid/hard Brønsted base cooperative catalyst was developed. This catalysis achieved chemoselective addition of a hydroxy group over an amino group. Moreover, soft metal alkoxide generation enabled chemoselective soft conjugate addition over hard transesterification. Various amino alcohols, including unprecedented cyclic β-amino alcohol, were applicable to the present catalysis..
|10.||Zhao Li, Ryo Yazaki, Takashi Ohshima, Chemo- and Regioselective Direct Functional Group Installation through Catalytic Hydroxy Group Selective Conjugate Addition of Amino Alcohols to α,β-Unsaturated Sulfonyl Compounds, Organic Letters, 10.1021/acs.orglett.6b01464, 18, 14, 3350-3353, 2016.07, [URL], A chemoselective functional group installation through catalytic hydroxy group selective conjugate addition of amino alcohols to a variety of functionalized α,β-unsaturated sulfonyl derivatives was developed. Azide group installation for click chemistry and facile fluorescent labeling onto the less reactive hydroxy group demonstrated the synthetic utility of the present chemoselective catalysis. Moreover, chemo- and regioselective reaction of an unprotected amino diol was achieved for the first time..|
|11.||Daiki Nakatake, Yuki Yokote, Yoshimasa Matsushima, Ryo Yazaki, Takashi Ohshima, A highly stable but highly reactive zinc catalyst for transesterification supported by a bis(imidazole) ligand, Green Chemistry, 10.1039/c5gc02056e, 18, 6, 1524-1530, 2016.03, [URL], We designed highly active and practical bis(imidazole)/zinc complexes for transesterification reactions. X-ray crystallographic analysis was used to confirm the structures of the zinc complexes and an equivalent of bis(imidazole) ligand was crucial for high catalytic activity. The octahedral zinc complex 8c was prepared in up to a multigram scale by mixing Zn(OCOCF3)2·xH2O and meta-bis(imidazolylmethyl)benzene ligand 7j (two equivalents per zinc ion) and storable under air at room temperature for at least 9 months. The stable nature of the catalyst was amenable to recovery/reuse at least five times without a significant loss of reactivity. The transesterification reaction proceeded without strict reaction conditions, and expanded substrate generalities, including sterically demanding secondary and tertiary alcohols, were applicable. Remarkably, the present zinc catalyst proved highly effective for valuable monomer synthesis from readily available methyl acrylate derivatives. Chemoselective transesterification reactions of unprotected-amino alcohols were also achieved, using not only a simple methyl ester but also an unprecedented dimethyl carbonate..|
|12.||Keisuke Tokumasu, Ryo Yazaki, Takashi Ohshima, Direct Catalytic Chemoselective α-Amination of Acylpyrazoles
A Concise Route to Unnatural α-Amino Acid Derivatives, Journal of the American Chemical Society, 10.1021/jacs.5b11773, 138, 8, 2664-2669, 2016.03, [URL], A direct copper-catalyzed highly chemoselective α-amination is described. Acylpyrazole proved to be a highly efficient enolate precursor of a carboxylic acid oxidation state substrate, while preactivation by a stoichiometric amount of strong base has been used in catalytic α-aminations. The simultaneous activation of both coupling partners, enolization and metal nitrenoid formation, was crucial for obtaining the product, and wide functional group compatibility highlighted the mildness of the present catalysis. The bidentate coordination mode was amenable to highly chemoselective activation over ketone and much more acidic nitroalkyl functionality. Deuterium exchange experiments clearly demonstrated that exclusive enolization of acylpyrazole was achieved without the formation of a nitronate. The present catalysis was applied to late-stage α-amination, allowing for concise access to highly versatile α-amino acid derivatives. The product could be transformed into variety of useful building blocks..
|13.||Daiki Nakatake, Ryo Yazaki, Yoshimasa Matsushima, Takashi Ohshima, Transesterification Reactions Catalyzed by a Recyclable Heterogeneous Zinc/Imidazole Catalyst, Advanced Synthesis and Catalysis, 10.1002/adsc.201600229, 358, 15, 2569-2574, 2016.01, [URL], We report the development of a universal and recyclable heterogeneous zinc/imidazole catalyst. The catalyst is recoverable through simple filtration and can be reused at least five times, retaining its catalytic activity. Leached zinc species were not responsible for the observed catalysis based on the hot filtration test and ICP-MS analysis. The heterogeneous zinc catalyst also promotes chemoselective transesterification over amidation. (Figure presented.)..|
|14.||Rikiya Horikawa, Chika Fujimoto, Ryo Yazaki, Takashi Ohshima, μ-Oxo-Dinuclear-Iron(III)-Catalyzed O-Selective Acylation of Aliphatic and Aromatic Amino Alcohols and Transesterification of Tertiary Alcohols, Chemistry - A European Journal, 10.1002/chem.201602801, 22, 35, 12278-12281, 2016.01, [URL], A highly chemoselective and reactive μ-oxo-dinuclear iron(III) salen catalyst for transesterification was developed. The developed iron complex catalyzed acylation of aliphatic amino alcohols with nearly perfect O-selectivity, even when using activated esters, for which chemoselectivity is more difficult to control. In addition, O-selective transesterification of aromatic amino alcohols was achieved for the first time. The high activity of the iron complex enabled the use of sterically congested tertiary alcohols, including unprecedented tert-butanol..|
|15.||Daiki Nakatake, Ryo Yazaki, Takashi Ohshima, Chemoselective Transesterification of Acrylate Derivatives for Functionalized Monomer Synthesis Using a Hard Zinc Alkoxide Generation Strategy, Liebigs Annalen der Chemie, 10.1002/ejoc.201600737, 2016, 22, 3696-3699, 2016, [URL], A new practical method for the synthesis of functionalized acrylate derivatives with the view to prepare functional polymers was explored. Hard zinc alkoxide generation enabled the highly chemoselective transesterification of acrylate derivatives over the undesired conjugate addition, which caused polymerization. The combined use of the catalytic zinc cluster Zn4(OCOCF3)6O and 4-(dimethylamino)pyridine delivered various functionalized acrylate derivatives through the transesterification of commercially available methyl acrylate derivatives with functionalized alcohols under mild conditions..|
|16.||Ryo Yazaki, Nucleophilic amination strategy for catalytic synthesis of α-amino carbonyl compounds, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 74, 7, 732-733, 2016, A nucleophilic amination strategy allows for expeditious access to various N-substituted α-amino carbonyl compounds. However, development of catalytic method remained unexplored in compared to an electrophilic amination strategy. The present review focused on the recent reports of a nucleophilic amination strategy for catalytic synthesis of α-amino carbonyl compounds..|
|17.||Martin McLaughlin, Ryo Yazaki, Thomas C. Fessard, Erick M. Carreira, Oxetanyl peptides
Novel peptidomimetic modules for medicinal chemistry, Organic Letters, 10.1021/ol501590n, 16, 16, 4070-4073, 2014.08, [URL], The synthesis of novel oxetanyl peptides, where the amide bond is replaced by a non-hydrolyzable oxetanylamine fragment, is reported. This new class of pseudo-dipeptides with the same H-bond donor/acceptor pattern found in proteins expands the repertoire of peptidomimetics..
|18.||Shuhei Uesugi, Zhao Li, Ryo Yazaki, Takashi Ohshima, Chemoselective catalytic conjugate addition of alcohols over amines, Angewandte Chemie - International Edition, 10.1002/anie.201309755, 53, 6, 1611-1615, 2014.02, [URL], A highly chemoselective conjugate addition of alcohols in the presence of amines is described. The cooperative nature of the catalyst enabled chemoselective activation of alcohols over amines, allowing the conjugate addition to soft Lewis basic α,β-unsaturated nitriles. Divergent transformation of the nitrile functionality highlights the utility of the present catalysis. The cooperative nature of a copper catalyst enabled the highly chemoselective activation of alcohols in the presence of amines and thus the conjugate addition of the hydroxy group to soft Lewis basic α,β-unsaturated nitriles. The presented method proceeds under proton-transfer conditions, reverses the innate reactivity of the OH and NH groups, and does not require protecting groups. dppe=1,2-bis(diphenylphosphino) ethane, MeSal=3-methylsalicylate..|
|19.||Liang Yin, Yasunari Otsuka, Hisashi Takada, Shinsuke Mouri, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric alkynylation of ketoimines, Organic Letters, 10.1021/ol3035609, 15, 3, 698-701, 2013.02, [URL], An efficient protocol for direct catalytic alkynylation of ketoimines is described. The simultaneous activation of a soft Lewis basic terminal alkyne and a ketoimine bearing a thiophosphinoyl group by soft Lewis acid Cu(I) is crucial for high conversion. The reaction can be rendered asymmetric with a chiral bisphosphine ligand (S,S)-Ph-BPE..|
|20.||Yuta Suzuki, Mitsutaka Iwata, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Concise enantioselective synthesis of duloxetine via direct catalytic asymmetric aldol reaction of thioamide, Journal of Organic Chemistry, 10.1021/jo300566p, 77, 9, 4496-4500, 2012.05, [URL], Direct catalytic asymmetric aldol reaction of thioamide offers a new entry to the concise enantioselective synthesis of duloxetine. The direct aldol protocol was scalable (>20 g) to afford the aldol product in 92% ee after LiAlH 4 reduction, and 84% of the chiral ligand was recovered after recrystallization. The following four steps of transformation delivered duloxetine..|
|21.||Takanori Ogawa, Shinsuke Mouri, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Intermediate as catalyst
Catalytic asymmetric conjugate addition of nitroalkanes to α,β-unsaturated thioamides, Organic Letters, 10.1021/ol202898e, 14, 1, 110-113, 2012.01, [URL], Catalytic asymmetric conjugate addition of nitroalkanes to α,β-unsaturated thioamides is promoted by a mesitylcopper/(R)-DTBM- Segphos precatalyst, affording γ-nitrothioamides in moderate to high syn-selectivity and excellent enantioselectivity. The intermediate Cu-thioamide enolate functions as a soft Lewis acid/hard Brønsted base cooperative catalyst to drive the catalytic cycle efficiently under proton transfer conditions..
|22.||Yuta Suzuki, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric intramolecular conjugate addition of thioamide to α,β-unsaturated esters, Chemistry - A European Journal, 10.1002/chem.201102332, 17, 43, 11998-12001, 2011.10, [URL], Proton transfer allows efficient access to optically active five- and six-membered ring systems bearing ester and thioamide functionalities in an anti fashion; these ring systems are amenable to differential functional group manipulation. Direct catalytic, asymmetric, intramolecular conjugate addition of thioamide to α,β-unsaturated esters is described. In situ generated Cu thioamide enolate, by catalytic deprotonation, underwent the conjugate addition/protonation, to achieve the complete transformation (see scheme)..|
|23.||Yuji Kawato, Mitsutaka Iwata, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, A simplified catalytic system for direct catalytic asymmetric aldol reaction of thioamides; Application to an enantioselective synthesis of atorvastatin, Tetrahedron, 10.1016/j.tet.2011.05.109, 67, 35, 6539-6546, 2011.09, [URL], A new catalytic system was developed for the direct catalytic asymmetric aldol reaction of thioamides. The new lithium-free Cu catalyst (second-generation catalyst) exhibited enhanced catalytic efficiency over the previously developed catalyst comprising [Cu(CH3CN) 4]PF6/Ph-BPE/LiOAr (first-generation catalyst), which required a tedious catalyst preparation process. In the reaction with the second-generation catalyst, the intermediate Cu-aldolate functioned as a Brønsted base to generate thioamide enolate, efficiently driving the catalytic cycle. The present aldol methodology culminated in a concise asymmetric synthesis of atorvastatin (Lipitor®: atorvastatin calcium), a widely prescribed HMG-CoA reductase inhibitor for lowering low-density lipoprotein cholesterol..|
|24.||Yuka Yanagida, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Asymmetric synthesis of isothiazoles through Cu catalysis
Direct catalytic asymmetric conjugate addition of allyl cyanide to α,β-unsaturated thioamides, Angewandte Chemie - International Edition, 10.1002/anie.201102467, 50, 34, 7910-7914, 2011.08, [URL], Twice the catalyst: The simultaneous activation of an allyl cyanide (pronucleophile) and an α,β-unsaturated thioamide (electrophile) was achieved using a Cu-based soft Lewis acid/hard Brønsted base cooperative catalyst, thus resulting in the formation of enethioamides 1 in a highly enantio- and Z-selective manner (see scheme). The sequential Cu-catalyzed intramolecular cyclization gave rise to enantioenriched fused isothiazoles 2..
|25.||Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Cooperative activation of alkyne and thioamide functionalities; Direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated thioamides, Chemistry - An Asian Journal, 10.1002/asia.201100050, 6, 7, 1778-1790, 2011.07, [URL], A detailed study of the direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated thioamides is described. A soft Lewis acid/hard Brønsted base cooperative catalyst, comprising [Cu(CH3CN)4]PF6, bisphosphine ligand, and Li(OC6H4-p-OMe) simultaneously activated both substrates to compensate for the low reactivity of copper alkynylide. A series of control experiments revealed that the intermediate copper-thioamide enolate functioned as a Brønsted base to generate copper alkynylide from the terminal alkyne, thus driving the catalytic cycle through an efficient proton transfer between substrates. These findings led to the identification of a more convenient catalyst using potassium hexamethyldisilazane (KHMDS) as the Brønsted base, which was particularly effective for the reaction of silylacetylenes. Divergent transformation of the thioamide functionality and a concise enantioselective synthesis of a GPR40 receptor agonist AMG-837 highlighted the synthetic utility of the present catalysis..|
|26.||Mitsutaka Iwata, Ryo Yazaki, I. Hon Chen, Devarajulu Sureshkumar, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic enantio- and diastereoselective aldol reaction of thioamides, Journal of the American Chemical Society, 10.1021/ja200250p, 133, 14, 5554-5560, 2011.04, [URL], A direct catalytic asymmetric aldol reaction of thioamides using a soft Lewis acid/hard Brønsted base cooperative catalyst comprising (R,R)-Ph-BPE/[Cu(CH 3CN) 4]PF 6/LiOAr is described. Exclusive enolate generation from thioacetamides through a soft-soft interaction with the soft Lewis acid allowed for a direct aldol reaction to α-nonbranched aliphatic aldehydes, which are usually susceptible to self-condensation under conventional basic conditions. A hard Lewis basic phosphine oxide has emerged as an effective additive to constitute a highly active ternary soft Lewis acid/hard Brønsted base/hard Lewis base cooperative catalyst, enabling a direct enantio- and diastereoselective aldol reaction of thiopropionamides. Strict control of the amount of the hard Lewis base was essential to drive the catalytic cycle efficiently with a minimized retro-aldol pathway, affording syn-aldol products with high stereoselectivity. Divergent transformation of the thioamide functionality is an obvious merit of the present aldol methodology, allowing for a facile transformation of the aldol product into the corresponding aldehyde, ketone, amide, amine, and ketoester. An aldehyde derived from the direct aldol reaction was subjected to a second direct aldol reaction, which proceeded in a catalyst-controlled manner to provide 1,3-diols with high stereoselectivity.(Figure Presented).|
|27.||Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Enantioselective synthesis of a GPR40 agonist AMG 837 via catalytic asymmetric conjugate addition of terminal alkyne to α,β-unsaturated thioamide, Organic Letters, 10.1021/ol102998w, 13, 5, 952-955, 2011.03, [URL], A concise enantioselective synthetic route to a potent GPR40 agonist AMG 837 is described. The crucial catalytic asymmetric conjugate addition of terminal alkyne was promoted by a soft Lewis acid/hard Brønsted base cooperative catalyst, allowing efficient construction of the requisite stereogenic center. The thioamide functional group is key to both activation in asymmetric alkynylation and facile transformation into carboxylic acid.(Figure Presented).|
|28.||Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated thioamides, Journal of the American Chemical Society, 10.1021/ja105141x, 132, 30, 10275-10277, 2010.08, [URL], Direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated thioamides under proton transfer conditions is described. Soft Lewis acid/hard Brønsted base cooperative catalysis is crucial for simultaneous activation of terminal alkynes and thioamides, affording the β-alkynylthioamides in a highly enantioselective manner. Control experiments suggested that the intermediate copper thioamide enolate can work as Brønsted base to drive the catalytic cycle via proton transfer. The divergent transformation of the thioamide functionality highlights the synthetic utility of the alkynylation products..|
|29.||Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric addition of allyl cyanide to ketones via soft lewis acid/hard brønsted base/hard lewis base catalysis, Journal of the American Chemical Society, 10.1021/ja101687p, 132, 15, 5522-5531, 2010.04, [URL], We report that a hard Lewis base substantially affects the reaction efficiency of direct catalytic asymmetric γ-addition of allyl cyanide (1a) to ketones promoted by a soft Lewis acid/hard Brønsted base catalyst. Mechanistic studies have revealed that Cu/(R,R)-Ph-BPE and Li(OC 6H4-p-OMe) serve as a soft Lewis acid and a hard Brønsted base, respectively, allowing for deprotonative activation of 1a as the rate-determining step. A ternary catalytic system comprising a soft Lewis acid/hard Brønsted base and an additional hard Lewis base, in which the basicity of the hard Brønsted base Li(OC6H4-p-OMe) was enhanced by phosphine oxide (the hard Lewis base) through a hard-hard interaction, outperformed the previously developed binary soft Lewis acid/hard Brønsted base catalytic system, leading to higher yields and enantioselectivities while using one-tenth the catalyst loading and one-fifth the amount of 1a. This second-generation catalyst allows efficient access to highly enantioenriched tertiary alcohols under nearly ideal atom-economical conditions (0.5-1 mol % catalyst loading and a substrate molar ratio of 1:2)..|
|30.||Mitsutaka Iwata, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric aldol reaction of thioamides
A concise asymmetric synthesis of (R)-fluoxetine, Tetrahedron Asymmetry, 10.1016/j.tetasy.2010.04.034, 21, 13-14, 1688-1694, 2010, [URL], A direct catalytic asymmetric aldol reaction of aromatic aldehydes and thioamides is described. A soft Lewis acid/hard Brønsted base cooperative catalyst comprising (R,R)-Ph-BPE/[Cu(CH3CN)4]PF 6/Li(OC6H4-p-OMe) promoted the title reaction efficiently, triggered by in situ generation of the active thioamide enolate through a soft-soft interaction of Cu(I) and the thioamide. The aldol product was transformed into (R)-fluoxetine, an antidepressant agent..
|31.||Mitsutaka Iwata, Ryo Yazaki, Yuta Suzuki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric aldol reactions of thioamides
Toward a stereocontrolled synthesis of 1,3-polyols, Journal of the American Chemical Society, 10.1021/ja909758e, 131, 51, 18244-18245, 2009.12, [URL], (Chemical Equation Presented) A direct catalytic asymmetric aldol reaction of thioamides with a soft Lewis acid/hard Brønsted base cooperative catalytic system comprising (R,R)-Ph-BPE/[Cu(CH3CN) 4]PF6/LiOAr is described. Highly chemoselective deprotonative activation of thioamides allows for a direct aldol reaction of α-nonbranched aliphatic aldehydes, which are susceptible to self-condensation. Facile reduction of the thioamide functionality and a catalyst-controlled second aldol reaction provides 1,3-diols in a highly stereoselective manner..
|32.||Yuta Suzuki, Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric mannich-type reaction of thioamides, Angewandte Chemie - International Edition, 10.1002/anie.200901588, 48, 27, 5026-5029, 2009.06, [URL], Taking the reins: The title transformation of thioamides and N-diphenylphosphinoyl imines is described. By harnessing the power of cooperative catalysis between a soft Lewis acid and a hard Brønsted base, thioamide carbon pronucleophiles can furnish Mannich products (see scheme). Divergent transformation of the thioamide functionality highlights the utility of this methodology..|
|33.||Ryo Yazaki, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric addition of allyl cyanide to ketones, Journal of the American Chemical Society, 10.1021/ja900001u, 131, 9, 3195-3197, 2009.03, [URL], A direct catalytic asymmetric addition of allyl cyanide to ketones with a bimetallic catalytic system comprising (R,R)-Ph-BPE/[Cu(CH3CN) 4]ClO4/LiOAr is described. Exclusive γ-addition of allyl cyanide was observed, affording optically enriched tertiary alcohols bearing Z-configured α,ß-unsaturated nitriles. The reaction proceeded under proton-transfer conditions, utilizing soft Lewis acid/hard Brønsted base bifunctional catalysis. The applicability of the reaction to aromatic, heteroaromatic, and aliphatic ketones demonstrates its wide substrate generality..|
|34.||Ryo Yazaki, Tatsuya Nitabaru, Naoya Kumagai, Masakatsu Shibasaki, Direct catalytic asymmetric addition of allylic cyanides to ketoimines, Journal of the American Chemical Society, 10.1021/ja806572b, 130, 44, 14477-14479, 2008.11, [URL], Direct catalytic asymmetric addition of allylic cyanides to N-diphenylphosphinoyl ketoimines with a bimetallic catalytic system comprising Ph-BPE/[Cu(CH3CN)4]ClO4/LiOAr is described. Intermediary α-adducts readily isomerized to afford synthetically useful α,β-unsaturated nitriles bearing an optically active tetrasubstituted carbon. Applicability to aromatic, heteroaromatic, and aliphatic ketoimines exemplifies wide substrate generality. Transformation of the product into densely functionalized material showcases the utility of the present protocol..|
|35.||Shu Kobayashi, Ryo Yazaki, Kazutaka Seki, Yasuhiro Yamashita, The fluorenone imines of glycine esters and their phosphonic acid analogues, Angewandte Chemie - International Edition, 10.1002/anie.200801322, 47, 30, 5613-5615, 2008.07, [URL], (Chemical Equation Presented) Much more reactive than the corresponding benzophenone imines, which have often been used in the synthesis of α-amino acids, the title compounds undergo Mannich-type reactions with imines in the presence of a catalytic amount of a base to afford α,β-diamino acid and α,β-diaminophosphonic acid derivatives with high syn diastereoselectivity (see scheme). An asymmetric version of the reaction is also described. Boc = tert-butoxycarbonyl..|
|36.||Shu Kobayashi, Ryo Yazaki, Kazutaka Seki, Masaharu Ueno, An air-stable chiral Hf-based catalyst for asymmetric Mannich-type reactions, Tetrahedron, 10.1016/j.tet.2007.05.115, 63, 35, 8425-8429, 2007.08, [URL], A new class of isolable, air-stable, storable, and Hf-based catalyst has been developed. In the presence of 10 mol % of the powdered Hf catalyst, the asymmetric Mannich-type reactions of imines with silicon enolates derived from esters proceeded smoothly to afford the corresponding Mannich-type adducts in high yields with high enantioselectivities. Hafnium single crystals for X-ray analysis were obtained, and the crystals also showed high performance in the asymmetric Mannich-type reactions..|
|37.||Shu Kobayashi, Jun Kobayashi, Ryo Yazaki, Masaharu Ueno, Toward the total synthesis of onchidin, a cytotoxic cyclic depsipeptide from a mollusc, Chemistry - An Asian Journal, 10.1002/asia.200600232, 2, 1, 135-144, 2007, [URL], The total synthesis of onchidin (1), a cytotoxic, C2-symmetric cyclic decadepsipeptide from a marine mollusc, according to the published structure, is described. A novel β-amino acid, (2S,3S)-3-amino-2-methyl-7- octynoic acid (AMO), was efficiently prepared in high yield with high diastereo- and enantioselectivity based on a catalytic asymmetric three-component Mannich-type reaction with a chiral zirconium catalyst. The formation of sterically unfavorable N-methyl amide and hindered ester bonds were successfully demonstrated, and final macrocyclization was achieved at a secondary-amide site. Completion of the synthesis of 1 suggested that a revision of the structure of the natural product is required. Two diastereomers were also synthesized as candidates for the actual structure of onchidin. Furthermore, efficient solid-phase methods were employed for the combinatorial synthesis of other derivatives to clarify the real structure of onchidin. The solid-phase assembly of a pentadepsipeptide containing all the building blocks was established followed by dimeric cyclization in solution..|