酵母还原5-羟基异噁唑烷类半缩醛的反应研究
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摘要
手性氨基醇是一类具有广泛应用前景的有机化合物,它们作为药物中间体、手性配体和手性合成砌块(building block)在药物合成、不对称合成等领域发挥着重要的作用。不对称还原α-取代β-氨基醛的动态动力学拆分是制备手性氨基醇的有效方法。
本文首先设计并合成了一系列烷基取代的5-羟基异噁唑类半缩醛,然后考察了α-位取代基对半缩醛的酵母还原反应的影响。α-位取代基从较小体积的甲基依次替换为乙基和苄基,研究这三种取代基的酵母还原反应的活性,发现α-位的取代基越大,酵母还原越慢。另外,尝试采用手性催化剂来催化苯甲酰羟胺与烯醛的加成反应,产物用NaBH4还原后测e.e.值,发现并没有明显的对应体过量。
接下来,将α-位无取代的半缩醛,分别利用D/L/DL-脯氨酰胺作为催化剂,用NCS对半缩醛进行氯代,得到不同构型过量的氯代半缩醛。先以外消旋的氯代醛为底物,考察了不同条件下的酵母还原反应,然后在最佳条件下对不同构型过量的醛进行酵母还原,测定产物的e.e.值。
在5-羟基异噁唑类半缩醛的面包酵母还原反应的研究中,发现α-位取代基与电负性均对5-羟基异噁唑类半缩醛的酵母还原反应有较大影响,α-甲基半缩醛可以被酵母完全还原,但产物e.e.值仅为13%,α-乙基半缩醛有63%的e.e.值,但是转化率只有60%左右。α-氯代半缩醛经酵母还原后不仅可以完全转化,且得到了最高76%的e.e.值。
Chiral amino alcohols are wildly used organic compounds. They play important roles in pharmacy and asymmetric synthesis as intermediates, building blocks and chiral ligands.Dynamic kenrtic resolution (DKR) via the reduction ofα-branched-β-amino- aldehydes presents an efficient way to chiral amino alcohols.
Firstly, a series of novel alkyl-substituted-5-Hydroxyl-isoxazolidine hemiacetals were synthesized, and then the effects ofα-substituents towards the baker’s yeast’s reduction were estimated. It was found that the bulkier the substituents were,the slower the bioreduction rate was. In addition, chiral catalysts were employed to catalyze the addition of benzoylhydroxylamines to aldehydes, but no enantiomer excess was detected.
In the following study,α-chloral hemiacetals were synthesized via chlorination ofα-unbrached hemiacetals catalyzed by D/L/racemic prolineamide. Then, the reduction of aldehydes with different configuration was investigated.
During the study of baker’s yeast mediated bioreduction of isoxazolidine-derived hemiacetals,It was indicated that both the bulky and the electronegativity ofα-substituent were found to show great effet on the reaction. In the case ofα-methyl hemiacetal, it can be totally converted but the e.e. value of the product was only 13%, while theα-ethyl hemiacetal was limited to 60% conversion, albeit with 63% e.e. Theα-chloral hemiactal give the best results totally conversion and 76%e.e.
本文首先设计并合成了一系列烷基取代的5-羟基异噁唑类半缩醛,然后考察了α-位取代基对半缩醛的酵母还原反应的影响。α-位取代基从较小体积的甲基依次替换为乙基和苄基,研究这三种取代基的酵母还原反应的活性,发现α-位的取代基越大,酵母还原越慢。另外,尝试采用手性催化剂来催化苯甲酰羟胺与烯醛的加成反应,产物用NaBH4还原后测e.e.值,发现并没有明显的对应体过量。
接下来,将α-位无取代的半缩醛,分别利用D/L/DL-脯氨酰胺作为催化剂,用NCS对半缩醛进行氯代,得到不同构型过量的氯代半缩醛。先以外消旋的氯代醛为底物,考察了不同条件下的酵母还原反应,然后在最佳条件下对不同构型过量的醛进行酵母还原,测定产物的e.e.值。
在5-羟基异噁唑类半缩醛的面包酵母还原反应的研究中,发现α-位取代基与电负性均对5-羟基异噁唑类半缩醛的酵母还原反应有较大影响,α-甲基半缩醛可以被酵母完全还原,但产物e.e.值仅为13%,α-乙基半缩醛有63%的e.e.值,但是转化率只有60%左右。α-氯代半缩醛经酵母还原后不仅可以完全转化,且得到了最高76%的e.e.值。
Chiral amino alcohols are wildly used organic compounds. They play important roles in pharmacy and asymmetric synthesis as intermediates, building blocks and chiral ligands.Dynamic kenrtic resolution (DKR) via the reduction ofα-branched-β-amino- aldehydes presents an efficient way to chiral amino alcohols.
Firstly, a series of novel alkyl-substituted-5-Hydroxyl-isoxazolidine hemiacetals were synthesized, and then the effects ofα-substituents towards the baker’s yeast’s reduction were estimated. It was found that the bulkier the substituents were,the slower the bioreduction rate was. In addition, chiral catalysts were employed to catalyze the addition of benzoylhydroxylamines to aldehydes, but no enantiomer excess was detected.
In the following study,α-chloral hemiacetals were synthesized via chlorination ofα-unbrached hemiacetals catalyzed by D/L/racemic prolineamide. Then, the reduction of aldehydes with different configuration was investigated.
During the study of baker’s yeast mediated bioreduction of isoxazolidine-derived hemiacetals,It was indicated that both the bulky and the electronegativity ofα-substituent were found to show great effet on the reaction. In the case ofα-methyl hemiacetal, it can be totally converted but the e.e. value of the product was only 13%, while theα-ethyl hemiacetal was limited to 60% conversion, albeit with 63% e.e. Theα-chloral hemiactal give the best results totally conversion and 76%e.e.
引文
[1] Ager D. J., Prakash I..Schaad D. R.et.al. 1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis.Chem. Rev. ,1996, 96:835-876.
[2] Lee R. E., MikuSova K., Brennan P. J., and Besra G. S. Synthesis of the Arabinose Donor .beta.-D-Arabinofuranosyl-1-monophosphoryldecaprenol, Development of a Basic Arabinosyl-Transferase Assay, and Identification of Ethambutol as an Arabinosyl Transferase Inhibitor .J. Am. Chem. Soc.,1995,117:11829-11832.
[3] Howard. T.β-Adrenergic Blocking Agents. 21. threo-l-(Aryloxy)-3-(alkylamino) butan-2-ols ,J. Med. Chem.,1981, 24:1364-1368.
[4]杨丰科,徐军伟,刘均洪.有机化学, 2003, 23:1205.
[5] Kakeya H., Morishita M. and Osada H.Cytoxazone: A Novel Cytokine Modulator Containing a 2-Oxazolidinone Ring Produced by Streptomyces sp.J. Org. Chem.,1999, 64:1052-1053.
[6] Huerta F. F.,Minidis A. B. E.,Backvall J.-E. Racemisation in asymmetric synthesis. Dynamic kinetic resolution and related processes in enzyme and metal catalysis. Chem Soc Rev,2001,,30:6:32l-331.
[7] Ebbers E. J.,AriaansG. J. A.,Houbiers J. P. M.,et al.Controlled racemization of optically active organic compounds: Prospects for asymmetric transformation. Tetrahedron., 1997,53:94l7-9476.
[8] Berkessel A, M.L.S.I., T. N., M.Lipase/Aluminum-Catalyzed Dynamic Kinetic Resolution of Secondary Alcohols. Angewandte Chemie International Edition ,2006,45: 6567-6570.
[9] Veum L., Hanefeld U., Enantioselective formation of mandelonitrile acetate: investigation of a dynamic kinetic resolution II. Tetrahedron: Asymmetry,2004, 15: 3707-3709.
[10] Akai S., K. T., Kanao Y.,et al.A Dynamic Kinetic Resolution of Allyl Alcohols by the Combined Use of Lipases and [VO(OSiPh3)3]. Angewandte ChemieInternational Edition,2006,45: 2592-2595.
[11] (a) Caddick S., Jenkins K., Treweeke N., Candeias S. X.,Afonso C. A. M. Rationalising diastereoselection in the dynamic kinetic resolution ofα-haloacyl imidazolidinones.Tetrahedron Lett.,1998, 39:2203-2206.(b) Caddick S., Afonso C. A. M.,Candeias S. X.,Hitchcock P. B.,Jenkins K.,Murtagh L.,Pardoe D., GilSantos A.,Treweeke N.,Weaving R. Synthesis ofα-amino esters by dynamic kinetic resolution ofα-haloacyl imidazolidinones.Tetrahedron, 2001,57: 6589-6605.
[12] Wolfe B., Livinghouse T. A Direct Synthesis of P-Chiral Phosphine-Boranes via Dynamic Resolution of Lithiated Racemic tert-Butylphenylphosphine-Borane with (-)-Sparteine .J. Am. Chem. Soc., 1998, 120:5116-5117.
[13] Amat M., Canto M., Llor N., et al.Dynamic Kinetic Resolution of Racemicγ-Aryl-δ-oxoesters. Enantioselective Synthesis of 3-Arylpiperidines.J. Org. Chem., 2002, 67: 5343-5351.
[14] Ros A., Magriz A., et al. Stereoselective synthesis of synβ-hydroxy cycloalkane carboxylates: transfer hydrogenation of cyclicβ-keto esters via dynamic kinetic resolution. Tetrahedron,2007, 63: 7532-7537.
[15] Trost B. M.,Bunt R. C.,Lemoine R. C., et al.Dynamic Kinetic Asymmetric Transformation of Diene Monoepoxides: A Practical Asymmetric Synthesis of Vinylglycinol, Vigabatrin, and Ethambutol.J. Am. Chem. Soc., 2000, 122:5968- 5976.
[16] List B. Catalytic asymmetric reductive amination of aldehydes via dynamic kinetic resolution. J. Am. Chem. Soc.,2006, 128: 13074-13075.
[17] Ward D. E., Jheengut V. Enantioselective Direct Intermolecular Aldol Reactions with Enantiotopic Group Selectivity and Dynamic Kinetic Resolution.Org. Lett., 2005,7: 1181-1184.
[18]杜灿平.生物合成与生物转化领域的研究.化学进展,1999,11:218-219.
[19] Paal T. A., Forro E.Lipase-catalyzed kinetic and dynamic kinetic resolution of-1,2,3,4-tetrahydroisoquinoline-1-carboxylicacid.Tetrahedron:Asymmetry,2007,18: 1428-1433.
[20] Gutierrez M.C., R. F. V. A. Microbiological Transformations 60. EnantioconvergentBaeyer-Villiger Oxidation via a Combined Whole Cells and Ionic Exchange Resin-Catalysed Dynamic Kinetic Resolution Process. Advanced Synthesis & Catalysis,2005, 347: 1051-1059.
[21]张数正.酶制剂工程.北京:科学出版社,1984,44.
[22]张玉彬.生物催化的手性合成.化学工业出版社.第一版.北京. 2002. 1-9.
[23] Rene C., Brigitte I. Baker's yeast mediated transformations in organic chemistry. Chemical Reviews, 1991, 91:49-97.
[24] T.H, MaughⅡ. Catalysis that break natures monopoly.Science, 1983,221:351-354.
[25] Kawai Y.,Saitou K.,Hida K.,et al. A Symmertic Reduction of a,b-Unsaturated Ketones with Bakers’Yeast.Tetrahedron:Aysmmetry,1995,6:2143-2144.
[26] Ohta H.,Kobayashi N.,Ozaki K.Asymmetric reduction of nitro olefins by fermenting bakers’yeast.J.Org.Chem,1989,54:1802-1804.
[27] Belan A., Bole J., Fauve A. Use of biological systems for the preparation of chiral molecules.3.Application in pheromone synthesis: preparation of sulcatol enantiomers. J. Org. Chem., 1987, 52: 256-260.
[28]樊晓焕,张明杰,陈小林.面包酵母在不对称合成中的应用.化学通报, 2003, 9 : 610-614.
[29] Fronza G., Fuganti C., Pinciroli M., et al.Stereochemical aspects of the bioreduction of the conjugated double bond of perillaldehyde. Tetrahedron: Asymmetry, 2004,15: 3073-3077.
[30] Huang Y.k., Zhang F.L. and Gong Y.F. A convenient approach to (S)-2-ethylhexan- 1-ol mediated by baker’s yeast. Tetrahedron Letters, 2005, 46:7217-7219.
[31] Gramatica P., Manitto P., Monti D., Speranza G. Regio- and stereoselective hydrogenation of methyl substituted pentadien-1-ols by baker's yeast. Tetrahedron, 1988, 44 : 1299-1304.
[32] Kantam M. L., Chaudhuri M. K. Cu(acac)2 Immobilized in Ionic Liquids: A Recoverable and Reusable Catalytic System for Azα-Michael Reactions. Adv. Synth. Catal.,2005, 347:763-766.
[33] Smitha G., Reddy Ch. S. ZrCl4-catalyzed azα-Michael addition of carbamates to enones: Synthesis of Cbz-protected b-amino ketones. Catalysis Communications,2002,8 :434.
[34] Mihir K., Chaudhuri, Hussain S., Kantam M. L. Boric acid: a novel and safe catalyst for azα-Michael reactions in water. Tetrahedron Letters,2005, 48 :8329.
[35] Lelais G., MacMillan D.W. C.Modern Strategies in Organic Catalysis: The Advent and Development of Iminium Activation. Aldrichimica Acta.,2006,39:79.
[36] Dalko P. I., Moisan L. In the Golden Age of Organocatalysis. Angew. Chem. Int. Ed., 2004, 43: 5138-5175.
[37] Ibrahem I., Rios R., Córdova A, et al. Organocatalytic asymmetric 5-hydroxyisoxazolidine synthesis: A highly enantioselective route toβ-amino acids. Chem. Commun., 2007,8: 849-851.
[38] Vesely J., Ibrahem I., Zhao G..L., etal.Organocatalytic Enantioselective Aziridination of a,b-Unsaturated Aldehydes. Angew. Chem. Int. Ed., 2007, 46:778.
[39] Giacomini D., Galletti P. Highly efficient asymmetric reduction of arylpropionic aldehydes by Horse Liver Alcohol Dehydrogenase through dynamic kinetic resolution. Chemical Communications,2007,39: 4038-4040.
[40] Jian H. X., Zhang T. Z., Wei L.K., et al.Ru-Catalyzed Asymmetric Hydrogenation of Racemic Aldehydes via Dynamic Kinetic Resolution: Efficient Synthesis of Optically Active Primary Alcohols.J. Am. Chem. Soc.,2007,129: 1868-1869.
[41] Strbing D., Bckvall J.E. Dynamic Kinetic Resolution of Primary Alcohols with an Unfunctionalized Stereogenic Center in theβ-Position.Adv.Synth.Catal., 2007, 349:1577-1581.
[42] Erkkila A. , Pihko P. M. Mild Organocatalytic r-Methylenation of Aldehydes. J. Org. Chem., 2006, 71: 2538.
[43] Li D.J.,Huang M.Q., Ge Z.H.Synthesis and structure characterization of 3-N- acetyl-2-aryl-5-(4-nitrophenyl)-1,3,4-oxadiazolines.Jingxi Huagong, 2005, 22:283- 286.
[44] Wei C.Y., Yang P., Wang L.H., et al.Synthesis characterization and in vitro antitumour activity of the di-n-butyltin(IV) complexes of some arylhydroxamates. Chinese Journal of Chemistry, 2002, 20:453-461.
[45] Angelo L., Giovanni S., Giovanni R.,et al. Direct conversion of hydroxamic acidsinto nitriles.Synthesis,1987, (2):168.
[46] Halland N., Braunton A., Bachmann S., et al.Direct Organocatalytic Asymmetricα-Chlorination of Aldehydes J. Am Chem. Soc.,2004, 126:4790-4791.
[47] Ibrahem S, Vesely J., Gui L. Z., et al.A.Organocatalytic asymmetric 5-hydroxyisoxazolidine synthesis: A highly enantioselective route toβ-amino acids. Chem. Commun., 2007,8:849-851.
[48] Halland N., Braunton A., Bachmann S., et al.Direct Organocatalytic Asymmetricα-Chlorination of Aldehydes. J. Am.Chem. Soc., 2004, 126: 4790-4791.
[2] Lee R. E., MikuSova K., Brennan P. J., and Besra G. S. Synthesis of the Arabinose Donor .beta.-D-Arabinofuranosyl-1-monophosphoryldecaprenol, Development of a Basic Arabinosyl-Transferase Assay, and Identification of Ethambutol as an Arabinosyl Transferase Inhibitor .J. Am. Chem. Soc.,1995,117:11829-11832.
[3] Howard. T.β-Adrenergic Blocking Agents. 21. threo-l-(Aryloxy)-3-(alkylamino) butan-2-ols ,J. Med. Chem.,1981, 24:1364-1368.
[4]杨丰科,徐军伟,刘均洪.有机化学, 2003, 23:1205.
[5] Kakeya H., Morishita M. and Osada H.Cytoxazone: A Novel Cytokine Modulator Containing a 2-Oxazolidinone Ring Produced by Streptomyces sp.J. Org. Chem.,1999, 64:1052-1053.
[6] Huerta F. F.,Minidis A. B. E.,Backvall J.-E. Racemisation in asymmetric synthesis. Dynamic kinetic resolution and related processes in enzyme and metal catalysis. Chem Soc Rev,2001,,30:6:32l-331.
[7] Ebbers E. J.,AriaansG. J. A.,Houbiers J. P. M.,et al.Controlled racemization of optically active organic compounds: Prospects for asymmetric transformation. Tetrahedron., 1997,53:94l7-9476.
[8] Berkessel A, M.L.S.I., T. N., M.Lipase/Aluminum-Catalyzed Dynamic Kinetic Resolution of Secondary Alcohols. Angewandte Chemie International Edition ,2006,45: 6567-6570.
[9] Veum L., Hanefeld U., Enantioselective formation of mandelonitrile acetate: investigation of a dynamic kinetic resolution II. Tetrahedron: Asymmetry,2004, 15: 3707-3709.
[10] Akai S., K. T., Kanao Y.,et al.A Dynamic Kinetic Resolution of Allyl Alcohols by the Combined Use of Lipases and [VO(OSiPh3)3]. Angewandte ChemieInternational Edition,2006,45: 2592-2595.
[11] (a) Caddick S., Jenkins K., Treweeke N., Candeias S. X.,Afonso C. A. M. Rationalising diastereoselection in the dynamic kinetic resolution ofα-haloacyl imidazolidinones.Tetrahedron Lett.,1998, 39:2203-2206.(b) Caddick S., Afonso C. A. M.,Candeias S. X.,Hitchcock P. B.,Jenkins K.,Murtagh L.,Pardoe D., GilSantos A.,Treweeke N.,Weaving R. Synthesis ofα-amino esters by dynamic kinetic resolution ofα-haloacyl imidazolidinones.Tetrahedron, 2001,57: 6589-6605.
[12] Wolfe B., Livinghouse T. A Direct Synthesis of P-Chiral Phosphine-Boranes via Dynamic Resolution of Lithiated Racemic tert-Butylphenylphosphine-Borane with (-)-Sparteine .J. Am. Chem. Soc., 1998, 120:5116-5117.
[13] Amat M., Canto M., Llor N., et al.Dynamic Kinetic Resolution of Racemicγ-Aryl-δ-oxoesters. Enantioselective Synthesis of 3-Arylpiperidines.J. Org. Chem., 2002, 67: 5343-5351.
[14] Ros A., Magriz A., et al. Stereoselective synthesis of synβ-hydroxy cycloalkane carboxylates: transfer hydrogenation of cyclicβ-keto esters via dynamic kinetic resolution. Tetrahedron,2007, 63: 7532-7537.
[15] Trost B. M.,Bunt R. C.,Lemoine R. C., et al.Dynamic Kinetic Asymmetric Transformation of Diene Monoepoxides: A Practical Asymmetric Synthesis of Vinylglycinol, Vigabatrin, and Ethambutol.J. Am. Chem. Soc., 2000, 122:5968- 5976.
[16] List B. Catalytic asymmetric reductive amination of aldehydes via dynamic kinetic resolution. J. Am. Chem. Soc.,2006, 128: 13074-13075.
[17] Ward D. E., Jheengut V. Enantioselective Direct Intermolecular Aldol Reactions with Enantiotopic Group Selectivity and Dynamic Kinetic Resolution.Org. Lett., 2005,7: 1181-1184.
[18]杜灿平.生物合成与生物转化领域的研究.化学进展,1999,11:218-219.
[19] Paal T. A., Forro E.Lipase-catalyzed kinetic and dynamic kinetic resolution of-1,2,3,4-tetrahydroisoquinoline-1-carboxylicacid.Tetrahedron:Asymmetry,2007,18: 1428-1433.
[20] Gutierrez M.C., R. F. V. A. Microbiological Transformations 60. EnantioconvergentBaeyer-Villiger Oxidation via a Combined Whole Cells and Ionic Exchange Resin-Catalysed Dynamic Kinetic Resolution Process. Advanced Synthesis & Catalysis,2005, 347: 1051-1059.
[21]张数正.酶制剂工程.北京:科学出版社,1984,44.
[22]张玉彬.生物催化的手性合成.化学工业出版社.第一版.北京. 2002. 1-9.
[23] Rene C., Brigitte I. Baker's yeast mediated transformations in organic chemistry. Chemical Reviews, 1991, 91:49-97.
[24] T.H, MaughⅡ. Catalysis that break natures monopoly.Science, 1983,221:351-354.
[25] Kawai Y.,Saitou K.,Hida K.,et al. A Symmertic Reduction of a,b-Unsaturated Ketones with Bakers’Yeast.Tetrahedron:Aysmmetry,1995,6:2143-2144.
[26] Ohta H.,Kobayashi N.,Ozaki K.Asymmetric reduction of nitro olefins by fermenting bakers’yeast.J.Org.Chem,1989,54:1802-1804.
[27] Belan A., Bole J., Fauve A. Use of biological systems for the preparation of chiral molecules.3.Application in pheromone synthesis: preparation of sulcatol enantiomers. J. Org. Chem., 1987, 52: 256-260.
[28]樊晓焕,张明杰,陈小林.面包酵母在不对称合成中的应用.化学通报, 2003, 9 : 610-614.
[29] Fronza G., Fuganti C., Pinciroli M., et al.Stereochemical aspects of the bioreduction of the conjugated double bond of perillaldehyde. Tetrahedron: Asymmetry, 2004,15: 3073-3077.
[30] Huang Y.k., Zhang F.L. and Gong Y.F. A convenient approach to (S)-2-ethylhexan- 1-ol mediated by baker’s yeast. Tetrahedron Letters, 2005, 46:7217-7219.
[31] Gramatica P., Manitto P., Monti D., Speranza G. Regio- and stereoselective hydrogenation of methyl substituted pentadien-1-ols by baker's yeast. Tetrahedron, 1988, 44 : 1299-1304.
[32] Kantam M. L., Chaudhuri M. K. Cu(acac)2 Immobilized in Ionic Liquids: A Recoverable and Reusable Catalytic System for Azα-Michael Reactions. Adv. Synth. Catal.,2005, 347:763-766.
[33] Smitha G., Reddy Ch. S. ZrCl4-catalyzed azα-Michael addition of carbamates to enones: Synthesis of Cbz-protected b-amino ketones. Catalysis Communications,2002,8 :434.
[34] Mihir K., Chaudhuri, Hussain S., Kantam M. L. Boric acid: a novel and safe catalyst for azα-Michael reactions in water. Tetrahedron Letters,2005, 48 :8329.
[35] Lelais G., MacMillan D.W. C.Modern Strategies in Organic Catalysis: The Advent and Development of Iminium Activation. Aldrichimica Acta.,2006,39:79.
[36] Dalko P. I., Moisan L. In the Golden Age of Organocatalysis. Angew. Chem. Int. Ed., 2004, 43: 5138-5175.
[37] Ibrahem I., Rios R., Córdova A, et al. Organocatalytic asymmetric 5-hydroxyisoxazolidine synthesis: A highly enantioselective route toβ-amino acids. Chem. Commun., 2007,8: 849-851.
[38] Vesely J., Ibrahem I., Zhao G..L., etal.Organocatalytic Enantioselective Aziridination of a,b-Unsaturated Aldehydes. Angew. Chem. Int. Ed., 2007, 46:778.
[39] Giacomini D., Galletti P. Highly efficient asymmetric reduction of arylpropionic aldehydes by Horse Liver Alcohol Dehydrogenase through dynamic kinetic resolution. Chemical Communications,2007,39: 4038-4040.
[40] Jian H. X., Zhang T. Z., Wei L.K., et al.Ru-Catalyzed Asymmetric Hydrogenation of Racemic Aldehydes via Dynamic Kinetic Resolution: Efficient Synthesis of Optically Active Primary Alcohols.J. Am. Chem. Soc.,2007,129: 1868-1869.
[41] Strbing D., Bckvall J.E. Dynamic Kinetic Resolution of Primary Alcohols with an Unfunctionalized Stereogenic Center in theβ-Position.Adv.Synth.Catal., 2007, 349:1577-1581.
[42] Erkkila A. , Pihko P. M. Mild Organocatalytic r-Methylenation of Aldehydes. J. Org. Chem., 2006, 71: 2538.
[43] Li D.J.,Huang M.Q., Ge Z.H.Synthesis and structure characterization of 3-N- acetyl-2-aryl-5-(4-nitrophenyl)-1,3,4-oxadiazolines.Jingxi Huagong, 2005, 22:283- 286.
[44] Wei C.Y., Yang P., Wang L.H., et al.Synthesis characterization and in vitro antitumour activity of the di-n-butyltin(IV) complexes of some arylhydroxamates. Chinese Journal of Chemistry, 2002, 20:453-461.
[45] Angelo L., Giovanni S., Giovanni R.,et al. Direct conversion of hydroxamic acidsinto nitriles.Synthesis,1987, (2):168.
[46] Halland N., Braunton A., Bachmann S., et al.Direct Organocatalytic Asymmetricα-Chlorination of Aldehydes J. Am Chem. Soc.,2004, 126:4790-4791.
[47] Ibrahem S, Vesely J., Gui L. Z., et al.A.Organocatalytic asymmetric 5-hydroxyisoxazolidine synthesis: A highly enantioselective route toβ-amino acids. Chem. Commun., 2007,8:849-851.
[48] Halland N., Braunton A., Bachmann S., et al.Direct Organocatalytic Asymmetricα-Chlorination of Aldehydes. J. Am.Chem. Soc., 2004, 126: 4790-4791.