The synthesis of opticallyactive 4-methyl-5-n-butyl- and 5-n-pentylpyrrolidin-2-ones, aza analogues of the corresponding Quercus lactones, has been achieved by a chemoenzymatic procedure, involving in the enantiodifferentiating step the enzymatic kinetic resolution of the corresponding γ-ketoester precursors, followed by reductive amination and subsequent cyclization of the enantiomerically pure hydrolysis
Baker's yeast-mediated approach to (−)-cis- and (+)-trans-Aerangis lactones
作者:Elisabetta Brenna、Claudia Dei Negri、Claudio Fuganti、Stefano Serra
DOI:10.1016/s0957-4166(01)00314-7
日期:2001.7
The first enantioselective synthesis of natural (-)-cis-Aerangis lactone (-)-1a and its (+)-trans-diastereoisomer (+)-lb is described. The key steps in the synthesis are: (i) the enantiospecific and 100% diastereoselective baker's yeast reduction of 1,4-keto acid 2, to afford enantiopure trans- cognac lactone (+)-10; (ii) the regioselective PPL-mediated hydrolysis of the primary acetate moiety of diacetate (+)-(3S,4R)-3, obtained from (+)-10. Chain elongation by one carbon atom via cyanide substitution, and inversion of the configuration of C(5) in nitrile derivative (+)-21a are also required to complete the synthetic route to (-)-1a. (C) 2001 Elsevier Science Ltd. All rights reserved.