Baker's yeast-mediated approach to (-)-cis- and (+)-trans-Aerangis lactones

The first enantioselective synthesis of natural (-)-cis-Aerangis lactone (- )-1a and its (+)-trans-diastereoisomer (+)-lb is described. The key steps i n the synthesis are: (i) the enantiospecific and 100% diastereoselective ba ker's yeast reduction of 1,4-keto acid 2, to afford enantiopure trans- cogn ac lactone (+)-10; (ii) the regioselective PPL-mediated hydrolysis of the p rimary acetate moiety of diacetate (+)-(3S,4R)-3, obtained from (+)-10. Cha in 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. A ll rights reserved.