Microbial Stereodifferentiating Reduction of (+/-)4-Methyl- and (+/-)-6-Methyl-1-oxometacyclophanes and Revision of the Absolute Configuration of 4-Substituted Metacyclophanes

Article abstract of DOI:10.1021/jo01296a018

Partial oxidative hydrolysis of 4-bromo-1,1,10,10-bis(trimethylenedithio)<2.2>metacyclophane (7) yielded the bromo ketones 8 and 9 which were respectively converted into (+/-)-4-methyl- (3) and (+/-)-6-methyl-1-oxo<2.2>metacyclophanes (4).The unambiguous synthesis of (+/-)-3 from 2,5-dimethylbenzoic acid (18) assigned their structures.Incubation of (+/-)-3 with Rhodotorula rubra gave a mixture of (-)-ketone 3, (-) axial alcohol 38, and (-) equatorial alcohol 39.The observed (-) Cotton effect indicated the pS configuration of (-)-3, and transformation of (-)-3 into (+)-4-methyl<2.2>metacyclophane (5) permitted the assignment of the pR configuration to (+)-5, opposite to Schloegl's proposal.This conclusion was further supported by the parallel sequence of the steps starting from (+/-)-6-methyl ketone.