UNEXPECTED REARRANGEMENT IN THE PEROXYTRIFLUOROACETIC ACID-MEDIATED BAEYER-VILLIGER OXIDATION OF TRANS-3-BETA-HYDROXY-4,4,10-BETA-TRIMETHYL-9-DECALONE FORMING A 7-OXABICYCLO[2.2.1]HEPTANE - STRUCTURE PROOF AND TOTAL SYNTHESIS OF (+/-)-FARNESIFEROL-C
A rearrangement in the Baeyer-Villiger oxidation of trans- 3 beta-hydroxy-4,4,10 beta-trimethyl-9-decalone (2a) and of OCH(2)OMe (2b) and OTHP (2c) derivatives using peroxytrifluoroacetic acid is reported. The reaction involves trifluoroacetic acid catalyzed rearrangement-of the initially formed hydroxy lactone 5a giving the 7-oxabicyclo[2.2.1]heptane carboxylic acid 6. This unexpected rearrangement is a useful preparation of the 7-oxabicyclo[2.2.1]heptane ring system and constitutes a stereoselective synthesis of the left-hand portion of the sesquiterpene-coumarin ether (+/-)-farnesiferol-C (10). The product 6 serves as an advanced, key intermediate from which a total synthesis and structure proof of this natural product is presented.