Diastereoselective opening of trisubstituted epoxy alcohols: Application in the studies directed toward the synthesis of octenoic acid moiety of cryptophycins

Stereoselective synthesis of the 5,7-acetonide of (2E,5S,6R,7R,8S)-5,7,8-tr ihydroxy-6-methyl-8-phenyl-2-octenoic acid ethyl ester (3), an isomer of 2, precursor of the epoxy octenoic acid moiety 1 present in depsipeptide cryp tophycins is achieved where diastereoselective opening of an intermediate t risubstituted epoxy alcohol 4 based on a radical-mediated method developed by us earlier furnishes the crucial '2-methyl-1,3-diol' moiety of the C-5-C -7 Segment of the molecule. The protocol also allows the synthesis of some of the other 16 diasteromers of this hydroxy acid having 4 chiral centres w hich can find useful applications in the structure-activity relationship (S AR) studies of these potent antitumor agents.