T. Chakraborty, Sanjib Das
Oct 3, 2000
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ChemInform
Abstract
Stereoselective synthesis of the 5,7-acetonide of (2E,SS,6R,7R,8S)-S,7,8-trihydroxy-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 cryptophycins is achieved where diastereoselective opening of an intermediate trisubstituted epoxy alcohol 4 based on a radical-mediated method de veloped 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 which can find useful applications in the structure-activity relationship (SAR) studies of these potent antitumor agents. The depsipeptide cryptophycins (Scheme l) found in the terrestrial blue-green algae (cyanobacterium) Nostoc sp.