Approach to the synthesis of side-chain eudesmanediols: synthesis of kudtriol from 1-(α)-santonin

Abstract

The synthesis of an eudesmanic alcohol, kudtriol (1), is described along with its 11-deoxy analogue (19) starting from 1 -(α)-santonin in ten steps. The known intermediate methyl (11S)-3-oxoeudesm-4-en-12-oate (5b) was taken through the new intermediates methyl (11S)-eudesm-4-en-12-oate (6), (11S)eudesm-4-en-12-al (17), 11-hydroxyeudesm-4-en-12-al (18), and eudesm-4-ene-11,12-diol (8). The construction of side-chain diol moiety in the last mentioned intermediate was achieved by the application of Vedejs' enolate hydroxylation on (17). The sensitised photo-oxygenation cum reduction sequence transformed the ene diol (8) into the title compound (1). A similar sequence on (11S)eudesm-4-en-12-ol (16) resulted in 11-deoxykudtriol (19).