NON-HEAD-TO-TAIL MONOTERPENES - SYNTHESIS OF (S)-LYRATOL AND (S)-LYRATYL ACETATE FROM (1R,3R)-CHRYSANTHEMIC ACID

(+)-(S)-Lyratol (1-OH) and (+)-(S)-lyratyl acetate (1-OAc) were synthesized from (1R,3R)-chrysanthemic acid ((LR, 3R)-2-OH). The key steps in the sequence were the stereospecific oxidation of the (E)-methyl group in the isobutenyl moiety of chrysanthemyl acetate ((1R,3R)-3-OAc) with selenium dioxide and the regiospecific cleavage of the C(1)-C(2) cyclopropane bond in aldehyde methanesulfonate (1R,3R)-4-OMs to give the santolinyl skeleton found in lyratol. Since the synthesis began with (1R,3R)-chrysanthemic acid ((1R,3R)-2-OH) and did not alter the configuration at C(3), (+)-lyratol and (+)-lyratyl acetate are the (S) enantiomers. The absolute configurations of synthetic lyratol and lyratyl acetate are the same as those of their naturally occurring counterparts isolated from Cyanthocline lyrata. © 1979, American Chemical Society. All rights reserved.