A Total Synthesis of the Styryllactone (+)-Goniodiol from Naphthalene

Abstract

The cytotoxic natural product (+)-goniodiol (1) has been prepared in twelve steps from the enantiomerically pure cis-dihydrocatechol (2), which is readily obtained by microbial oxidation of naphthalene. Elaboration of compound (2) involves an initial oxidative cleavage to dialdehyde (7) followed by reduction to give diol (12). Conversion of compound (12) into acetal (17) required, inter alia, selective oxidation of the benzylic alcohol moiety followed by a metal-catalyzed decarbonylation of the resulting aldehyde. Allylation of compound (17) with allyltributylstannane in the presence of lithium perchlorate gave a ca. 2.7:1 mixture of alcohols (18) and (19), each of which was converted into the corresponding acrylate under standard conditions. Subjection of these ester derivatives to a ring-closing metathesis (RCM) reaction with Grubbs' first-generation catalysts gave the anticipated lactones (22) and (23). Acid-catalyzed removal of the acetonide protecting group within compound (22) then afforded (+)-goniodiol (1), while analogous deprotection of congener (23) afforded 6-epi-(+)-goniodiol (24).