Asymmetric synthesis of 1,2-dioxolane-3-acetic acids: Synthesis and configurational assignment of plakinic acid A

The first asymmetric synthesis of 1,2-dioxolane-3-acetic acids is reported. Key features include the stereoselective opening of enantiomerically enriched oxetanes by hydrogen peroxide, conversion of the resulting 4-hydroperoxy-2- alkanols to 3-alkoxy-1,2-dioxolanes, and Lewis acid mediated homologation of the latter with a thioester silyl ketene acetal. The approach is modeled on 3,5-dimethyl-5-hexadecyl-1,2-dioxolane-3-acetic acid (1a), an unnamed natural product, and an optimized strategy is applied to the synthesis of four stereoisomers of plakinic acid A (2), allowing a configurational assignment of this incompletely characterized natural product.