Highly Diastereoselective Synthesis of Pederic Acid Derivatives

A highly diastereoselective synthesis of methyl pederate (2) is described. A critical feature of the successful route is the introduction of the key C(7)-stereocenter at the stage of 4 via an enantioselective, syn-selective aldol reaction of aldehyde 5 and the chiral acyl oxazolidinone 6. Aldehyde 5, in turn, was prepared from the readily available aldol derivative 7 via a chelate-controlled reaction with allyltrimethylsilane. Intermediate 4 was elaborated to 2 via the intermediacy of 7-O-(3,4-dimethoxybenzyl)pederic acid (3), an intermediate in Kishi's syntheses of mycalamides A and B and onnamide A, by way of methyl pyranoside 10 and the fully protected pederic acid derivative 11.