Synthesis of the C1-C12 fragment of iriomoteolide 1a by sequential catalytic asymmetric vinylogous aldol reactions.

An efficient synthesis of the C1-C12 fragment of iriomoteolide 1a has been accomplished via sequential application of two catalytic, asymmetric, vinylogous aldol reactions: a catalytic vinylogous aldol reaction was used to enantioselectively introduce the C5-C8 segment, and a second catalytic vinylogous aldol reaction was used to install the remaining two stereocenters and a stereodefined alkene in the form of an alpha,beta-unsaturated delta-lactone in one step.