Efficient and Selective Syntheses of (all-E)- and (6E,10Z)-2′-O-Methylmyxalamides D via Pd-Catalyzed Alkenylation−Carbonyl Olefination Synergy

Abstract

Highly efficient and selective syntheses of both (all- E) and (6 E,10 Z)-isomers of 2'- O-methylmyxalamide D ( 2 and 3), in which the crucial conjugated pentaene moieties were assembled in > or =98% stereoselectivity through the use of two Pd-catalyzed alkenylation reactions, the Horner-Wadsworth-Emmons (HWE) olefination, and either the Corey-Schlessinger-Mills modified (CSM-modified) Peterson olefination for 2 or the Still-Gennari olefination for 3, are reported. Either 2 or 3 was prepared in 16% yield in seven steps from propargyl alcohol.