Synthetic studies on electron transport inhibitors. Part 2. Approaches to the synthesis of myxalamide D

Abstract

In a synthetic approach to ethyl myxalate-D 5(X = OEt) the butendial monoacetals 12 and 15 were transformed by a Wadsworth–Emmons reaction and controlled hydrolysis into the (E,E)-aldehydoester (17); a Z-selective reaction with Bestmann's ylide 18 afforded ethyl (2E,4E,6Z)-8,8-diethoxy-2-methylocta-2,4,6-trienoate 21 and hence the corresponding aldehyde 22. Reaction of aldehyde 22 with lithiated (+)-(4R,5R,2E,6E)-suIphone 24 afforded the coupled benzoyloxy sulphone 25. Reductive elimination from 25 with sodium amalgam–methanol gave only the vinyl sulphone 27; the use of sodium naphthalenide provided the required pentaene ester 30 but with loss of stereochemical integrity.