Stereocontrolled synthesis of the diene and triene macrolactones of oximidines I and II: organometallic coupling versus standard macrolactonization.

[structure: see text]. Stereocontrolled construction of the 12-membered diene and triene lactones 1, 2, and 3, characteristic of the antitumor agent oximidines I and II, are reported and were based on an intramolecular Castro-Stephens coupling for the construction of a cyclic enyne or dienyne followed by stereoselective reduction of the cyclic alkyne for introduction of the cis-olefin of the targets. A comparison of the effectiveness of this protocol is made with standard macrolactonization.