Synthesis of Erythronolide

Significance

Carreira and co-workers twice deployed Kanemasa’s Mg(II)-mediated 1,3-dipolar cycloaddition of nitrile oxides to simple allylic alcohols to construct two stereogenic centers simultaneously. The presence of the Mg(II) ions dramatically accelerates the rate of cycloaddition and improves the regio- and stereoselectivity (S. Kanemasa et al. J. Am. Chem. Soc. 1994, 116, 2324-2339). The method offers a useful alternative to the ubiquitous aldol-based methods. This is the shortest synthesis of Erythronolide A reported to date (21 linear steps, 4% overall).