Concise syntheses of (+)-macrosphelides A and B

(Chemical Equation Presented) Unified and highly convergent total syntheses of (+)-macrosphelides A and B are described. Key features of the syntheses include (1) concise synthesis of the optically active δ-hydroxy-γ- keto α,β-unsaturated acid fragment via the direct addition of a trans-vinylogous ester anion equivalent to the readily available Weinreb amide and (2) facile construction of the 16-membered macrolide core of the macrosphelide series via an intramolecular nitrile-oxide cycloaddition (INOC).