Organocatalytic Enantioselective Approach to the Synthesis of Verbalactone and (R)-Massoialactone

Abstract

The organocatalytic enantioselective synthesis of verbalactone and (R)-massoialactone is described. The requisite stereogenic centers of the target molecules were constructed using l-proline-catalyzed α-aminoxylation and Horner-Wadsworth-Emmons­ (HWE) olefination. Yamaguchi macrolactonization and ring-closing metathesis were employed as key steps in the syntheses.

Key words

l-proline - α-aminoxylation - Horner-Wadsworth-Emmons­ olefination - Yamaguchi macrolactonization - ring-closing metathesis - verbalactone - massoialactone

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12

The enantiomeric excess(ee) of 7 was determined by derivatizing its precursor α,β-unsaturated γ-hydroxy ester with Mosher’s acid and analyzing the ^¹9F NMR spectrum. The ee was found to be >97%.