A Chemoenzymatic Synthesis of The Macrocyclic Lactone (S)-Curvularin

The macrocyclic lactone (S)-curvularin (7) was prepared in six steps starting from known (S)-2-(2-hydroxypropyl)l,3-dithiane (2). Key steps are the C-alkylation of a dianion derived from 2 with trimethyl 4-bromoorthobutyrate followed by reductive desulfurization of the dithiane moiety and the selective cleavage of a methyl ester group of the diester 6 with NaCN/ HMPA.