Total synthesis of the aromatase inhibitor dihydroisocoumarin via protective opening of lactones

Asymmetric total synthesis of a dihydroisocoumarin, (3R,4R)-(−)-6-methoxy-1-oxo-3-pentyl-3,4-dihydro-1H-isochromen-4-yl acetate (1) starting from commercially available m-anisic acid is described. Herein, we depict the use of protective opening of lactones and construction of δ lactone. The synthesis involves Wittig, Grubbs cross metathesis, and Sharpless dihydroxylation reactions.