Nonracemic γ‐Lactones from the Sharpless Asymmetric Dihydroxylation of β,γ‐Unsaturated Carboxylic Esters

Abstract

Since Sharpless' discovery of the asymmetric dihydroxylation of C=C double bonds in the late 1980s this reaction has become a powerful tool of synthetic organic chemistry. As a consequence, this transformation has been reviewed repeatedly and extensively. The present microreview focuses on Sharpless' asymmetric dihydroxylations (from here on “SADs”) of β,γ‐unsaturated carboxylic esters. These SADs differ from most others in that they provide not nonracemic 1,2‐diols but follow‐up products thereof. Bearing ester groups at appropriate distances, the SAD‐based 1,2‐diols obtained from β,γ‐unsaturated carboxylic esters lactonize readily under SAD conditions. Accordingly, SADs of β,γ‐unsaturated carboxylic esters furnish nonracemic β‐hydroxy‐γ‐lactones in a single operation. We show that this SAD route represents a – or even the most – potent easy‐to‐handle route to nonracemic butanolides and butenolides “of almost all kinds”. The span covered is from pioneering racemic work to applications in natural product synthesis. Some non‐butanolide and non‐butenolide target syntheses are included, especially those of tetrahydrofurans.