Chiral synthesis via organoboranes. 39. A facile synthesis of γ- substituted-γ-butyrolactones in exceptionally high enantiomeric purity

Article abstract of DOI:10.1021/jo00081a014

Optically active homoallylic alcohols of exceptionally high enantiomeric purity (98-≥99% ee) readily available via asymmetric allylboration were converted into p-nitrobenzoate esters and subjected to hydroboration followed by oxidation with CrO₃ in aqueous acetic acid (10% H₂O) to obtain the corresponding carboxylic acids with the same number of carbon atoms. The protecting ester group was hydrolyzed and the product lactonized in situ to the γ-substituted γ-butyrolactones 5 (R = Me, Pr, i-Pr, t-Bu, Ph, (E)- CH=CHCH₃) usually without racemization and in good yields. The method is convenient and potentially valuable for the synthesis of highly functionalized γ-butyrolactones in high optical purity.