Syntheses of chiral lactones via asymmetric allylboration

The syntheses of lactenones and lactones of different ring sizes in high enantiomeric excesses involving asymmetric allylboration with B-allyldiisopinocampheylborane have been described (1). γ-Substituted γ-butyolactones have been synthesized from homoallyl alcohols via a protection-hydroboration-oxidation-deprotection-cyclization sequence. The unique nature of α-perfluoroalkyl homoallyl alcohols has been exploited for the synthesis of γ-perfluoroalkyl γ-butyrolactones without protecting the alcohols. Allylboration of formyl esters provide a general route to prepare ω-allyl and ω-propyllactones. The ring-closing metathesis of homoallyl enoates provides a methodology to prepare a variety of α-pyranone-containing natural products.