Radical cyclisations onto 2(5 [formula omitted])-furanone and maleate electrophores. An approach to the spiro- and linear-fused γ-lactone ring systems found in the ginkgolides

Abstract

Intramolecular radical cyclisations involving α-acetal methyl centres, and 2(5 H )-furanone and maleate electrophores, allow the facile synthesis of spiro- and linear-fused γ-lactone ring systems e.g. (5), (6), (7) and (8) present in the ‘ginkgolides’ viz (1) and (2) produced by the ginkgo tree Ginkgo biloba .