Spectroscopic properties of two nonenolizable α-keto-γ-lactones, dehydroginkgolide A and 3,3-dimethyl-2-oxo-γ-butyrolactone
Abstract
Dehydroginkgolide A (IIa) is converted into a 4:1 mixture of the ester hemiacetal (IIb) and ester aldehyde (IIc) in 30 min. when dissolved in methanol, whereas 3,3-dimethyl-2-oxo-γ-butyrolactone (IV) rapidly adds methanol to give (V).