OA quantitative yield can be obtained in 5 h at 50" C. bThese yields have not been optimized. boxyl group is destined to undergo reaction with an organometallic reagent.'Unfortunately, these protecting groups have frequently proved troublesome to remove. A variety of deprotection methods have been used, either hydrolytic2 or reductive, comprising dissolving metals or complex aluminum hydride^,^ electrochemical reduction: ...