L(+)-2-Tropinone

The title compound was prepared from cocaine by the following steps: hydrolysis to ecgonine, treatment with phosphorus oxychloride and then ammonia to give anhydroecgonine amide, followed by a Hofmann rearrangement to L(+)-2-tropinone. Reduction of the latter with lithium aluminum hydride furnished the expected equatorial alcohol; This proved to be identical with a degradation product of dioscorine, thus establishing the absolute configuration of the alkaloid. By proper choice of conditions it was possible to prepare the axial 2-tropanol substantially free of the equatorial isomer by means of a sodium-3-pentanol reduction.