The Synthesis of Ethyl 5-Vinyl-2-Quinuclidine Carboxylate

Abstract

The synthesis of the minor indolic cinchona alkaloid, cinchonexine (1), from ethyl-5-vinyl-2-quinuclidine carboxylate (2) was reported in 1958¹ but the preparation of 2 was not described until several years later². No further reports on this problem have since appeared. Since 2 was previously obtained in very poor yield from the Beckmann rearrangement of quininene oxine² a more direct approach to its preparation was initiated in order to complete the total synthesis of cinchonexine from synthetically available precursors. Maroquinine (3a) which not only has been prepared in both racemic ³ and optically active^3b forms but is also readily available from quinine⁴ was selected as the starting material fro this synthetic sequence.