Stereoselective route towards 2,5-disubstituted piperidine alkaloids. Synthesis of (+)-pseudoconhydrine and (+/-)-epi-pseudoconhydrine

This paper describes a new general approach towards functionalized piperidi ne alkaloids, based on the stereo- and regioselective palladium(0)-catalyze d nucleophilic ring-opening of vinyl epoxides by nitrogen nucleophiles. The latter reaction provides access to stereo-defined and and syn aminoalcohol derivatives, 1-benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols (5), which were transformed to (+)-pseudoconhydrine (3) and (+/-)-epi-pseudoconhydrin e (9), respectively, via protection (silyl ether), hydrogenation, debenzyla tion and cyclization. Detosylation-deprotection gave the final products in good yields and high stereoisomeric purity. (C) 2000 Elsevier Science Ltd. All rights reserved.