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[摘要]：The first total syntheses of (-)-brunsvigine (I) and (-)-manthine (II) were accomplished in 10 and 18 steps, resp. Iodination of an enone followed by stereoselective redn. yielded an a-iodo allylic alc. Conversion of the alc. into Weinreb amide followed by anionic cyclization gave a bicyclic enone. Stereoselective redn. of the enone and subsequent protection afforded a pivaloate. Grignard addn. of 3,4-(methylenedioxy)phenylmagnesium bromide to the pivaloate and detosylation afforded amine deriv. III. Pictet-Spengler cyclization of III with Eschenmoser's salt and subsequent hydrolysis gave enantiomerically pure I. For the total synthesis of II, the key intermediate IV was used, and the II was finally synthesized via several steps, such as hydrolysis, methylation, detosylation and Pictet-Spengler cyclization. |
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