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Concise enantiospecific, stereoselective syntheses of (+)-crispine A and its (-)-antipode
Mahender Gurram1, Balázs Gyimóthy, Ruifang Wang
1Medicinal Chemistry Department, Albany Molecular Research, Inc. (AMRI), P.O. Box 15098, 26 Corporate Circle, Albany, New York 12212-5098, USA.
Abstract:
An enantiospecific and stereoselective total synthesis of the natural product (+)-crispine A has been demonstrated employing a Pictet-Spengler bis-cyclization reaction between commercially available (R)-(-)-methyl 2-amino-3-(3,4-dimethoxyphenyl)propanoate and 4-chloro-1,1-dimethoxybutane to preferentially provide the cis tricyclic adduct. Decarboxylation by a convenient two-step protocol provided the enantiopure natural product in three steps with an overall isolated yield of 32% from the amino acid. The unnatural antipode (-)-crispine A was similarly prepared in three steps from the commercially available (S)-(+)-amino acid.
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