Total Synthesis of Phenanthropiperidine Alkaloids by Sequential Alkylation of N,N‐Dibenzylaminoacetonitrile

European Journal of Organic Chemistry
2021.0

Abstract

Two representative members of the phenanthropiperidine alkaloid family, tylophorine (1) and cryptopleurine (2), were synthesized by a bidirectional alkylation strategy employing dibenzylaminoacetonitrile as a substrate. This approach relies on the unprecedented condensation of metallated α-aminonitriles with bromomethylphenanthrenes to provide fully substituted α-aminonitriles, which are subjected to a NaBH4-mediated reductive decyanation process to form homobenzylic amines. From these intermediates, a terminal leaving group was introduced by simple chemical manipulation, and its displacement by a free primary amine under two favorable cyclization processes led to the formation of the future E-ring of both alkaloids in high yields. Finally, a late Pictet-Spengler cyclization ensured the formation of a D-ring for the alkaloids 1 and 2. © 2021 Wiley-VCH GmbH

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