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 NaBH 4 -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.
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