Concise Formal Synthesis of Porothramycins A and B via Zincke Pyridinium Ring-Opening/Ring-Closing Cascade
摘要:
Short formal syntheses of the antitumor antibiotics porothramycins A and B from a commercially available ester of the unnatural amino acid 3-(3-pyridyl)alanine are presented. A rearrangement cascade that presumably involves a Zincke-type pyridinium ring-opening followed by cyclization of a pendant nucleophilic amide generates the salient pyrroline ring of the alkaloids.