Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine,and (−)‐Trachelanthamidine |
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| Authors: | Dr Dipankar Koley Yarkali Krishna Kyatham Srinivas Afsar Ali Khan Ruchir Kant |
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| Affiliation: | 1. Medicinal and process Chemistry Division, CSIR‐Central Drug Research Institute, Lucknow, 226031 (India);2. Molecular and Structural Biology Division, CSIR‐Central Drug Research Institute, Lucknow, 226031 (India) |
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| Abstract: | An asymmetric, organocatalytic, one‐pot Mannich cyclization between a hydroxylactam and acetal is described to provide fused, bicyclic alkaloids bearing a bridgehead N atom. Both aliphatic and aromatic substrates were used in this transformation to furnish chiral pyrrolizidinone, indolizidinone, and quinolizidinone derivatives in up to 89 % yield and 97 % ee. The total syntheses of (?)‐epilupinine, (?)‐tashiromine, and (?)‐trachelanthamidine also achieved to demonstrate the generality of the process. |
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| Keywords: | acetals alkaloids cyclization natural products organocatalysis |
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