Concise and Enantioselective Total Synthesis of (−)-Mehranine, (−)-Methylenebismehranine, and Related
We report an efficient and highly stereoselective strategy for the synthesis of Aspidosperma alkaloids based on the transannular cyclization of a chiral lactam precursor. Three new stereocenters are formed in this key step with excellent diastereoselectivity due to the conformational bias of the cyc...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
Wiley Blackwell
2017
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| Online Access: | http://hdl.handle.net/1721.1/110416 https://orcid.org/0000-0003-3080-1063 |
| Summary: | We report an efficient and highly stereoselective strategy for the synthesis of Aspidosperma alkaloids based on the transannular cyclization of a chiral lactam precursor. Three new stereocenters are formed in this key step with excellent diastereoselectivity due to the conformational bias of the cyclization precursor, leading to a versatile pentacyclic intermediate. A subsequent stereoselective epoxidation followed by a mild formamide reduction enabled the first total synthesis of the Aspidosperma alkaloids (−)-mehranine and (+)-(6S,7S)-dihydroxy-N-methylaspidospermidine. A late-stage dimerization of (−)-mehranine mediated by scandium trifluoromethanesulfonate completed the first total synthesis of (−)-methylenebismehranine. |
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