Pyrrole Strategy for the γ-Lactam-Containing Stemona Alkaloids: (±)Stemoamide, (±)Tuberostemoamide, and
Xianglin Yin1, Kaiqing Ma1, Ying Dong1
1Department of Chemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907, United States.
Abstract:
Stemona alkaloids contain family members with diverse structural scaffolds. Many of them feature a γ-lactam ring embedded in their characteristic 5-7-5 fused tricyclic core. Herein a pyrrole strategy was developed to enable the total syntheses of three Stemona alkaloids: (±)stemoamide, (±)tuberostemoamide, and (±)sessilifoliamide A. In these cases, a substituted pyrrole was used as the γ-lactam precursor. A sequential pyrrole oxidation and enamide reduction were realized to convert the pyrrole to the corresponding γ-lactam in those three natural products. The use of a pyrrole in an early stage of the synthesis offers the advantage of rapid construction of the key intermediates by exploiting its nucleophilicity.
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