Asymmetric Total Syntheses and Biological Studies of Tuberostemoamide and Sessilifoliamide A.

The first asymmetric total syntheses of tuberostemoamide, sessilifoliamide A, and their epimers have been accomplished via the common intermediate ethylstemoamide. The stereochemistry control relationship at C8/C9/C10 of ethylstemoamide is clearly revealed for the first time, and a subtle difference of substituent at the C10 position between stemoamide and ethylstemoamide (Me vs Et) drastically changes the stereoselectivity, which is significantly valuable for syntheses of ethylstemoamide structurally related Stemona alkaloids. Biological studies reveal that the activities of each epimer show a significant difference. 11,13-Bis- epi-sessilifoliamide A is expected to be a selective and reversible BChE inhibitor for the treatment of neurodegenerative diseases, and sessilifoliamide A may be a part of the anti-inflammatory substances in Stemonaceae plants.