A new ester alkaloid, zygacine, has been isolated from Zygadenus venenosus. Zygacine, C29H45O8N, is a monoacetate ester of the alkamine zygadenine. Methanolysis of zygacine yields zygadenine and acetic acid. Acetylation of zygacine and of zygadenine with acetic anhydride at steam-bath temperature affords zygadenine triacetate. Treatment of zygacine, zygadenine or zygadenine triacetate with acetic anhydride and pyridine at steam-bath temperature yields zygadenine tetraacetate. Crystalline acetonides of zygacine and zygadenine have been prepared. © 1955, American Chemical Society. All rights reserved.