The pyrrolizidine alkaloids of Amsinckia menziesii

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Abstract
Methanolic extracts of fresh Arnsinckia menziesii (Lehm.) Nels, and Macbr. (Boraginaceae) yielded three known pyrrolizidine alkaloids, intermedinet (I), lycopsaminet (2) and 7-acetyllycopsaminet (3). In addition, two new alkaloids were isolated and shown to be 9-[(2'S,3'S)-3'-acetoxy-2'-hydroxy- 2'-isopropylbutanoyl]retronecine,t (3'-acetyllycopsamine) (4) and 7-acetoxy-9-[(2'S,3'S)-3'-acetoxy- 2'-hydroxy-2'-isopropylbutanoyl]retronecine, (3',7-diacetyllycopsamine) (5). Structures of all of the alkaloids were determined by means of mass spectrometry and 13C and 1H n.m.r. spectroscopy. The structures of the new alkaloids were confirmed by acetylation of lycopsamine (2) to give 3'-acetyl- lycopsamine (4) and 3',7-diacetyllycopsamine (5).