ChemInform Abstract: Solanum Alkaloids. Part 121. Partial Synthesis of the Steroid Alkaloids Teinemine, 22‐Isoteinemine, Etioline, and 25‐Isoetioline.

Abstract

(muldamine) from V. californicurn Durand9). Recently, 25-isoetioline (21) has been isolated from S. canense and S. ,fraxinifolium6310). In general, these alkaloids are occurring in plants as 0(3)-glycosides, but 10 and U5' as well as muldamine') were found to occur also as nonglycosylated alkamines.The configurations of teinemine and 22-isoteinemine at C-22 was a subject of controversy. Thus, Kaneko et al.71 had elucidated the structures of both alkaloids, but proposed configurations at C-22 opposite (22R for 8 and 22s for 10) to those later definitely established by Gaffield et al.9' and finally proved by an X-ray analysis of 815).In the following, the syntheses of teinemine ( . l23l3)). These syntheses unequivocally confirm the above-mentioned structural and especially stereochemical statements. Because tomatid-5-en-3P-01 (1) and solasodine (15) had been already synthesized from pregnane derivatives available by total syntheses 17), the described syntheses of teinemine (8), 22-isoteinemine (lo), etioline (12), and 25-isoetioline (21) represent also the formal total syntheses of these rare alkaloids.