| Abstract
| - An alternative asymmetric synthesis of (+)-(lS,9aS)-homopumiliotoxin 223G (1) was accomplished via(1R,2R,9aS)-1-(benzyloxy)-2-hydroxy-1-methyl-3[(E)-isobutylidene]quinolizidine (4), which was synthesizedaccording to the intramolecular nickel(II)/chromium(II)-mediated cyclization of the N-(iodoalkenyl)aldehyde2. Compound 4 was converted to the acetate and subjected to reduction with lithium in ammonia,whereupon deprotection of the O-benzyl group and removal of the acetoxyl group occurred in a singleoperation to afford (+)-homopumiliotoxin 223G. The same sequence using (±)-4 was applied to thesynthesis of racemic 223G. Gas chromatography of a sample of racemic 223G showed no separation intoenantiomers on four different cyclodextrin-based chiral GC columns. We found, however, that theO-acetates of (±)-223G gave a nearly baseline separation on either a β-cyclodextrin column or apermethylated β-cyclodextrin column. The O-acetate of synthetic (+)-223G was identical on either ofthese two columns, with the first eluting O-acetate from acetylated (±)-223G and also with the acetylated223G present in a frog skin extract, thus allowing us to confirm unambiguously the 1S,9aS absoluteconfigurations of natural 223G.
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