On papaver bracteatum—XIV : Ready access to benzylidene phthalimidine compounds from rhoeadine alkaloid-derived nitriles

Abstract

The B D trans lactole alpinigenine ( 1a) isolated from Papaver bracteatum Lindl. was shown to form the oxime 2a which in turn was transformed to the nitrile 3a by dehydration, the methiodide 4a, and — by treatment with alkali under mild conditions — to the benzylidene phthalimidine derivative 5a, whose structure was elucidated by spectral analysis as well as oxidative fragmentation into 6 and 7. The unique reaction leading to 5a apparently is bound with certain structural prerequisites inherent to 3a, including stereochemistry. When cis-alpinigenine ( 1b) was subjected to the same sequence, little of 5a accordingly could be obtained, and even none of any phthalimidine was formed from the non-acetoxylated nitrile 11.