Biosynthetic studies on adaline and adalinine,two alkaloids from ladybird beetles (Coleoptera: Coccinellidae)

摘要

The biosynthesis of the homotropane alkaloid (-)-adaline in the coccinelid beetle Adalia bipunctata has been studied by incorporation experiments with [1-~(14)C] and [2-~(14)C]acetate.A degradation scheme was developed which selectively afforded benzoic acid containing the carbonyl carbon atom of adaline.The labelling pattern thus obtained indicated that the alkaloid is biosynthesized via a polyacetate pathway.Moreover,feeding A.bipunctata adults with (-)-[10,10,11,11,12,12,13,13,14,14,14-~2H_(11)]adaline centre dot HCl afforded (-)-[7,7,8,8,9,9,10,10,11,11,11-~2H_(11)] addalinine,demonstrating a biogenetic relationship between the two alkaloids.Possible mechanisms for this conversion are discussed.Finally,the synthetic scheme devised to obtain (+-)-6-acetonyl-2-pentyl-1-piperideine did not yield the target compound,but afforded instead (+-)-adaline in moderate yields.This unexpected result gives support to the hypothesis that this piperideine could be a key intermediate in teh biosynthesis of adaline.