Asymmetric synthesis of (+)-citrinin using an ortho-toluate carbanion generated by a chiral base
作者:Andrew C. Regan、James Staunton
DOI:10.1039/c39870000520
日期:——
The carbanion (3), generatedusing the chiral lithium amide base (1), undergoes enantioselective addition to acetaldehyde and acetone with a high degree of asymmetric induction at the nucleophilic centre; the reaction with acetaldehyde is exploited in an enantioselective synthesis of (+)-citrin (10).
The biosynthetic pathway to citrinin is elucidated by incorporation studies with advanced precursors; the first step of biosynthesis involves methylation of a pentaketide, followed by cyclization, reduction to the ketoaldehyde and then to the hydroxyaldehyde, dehydration, and finally oxidation of the methyl group at C(7) to a carboxy-group.
Lunatoic acid A and (-)-mitorubrinic acid have been isolated as chlamydospore-like cellinducing substances from Cochliobolus lunatus. (+)-Sclerotiorin, (+)-rotiorin, citrinin and sclerin were shown to have the same activity. Although they share no common structural feature, all these active substances react with methylamine. The reaction products do not have this activity. The reaction curves showed a positive correlation between the chemical reactivity of chlamydospore-like cell-inducing substances with methylamine and their biological activities.