Biomimetic Synthesis of Ascididemin and Derivatives

Abstract

A two-step biomimetic synthesis of the pentacyclic pyrido[2,3,4-klacridine marine alkaloid ascididemin (3a) from quinolinequinone 5a and N-trifluoroacetamidokynuramine (4) is described. The crucial step (6 to 7) involves the simultaneous formation of two pyridine rings in a process which might well offer an explanation for the biogenetic synthesis in marine organisms. The preparation of substituted ascididemins by either starting from substituted quinoline-quinones, e.g., 5b to afford 11-methoxyascididemin (3b), or by nitration of 3a to the mono 1- or 3-nitroascididemins (8 and 9 respectively) is reported.