Novel strategies for the synthesis of anthrapyranantibiotics: discovery of a new antitumor agent and total synthesis of (S)-espicufolin

Abstract

Two high-yielding strategies for the synthesis of 4H-anthra[1,2-b]pyran antibiotics have been developed giving access to novel antitumor agent 24 (ED₅₀ 1.5 µM) and to (S)-espicufolin (3). A key step for the assembly of the tetracyclic 4H-anthra[1,2-b]pyran-4,7,12-trione skeleton is the nucleophilic addition of an aryl lithium species onto an aldehyde which allows the introduction of either an ynone or 1,3-diketo side chain, serving as precursors for an acid-catalysed cyclisation.