Simple novel synthesis of the anthracyclinone system using a new modification of the marschalk reaction and a carbohydrate as a chiral centre source

Abstract

Leuco-quinizarin (4) with ethanal in alkaline solution at 0 °C followed by aerial oxidation gave 2-(1-hydroxyethyl)quinizarin (2c) in high yield and similarly (4) with aldehydo-2,3:4,5-di-O-isopropylidene-D-arabinose (3) at 0 °C and aerial oxidation gave a good yield of the crystalline 2-(1-hydroxy-D-arabinityl)quinizarin (5) which after treatment with acid, periodate, and cold alkaline dithionite, aerial oxidation, and treatment with mild acid gave the crystalline anthracyclinone (10) in excellent yield.