A facile synthesis of emodin derivatives, emodin carbaldehyde, citreorosein, and their 10-deoxygenated derivatives and their inhibitory activities on μ-calpain
Abstract A new procedure for the preparation of emodin carbaldehyde and citreorosein was described, in which, ω, ω′-dibromomethylemodin triacetate was prepared as a key intermediate by NBSmediated bromination of 1, 3, 8-triacetylemodin. Reduction of emodin and citreorosein with SnCl 2 in a 1: 1 mixture of HOAc and HCl afforded the corresponding anthrones in 90% and 92% yield, respectively, while the corresponding 10-desoxyemodin ...