An Expedite Synthesis of Some Angularly Fused Novel 'U'-Shaped Tetracyclic Furophenanthraquinones Simulating ABCD Rings of Isotanshinone-II

摘要

An expedite general synthesis of three angularly fused furophenantharquinones is described from 1-(2-furyl)-naphthalen-2-carbaldehyde derivatives. 1-(2-furyl)-naphthalen-2-carbaldehyde derivatives on sequential functional group transformation of the -CHO group afforded 2-[1-(2-furyl])-naphthalen-2-acetic acid derivatives in reasonably overall good yields. Cyclization of the carboxylic acids lead to the formation of furophenanthrenol derivatives. The phenolic intermediates were oxidized with Fremy's salt to furnish the condensed furophenanthraquinone derivatives in excellent yields. The synthesized compounds simulate the ABCD core nucleus of the naturally occurring isotanshinone-II isolated from Salvia glutinosa.