A Novel Synthesis of Berbines¹-Synthesis of (2, 3) (10, 11)-Bis(methyl en edioxy) berbine by Use of a Lactone²

Abstract

Recently we have evolved an efficient synthesis of the tetrahydroisoquinoline alkaloids by the use of a bromoester essentially like 2 derived from lactone³. In connection with our continuing studies on berbines^1,4 we now wish to report a novel total synthesis of (2,3) (10,11) -bis(methylenedioxy) berbine by the use of the bromoester 2. The approach (Scheme 1), as we believe, is the first report of the successful utilization of the bromoester 2 for the effective formation of the ring D of the berbines. The key intermediate in this projected work was ethyl 2-bromomethyl-3,4-methylene-dioxyphenylacetate 2 which was prepared readily by