Synthesis of (±)-eleutherin, (±)-isoeleutherin, and their demethoxy analogues. A novel synthetic approach

Abstract

(±)-Eleutherin (1) and (±)-isoeleutherin (3) are prepared by intramolecular cyclization to the naphthopyrans of 2-acetyl-3-allyl-8-methoxy-1, 4-napthoquinone, which is itself obtained by the Lewis acid-mediated allylation of 2-acetyl-8-methoxy-1, 4-naphthoquinone (5) with allyltrimethylstannane (7).