SYNTHESIS OF NATURAL LIGNAN ARYLNAPHTHALENE LACTONES, DAURINOL AND RETROCHINENSIN

Two natural arylnaphthalene lignan lactones, daurinol [4] and retrochinensin [5], have been synthesized by a short reaction pathway from isovanillin. By heating in xylenes, the ester 3-benzyloxy-4-methoxyphenylpropargyl 3,4-methylenedioxyphenylpropiolate [14] yielded daurinol benzyl either [15] and 1-(3'-benzyloxy-4'-methoxyphenyl)-2-hydroxymethyl-6,7-methylenedioxy-3-naphthoic acid lactone [17]. Debenzylation of 15 gave daurinol [4], and debenzylation of 17 followed by methylation yielded retrochinensin [5].