Conversion of 12α-Hydroxyandrosta-1,4-diene-3,17-dione into a Derivative of 12-Oxoestradiol: a Novel C9–C 10 Cleavage Reaction

Abstract

Reaction of 12α-hydroxyandrosta-1,4-diene-3,17-dione (1) with 2,2-dimethylpropane-1,3-diol in the presence of pyridinium p-toluenesulfonate gave the corresponding 17,17-cyclic acetal (2). Oxidation of (2) with chromium trioxide in pyridine gave 5′,5′-dimethylspiro[androsta-1,4-diene-17,2′-[1,3]dioxan]-3,12-dione (5) which underwent base-catalysed cleavage to give the novel 9,10-secosteroid (8). Selective reduction of (1) at C17 gave 12α,17β-dihydroxyandrosta-1,4-dien-3-one (9a); selective protection of this at C17, followed by oxidation with chromium trioxide in pyridine gave 17β-(t-butyldimethylsilyloxy)androsta- 1,4-diene-3,12-dione (10), regioselectively protected as the 12,12-ethylenedioxy acetal (12). Treatment of (12) with lithium in tetrahydrofuran in the presence of biphenyl and diphenylmethane effected reductive aromatization of ring A to give a mixture of 17β-(t-butyldimethylsilyloxy)-12,12-ethylenedioxyestra-1,3,5(10)-trien-3-ol (15a) and the corresponding 17-alcohol (15b). Conversion of (15a) into the corresponding 3-benzyl ether (14a), followed by acid-catalysed hydrolysis gave 12-oxoestradiol 3-benzyl ether (13).