Studies on gibberellin synthesis. The preparation of phenanthrenoid intermediates for the synthesis of gibberellin A₂₁

Abstract

Methyl 3-(6'-oxo-4'-methoxy-5',6',7',8'-tetrahydronaphthalen-1'-yl)propanoate (11) was converted by conventional methods into diazoketone (17) which underwent acid-promoted cyclization to dienone (18). Refunctionalization gave dienone (20) which was subjected to a tandem alkylation, conjugate addition process with the sodium enolate of dimethyl malonate to furnish a 2: 1 mixture of dimethyl (2RS,8aSR,10aSR)-2-methoxymethyloxy-10,12-dioxo-2,3,4,5,6,7,8a,9,10-decahydro-1 H-2,10a-ethano- phenanthrene-8,8-dicarboxylate (21) and its 8a-epimer, respectively. Subsequent manipulations led to lactone (26), but attempts to convert this compound into a gibbane derivative were unsuccessful.