Methyl 3-(6'-oxo-4'-methoxy-5', 6', 7', 8'-tetrahydronaphthalen-l'-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-l0, 12-dioxo-2, 3, 4, 5, 6, 7, 8a, 9, 10-decahydro-1H-2, lOa-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. © 1981, CSIRO. All rights reserved.