HYLENEDIOXY)-1,5-DIMETHYLBICYCLO[4.4.0]DECAN-4-ONE

The title compound (1) [alternative name: ydronaphthalene)-1-spiro-2'- (1',3'-dioxolan)-6one, C14H22O3] was obtained as the major product upo n Pd/CaCO3-catalyzed hydrogenation of the corresponding enone (2). The analysis of the crystal structure of (1) has established that the mon oacetal is cis-fused and that both rings adopt nearly perfect chair fo rms. The C(5) methyl group is in an alpha position, resulting directly from syn-hydrogenation of the enone. While there are two possible cha ir-chair conformations for cis-decalins, the title compound crystalliz ed in the conformation which places the C(5) methyl group in an equato rial position.