Abstract Treatment of a chloroform solution of ethyl 5-hydroxy-7a-methyl-1-oxo-2, 6, 7, 7a- tetrahydro-1H-indene-4-carboxylate with dry hydrogen chloride at room temperature gave ethyl 5-hydroxy-7a-methyl-1-oxo-cis-3a, 6, 7, 7a-tetrahydro-1H-indene-4-carboxylate, and the corresponding trans-hydrindan in the ratio 9: 1. Hydrogenation of this mixture gave ethyl 5-hydroxy-7a-methyl-1-oxo-cis-3a, 6, 7, 7a-tetrahydroindan-4-carboxylate, and ethyl t-7a- ...