NEW MATERIAL:A compound shown by the formula I (X is a group shown by the formula II-IV, etc.; Y is α- or β-hydroxyl group).

EXAMPLE: 5β-Hydroxy-6,7,8,8a-tetrahydro-8aβ-methyl-1(5H)-naphthalenone.

USE: An antibacterial agent. An intermediate for drugs.

PROCESS: A compound shown by the formula V (X' is a group shown by the formula II, etc.) is reacted with a phenylselenenyl halide in the presence of a strong base and then with an aqueous solution of H2O2 so that double bonds are introduced to 2- and 3-positions, to give a compound shown by the formula I where X is a group shown by the formula II, etc. This compound is epoxidized to give a compound shown by the formula I where X is a group shown by the formula III, IV, etc. The compound shown by the formula V is also a novel compound and derived from 3,4,6,7,8,8a-hexahydro-8a-methyl-1(2H)-naphthalenone.