The present invention provides a simplified and convenient process for the preparation of an optically active enone such as 7,7-dimethyl-6,8-dioxabicyclo-[3,3,0]oct-3-en-2-one. The invention further provides novel optically active intermediate compounds. The process for the preparation of an optically active enone represented by the formula (4) comprises steps of (A) deprotecting the protecting group for the hydroxyl group at the 1-position in a compound represented by the formula (1) to a hydroxyl group (compound (2)), (B) oxidizing the hydroxyl group to a ketone group (compound (3)) and (C) deprotecting the protecting group for the hydroxyl group at the 4-position to form a double bond between the carbon atom at the 4-position and the carbon atom at the 5-position, according to the following reaction schemes: ##STR1## wherein R.sup.1 and R.sup.4 independently represent a cumyl group, .alpha.,.alpha.-diethylbenzyl, .alpha.,.alpha.-dimethyl-p-methoxybenzyl, t-butyldimethylsilyl, trimethylsilyl, triethylsilyl, triisopropylsilyl, isopropyldimethylsilyl or ethyldimethylsilyl, R.sup.2 and R.sup.3 jointly represent acetonide, methyl ethyl ketal or diethyl ketal, and R.sup.5 represents a hydrogen atom, an alkyl group having not more than 20 carbon atoms or a phenyl group.