Abstract: Bicyclo[3.3.0]octenylaldehyde derivatives represented by the formula: ##STR1## wherein R.sup.1 is a substituent selected from the group consisting of a hydrogen atom and a protective group of a hydroxy group;R.sup.2 is a substituent selected from the group consisting of --CH.sub.2 OR.sup.5, ##STR2## where R.sup.5 is a substituent selected from the group consisting of a hydrogen atom and a protective group of a hydroxy group,R.sup.6 is a substituent selected from the group consisting of an alkyl group, an alkenyl group and an alkynyl group, said substituent being straight, branched or cyclic and having 5 to 10 carbon atoms,X is a substituent selected from the group consisting of a vinylene group and an acetylene group, andR.sup.7 is a substituent selected from the group consisting of an alkyl, an alkenyl group, and an alkynyl group, said substituent being straight, branched or cyclic and having 5 to 10 carbon atoms; andR.sup.

Abstract: A method for preparing a cis-bicyclo[3.3.0]octylidene derivative represented by the formula: ##STR1## wherein R.sup.1 is a hydrogen atom or an alkyl group; R.sup.2 is a hydrogen atom or a protective group for hydroxyl group; and Y is ##STR2## where R.sup.3 is a hydrogen atom or a protective group for hydroxyl group; R.sup.4 is a hydrogen atom or a straight, branched or cyclic alkyl group, alkenyl group or alkynyl group; and X is a group represented by CH.dbd.CH or C.tbd.C,comprises carrying out the catalytic hydrogenation reaction of a (1-alkenyl)-cis-bicyclo[3.3.0]octene derivative represented by the formula: ##STR3## wherein R.sup.1, R.sup.2 and Y have the same meanings as defined above, in the presence of a metal carbonyl compound or its complex represented by the formula:Mw(CO)x(H)y(R)zwherein M is a metal element of the group VIB; R is a .pi. ligand or a phosphine ligand; w is 1 or 2; x is an integer of 3 to 6; y is 0 or 1; and z is 0 or an integer of 1 to 3.