The compound of the type (A-4) is an alkane compound having a decahydronaphthyl group and a cyclohexyl group bonded to one and the same carbon atoms of the alkane structure and represented by the general formula ##STR11## in which each of the group denoted by the symbols R4, R5, R6 and R7 is a hydrogen atom or a methyl group, R8 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms and t