Geranyl compounds

A geranyl compound represented by the following formula (I-2) or (I-3):

• in which R2 stands for a residual group remaining after removing all carboxyl groups present in a carboxylic acid selected from the group consisting of malic acid, citric acid, succinic acid, fumaric acid, 2-oxoglutaric acid, pyruvic acid, p-pyruvoaminobenzoic acid, retinoic acid, tyrosine, cysteine, glutamic acid and serine, and where hydroxyl or amino group(s) are present in the residual group, they may optionally be protected by acyl (e.g., lower alkanoyl) or benzyloxycarbonyl group(s),
• m is 1, 2 or 3,
• n is 0, 1 or 2,
• m+n show the number of carboxyl groups which are present in said carboxylic acid, and
• R3 stands for p-hydroxyphenyl or mercapto group.