Compounds complying with the general formula (I) in which R either represents a halogen atom or a phenyl group substituted by one or more groups chosen from halogen atoms and (C1-C6)alkyl, (C1-C6)alkoxy, nitro, amino, trifluoromethyl, cyano, hydroxy, acetyl or methylenedioxy groups, or represents a pyridinyl group, a thienyl group, an indolyl group, or a pyrimidinyl group optionally substituted by one or more (C1-C6)alkoxy groups, where, of the two carbon-carbon bonds represented by , one is single and the other may be single or double. Therapeutic application.