Derivatives of butynylamine

Butynylamine derivatives represented by the following general formula I and their pharmacologically acceptable salts: (CF DRAWING IN BOPI) ** wherein R 1 ** and R 2 are cycloalkyl, phenyl or 2 identical or different -thienyl; R ** 3 ** and R 4 are a hydrogen atom or an alkyl group the same or different or together form a cycloalkyl group together with the adjacent carbon atom; R ** 5 ** and R 6 are a hydrogen atom or an alkyl group the same or different, or together form a cyclic amino group together with the adjacent nitrogen atom, and A denotes O or NR (where R is a hydrogen atom or an alkyl group), excluding the case where R ** and R 3 ** 4 are both hydrogen atoms, a is O, and either one of the symbols R ** 1 ** and R 2 is phenyl.