. "Examples which may be mentioned are unsubstituted or substituted ethinyl, 2-propinyl, 2-butinyl, 3-butinyl and 1-methyl-2-propinyl.Unsubstituted or substituted cycloalkyl in the definitions R.sup.1 and R.sup.2 and cycloalkyl in the definition of R.sup.6 represent cycloalkyl, preferably having 3 to 8, in particular 3, 5 or 6, carbon atoms." . . .