Abstract: 1. A compound of the formula: ##STR1## wherein the symbol of a solid line with a broken line means a single bond or a double bond,R and R' are independently selected from the group consisting of hydrogen atom, halogen atom, lower alkyl, nitro, unsubstituted amino and substituted amino,A and B are independently selected from the group consisting of hydrogen atom, lower alkyl optionally substituted with a lower cycloalkyl, aryl optionally substituted with one or more halogen atoms and the group: -Y-R.sup.2wherein Y is lower alkylene and R.sup.2 is the group: ##STR2## wherein m is integer of 1 to 3, n is 0 or 1, Z is >N-, >CH-- or >C=, R.sup.3 is diaryl (lower) alkyl optionally substituted with one or more halogen atoms or is condensed heterocyclic group optionally substituted with oxo, with the proviso that(a) at least one of A and B is the group -Y-R.sup.2 and(b) when A is hydrogen atom and B is the group -Y-R.sup.2, then Z is >CH-- or >C= if R.sup.