The present invention is to provide an aliphatic nitrogen-containing 5-membered ring compound represented by the formula [I]: ##STR00001## wherein symbols in the formula have the following meanings; A: --CH.sub.2-- or --S--, B: CH or N, R.sup.1: H, a lower alkyl group, etc., X: a single bonding arm, --CO--, -Alk-CO--, --COCH.sub.2--, -Alk-O--, --O--CH.sub.2--, --SO.sub.2--, --S--, --COO--, --CON(R.sup.3)--, -Alk-CON(R.sup.3)--, --CON(R.sup.3)CH.sub.2--, --NHCH.sub.2--, etc., R.sup.3: hydrogen atom or a lower alkyl group, Alk: a lower alkylene group, and R.sup.2: (1) a cyclic group which may be substituted, (2) a substituted amino group, etc., provided that when X is --CO--, then B is N, or a pharmaceutically acceptable salt thereof.