X is a member selected from the group consisting of hydroxylower alkyl, lower alkyloxylower alkyl, aminocarbonyl, mono- and di(lower alkyl)aminocarbonyl, carboxyl, lower alkyloxycarbonyl, (aminocarbonyl)lower alkyl, [mono- and di(lower alkyl)aminocarbonyl]lower alkyl, carboxylower alkyl, (lower alkyloxycarbonyl)lower alkyl and (hydroxylower alkyl)aminocarbonyl;