| abstract |
Compounds represented by general formula (I) or pharmaceutically acceptable salts thereof wherein ------ represents a single or double bond; R1 and R2 are each independently hydrogen, lower alkyl, aralkyl, alkenyl, alkynyl, acyl or the like, provided the cases wherein both R1 and R2 are simultaneously hydrogen or lower alkyl are excepted; R3 is hydrogen or methyl; X is O or S; and A is a group represented by, e.g., the general formula (a): -(CH2)m-(NH)nS(O)p(NH)q-R4 wherein R4 is alkyl or haloalkyl; m is an integer of 3 to 10; n is 0 or 1; p is 0, 1 or 2; q is 0 or 1; and r is an integer of 1 to 6. |