
A compound of the formula (I) or a pharmacologically acceptable salt, ester or other derivative thereof: ##STR1## R.sup.1 is H or NHOH. R.sup.2 is H, optionally substituted alkyl, cycloalkyl or a group --AR.sup.6. A is an alkylene which may be optionally interrupted by O, --S(O)m-- or --N(R.sup.9). R.sup.6 is a group (II), (III), (IV) ##STR2## X is O, S, --N(R.sup.10)--, --C(R.sup.11)(R.sup.12)--. Y is O, CO, --S(O)n--, --N(R.sup.10)--, --C(R.sup.11)(R.sup.12)--. Each of R.sup.7 and R.sup.8 is H...











