Compounds

A compound of formula (I) or a pharmaceutically acceptable salt thereof:

• ##STR39## in which, R is hydrogen, C.sub.1-6 alkyl or optionally substituted benzyl of the group in which the phenyl moiety is optionally substituted by a moiety selected from --OH, C.sub.1-6 alkyl, C.sub.1-6 alkoxy, halogen, --NHCO C.sub.1-6 alkyl, --NHCOPh and --CONR.sub.5 R.sub.6 ;
• R.sub.1 is hydrogen or C.sub.1-6 alkyl;
• R.sub.2 is C.sub.3-6 alkyl;
• R.sub.3 is hydrogen, C.sub.1-8 alkyl, --CH--Z where Z is a phenyl group or a indolyl group, said phenyl or indolyl group optionally substituted by a moiety selected from --OH, C.sub.1-6 alkyl, C.sub.1-6 alkoxy, halogen, --NHCO C.sub.1-6 alkyl, --NHCOPh and --CONR.sub.5 R.sub.6, or R.sub.3 is a group ##STR40## where R.sub.7 is hydrogen, alkyl or --CH.sub.2 --Ph where Ph is a phenyl group optionally substituted by a moiety selected from --OH, C.sub.1-6 alkyl, C.sub.1-6 alkoxy, halogen, --NHCO C.sub.1-6 alkyl, --NHCOPh and --CONR.sub.5 R.sub.6 and R.sub.8 is hydrogen or C.sub.1-8 alkyl;
• and
• R.sub.4 is --CH.sub.2 --(CH.sub.2).sub.n OR.sub.5 or --CH.sub.2 --(CH.sub.2).sub.n OCOR.sub.6 or ##STR41## where n is an integer from 1 to 6;
• R.sub.5, R.sub.6, and R.sub.9 are hydrogen or C.sub.1-6 alkyl;
• and R.sub.10 is hydroxy or --O--C.sub.1-6 alkyl or --NR.sub.5 R.sub.6, where R.sub.5 and R.sub.6 may be linked to form an indolyl group which may be unsubstituted or substituted by C.sub.1-6 alkyl, phenyl, or benzyl;
• or R.sub.3 and R.sub.4 are joined together as --(CH.sub.2).sub.m -- where m is an integer from 4 to 12.