Compounds

A compound of the formula ##STR28## wherein R' is a carboxyl group in a free acid, salt or ester form, a thiocarboxyl group in free acid or ester form, or a carbamoyl group;

• ##STR29## R and R.sub.1 taken together form 2 to 4 membered alkylene, alkenylene or mixed alkylenealkenylene bridge which may bear one or more substituents selected from halogen, C.sub.1-4 alkyl, C.sub.1-4 alkoxy or phenyl optionally substituted with halogen, C.sub.1-4 alkyl, C.sub.1-4 haloalkyl or C.sub.1-4 alkoxy, and in which any methylene may be replaced by a group selected from oxygen, sulfur, NR.sub.12, carbonyl or thiocarbonyl;
• R.sub.2 and R.sub.3 are each independently hydrogen, C.sub.1-4 alkyl, C.sub.1-4 alkoxy, C.sub.1-4 alkylamino, C.sub.1-4 alkoxyC.sub.1-4 alkyl, or hydroxyC.sub.1-4 alkyl;
• R.sub.20, R.sub.21 and R.sub.22 are each independently hydrogen, halogen, C.sub.1-4 alkyl, C.sub.2,4 alkenyl, C.sub.2-4 alkynyl, C.sub.1-4 alkoxy, C.sub.2-4 alkenyloxy, C.sub.2-4 alkynyloxy, or C.sub.1-4 alkylthio each optionally substituted by 1 to 4 halogen atoms;
• phenyl or phenoxy each optionally substituted with nitro, cyano, hydroxy, amino, alkylamino, dialkylamino, alkylcarbonyl or alkoxycarbonyl;
• and
• R.sub.12 is hydrogen, alkyl or alkoxy.