Abstract: Compounds of formula (I) ##STR1## wherein each X separately is halogeno, hydroxy, C.sub.1-4 alkyl, C.sub.1-4 alkoxy, nitro or an unsubstituted or substituted amino group NRR' in which R and R' are each separately selected from hydrogen, C.sub.1-4 alkyl groups and C.sub.2-4 halogenated alkyl groups;wherein Y is halogeno, hydroxy, C.sub.1-4 alkoxy or an unsubstituted or substituted amino group NRR' in which R and R' are as defined above;wherein n represents 0, 1, 2 or 3 and n' represents 1, 2, 3 or 4;wherein R.sup.1 and R.sup.2 each separately represent hydrogen, halogeno, phenyl or a C.sub.1-4 alkyl group, or together represent a group .dbd.NOR" in which R" is hydrogen or is a group ZC(O)-- or (ZO).sub.2 P(O)-- where Z is a C.sub.1-4 alkyl group; andwherein R.sup.3 and R.sup.4 each separately represent hydrogen, acetyl, phenyl, 2,2,2-trichloro-1-hydroxyethyl or a C.sub.1-4 alkyl group, or together represent a group .dbd.CHR"' in which R"' is a C.sub.1-4 alkyl, C.sub.