Hydroxylamine derivatives

A hydroxylamine derivative of the formula I ##STR9## wherein R.sup.4 is hydrogen, carbamoyl, (1-4C)alkyl, cyclopentyl, cyclohexyl, tetrahydrofuran-3-yl, tetrahydropyran-4-yl, piperidin-4-yl, N-(1-4C)alkylpiperidin-4-yl, (2-5C)alkanoyl, (1-4C)alkylsulphonyl, N-(1-4C)alkylcarbamoyl, N,N-di-(1-4C)-alkylcarbamoyl, phenyl, phenyl-(1-4C)alkyl, di-phenyl-(1-4C)alkyl, benzoyl, phenylsulphonyl or a heteroarylmethyl group wherein the heteroaryl moiety is selected from pyridyl, pyrimidinyl, furyl, thienyl, oxazolyl and thiazolyl;

• R.sup.5 is hydrogen, (1-4C)alkyl, (3-4C)alkenyl, (3-4C)alkynyl, cyano-(1-4C)alkyl, phenyl or phenyl-(1-4C)alkyl;
• A.sup.4 is (1-4C)alkylene which may optionally bear one or two substituents selected from (1-4C)alkyl, phenyl and phenyl-(1-4C)alkyl;
• wherein each phenyl, phenyl-(1-4C)alkyl, di-phenyl-(1-4C)alkyl, benzoyl, phenylsulphonyl or heteroarylmethyl group in R.sup.4, R.sup.5 or A.sup.4 may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, nitro, (1-4C)alkyl and (1-4C)alkoxy;
• Ar.sup.1 is phenylene, pyridinediyl or pyrimidinediyl which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;
• A.sup.1 is a direct link to X.sup.1, or A.sup.1 is (1-4C)alkylene;
• X.sup.1 is oxy, thio, sulphinyl or sulphonyl;
• Ar.sup.2 is phenylene, pyridinediyl, pyrimidinediyl, thiophenediyl, furandiyl or thiazolediyl which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;
• R.sup.1 is hydrogen, (1-4C)alkyl, (3-4C)alkenyl or (3-4C)alkynyl;
• and
• R.sup.2 and R.sup.3 together form a group of the formula --A.sup.2 --X.sup.2 --A.sup.3 -- which together with the carbon atom to which A.sup.2 and A.sup.3 are attached define a ring having 5 or 6 ring atoms, wherein each of A.sup.2 and A.sup.3 is independently (1-3C)alkylene and X.sup.2 is oxy, and which ring may optionally bear one or two substituents selected from hydroxy, (1-4C)alkyl and (1-4C)alkoxy;
• R.sup.3 is (1-4C)alkyl, (2-4C)alkenyl or (2-4C)alkynyl;
• or a pharmaceutically-acceptable salt thereof.