u2014 cooch 3 phenyl cyclopropyl cyclopentyl cyclohexyl pyridyl furyl thienyl or oxazolyl and r 7 may be for example h or when taken together with the atom or atoms to which they are attached r 6 and r 7 may form a heterocyclic ring of 5 6 or 7 members specific examples of r 4 groups include those present in the compounds of the examples herein compounds of the invention may be prepared by synthetic methods known in the literature from compounds which are commercially available or are accessible from commercially available compounds for example compounds of formula i wherein r 4 is a group u2014 nr 7 c u2550 o r 6 may be prepared by acylation of an amine of formula ii with an acid chloride of formula iii compounds of the invention wherein r 4 is a group u2014 nhc u2550 o nhr 6 may be prepared by reaction of an amine of formula iia with an isocyanate of formula iiia compounds of the invention wherein r 4 is a group u2014 c u2550 o nhr 6 may be prepared by reaction of an acid chloride of formula iib with an amine nhr 6 r 7 compounds of the invention wherein r 4 is a group u2014 nr 7 c u2550 o or 6 may be.