Morpholine derivatives, compositions and medicinal use

Compounds of formula (I): (I) or a salt thereof, in which W is phenyl optionally substituted by halogen or trifluoromethyl, or a benzofuran-2-yl group, R1 is hydrogen or methyl, R2 is carboxyl or a group O-Z-CO2 H or an ester or amide thereof; a group O-E-NR3R4 or a group O-E-OR5, wherein R3, R4 and R5 each represents hydrogen or C1-6 alkyl, Z is a C1-6 straight or branched alkylene chain, n is 1 or 2, a is 2 or 3, and E is a C2-7 straight or branched alkylene chain with at least two carbon atoms separating the two heteroatoms in the group R2; a process for the production of such compounds and their use in treating hyperglycaemia and/or obesity.