Compounds of the formula (I) in which: R.sup.1 is (CH.sub.2).sub.nY; n is 1 or 2; Y is NHSO.sub.2R.sup.2 or X.sup.1--W--X.sup.2--R.sup.3; X.sup.1 is O or NH; W is C.dbd.O, C.dbd.S, C.dbd.NH, or SO.sub.2; X.sup.2 is O or NH, provided that X.sup.1 and X.sup.2 are not both O; R.sup.2 is C.sub.1-10 alkyl; C.sub.2-10 alkenyl; C.sub.2-10 alkynyl; aryl; aryl-C.sub.1-10 alkyl; aryl-C.sub.2-10 alkenyl; aryl-C.sub.2-10alkynyl; C.sub.3-8 cycloalkyl or C.sub.3-8-cycloalkyl-C.sub.1-10 alkyl; and R.sup.3 is hydrogen, C.sub.1-10alkyl; C.sub.2-10 alkenyl; C.sub.2-10 alkynyl; aryl; aryl-C.sub.1-10 alkyl; aryl-C.sub.2-10 alkenyl; aryl-C.sub.2-10 alkynyl; C.sub.3-8 cycloalkyl; or C.sub.3-8-cycloalkyl-C.sub.1-10 alkyl; or a salt or ester thereof, modulate metabotropic glutamate receptor function and are useful in treating disorders of the central nervous system.