Compounds of the formula (I) in which R.sup.1 is C.sub.1-10 allyl; C.sub.2-10 alkenyl; C.sub.2-10 alkynyl; phenyl-C.sub.2-10 alkyl or phenyl-C.sub.2-10 alkenyl; and salts and esters thereof, modulate metabotropic glutamate receptor function and are useful in treating disorders of the central nervous system ##STR1##

Residui della formula (i) in cui R.sup.1 è allilico C.sub.1-10; Alchenile C.sub.2-10; Alkynyl C.sub.2-10; alchile phenyl-C.sub.2-10 o alchenile phenyl-C.sub.2-10; ed i sali e gli esteri di ciò, modulano la funzione metabotropic del ricevitore del glutammato e sono utili nei disordini trattanti del ## del ## STR1 del sistema nervoso centrale