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A compound of formula I ##STR9## wherein:

• R is naphthyl;
• X.sup.1 is --(CH.sub.2).sub.n --, --(CH.sub.2).sub.m --O--(CH.sub.2).sub.n -- or --(CH.sub.2).sub.m --NR.sup.0 --(CH.sub.2).sub.n --, where
• m and n are independently 0, 1 or 2;
• R.sup.0 is hydrogen or C.sub.1 -C.sub.4 alkyl;
• R.sup.1 is phenyl;
• R.sup.2 is cyno(C.sub.1 -C.sub.4)alkyl
• Y is phenyl;
• R.sup.3 is a group having the structure:
• ##STR10## where p is 4 or 5;
• R.sup.4 at each occurrence is independently hydrogen, C.sub.1 -C.sub.6 alkyl or hydroxy(C.sub.1 -C.sub.4)alkyl;
• R.sup.5 and R.sup.6 are independently selected from hydrogen, hydroxy, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, amino, C.sub.1 -C.sub.4 alkylamino, hydroxy(C.sub.1 -C.sub.4)alkyl, carboxy, C.sub.1 -C.sub.4 alkoxycarbonyl, carbamoyl, N-(C.sub.1 -C.sub.4)alkylcarbamoyl, and aryl;
• or a pharmaceutically acceptable salt thereof.