Use of pentanoate derivant

The compound of the formula (I) : wherein R is alkyl substituted by fluorine(s); R is hydroxy, alkoxy, alkoxy substituted by phenyl, NR R , in which R , R is (i) hydrogen, (ii) alkyl, (iii) phenyl, (iv) phenyl substituted by alkoxy or carboxyl, (v) heterocyclic ring containing nitrogen atom, (vi) alkyl substituted by phenyl, phenyl substituted by alkoxy or carboxyl, heterocyclic ring containing nitrogen atom, (vii) the nitrogen bonded to R and R , taken together a saturated heterocyclic ring or amino acid residues; and non-toxic salts thereof and acid addition salts thereof. The compounds of the present invention of the formula (I) and the compounds of the formula (X): wherein n is 0 or 1, R is hydrogen and chlorine, R is R -CH2- or R , or R and R , taken together is alkylidene; R is hydroxy, alkoxy, alkoxy substituted by phenyl, NR R , in which R , R is (i) hydrogen, (ii) alkyl, (iii) phenyl, (iv) phenyl substituted by alkoxy or carboxyl, (v) heterocyclic ring containing nitrogen atom, (vi) alkyl substituted by phenyl, phenyl substituted by alkoxy or carboxyl, heterocyclic ring containing nitrogen atom, (vii) the nitrogen bonded to R and R , taken together a saturated heterocyclic ring or amino acid residues, R is (i) F-(CH2)m- or F3C-CH2- , (ii) alkyl substituted by chlorine, (iii) alkyl substituted by alkoxy, cycloalkyl, phenyl, phenoxy; R is alkyl, alkenyl, alkoxy, alkylthio, cycloalkyl, phenyl, phenoxy; non-toxic salts and acid addition salts thereof are useful for prevention and / or treatment for neurodegenerarive disease (Alzheimer's disease etc.) and neuronal dysfunction by stroke or traumic injury (Multiple sclerosis etc.) etc..