Patent ID: 8076493

Claim:
A compound of formula (I), or a geometrical isomer, enantiomer, or diastereoisomer thereof, wherein, R 1 is —COOH, —COOM or —COOR 4 , R 2 is hydrogen or C 1-10 alkyl, R 3 is C 1-10 alkyl or C 2-6 alkenyl, X is —CONR 5 R 6 , —COOH, —COOR 4 or —CN, M is an alkali metal, R 4 is C 1-10 alkyl, R 5 is hydrogen or C 1-10 alkyl, R 6 is hydrogen or C 1-10 alkyl, 1* and 2* denote a stereogenic center, provided that compound of formula (I) is not 1-((1S)-1-carbamoyl-propyl)-2-oxo-pyrrolidone-3-carboxylic acid or 2(S)(3-carboxy-2-oxo-1-pyrrolidinyl)-4-methyl pentanoic acid methyl ester.