A new natural product, 2(S),3(S)-3-hydroxy-4-methyleneglutamic acid (G3) has been isolated from seeds of Gleditsia caspica. The structure has been established by chemical and spectroscopic methods. Catalytic reduction of G3 yields 2(S),4(S)-4-methylglutamic acid and a new amino acid, 2(S).3(S),4(S)-3-hydroxy-4-methylglutamic acid. Ozonolysis of G3 followed by oxidation gives 2(S),3(R)-3-hydroxyaspartic acid. The S- (or L-) configurations at CZ in G3 and in 2(S),3(S)$(S)-3-hydroxy-4-methyglutamic acid and the S-configurations at C, for G3 and 2(S),3(S).4(S)-3-hydroxy-4-methylglutamic acid and at C4 for 2(S),3(S).4(S)-3-hydroxy-4-methylglutamic acid are inferred from the configurations at C, in 2(S),4(S)-4-methylglutamic acid and at Cz and C, in 2(S),3(R)-3 hydroxyaspartic acid. The seeds also contain appreciable quantities of 2(S),3(S),4(R)-3-hydroxy-4-methylglutamic acid (Gl) and 2(S),4(R)-4-methylglutamic acid.