(4S)-2-methyl-3,4,5,6-tetrahydropyrimidine-4-carboxylic acid L-Ectoine E2271_SIGMA (S)-2-Methyl-1,4,5,6-tetrahydropyrimidine-4-carboxylic acid 81619_FLUKA 1,4,5,6-Tetrahydro-2-methyl-4-pyrimidinecarboxylic acid C06231 (4S)-2-methyl-3,4,5,6-tetrahydropyrimidin-1-ium-4-carboxylate ZINC01612568