2H-1,4-Thiazine-3-carboxylic acid, 5,6-dihydro- 2H-1,4-Thiazine-5,6-dihydro-3-carboxylic acid 68006-11-1 AECK Aminoethylcysteine-ketimine S-Aminoethyl-L-cysteine ketimine Thialysine ketimine