2-aminoprop-2-enoic acid 2-aminoacrylic acid 1948-56-7 28453-71-6 2,3-DIDEHYDROALANINE 2-AMINO-ACRYLIC ACID anhydroserine2-aminopropenoic acid CHEBI:17123 alpha-Aminoacrylate 2-Propenoic acid, 2-amino- 2-Aminoacrylate C02218 Dehydroalanine alpha,beta-dehydroalanine