159694-16-3 2-Hydroxypenta-2,4-dienoate 2-hydroxy-2,4-pentadienoate 2-keto-4-pentenoate 2-keto-4-pentenoic acid 2-ketopent-4-enoic acid 2-oxopent-4-enoate OXOPENTENOATE cis-2-Hydroxypenta-2,4-dienoate oxopent-4-enoate