(-)-Catechol (2S-trans)-2-(3,4-Dihydroxyphenyl)-3,4-dihydro-2H-1-benzopyran-3,5,7-triol 18829-70-4 1H-Benzopyran-3,5,7-triol, 2-(3,4-dihydroxyphenyl)-3,4-dihydro-, (2S,3R)- Catechin l-form Catechin, alpha EINECS 242-611-7 NSC 81746