(2R,3R)-2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychroman-4-one (2R,3R)-2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-chroman-4-one (2R,3R)-2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4-chromanone 18422-83-8 NSC327431