(R)-4-(4'-Hydroxyphenyl)oxazolidine-2,5-dione

(R)-4-(4-Hydroxyphenyl)-2,5-oxazolidinedione is a cyclic anhydride and intermediate in the synthesis of 3-(4-Hydroxyphenyl)-2(1H)-pyrazinone (H951260), which is a potential impuritiy of the penicillins, ampicillin and amoxicillin, which have not been reported previously. 3-(4-Hydroxyphenyl)-2(1H)-pyrazinone impurity may be formed during the semi-synthetic preparation of these antibiotics or upon their degradation.