Amoxicillin Diketopiperazine ; (4S)-2-[5-(4-hydroxyphenyl)-3,6-dioxopiperazin-2-yl]-5,5- dimethylthiazolidine-4-carboxylic acid ;Amoxicillin Sodium - Impurity C (EP); (4S)-2-[5-(4-Hydroxyphenyl)-3,6-dioxo-2-piperazinyl]-5,5-dimethyl-4-thiazolidinecarboxylic Acid; 4-Thiazolidinecarboxylic acid, 2-[5-(4-hydroxyphenyl)-3,6-dioxo-2-piperazinyl]-5,5-dimethyl-, (4S)-; Amoxicillin rearrangement product; (4S)-2-[5-(4-Hydroxyphenyl)-3,6-dioxopiperazin-2-yl]-5,5-dimethylthiazolidine-4-carboxylic Acid; Amoxicillin Related Compound C (USP);