Amoxicillin EP Impurity C Catalogue A536303 CAS 2088961-37-7 M.W 365.40 M.F C16H19N3O5S Specifications FAQs (4S)-2-[5-(4-Hydroxyphenyl)-3,6-dioxopiperazin-2-yl]-5,5-dimethylthiazolidine-4-carboxylic acid