CAS 178738-48-2 and 178738-49-3 is the registry number for (2RS,4S)-2-((((2R)-2-Amino-2-(4-hydroxyphenyl)acetyl)amino)methyl)-5,5-dimethylthiazolidine-4-carboxylic Acid (Penilloic Acids of Amoxicillin). Offered by: Mikromol. Available pack sizes: 50mg.