Methylprednisolone EP Impurity E Catalogue G112645 CAS 229019-44-7 M.W 344.45 M.F C21H28O4 Specifications FAQs (6S,8S,9S,10R,11S,13S,14S,17S)-11-hydroxy-6,10,13-trimethyl-3-oxo-6,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-3H-cyclopenta[a]phenanthrene-17-carboxylic acid