Estradiol Valerate EP Impurity B Catalogue C206532 CAS 21881-45-8 M.W 356.51 M.F C23H32O3 Specifications FAQs (8R,9S,13S,14S,17S)-17-hydroxy-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthren-3-yl pentanoate