Betamethasone Dipropionate EP Impurity D (Betamethasone 21-Acetate 17-Propionate);(8S,9R,10S,11S,13S,14S,16S,17R)-17-(2-acetoxyacetyl)-9-fluoro-11-hydroxy-10,13,16-trimethyl-3-oxo-6,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-3H-cyclopenta[a]phenanthren-17-yl propionate