Crystal structure and electrostatic properties of prednisolone acetate studied using a transferred multipolar atom model.

Prednisolone acetate {systematic name: 2-[(8S,9S,10R,13S,14S,17R)-11,17-dihydroxy-10,13-dimethyl-3-oxo-6,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-3H-cyclopenta[a]phenanthren-17-yl]-2-oxoethyl acetate}, is an ophthalmic drug that belongs to the class of corticosteroids. Its crystal structure was refined using the classical independent atom model (IAM) and a transferred multipolar atom model using the ELMAM2 database. The results of both refinements have been compared. The ELMAM2 refinement was found to be superior in terms of the refinement statistics. It has been shown that certain electron-density-derived properties can be calculated on the basis of the transferred parameters for crystals which diffract to ordinary resolution. The procedure proves helpful in understanding the mode of action of the drug molecule.