A compound that is crystalline 1- (2,2-difluoro-2-deoxy-β-D-ribofuranosyl) -4- (2-propyl-1-oxopentyl) mono-p-crystalline aminopyrimidin-2-one or hemibenzenesulfonate of 1- (2,2-Difluoro-2-deoxy-β-D-ribofuranosyl) -4- (2-propyl-1-oxopentyl) aminopyrimidin-2-one crystalline hemihydrate.Un compuesto que es mono-p-toluenosulfonato de 1-(2,2-difluoro-2-desoxi-β-D-ribofuranosil)-4-(2-propil-1-oxopentil)aminopirimidin-2-ona cristalino y o hemibencenosulfonato de 1-(2,2-difluoro-2-desoxi-β-D-ribofuranosil)-4-(2-propil-1-oxopentil)aminopirimidin-2-ona hemihidrato cristalino.