A salt selected from the group consisting of: (R) -3- (4- (7H-pyrrolo [2,3-d] pyrimidin-4-yl) -1 H-pyrazol-1-yl) phosphoric acid salt -3-cyclopentylpropanonitrile； sulfuric acid salt of (R) -3- (4- (7 H -pyrrolo [2,3-d] pyrimidin-4-yl) -1 H -pyrazol-1-yl) -3-cyclopentylpropanonitrile； and (R) -3- (4- (7H-pyrrolo [2,3-d] pyrimidin-4-yl) -1 H-pyrazol-1-yl) -3-cyclopentylpropanitrile maleic acid salt； in which the salt is crystalline.Una sal seleccionada del grupo que consiste en: sal de ácido fosfórico de (R)-3-(4-(7H-pirrolo[2,3-d]pirimidin-4-il)-1 H-pirazol-1-il)-3-ciclopentilpropanonitrilo ； sal de ácido sulfúrico de (R)-3-(4-(7H-pirrolo[2,3-d]pirimidin-4-il)-1 H-pirazol-1-il)-3-ciclopentilpropanonitrilo； y sal de ácido maleico de (R)-3-(4-(7H-pirrolo[2,3-d]pirimidin-4-il)-1 H-pirazol-1-il)-3-ciclopentilpropanitrilo； en la que la sal es cristalina.
