Pyrrolo[2,3-d] Pyrimidine Compounds.

A compound of formula (I) wherein R1,R2 and R3 are as defined above, which are inhibitors of the enzyme protein kinases such as Janus Kinase 3 and as such are useful therapy as immunosuppressive agents for organ transplants, xeno transplantation, lupus, multiple scelerosis, rheumatoid arthritis, psoriasis, Type I diabetes and complications from diabetes, cancer, asthma, atopic dermatitis, autoimmune thyroid disorders, ulcerative colitis, Crohn's disease, Alzheimer's disease, Leukemia and other autoimmune diseases.