(3S,4S)-Tofacitinib (Tofacitinib Impurity C) is a less active enantiomer of Tofacitinib (
tasocitinib;
CP-690550; Xeljanz), which is an inhibitor of JAK3 (Janus-Associated kinase) and an FDA approved drug for the treatment of rheumatoid arthritis (RA),
psoriatic arthritis, and ulcerative colitis. 
m.cnreagent.com
