Efficient synthesis of CN2097 using in situ activation of sulfhydryl group.

CN2097 (RCs-sCYK[KTE(β-Ala)]V) is a rationally designed peptidomimetic that shows effectiveness in preclinical models for the treatment of neurological disorders, such as Angelman syndrome, traumatic brain injury (TBI) and stroke. Because of its therapeutic activity for the treatment of human CNS disorders, there was an urgent need to develop an efficient strategy for large-scale synthesis of CN2097. The synthesis of CN2097 was accomplished using Fmoc/tBu solid phase chemistry in multiple steps. Two different peptide fragments (activated polyarginine peptide Npys-sCR and CYK[KTE(β-Ala)]V) were synthesized, followed by solution phase coupling in water. Activation of the polyarginine (CR) was achieved in situ during cleavage of protected peptide (C(Trt)R(Pbf)) from the Rink amide resin using 5 equiv. of 2,2-dithopyridine in TFA:TIS:HO (95:2.5:2.5, v/v/v) for 4 h. The disulfide coupling was efficient which provided a 60% yield.