Tert-butyl ((3S,4S,5R)-1-(3-((tert-butoxycarbonyl)amino)pyridin-4-yl)-4-cyano-5-methylpiperidin-3-yl)carbamate (1.0 equiv.) was treated with 4 M HCl in dioxane (30.0 equiv.) at rt for 1 hour. The volatiles were removed in vacuo and the solid was pumped on for 5 minutes on the high vac. To the residue was added CH2Cl2 (0.05 M), DIEA (5.0 equiv.) and Boc-OSu (1.6 equiv.). The solution was left stirring at rt for 1 hr. The volatiles were removed in vacuo and the residue was partitioned between EtOAc and H2O. The organic layer was washed with Na2CO3(sat.), NaCl(sat.), dried over MgSO4, filtered, concentrated to yield tert-butyl (3S,4S,5R)-1-(3-aminopyridin-4-yl)-4-cyano-5-methylpiperidin-3-ylcarbamate in 100% yield. LC/MS (m/z)=332.1 (MH+), Rt=0.59 min.
