A solution of 80 mg (0.14 mmol) (R)-1-(4-methyl-2-oxo-2,3-dihydro-benzoxazol-6-ylmethyl)-2-oxo-2-(4-oxo-piperidin-1-yl)-ethyl 4-(2-oxo-1,2,4,5-tetrahydro-1,3-benzodiazepin-3-yl)-piperidine-1-carboxylate and 32 mg (0.27 mmol) thiomorpholin-1-oxide in 5 mL DCM was stirred overnight at RT. After the solution had been cooled to 0° C., 15 μL (0.27 mmol) of AcOH and 50 mg (0.33 mmol) of sodium triacetoxyborohydride were added and the reaction mixture was stirred for 4 h at this temperature. It was evaporated down i.vac., the residue was taken up in 1 mL MeOH, filtered to remove any insoluble constituents and the crude product was purified by HPLC. The fractions containing the product were combined and lyophilised.
