A solution of tert-butyl carbamate (7.06 g) in n-propanol (120 mL) was sequentially treated with 0.4M. NaOH (218 mL) and tert-butyl hypochlorite (10.6 mL; freshly prepared as described in Org. Lett. (2003), 5 (12), 2123-2126 (S-2)). The reaction mixture was treated with a solution of (DHQD)2PHAL (565 mg) and (DHQ)2PHAL (565 mg) in n-propanol (100 mL) and after 5 min cooled to 10° C. and sequentially treated with a suspension of intermediate BQ.i. (7.07 g) in water/n-propanol (1:1; 140 mL) and potassium osmate(VI) dihydrate (428 mg). After stirring at +10° C. for 20 min the reaction mixture was treated with Na2SO3 (15 g) and further stirred at rt for 10 min. The reaction mixture was extracted with EA and the org. layer was sequentially washed with 5% aq. K2CO3, sat. aq. NaHCO3 and brine. After drying over MgSO4 and evaporation of the solvent, the residue was purified by CC (DCM/MeOH 10-1 containing 1% NH4OH), affording a pale yellow foam (6.85 g; 63% yield).
