3-[6-bromo-3,5-dioxo-4-(phenylcarbonyl)-4,5-dihydro-1,2,4-triazin-2(3H)-yl]propanal (P7, 201 mg, 0.572 mmol) was dissolved in dry 1,2-Dichloroethane (DCE) (1.144 mL), then 1-methyl-5-[4-(trifluoromethyl)phenyl]-3-azabicyclo[3.1.0]hexane (P15, Enantiomer 2, 138 mg, 0.572 mmol) was added and the mixture was stirred at room temperature for 10 minutes. The mixture was then cooled to 0° C. and left stirring at that temperature for 15 minutes. Afterwards, sodiumtriacetoxy borohydride (133 mg, 0.629 mmol) was added and the mixture was stirred at 0° C. for 2 hours. In situ cleavage of the benzoyl nitrogen protecting group was observed. It was then quenched with NH4Cl saturated solution and extracted with DCM. Organic phase was dried and concentrated under reduced pressure affording a crude as a yellow oil. The latter was purified by flash chromatography (SiO2, eluent: DCM to DCM/MeOH 95:5) affording 6-bromo-2-(3-{1-methyl-5-[4-(trifluoromethyl)phenyl]-3-azabicyclo[3.1.0]hex-3-yl}propyl)-1,2,4-triazine-3,5(2H,4H)-dione (Enantiomer 2, 48 mg, 0.101 mmol, 17.73% yield) as a white powder.
