A diastereomeric mixture. of tert-butyl 1-oxo-4-phenyl-2,8-diazaspiro[4.6]undecane-8-carboxylate (step 4) (669.5 mg; 1.944 mmol) in THF (19.5 ml) under nitrogen was cooled in an ice/brine bath. 1M LHMDS (2.5 ml, 2.53 mmol) was added and the mixture was stirred at 0° C. for 40 minutes. Iodomethane (182 ul, 2.92 mmol) was added and the mixture was allowed to warm slowly to RT overnight. The reaction was quenched with saturated ammonium chloride solution and extracted with EtOAc. The combined organic extracts were washed with brine, dried (MgSO4) and concentrated in vacuo. Purification by chromatography on silica eluting with EtOAc afforded the title compound;
