To a solution of crude compound A in N,N-dimethyl-formamide (5 mL) is added K2CO3 (1.16 g, 8.4 mmol) and benzyl bromide (665 uL, 5.6 mmol). The solution is stirred at room temperature for 1 hr. The mixture is diluted with EtOAc and washed with brine. The organic layer is dried and concentrated under vacuum. The residue is purified by flash column chromatography (Hexanes/EtOAc) to provide 404 mg of the title compound M+H+=330, and 401 mg of the other region isomer (S)-2-(1-Benzyl-1H-tetrazol-5-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (C). M+H+=330. Combined yield is 87% for 2 steps.
