To a solution of (2R,5R)-1-((4-chlorophenoxy)methyl)carbonyl-2-methyl-4-(4-fluorobenzyl)-5-((hydroxy)methyl)piperazine (0.17 g, 0.42 mmol) in CH2Cl2(50 mL) at 0° C. was added triethylamine (excess) and methane sulfonyl chloride (0.050 mL, 0.5 mmol). The resultant mixture was stirred at 0° C. until consumption of alcohol was observed by TLC analysis. The mixture was concentrated of volatiles in vacuo. Residue was taken up in anhydrous DMF (5 mL) and K2CO3 (excess) added, followed by tetrazole (0.050 g, 0.71 mmol). The resulting mixture was stirred at ambient temperature for 3 days and filtered. The filtrate was concentrated in vacuo and the residue taken up in ethyl acetate. This was washed with water then brine, then dried over MgSO4 and concentrated in vacuo to afford a yellow oil. Purification by flash column chromatography on silica gel afforded 25 mg of (2R,5R)-1-((4-chlorophenoxy)methyl)carbonyl-2-methyl-4-(4-fluorobenzyl)-5-((tetrazolyl)methyl)piperazine as a white solid: NMR (CDCl3) 7.3 (m, 5), 7.0 (m, 4), 4.8-4.1 (m, 5), 3.8 (m, 3), 3.2 (m, 2), 2.8 (dd, 1), 2.5 (dd, 1), 1.4 (d, 3) ppm, MS (ESI) 458.
