(S)-3-Formylpyrrolidine-1-carboxylic acid t-butyl ester (2.8 g, 13.8 mmol) was dissolved in THF (50 mL) under nitrogen and cooled at −78° C. Cyclohexylmagnesium chloride (2.0M in ether; 10.0 mL, 20.0 mmol, 1.4 eq) was added via syringe over approximately 10 minutes. The resulting mixture was stirred at −78° C. for 20 minutes, then placed in an ice bath for 30 minutes. The reaction was quenched with saturated aqueous NH4Cl (15 mL). THF was removed under reduced pressure, and the remaining material was extracted with EtOAc (3×30 mL). The organics were washed with water (25 mL) and saturated aqueous NaCl (25 mL), dried over Na2SO4, and concentrated to yield the crude product. This material was dissolved in MeCN (10 mL), water (8 mL), and MeOH (11 mL). The material was purified by preparative HPLC in 3 portions (2″ C18 column; 20-50% MeCN over 1 hour; the desired compound was recovered at ˜46%). The fractions were collected from the first eluting and second eluting, separately, and the MeCN was removed. Each fraction was extracted with DCM (3×125 mL), dried over Na2SO4, and concentrated to yield (S)-3-((S)-cyclohexylhydroxymethyl)pyrrolidine-1-carboxylic acid t-butyl ester (1.1 g; 1st eluting peak) and (S)-3-((R)-cyclohexylhydroxymethyl)pyrrolidine-1-carboxylic acid t-butyl ester (1.7 g; 2nd eluting peak).
