Water → benzyl 2-(hydroxymethyl)pyrrolidine-1-carboxylate

N-Carbobenzyloxy-L-proline (0.048 moles, 12.0 g) was dissolved in 50 ml THF and cooled to 0° C. Borane-methyl sulfide complex (0.05 moles, 25 ml of 2M in THF) was added dropwise. The reaction was stirred for 16 hours at room temperature and then cooled to 0° C. water (50 ml) was added dropwise. The solution was filtered. The solid was washed with ethyl acetate. The organic solutions were combined, washed with water, dried over sodium sulfate and concentrated to yield 10.3 g of N-carbobenzyloxy-2-hydroxymethyl pyrrolidine. N-carbobenzyloxy-2-hydroxymethyl pyrrolidine (0.038 moles, 9.0 g) and triethylamine (0.076 mole) were dissolved in 150 ml of chloroform. Tosyl chloride (0.0475 moles, 9.05 g) was added portionwise followed by dimethylaminopyridine (200 mg). The solution was stirred overnight at room temperature. Chloroform was added. The solution was washed with water, dried over sodium sulfate, and concentrated. The resulting tosylate (0.0385 moles, 15.0 g) and sodium cyanide (0.048 moles, 2.35 g) were dissolved in 150 ml DMSO. The reaction was heated to reflux until completion as measured by thin layer chromatography. The reaction was cooled; water was added. The intermediate was extracted with ethyl acetate and concentrated to yield 9.56 g of 2-pyrrolidineacetonitrile. The nitrile was hydrolyzed by dissolving in 150 ml ethanolic HCl and slowing adding water to the solution. The solution was then concentrated in vacuo. Ethyl acetate and sodium bicarbonate were added. The ethyl acetate solution was concentrated. The residue dissolved in ethyl acetate, filtered and concentrated. The resulting acetate was chromatographed on silica gel eluted with a gradient of 5.0-100% ethyl acetate in hexane followed by a gradient of 0-20% ethanol in ethyl acetate to yield 4.35 g of ethyl 2-pyrrolidineacetate. (MS)