Triethylamine → methyl N-(6-cyanohexyl)-D-serinate

To a solution of D-serine methyl ester hydrochloride (0.91 g) in ethanol (18 mL) was added 7-oxoheptanenitrile (0.67 g) and triethylamine (0.6 mL) (see: Kubodera, N. et al, Heterocycles 1982, 19, 1285) and the mixture was stirred under N2 for 1 h. To the solution was then added Na(CN)BH3 (0.4 g) and the resultant cloudy suspension was further stirred under N2 for 1 h. The mixture was quenched with water and concentrated in vacuo and the residue diluted with ethyl acetate/saturated NaHCO3. The organic layer was separated and the aqueous layer extracted with ethyl acetate (3×). The organic layers were washed with water, brine, dried over Na2SO4 and filtered. The filtrate was concentrated and the residue was purified by chromatography. Eluting with 5–10% (v) methanol in dichloromethane gave the desired product 2-1 (620 mg). 1H NMR (400 MHz, CDCl3): δ 3.78 (m, 1H), 3.77 (s, 3H), 3.59 (dd, 1H), 3.38 (dd, 1H), 2.72 (m, 1H), 2.53 (m, 1H), 2.36 (t, 2H), 1.70 (m, 2H), 1.55–1.35 (m, 6H).