Methanol → Thionyl Chloride

Methanol (400 mL) was cooled to 0° C. and thionyl chloride (217 mL, 3.0 moles, 20 eq) was added dropwise under argon. After addition was completed, the solution was warmed to RT for 20 min. 2(S),3-Diaminopropanoic acid 2-1 (20 g, 0.143 mole) (Schweizerhall Chemicals) was crushed to a fine powder and added to the solution. The reaction was heated to reflux for 48 h, at which time TLC showed a small amount of starting material remaining. An additional portion of methanol (100 mL) and thionyl chloride (72 mL) was prepared as before and added to the reaction at RT; the reaction was then stirred overnight at RT. The reaction was worked up by removal of solvent at 40° C. in vacuo to give 2-2 as foam. Rf 0.72 (9:1:1 EtOH/H2O/NH4OH). 1H NMR (400 MHz, D2O) δ4.55 (dd, J=5.4 8.2 Hz, 1H), 3.92 (s, 3H), 3.64 (dd, J=8.2, 13.8 Hz, 1H), 3.55 (dd, J=5.4, 13.8 Hz, 1H).