diethyl (2R,3R)-2-bromo-3-hydroxybutanedioate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 2a (38.1 g, 142 mmol) was dissolved in anhydrous Et2O (100 ml) and DBU (32.3 g, 212.4 mmol, in Et2O [50 ml]) was added dropwise at 0° C. for 1 h. The reaction was allowed to warm to r.t. and stirred for an additional 4 h. Reaction was quenched with cold 1N HCl to pH˜5. The resulting aqueous layer was extracted with Et2O (3×150 ml). The combined organic extracts were washed with brine (2×100 ml), dried over Na2SO4, and concentrated to give the pure product as faintly yellow oil (21.5 g, 80.7% yield). Product purity typically reflects that of the bromohydrin starting material. If necessary, fractional vacuum distillation can be used for purification. 1H NMR (CDCl3, 400 MHz): δ 4.36-4.22 (m, 4H); 3.67 (s, 2H); 1.35-1.31 (t, 6H). 13C NMR (CDCl3, 100 MHz): 166.75, 62.21, 52.01, 14.01. Reaction was quenched with cold 1N HCl to pH˜5 The resulting aqueous layer was extracted with Et2O (3×150 ml) The combined organic extracts were washed with brine (2×100 ml) dried over Na2SO4 concentrated