N-(tert-Butoxycarbonyl)-L-serine beta-lactone

3262-72-4

98541-64-1

The general procedure for the synthesis of N-(tert-butoxycarbonyl)-L-serine-β-lactone (AA2-1) from Boc-L-serine was as follows: to a dry 250 mL three-necked flask (equipped with a mechanical stirrer) under nitrogen protection was added triphenylphosphine (4.5 g, 17.1 mmol, 1.1 equiv.) and 100 mL of anhydrous THF:CH3CN (1:9 ) solvent mixture. The mixture was stirred until completely dissolved and then cooled to -55 °C (bath temperature). Dimethyl azodicarboxylate (DMAD, 1.9 mL, 17.1 mmol, 1.1 eq.) was slowly added dropwise over 10 minutes. After dropwise addition, stirring was continued for 20 minutes. Subsequently, Boc-Ser-OH (3.18 g, 15.5 mmol, 1.0 eq.) dissolved in 50 mL of anhydrous THF:CH3CN (1:9) was added dropwise over 30 minutes. The reaction mixture was stirred at -55 °C for 1.5 h. After removing the cooling bath, the reaction solution was allowed to slowly warm up to room temperature. After reaching room temperature, the solvent was removed by concentration under reduced pressure. The resulting yellow oil was purified by fast column chromatography [elution gradient: hexane:EtOAc (80:20) to (60:40)] to give 2.10 g AA2-1 as a white solid in 72% yield. It is recommended that purification of the feedstock be completed on the day of the reaction to avoid decomposition. DCM can be added if necessary to help dissolve the crude product.TLC assay conditions (Hex/EtOAc, 60/40): rf = 0.55 (CMA).