Z-NVA-OH is also known as Cbz-L-norvaline. It could be used to synthesise Z-Nva-Ser(Bu’)-Gly-OPh. In specific steps, as follows: the protected dipeptide(53.1 g. 124mM) and Tos.OH.H2O (33.6g. 124mM) were dissolved in DMF (200) and hydrogenolysed overnight in the presence of 10% Pd/C (6g), then filtered and concentrated to 100ml. Z-Nva-OH (37.4g. 149mM) was dissolved in CH2Cl2 (170ml) and NMM (16.4ml. 149mM) added. After cooling to -20℃, pivaloyl chloride (17.8ml. 145 mM) was added, and the solution was stirred for 20 minutes before the precooled DMF solution from above was added. Following the addition of NMM (13.6 ml, 124 mM), the reaction was stirred at - 20℃ for 3 hr, then maintained at room temperature overnight. The solution was evaporated, and the product dissolved in EtOAc. Washing with acid and base in the usual way, followed by crystallisation from EtOAc/petroleum ether yielded Z-Nva-Ser(Bu’)-Gly-OPh[1].
