Yield:-

Steps:

Multi-step reaction with 3 steps
1.1: benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; N-ethyl-N,N-diisopropylamine / N,N-dimethyl-formamide / 12 h / 0 - 25 °C / Inert atmosphere
2.1: lithium hydroxide monohydrate; water / tetrahydrofuran / 2 h
3.1: 4-methyl-morpholine; isobutyl chloroformate / tetrahydrofuran / 1 h / -25 - -15 °C / Inert atmosphere
3.2: 4 h / -78 - 0 °C / Inert atmosphere

References:

Yang, Peng-Yu;Wang, Min;Li, Lin;Wu, Hao;He, Cynthia Y.;Yao, Shao Q. [Chemistry - A European Journal,2012,vol. 18,# 21,p. 6528 - 6541]