Crystal structure and conformation of N-(t-Butoxycarbonyl)-L-isoleucyl-L-valine methyl ester (Boc-Ile-Val-OMe)

摘要

N-(t-Butoxycarbonyl)-L-Isoleucyl-L-Valine Methyl ester, C17H32N2O5, F W. = 344.46, crystallizes in hexagonal space group P65 with parameters, a=b = 20.28565), c=27.160(5)&ANGS;(3), Z=18, Dcal = 1.064 Mg cm(-3), λ(CuKα)= 1.5478&ANGS;, μ(CuKα). The dipeptide Boc-Ile-Val-OMe has three crystallographically indepedlent molecules A, B, and C in the asymmetric unit. The peptide units are in trans conformation and the three molecules adopt an extended conformation. The side chains of isoleucine and valine for the three molecides A, B, and C take up g(-)t, g(-)g(-), and g(-)t; and g(-)g(+), g(+)t, and tg(-) conformations, respectively. The molecides form an infinite ribbon of β-sheet structure, which, in turn forms helical arrangement along the c-direction. They are stabilized by N-H••• 0 C-H••• 0 types of intermoleular interactions.