title: C9 conformation of N-(N alpha-[(tert.-butyloxy)-carbonyl]-L-alanyl)-N,N'-dicyclohexylu rea in solid and solution.
abstract: An X-ray diffraction study was carried out on a single crystal of N-(N alpha-[(tert.-butyloxy)-carbonyl]-L-alanyl)-N,N'-dicyclohexylur ea belonging to the tetragonal space group P4(1)2(1)2, having cell dimensions a = b = 10.102(3) A, c = 46.067(7) A, V = 4701.2 A3, Z = 8. The crystal structure was solved by direct methods and refined to an R value of 0.056 for 1602 unique reflections with I greater than 2.5 sigma(I). Crystal structure analysis shows the presence of an intramolecular N-H ... O=C H-bond stabilizing the molecule in a folded form similar to that of a beta turn, forming a nine-membered ring. IR and 1H-NMR studies in CDCl3 solution confirm the stable folded conformation found in the crystalline state, as well as the existence of N-H ... O=C H-bonds in the title compound, as in peptides.
authors.affiliation: Department of Physics, Indian Institute of Technology, Madras.
authors.forename: C
authors.initials: C
authors.lastname: Sudarsanakumar
authors.forename: S
authors.initials: S
authors.lastname: Srinivasan
authors.forename: R
authors.initials: R
authors.lastname: Jayakumar
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D014508:Urea / Q000031:analogs & derivatives* / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: C077700:N-(N(alpha)-(tert-butyloxycarbonyl)alanyl)-N,N'-dicyclohexylurea; D014508:Urea; D000409:Alanine