title: Conformational preferences of cyclopropyl peptides. Crystal structure of (E)-DL-1-benzamido-1-methoxycarbonyl-2-chlorcyclopropane (BCP).
abstract: Crystal structure analysis of (E)-DL-1-benzamido-1-methoxycarbonyl-2-chlorocyclopropane (C12H12NO3Cl) is reported. The phi' (about N1-C1 bond) and psi' (about C1-C11 bond) torsional angles for this compound are -62.5 degrees and -33.0 degrees, respectively, and are close to the phi, psi values of the 3(10) helix and the alpha-helix. Semi-empirical potential energy calculations are performed on a cyclopropyl dipeptide which is a special case of alpha,alpha-disubstituted dipeptide where the alpha-carbon and the two substituent carbon atoms form a 3-membered ring. Our calculations show that different types of helics: alpha-, gamma-, pi-, omega-, 3(10-) and delta-helices, are energetically favorable. Another interesting possibility is the formation of a cyclic pentapeptide with five-fold symmetry. The effect of substitutions on C beta atom are also studied with the help of potential energy maps. Selective substitutions on C beta atom may be used effectively to restrict either phi or psi values into a very narrow range.
mesh_terms: D003521:Cyclopropanes; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D011487:Protein Conformation; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D003521:Cyclopropanes; C047209:1-benzamido-1-methoxycarbonyl-2-chlorocyclopropane