title: Molecular structure of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea.
abstract: The three-dimensional structure  of  1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (MeCCNU, NSC-95441), an effective antitumor agent, has been determined by single-crystal x-ray diffraction. MeCCNU crystallizes in monoclinic space group P21/c, with  cell dimensions  a =  12.387, b  =  10.810, and  c  =  10 .198  A , beta  =  102.62  degrees , and  Z  =  four  molecules  per  unit  cell. The structure was solved by direct phasing procedures and refinement by anisotropic least squares converged at a discrepancy index R = 0.065. The cyclohexyl ring is in the chair conformation with the plane of the nitrosourea moiety twisted approximately 90 degrees from the cyclohexyl ring. The carbon-nitrogen bonds of the urea group are significantly asymmetric.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009607:Nitrosourea Compounds; D012673:Semustine
chemical_list: D009607:Nitrosourea Compounds; D012673:Semustine