title: Conformational polymorphism in sulfonylurea drugs: electronic structure analysis.
abstract: Quantum chemical calculations have been performed using HF, B3LYP, and MP2 methods on the model sulfonylurea PhSO(2)NHC(=O)NHMe to understand the conformational and tautomeric preferences. The results indicate that a conformer with intramolecular hydrogen bond SLU-1 (hitherto not considered) is more stable than the conformer SLU-2 (which is generally considered) for sulfonylureas. The energy difference between these two conformers is about 4 kcal/mol in the gas phase; however, the energy differences between the two rotamers become negligible in the solvent phase. Iminol tautomeric forms of sulfonylurea (which were also not studied until now) are only about 5-6 kcal/mol higher in energy as per both gas-phase and solvent-phase analyses, indicating easy accessibility of tautomeric states in sulfonylureas. Quantum chemical analysis has also been carried out on the possible dimeric structures of these three important isomers of sulfonylurea, and correlations have been made to the known crystal structures of polymorphic states of sulfonylurea drugs.
authors: Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S. A. S. Nagar 160 062, Punjab, India.
authors: Yoganjaneyulu
authors: Y
authors: Kasetti
authors: Nikunj K
authors: NK
authors: Patel
authors: Sandeep
authors: S
authors: Sundriyal
authors: Prasad V
authors: PV
authors: Bharatam
mesh_terms: D005740:Gases / Q000737:chemistry; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D011789:Quantum Theory; D013453:Sulfonylurea Compounds / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D005740:Gases; D013453:Sulfonylurea Compounds