version date: 1 December 2006 tools, whole substructures ready in the program and the dialog box, where formulae in linear representation are typed. In parallel, molecules generated in ChemDraw(copy)can be converted to the 3D model in Chem3D (paste), as shown in Fig. 2 for sulfamethoxazole(3) CH3 H2N (3) Fig. 2 Conversion of the 3D sulfamethoxazole (3)structure into the cylindrical bond 3D display( ChemDraw- Chem In the Chem3D program, the molecule can be drawn in different formats, such backbone, ball and stick, and space filling by using standard length and bond angle values, Fig 3 3c) Fig 3 Different representations of sulfamethoxazole: (3a)wire,(3b)cylinder and sphere, (3c)cylinder, and (3d) space filling( Chem3D) Handling 3D molecular models from Chem3D or Molecular Modeling Pro programs can assess relevant stereofeatures of drugs, allowing information about the size volume, and shape of the molecules The importance of the stereochemistry in the mechanism of action of drugs is illustrated by epinephrine (4)and propranolol (5), acting on B-adrenergic receptors, Fig. 4 Compounds 4 and 5 can be easily drawn in their active configurations, R and s, respectively, by rotating the molecules around the x,Y, z axis and attributing according to the classical rule of Cahn-Ingold-Prelog. The configurations of the asymmetrical carbon in the side chains are apparently opposite, due to r and s nomenclature, but in comparison the 3D representations show that the disposition and spatial orientation of the hydroxyl groups are similar, both directed to the same face. The difference in their naming, R and s, is due to the priority rule, the aryloxy group in the antagonist(5) has priority over the methylenamino group of the side chain, which is not the case in the epinephrine molecule <www.iupac.org/publications/cd/medicinalchemistry/>4 tools, whole substructures ready in the program and the dialog box, where formulae in linear representation are typed. In parallel, molecules generated in ChemDraw (“copy”) can be converted to the 3D model in Chem3D (“paste”), as shown in Fig. 2 for sulfamethoxazole (3). H2N N H S N O O O CH3 (3) Fig. 2 Conversion of the 3D sulfamethoxazole (3) structure into the cylindrical bond 3D display (ChemDraw￾Chem3D). In the Chem3D program, the molecule can be drawn in different formats, such as backbone, ball and stick, and space filling by using standard length and bond angle values, Fig. 3. (3a) (3b) ( (3c) 3d) Fig. 3 Different representations of sulfamethoxazole: (3a) wire, (3b) cylinder and sphere, (3c) cylinder, and (3d) space filling (Chem3D). Handling 3D molecular models from Chem3D7 or Molecular Modeling Pro9 programs can assess relevant stereofeatures of drugs, allowing information about the size, volume, and shape of the molecules. The importance of the stereochemistry in the mechanism of action of drugs is illustrated by epinephrine (4) and propranolol (5), acting on β-adrenergic receptors, Fig. 4. Compounds 4 and 5 can be easily drawn in their active configurations, R and S, respectively, by rotating the molecules around the X, Y, Z axis and attributing according to the classical rule of Cahn–Ingold–Prelog. The configurations of the asymmetrical carbon in the side chains are apparently opposite, due to R and S nomenclature, but in comparison, the 3D representations show that the disposition and spatial orientation of the hydroxyl groups are similar, both directed to the same face. The difference in their naming, R and S, is due to the priority rule, the aryloxy group in the antagonist (5) has priority over the methylenamino group of the side chain, which is not the case in the epinephrine molecule (4).10 <www.iupac.org/publications/cd/medicinal_chemistry/> version date: 1 December 2006