Abstract
Building 3-dimensional (3D) molecules is the starting point in molecular modeling. Conformer search and identification of a global energy minimum structure are often performed computationally during spectral analysis of data from NMR, IR, and VCD or during rational drug design through ligand-based, structure-based, and QSAR approaches. I herein report a convenient script that allows for automated building of 3D structures and conformer searching from 2-dimensional (2D) drawing of chemical structures. With this Bash shell script, which runs on Mac OS X and the Linux platform, the tasks are consecutively and iteratively executed without a 3D molecule builder via the command line interface of the free (academic) software OpenBabel, Balloon, and MOPAC2012. A large number of 2D chemical drawing files can be processed simultaneously, and the script functions with stereoisomers. Semi-empirical quantum chemical calculation ensures reliable ranking of the generated conformers on the basis of energy. In addition to an energy-sorted list of file names of the conformers, their Gaussian input files are provided for ab initio and density functional theory calculations to predict rigorous electronic energies, structures, and properties. This script is freely available to all scientists.