A New Approach to Probing Conformational Space with Molecular Mechanics: Random Incremental Pulse Search

A computational method is described that permits reliable searching for different molecular conformations. A Monte Carlo type routine is employed to randomly search the potential energy surface for a given molecule, and Allinger's MM2 force field is employed for energy calculations and minimizations. The method has two modes of operation: conformational search (by torsional or energetic criterion) and global minimum location. The Monte Carlo type routine, called random incremental pulse search (Rips), logically couples the benefits of random searching with those of analytical minimization. The method has been tested by searching conformational space for a series of cycloalkanes. All conformational families and minimum-energy structures are reliably located in each case.