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592. CONFLEX: Generation of Ring Conformers by Corner-
Flapping Algorithm
by Hitoshi Goto and Eiji Osawa, Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060, Japan CONFLEX systematically generates all conformers for a flexible ring structure by the "corner-flapping" algorithm.1 Four adjacent bonds on the ring are rotated simultaneously in one corner-flap operation. The central ring atom in these bonds is the "corner". For a given initial structure, all the corners are exhaustively flapped, while each conformation resulting from flapping is geometry-optimized with MM2(87)2 as a minimizer. In order to turn the MM2(87) program into a minimizer routine, it is necessary to make a few changes; the conformer that results from each flapping/energy minimization cycle is tested for redundancy by comparing the total steric energy and the dihedral angle values along the ring with those of the already saved conformers. The new conformer is saved as the candidate for the initial structure. Total computer time is approximately equal to nNt, where n is the number of corner atoms on the ring, N is the number of conformers, and t is the average time of energy- minimization for a flapped conformation. CONFLEX also generates all the rotamers of side chains, conserves configuration of asymmetric atoms and automatically removes redundancy due to symmetry. With several provisions to increase computing speed, CONFLEX is probably one of the fastest programs to cover the torsional energy surface of cyclic molecules of medium size. What QCPE is delivering in this package is a main program and a series of subroutines which will not execute alone. In order to use this package you must have or obtain the MM2(87) system. QCPE distributes this system to academic institutions only. For such institutions who do not now have MM2(87), it can be ordered from QCPE. A signed use agreement must accompany the order. Please call QCPE for details. Nonacademic users will have to be prepared to adapt this system to whatever minimizer they have. CONFLEX will be distributed in ANSI D (VAX COPY) format as multiple files. _________ References: 1. H. Goto and E. Osawa, J. Am. Chem. Soc., 111, 8950-51 (1989). 2. N. L. Allinger, QCPE Bull., 9, 58 (1989). _________ FORTRAN 77 (VAX) Lines of Code: 3200 |