HUNTER: A conformational search program for acyclic to polycyclic molecules with special emphasis on stereochemistry

Abstract

A new conformational search program, HUNTER, connected with the force fields MMP2 and MM3(92) is presented. The program accepts all types of molecules with most different substructures, considers stereochemical facts, and covers conformational space efficiently and completely. The most important facilities are an automated analysis of the stereochemistry including topographical facts, a separate perturbation of the acyclic and cyclic parts of the molecule using modified corner flapping, and an incremental rotation around single bonds with fixed flap and rotation angles, respectively; an exclusion of high energy structures by simulated annealing; the choice of the conformer lowest in energy, which is new as an initial structure for the next sampling run; and the use of a reduced set of dihedral angles to define a conformation. A specifically devised graphic interface, SERVANT, is used to feed in and control all informations necessary for a program run and to visualize the results. Most of the parameters are user‐defined and thereby allow a flexible search, including a search for the most stable diastereomer. The efficiency of the different parameter sets was tested in calculation with cycloundecane (12), (Z)‐oct‐3‐ene (13), and sipholenol‐A monoacetate (14). The best performance regarding the number of different low‐energy conformers was achieved with 60° (14) and 90° flaps (12), respectively, including substituent correction for the cyclic parts, and with 105° (14) and 120° rotations (13), respectively, for the acyclic parts. In comparison to the stochastic search routine implemented in MM3(92), HUNTER performed two (12) to six (14) times better. © 1997 John Wiley & Sons, Inc. J Comput Chem 18: 1264–1281, 1997

Akashins A, B, and C: Novel Chlorinated Indigoglycosides fromStreptomyces sp. GW 48/1497

“…To confirm further the configuration of the sugar residue, the absolute energy minimum of 3 a was calculated by using the HUNTER program. [14] The coupling constants determined for the calculated conformation by using PCModel agreed well with the experimental values.…”

“…[13] This finding was used later by Wilke et al to explain the πnickel effect™ in the polymerization reaction of ethene on AlR 3 ; [14] in this context the reactions of organonickel complexes such as [Ni(bpy)Me 2 ] (bpy 2,2 À -bipyridine), [Ni(cdt)] (cdt cyclododeca-1,5,9-triene), and [NiCl 2 (PR 3 ) 2 ] with AlR 3 or AlHR 2 were also investigated. Wilke et al concluded that in these reactions thermolabile addition compounds of nickel core complexes were formed with AlR 3 or AlHR 2 .…”

“…Wilke et al concluded that in these reactions thermolabile addition compounds of nickel core complexes were formed with AlR 3 or AlHR 2 . [14] Repeating the Ziegler experiments in an autoclave under H 2 we obtained a black dispersion, which according to transmission electron microscopy (TEM) contained colloidal nickel [Eq. (1)] The reaction of [Ni(acac) 2 ] with AliBu 3 gave particles with a mean diameter of AE 2.8 nm.…”

Akashine A, B und C: Neuartige chlorierte Indigoglycoside ausStreptomyces sp. GW 48/1497

“…B. in Spicamycintetraacetat11 ( 3 J =3.0 und 3.5 Hz) und Methyl‐4‐brom‐4,6‐didesoxy‐ α ‐ D ‐talopyranosid13 ( 3 J =1.5–4.1 Hz), bestätigt. Zur weiteren Absicherung der Konfiguration des Zuckers wurde mit HUNTER14 das absolute Energieminimum für 3 a gesucht. Eine Berechnung der Kopplungskonstanten mit PCModel ergab für die berechnete Konformation mit dem Experiment sehr gut übereinstimmende Werte.…”

cis-syn-cis-1,2,4,5-Tetracyclohexylcyclohexane. A Moderately Crowded Saturated Hydrocarbon Adopting a Twist-Boat Conformation

“…1,2,4,5-Tetracyclohexylcyclohexane ( 3 ) exists in seven stereoisomeric forms (three meso forms and two enantiomeric pairs, Scheme ) . Calculations of the TB/chair gaps of 1,2,4,5-tetracyclohexylcyclohexanes were performed with the MM3(92) program together with the HUNTER conformational search procedure (Table ) . As indicated by the calculations, the cis,syn,cis form is predicted to adopt a TB conformation.…”