C.V. Stevens

Conformational Sampling of Macrocyclic Alkenes Using a Kennard−Stone-Based Algorithm

D.D. Claeys, T. Verstraelen, E. Pauwels, C.V. Stevens, M. Waroquier, V. Van Speybroeck
Journal of Physical Chemistry A
114 (25), 6879–6887
2010
A1

Abstract 

The properties and functions of (bio)molecules are closely related to their molecular conformations. A variety of methods are available to sample the conformational space at a relatively low level of theory. If a higher level of theory is required, the computational cost can be reduced by selecting a uniformly distributed set of conformations from the ensemble of conformations generated at a low level of theory and by optimizing this selected set at a higher level. The generation of conformers is performed using molecular dynamics runs which are analyzed using the MD-Tracks code [ J. Chem. Inf. Model. 2008, 48, 2414]. This article presents a Kennard−Stone-based algorithm, with a distance measure based on the distance matrix, for the selection of the most diverse set of conformations. The method has been successfully applied to macrocyclic alkenes. The correct thermodynamic stability of the double-bond isomers of a flexible macrocyclic alkene containing two chiral centers is reproduced. The double-bond configuration has a limited effect on the conformation of the whole macrocycle. The chirality of the stereocenters has a larger effect on the molecular conformations.

Experimental and computational study of the ring opening of tricyclic oxanorbornenes to polyhydro isoindole phosphonates

D.D. Claeys, C.V. Stevens, B.I. Roman, P. Van De Caveye, M. Waroquier, V. Van Speybroeck
Organic & Biomolecular Chemistry
8, 3644-3654
2010
A1

Abstract 

Phosphonylated azaheterocycles are an important class of compounds with high biological potential as conformationally restricted bioisosteres of amino acids. Therefore, it is of interest to synthesize conformationally constrained amino phosphonates. We wanted to investigate possible routes via ring opening of α-amino phosphonates with an oxanorbornene skeleton, as these can be synthesized with high stereoselectivity. This was achieved using different Lewis acids, leading to a range of products. The reaction with TiCl4 and FeCl3 was modelled at a DFT level of theory to get insight in the pathways towards the corresponding products. To ease the work up, the Fe(III) catalyst was coated on montmorillonite clay, but this accelerated aromatization after ring opening. Quenching the FeCl3 catalyzed reaction mixture on celite caused complete aromatization.

The Formation of Trans-Fused Macrocycles from N(3),N’(3)-Polymethylenebishydantoins Using Second-Generation Grubbs’ Catalyst

Poster

Conference / event / venue 

IXth Netherlands' Chemistry and Catalysis Conference (NCCC IX)
Noordwijkerhout, The Netherlands
Monday, 3 March, 2008 to Wednesday, 5 March, 2008

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