Towards crystal structure prediction of complex organic compounds - a report on the fifth blind test

Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1: 1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories - a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome

Crystal Structures of Fluorinated Pyridines from Geometrical and Energetic Perspectives

The low melting compounds 3-fluoropyridine, 3,5-difluoropyridine, 2,3,5-trifluoropyridine, and 2,3,5,6-tetrafluoropyridine were crystallized in situ on the diffractometer and analyzed by X-ray diffraction. The comparison with pentafluoropyridine shows a consecutive dependence of the arrangement of pyridine molecules with the increasing fluorine substitution. Starting with the monosubstituted representative, the crystal packing changes stepwise from herringbone packing to parallel arrangement of the molecules in the trifluorinated pyridine and then switches back to the edge-to-face form by the perfluorinated compound. To get a deeper insight into the aggregation behavior of the flourinated pyridines, the crystal packing motives were also analyzed on the basis of ab initio quantum-chemical calculations of the intermolecular interaction energy, using the MP2/6-311G­(d,p) method. This approach allows the indication of energetically rich fragments in the crystal structures, called basic structural motifs, and the very weak attractive or rather repulsive nature of F···F interactions

Synthesis and biological evaluation of novel non-racemic indole-containing allocolchicinoids

Two novel indole-containing allocolchicinoids were prepared from naturally occurring coichicine exploiting the Curtius rearrangement and tandem Sonogashira coupling/Pd-catalyzed cyclization as the key transformations. Their cytotoxic properties, apoptosis-inducing activity, tubulin assembly inhibition and short-time cytotoxic effects were investigated. Compound 7 demonstrated the most pronounced anti-cancer activity: IC50 < 1 nM, cell cycle arrest in the G2/M phase, 25% apoptosis induction, as well as lower destructive short-time effects on HT-29 cell line in comparison with colchicine. Docking studies for prepared indole-derived allocolchicine analogues were carried out. (C) 2017 Elsevier Masson SAS. All rights reserved