Consequences of Chirality on the Aggregation Behavior of Poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV)

Poly[2-methoxy-5(2'-ethylhexoxy)-p-phenylenevinylene] (MEH-PPV) has been for the first time prepared and fully characterized in enantiopure (R) form. If the polymer molecular weight is sufficiently low, (R)-MEH-PPV assumes a helical supramolecular structure in the solution aggregates, with consequences on the tendency to aggregation and on the fluorescence quenching, both of which are reduced with respect to the racemic analogue

Oxazolidinone Synthesis through Halohydrin Dehalogenase-Catalyzed Dynamic Kinetic Resolution

An efficient dynamic kinetic resolution protocol using a single enzyme is described. Both the kinetic resolution and substrate racemization are catalyzed by halohydrin dehalogenase from Agrobacterium radiobacter AD1 (HheC). The HheC-catalyzed reaction of epibromohydrin and 2-bromomethyl-2-methyloxirane with sodium cyanate afforded 5-substituted 2-oxazolidinones in high yields (97% and 87%) and high optical purity (89% and > 99% ee) in the presence of catalytic amounts of bromide ion. These compounds are valuable building blocks with diverse synthetic applications

A single point mutation enhances hydroxynitrile synthesis by halohydrin dehalogenase

The cyanide-mediated ring opening of epoxides catalyzed by halohydrin dehalogenases yields β-hydroxynitriles that are of high interest for synthetic chemistry. The best studied halohydrin dehalogenase to date is the enzyme from Agrobacterium radiobacter, but this enzyme (HheC) exhibits only low cyanolysis activities. Sequence comparison between a pair of related halohydrin dehalogenases from Corynebacterium and Mycobacterium suggested that substitution of a threonine that interacts with the active site might be responsible for the higher cyanolytic activity of the former enzyme. Here we report that a variant of HheC in which this substitution (T134A) is adopted displays an up to 11-fold higher activity in cyanide-mediated epoxide ring-opening. The mutation causes removal of the hydrogen bond between residue 134 and the side chain O of the active site serine 132, which donates a hydrogen bond to the substrate oxygen. The mutation also increases dehalogenase rates with various substrates. Structural analysis revealed that the anion-binding site of the mutant enzyme remained unaltered, showing that the enhanced activity is due to altered interactions with the substrate oxygen rather than changes in the nucleophile binding site

CCDC 680924: Experimental Crystal Structure Determination

Related Article: M.M.Elenkov, Lixia Tang, A.Meetsma, B.Hauer, D.B.Janssen|2008|Org.Lett.|10|2417|doi:10.1021/ol800698t,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.