Crystal and molecular structures of pyridazinone cardiovascular agents

Diclomezine: 6-(3,5-dichloro-4-methyl-phen-yl)pyridazin-3(2H)-one

In the title compound, C₁₁H₈Cl₂N₂O, the benzene and pyridazine rings are tilted by 8.6 (1)° relative to each other. In the crystal, pairs of inter­molecular N—H⋯O hydrogen bonds form centrosymmetric dimers. π–π contacts with centroid–centroid distances of 3.698 (2) and 3.751 (1) Å and halogen–halogen inter­actions [3.379 (1) Å] also stabilize the structure.

The synthesis and enzymatic incorporation of sialic acid derivatives for use as tools to study the structure, activity, and inhibition of glycoproteins and other glycoconjugates

Methods have been developed for the enzymatic synthesis of complex carbohydrates and glycoproteins containing in the sialic acid moiety the heavy metal mercury or the transition-state analog phosphonate of the influenza C 9-O-acetyl-neuraminic acid esterase-catalyzed reaction. 5-Acetamido-3, 5-dideoxy-9-methylphosphono-beta-D-glycero-D-galacto-nonulopyra nosidonic acid (1), 5-acetamido-3,5-dideoxy-9-methylphosphono-2-propyl-alpha-D- glycero-D-galacto-nonulopyranosidonic acid triethylammonium salt (2), and 5-acetamido-9-thiomethylmercuric-3, 5,9-trideoxy-beta-D-glycero-D-galacto-nonulopyranosidonic acid (3) were synthesized. Compounds 1 and 2 are proposed transition state inhibitors of an esterase vital for the binding and infection of influenza C. Compound 3 was enzymatically incorporated into an oligosaccharide and a non-natural glycoprotein for use as an aid in the structure determination of these compounds by X-ray crystallography.

The matching of electrostatic extrema: a useful method in drug design? A study of phosphodiesterase III inhibitors

Ligands which bind to a specific protein binding site are often expected to have a similar electrostatic environment which complements that of the binding site. One method of assessing molecular electrostatic similarity is to examine the possible overlay of the maxima and minima in the electrostatic potential outside the molecules and thereby match the regions where strong electrostatic interactions, including hydrogen bonds, with the residues of the binding site may be possible. This approach is validated with accurate calculations of the electrostatic potential, derived from a distributed multiple analysis of an ab initio charge density of the molecule, so that the effects of lone pair and pi-electron density are correctly included. We have applied this method to the phosphodiesterase (PDE) III substrate adenosine-3',5'-cyclic monophosphate (cAMP) and a range of nonspecific and specific PDE III inhibitors. Despite the structural variation between cAMP and the inhibitors, it is possible to match three or four extrema to produce relative orientations in which the inhibitors are sufficiently sterically and electrostatically similar to the natural substrate to account for their affinity for PDE III. This matching of extrema is more apparent using the accurate electrostatic models than it was when this approach was first applied, using semiempirical point charge models. These results reinforce the hypothesis of electrostatic similarity and give weight to the technique of extrema matching as a useful tool in drug design.