Veterinary trypanocidal benzoxaboroles are peptidase-activated prodrugs

Livestock diseases caused by Trypanosoma congolense, T. vivax and T. brucei, collectively known as nagana, are responsible for billions of dollars in lost food production annually. There is an urgent need for novel therapeutics. Encouragingly, promising antitrypanosomal benzoxaboroles are under veterinary development. Here, we show that the most efficacious subclass of these compounds are prodrugs activated by trypanosome serine carboxypeptidases (CBPs). Drug-resistance to a development candidate, AN11736, emerged readily in T. brucei, due to partial deletion within the locus containing three tandem copies of the CBP genes. T. congolense parasites, which possess a larger array of related CBPs, also developed resistance to AN11736 through deletion within the locus. A genome-scale screen in T. brucei confirmed CBP loss-of-function as the primary mechanism of resistance and CRISPR-Cas9 editing proved that partial deletion within the locus was sufficient to confer resistance. CBP re-expression in either T. brucei or T. congolense AN11736-resistant lines restored drug-susceptibility. CBPs act by cleaving the benzoxaborole AN11736 to a carboxylic acid derivative, revealing a prodrug activation mechanism. Loss of CBP activity results in massive reduction in net uptake of AN11736, indicating that entry is facilitated by the concentration gradient created by prodrug metabolism.

Study of the Effect of Substituents of ortho-Phenylenediamines in the Opening of Lactones and Lactams for Access to Benzimidazol-2-yl Alkanols and Benzimidazol-2-yl Alkylamines

Benzimidazoles represent common chemical moieties in bioactive compounds. The synthesis of this heterocycle often involves a condensation of an ortho-phenylenediamine with a carboxylic acid derivative. The observed dialkylation of the starting ortho-phenylenediamine is avoided by opening of lactones or lactams. This strategy can directly yield 1H-benzimidazoles substituted at the 2-position by a functionalized chain. We present herein a study of the effect of different electron-withdrawing or electron-donating groups at the 4-position of ortho-phenylenediamines on the opening of lactones or lactams to synthesize benzimidazol-2-yl alkanols and benzimidazol-2-yl alkylamines.

Structure analysis of a phenylpyrazole carboxylic acid derivative crystallizing with three molecules in the asymmetric unit (Z′ = 3) using X-ray powder diffraction

Crystal structure analysis of a pyrazole carboxylic acid derivative, 5-(trifluoromethyl)-1-phenyl-1H-pyrazole-4-carboxylic acid (1) has been carried out from laboratory powder X-ray diffraction data. The crystal packing in the pyrazole carboxylic acid derivative exhibits an interplay of strong O–H…O, C–H…N and C–H…F hydrogen bonds to generate a three-dimensional molecular packing via the formation ofR22(8) andR22(9) rings. Molecular electrostatic potential calculations indicated that carbonyl oxygen, pyrazole nitrogen and fluorine atoms to be the strongest acceptors. The relative contribution of different interactions to the Hirshfeld surface of pyrazole carboxylic acid and a few related structures retrieved from CSD indicates that H…H, N…H and O…H interactions can account for almost 70% of the Hirsfeld surface area in these compounds.