Mariappan Anbazhagan

Unusual Dehydroxylation of Antimicrobial Amidoxime Prodrugs by Cytochrome b5 and NADH Cytochrome b5 Reductase

Furamidine is an effective antimicrobial agent; however, oral potency of furamidine is poor. A prodrug of furamidine, 2,5-bis(4-amidinophenyl)furan-bis-O-methylamidoxime (DB289), has greatly improved oral potency. DB289 is transformed to furamidine via O-demethylation, and N-dehydroxylation reactions with four intermediate metabolites formed. The O-demethylation reactions have been shown to be catalyzed by cytochrome P450. The enzymes catalyzing the reductive N-dehydroxylation reactions have not been determined. The objective of this study was to identify the enzymes that catalyze N-dehydroxylation of metabolites M1, a monoamidoxime, and M2, a diamidoxime, formed during generation of furamidine. M1 and M2 metabolism was investigated using human liver microsomes and human soluble cytochrome b5 and NAD cytochrome b5 reductase, expressed in Escherichia coli. Kinetics of M1 and M2 reduction by human liver microsomes exhibited high affinity and moderate capacity. Metabolism was significantly inhibited by antibodies to cytochrome b5 and b5 reductase and by chemical inhibitors of b5 reductase. The amidoximes were efficiently metabolized by liver mitochondria, which contain cytochrome b5/b5 reductase, but not by liver cytosol, which contains minimal amounts of these proteins. Expressed cytochrome b5/b5 reductase, in the absence of any other proteins, efficiently catalyzed reduction of both amidoximes. Km values were similar to those for microsomes, and Vmax values were 33- to 36-fold higher in the recombinant system compared with microsomes. Minimal activity was seen with cytochrome b5 or b5 reductase alone or with cytochrome P450 reductase alone or with cytochrome b5. These results indicate that cytochrome b5 and b5 reductase play a direct role in metabolic activation of DB289 to furamidine.

Palladium-catalyzed N-arylation of O-methylamidoximes

Pd-catalyzed coupling of O-methylbenzamidoximes gave N-aryl O-methylbenzamidoximes using aryl halides with electron attracting or moderate electron donating groups. Under the same conditions, benzamidoxime failed to undergo coupling and O-acetylbenzamidoxime underwent cyclization to form the corresponding [1,2,4]oxadiazole.

Conversion of carbonimidodithioates into unsymmetrical Di- and Tri- substituted ureas including urea dipeptides

Selective hydrolysis of carbonimidodithioates (3) leads to the thiocarbamates (4), which can be easily transformed to the unsymmetrical ureas (5) by treatment with the appropriate amines. This constitutes a synthesis of ureas without the use of phosgene or carbon monoxide.

In Vivo Investigations of Selected Diamidine Compounds against Trypanosoma evansi Using a Mouse Model

ABSTRACT Surra is an animal pathogenic protozoan infection, caused by Trypanosoma evansi, that develops into a fatal wasting disease. Control measures rely on diagnosis and treatment. However, with the continuous emergence of drug resistance, this tactic is failing, and the pressing need for new chemotherapeutic agents is becoming critical. With the introduction of novel aromatic diamidines, a new category of antitrypanosomal drugs was discovered. Nevertheless, their efficacy within a T. evansi-infected mouse model was not known. In total, 30 compounds previously selected based on their in vitro activity were tested in a T. evansi mouse model of infection. Six of the compounds were capable of curing T. evansi-infected mice at drug doses as low as 0.5 and 0.25 mg/kg of body weight administered for 4 consecutive days, and they were more effective than the standard drugs suramin, diminazene, and quinapyramine. After all selection criteria were applied, three diamidine compounds (DB 75, DB 867, and DB 1192) qualified as lead compounds and were considered to have the potential to act as preclinical candidates against T. evansi infection.

Regioselective cleavage of O-benzyl-N-arylamidoximes: synthesis of N-aryl amidines and amidoximes

O-Benzyl-N-arylamidoximes have been regioselectively deprotected to provide either N-aryl amidines or amidoximes. As a result, the targeted compounds can now be prepared using palladium-catalyzed N-arylation chemistry.

Synthesis of Benzyloxybromobenzonitriles

Abstract The synthesis of four new benzyloxybromobenzonitriles including: 2‐benzyloxy‐4‐bromobenzonitrile (3), 3‐benzyloxy‐4‐bromobenzonitrile (7), 5‐benzyloxy‐2‐bromobenzonitrile (11) and 3‐benzyloxy‐2‐bromobenzonitrile (12) is reported.