Biological effects of acetomycin. II. Inactivation by esterases in vitro.

Acetomycin has antitumor activity in vitro but not in vivo. HCT-8 human colon adenocarcinoma assays in the presence of a drug metabolizing system (rat liver S9 fraction) demonstrated that liver enzymes inactivated acetomycin. The structure of acetomycin suggested that an esterase could be the key inactivating enzyme. Assays with porcine liver esterase (EC 3.1.1.1) showed that this enzyme rapidly abolishes the activity of acetomycin against HCT-8 cells. The potential utility of acetomycin as an antitumor agent thus depends on finding a means of preventing esterase inactivation.

Metabolic disposition of isoxicam in man, monkey, dog, and rat.

Isoxicam a new nonsteroidal antiinflammatory agent was radiolabeled with 14C at the 3-position of the benzothiazine nucleus. It was well absorbed following peroral administration to man, monkey, dog, and rat, reaching peak plasma concentrations in 4-8 hr. Over 90% of the plasma radioactivity was due to unchanged drug. Plasma elimination half-lives were 22-45 hr in man and 49-53 hr in dogs and 20-35 hr in rats and monkeys. Isoxicam was distributed to most tissues in rats, but the tissue-plasma ratio did not exceed unity, indicating a small volume of distribution. It was extensively metabolized with only a few per cent of the dose appearing as unchanged drug in the urine. The principal urinary metabolite in man was formed by hydroxylation of the methyl group on the isoxozole ring and accounted for 30-35% of an isoxicam dose. In the rat, oxoacetic acid, the major urinary metabolite, was formed by opening of the benzothiazine ring followed by hydrolytic cleavage of the C-3 to N-2 bond. In addition to the hydroxymethyl and oxoacetic acid, two unknown metabolites, accounting for only a small percentage of dose, were detected in the urine of all four species. Urinary excretion of 14C activity accounted for about 60% of a dose in man and rats, 31% in monkeys, and 17% in dogs. These results indicate that there is only a quantitative rather than a qualitative species difference in the metabolic disposition of isoxicam.

Adenosine deaminase inhibitors. Synthesis and biological evaluation of (+/-)-3,6,7,8-tetrahydro-3-[(2-hydroxyethoxy)methyl]imidazo[4,5-d] [1,3]diazepin-8-ol and some selected C-5 homologues of pentostatin.

The synthesis of several analogues of (8R)-3-(2-deoxy-beta-D-erythro- pentofuranosyl)-3,6,7,8-tetrahydroimidazo[4,5-d][1,3]diazepin-8-ol (pentostatin, 1a) is described. Ring closure of 2-amino-1-(5-amino-1H-imidazol-4-yl)ethanone dihydrochloride (3) with triethyl orthoacetate or triethyl orthopropionate gave the C-5 methyl and ethyl ketoaglycons, 6,7-dihydro-5-methylimidazo[4,5-d][1,3]diazepin-8(3H)-one (4b) and 5-ethyl-6,7-dihydroimidazo[4,5-d][1,3]diazepin-8(3H)-one (4c), respectively. Stannic chloride catalyzed condensation of the pertrimethylsilyl derivatives of 4b and 4c with a protected glycosyl halide afforded anomeric mixtures of ketonucleosides 3-(2-deoxy-3,5-di-O-p-toluoyl-beta- and -alpha-D-erythro-pentofuranosyl)-6,7-dihydro-5-methylimidazo[4,5-d] [1,3]diazepin-8(3H)-one (5b and 6b) and 3-(2-deoxy-3,5-di-O-p-toluoyl)-beta- and -alpha-D-erythro-pentofuranosyl)-5-ethyl-6,7-dihydroimidazo[4,5-d]- [1,3]diazepin-8(3H)-one (5c and 6c), respectively. Subsequent separation of the anomers, followed by deprotection and reduction of 5b, 6b, and 5c, afforded the respective 8R and 8S isomers. Stannic chloride catalyzed condensation of pertrimethylsilyl ketoaglycon 4a with 2-(chloromethoxy)-1-(p-toluoyloxy) ethane to give ketonucleoside 6,7-dihydro-3-[[2-(p-toluoyloxy)ethoxy] methyl]imidazo[4,5-d][1,3]diazepin-8(3H)-one (9a) was followed by deprotection to 6,7-dihydro-3[(2-hydroxyethoxy)methyl]imidazo[4,5-d][1,3] diazepin-8(3H)-one (9b) and then reduction to the racemic acyclic pentostatin analogue (+/-)-3,6,7,8-tetrahydro-3-[ (2-hydroxyethoxy)methyl]imidazo[4,5-d][1,3]diazepin-8-ol (2). Ki values for the in vitro adenosine deaminase (EC 3.5.4.4; type I; calf intestinal mucosa) inhibitory activities of 1b, 1c, and 2 were determined to be 1.6 X 10(-8), 1.5 X 10(-6), and 9.8 X 10(-8) M, respectively. When compounds 2 and 9b were tested in combination with vidarabine against herpes simplex virus, type 1, in an HEp-2 plaque reduction assay, only compound 2 was able to potentiate the antiviral activity of vidarabine.