The discovery and optimization of naphthalene-linked P2-P4 Macrocycles as inhibitors of HCV NS3 protease.

Naphthalene-linked P2-P4 macrocycles within a tri-peptide-based acyl sulfonamide chemotype have been synthesized and found to inhibit HCV NS3 proteases representing genotypes 1a and 1b with single digit nanomolar potency. The pharmacokinetic profile of compounds in this series was optimized through structural modifications along the macrocycle tether as well as the P1 subsite. Ultimately a compound with oral bioavailability of 100% in rat, and a long half-life in plasma was obtained. However, compounds in this macrocyclic series exhibited cardiac effects in an isolated rabbit heart model and for this reason further optimization efforts were discontinued.

Structure-activity relationships in toll-like receptor-2 agonistic diacylthioglycerol lipopeptides.

The N-termini of bacterial lipoproteins are acylated with a (S)-(2,3-bisacyloxypropyl)cysteinyl residue. Lipopeptides derived from lipoproteins activate innate immune responses by engaging Toll-like receptor 2 (TLR2) and are highly immunostimulatory and yet without apparent toxicity in animal models. The lipopeptides may therefore be useful as potential immunotherapeutic agents. Previous structure-activity relationships in such lipopeptides have largely been obtained using murine cells, and it is now clear that significant species-specific differences exist between human and murine TLR responses. We have examined in detail the role of the highly conserved Cys residue as well as the geometry and stereochemistry of the Cys-Ser dipeptide unit. (R)-Diacylthioglycerol analogues are maximally active in reporter gene assays using human TLR2. The Cys-Ser dipeptide unit represents the minimal part-structure, but its stereochemistry was found not to be a critical determinant of activity. The thioether bridge between the diacyl and dipeptide units is crucial, and replacement by an oxoether bridge results in a dramatic decrease in activity.

Intramolecular azide-alkyne [3 + 2] cycloaddition: versatile route to new heterocyclic structural scaffolds.

Investigating the relatively unexplored intramolecular version of the azide-alkyne [3 + 2] cycloaddition, the present studies demonstrate the utility of the above reaction in the synthesis of a variety of as yet unreported heterocyclic structural scaffolds. The approach involved initial installation of strategic azide and alkyne moieties on a common structural framework, followed by their intramolecular cycloaddition studies. The pivotal azidoalkyne intermediates were efficiently accessed from a variety of easily available starting materials such as olefins, epoxides, amino acids, amino alcohols, ketones etc. The key reactions for incorporation of the azide functionality into the desired framework involved azidolysis of epoxides, displacement of hydroxy groups with azide nucleophiles, and diazo transfer on amine. Attachment of the desired alkyne functionalities was accomplished by either N-, or, O-alkylation with appropriate propargylic halides. The azidoalkynes thus prepared underwent smooth intramolecular cycloaddition, resulting in a variety of novel triazolooxazine and triazolopyrazine derivatives. Interestingly, unlike in the intermolecular version, metal catalysis was not necessary for the performance of the above cycloadditions. It is expected that the results from the present studies and its further extension will provide a potentially fertile pathway to a variety of unique chemical entities of structural and biological significance.

Pharmacokinetics of DS-96, an alkylpolyamine lipopolysaccharide sequestrant, in rodents.

The pharmacokinetics of DS-96, an N-alkylhomospermine analog designed to sequester bacterial lipopolysaccharides, has been determined in rodent species. The elimination half-life in mice and rats are about 400 and 500 min, respectively, with other PK parameters being quite similar in the two rodent species. Interestingly, the mouse intravenous plasma concentration time curves exhibit an apparent absorption phase. While the rat intravenous data did not exhibit a pronounced apparent absorption phase immediately following injection, plasma levels did increase between 10 and 30 min following an expected drop from time 0 to 5 min. The data are consistent with first-pass uptake, possibly by the lung, with back diffusion as a function of time. The observed C(max) values of 1.36 microg/mL in the mouse intraperitoneal model suggest that a plasma concentration of 0.5-1 microg/mL corresponds to complete protection for a 200 ng/animal dose of intraperitoneally administered LPS in the D-galactosamine-primed model of endotoxin-induced lethality.