Synthesis of thiophene-2-carboxamidines containing 2-aminothiazoles and their biological evaluation as urokinase inhibitors.

The serine protease urokinase (uPa) has been implicated in the progression of both breast and prostate cancer. Utilizing structure based design, the synthesis of a series of substituted 4-[2-amino-1,3-thiazolyl]-thiophene-2-carboxamidines is described. Further optimization of this series by substitution of the terminal amine yielded urokinase inhibitors with excellent activities.

1,3,5-Trialkyl-2,4,6-triiodobenzenes: novel X-ray contrast agents for gastrointestinal imaging.

Examination of the gastrointestinal (GI) tract has been performed for decades using barium sulfate. Although this agent has many recognized limitations including extreme radiopacity, poor intrinsic affinity for the GI mucosa, and very high density, no alternative contrast agents have emerged which produce comparable or better contrast visualization. In fact, the various techniques of the GI radiologic examination (i.e., single contrast, double contrast, biphasic) were developed to compensate for its limitations. Each of these techniques requires complex patient manipulation to achieve adequate mucosal coating or compression to overcome the marked radiopacity of barium sulfate in order to obtain a diagnostically useful examination. A series of novel radiopaque oils, the 1,3, 5-trialkyl-2,4,6-triiodobenzenes, was designed to improve the efficacy, stability, and safety of barium formulations. These substances were prepared in two steps from 1,3,5-trichlorobenzene. Compound 17 (1,3,5-tri-n-hexyl-2,4,6-triiodobenzene), formulated as an oil-in-water emulsion, was found to be well-tolerated in rodents (mice, hamsters, rats) following acute oral and/or intraperitoneal administrations at 4 times the anticipated human clinical dose. No metabolism of 17 was detected in rat, hamster, dog, monkey, or human hepatic microsomes, suggesting the lack of oral toxicity was a consequence of poor absorption. In imaging experiments in dogs, emulsions of 17 have demonstrated excellent mucosal coating and improved radiodensity relative to barium sulfate suspensions. On the basis of the preliminary imaging and toxicity data, compound 17 was selected as a potential development candidate.

Amidinohydrazones as guanidine bioisosteres: application to a new class of potent, selective and orally bioavailable, non-amide-based small-molecule thrombin inhibitors.

We describe a new class of potent, non-amide-based small molecule thrombin inhibitors in which an amidinohydrazone is used as a guanidine bioisostere on a non-peptide scaffold. Compound 4 exhibits nM inhibition of thrombin, is selective for thrombin, and shows 60 and 23% bioavailability in rabbits and dogs, respectively. Crystallographic analysis of 4 bound to thrombin confirmed the amindinohydrazone binding mode.

Structure-activity and crystallographic analysis of a new class of non-amide-based thrombin inhibitor.

The structure activity relationships of a novel series of non-amide-based thrombin inhibitors are described. Exploration of the P2 and the aryl binding region for this series has identified optimal groups for achieving nanomolar potency. The binding modes of these optimal groups have been confirmed by X-ray structural analysis.

Structural analysis of thrombin complexed with potent inhibitors incorporating a phenyl group as a peptide mimetic and aminopyridines as guanidine substitutes.

The structure of the noncovalent complex of human alpha-thrombin with a nonpeptide inhibitor containing a central phenyl scaffold, N-[2-[5-methyl-3-(2-chlorophenylsulfonyloxy)phenoxy]ethyl]-N- methyl-4 -aminopyridine (1), has been determined to 2.20 A resolution. In addition, the thrombin-bound structures of two distinct amino acid-based inhibitors (3 and 4) containing different aminopyridine-derived guanidine mimetics have been determined. Each compound occupies the same region of the active site and projects an aminopyridine, a central hydrophobic group, and an aryl group, into the S1, S2, and aryl subsites on thrombin. Nonpeptide 1 forms only one direct intermolecular hydrogen bond to the thrombin active site and forms no hydrogen bonds to ordered molecules of solvent. Close contacts are observed between main-chain carbonyl groups on thrombin and the edges of the central phenyl and aminopyridine rings and the sulfonyl group of 1 such that atoms carrying opposite partial charges are juxtaposed. Aminopyridine groups in 3 and 4 also form close contacts with the edges of carbonyl groups on thrombin and are flexibly accommodated in the S1 subsite. Superposition of the bound conformations of 1 and D-Phe-Pro-amidobutylguanidine (2) revealed that the central phenyl scaffold of 1 substitutes for the peptide main chain of 2.

In vitro evaluation and crystallographic analysis of a new class of selective, non-amide-based thrombin inhibitors.

We describe the in vitro evaluation and crystallographic analysis of a new class of potent and selective, non-amino acid-based, small-molecule thrombin inhibitors, exemplified by 14. This class of achiral inhibitors lacks an amide-based backbone, exhibits nM inhibition of thrombin, and is selective for thrombin. Compound 14 does not interact with the active-site catalytic apparatus and is anchored to the enzyme via a single network of hydrogen bonds to Asp189 of the S1 pocket.