Non-covalent thrombin inhibitors featuring P3-Heterocycles with P1-Bicyclic arginine surrogates

2(1H)-Pyrazinones from acyclic building blocks: methods of synthesis and further derivatizations

Pyrazinones (2(1H)-pyrazinones) are found as components of a range of natural substances and are involved in the preparation of a great number of bioactive molecules. Synthesis of such compounds, and analogues, requires knowledge of the heterocyclic properties of pyrazinones and, in particular, methods for their ring construction. This review deals with the strategies that have been developed for the synthesis of pyrazinones from acyclic precursors, especially α-amino acid-derived units, from the first examples in 1905 up to the most recent in 2021.

Regio- and Enantioselective Synthesis of 1,2-Diamine Derivatives by Copper-Catalyzed Hydroamination

A highly regio- and enantioselective synthesis of 1,2-diamine derivatives from γ-substituted allylic pivalamides using copper-catalyzed hydroamination is reported. The N-pivaloyl group is essential, in both facilitating the hydrocupration step and suppressing an unproductive β-elimination from the alkylcopper intermediate. This approach enables an efficient construction of chiral differentially protected vicinal diamines under mild conditions with broad functional group tolerance.

Discovery of Potent and Orally Bioavailable Macrocyclic Peptide-Peptoid Hybrid CXCR7 Modulators

The chemokine receptor CXCR7 is an attractive target for a variety of diseases. While several small-molecule modulators of CXCR7 have been reported, peptidic macrocycles may provide advantages in terms of potency, selectivity, and reduced off-target activity. We produced a series of peptidic macrocycles that incorporate an N-linked peptoid functionality where the peptoid group enabled us to explore side-chain diversity well beyond that of natural amino acids. At the same time, theoretical calculations and experimental assays were used to track and reduce the polarity while closely monitoring the physicochemical properties. This strategy led to the discovery of macrocyclic peptide-peptoid hybrids with high CXCR7 binding affinities (K_i < 100 nM) and measurable passive permeability (P_app > 5 × 10^-6 cm/s). Moreover, bioactive peptide 25 (K_i = 9 nM) achieved oral bioavailability of 18% in rats, which was commensurate with the observed plasma clearance values upon intravenous administration.

Ni and Cu-catalyzed one pot synthesis of unsymmetrical 1,3-di(hetero)aryl-1H-indazoles from hydrazine, o-chloro (hetero)benzophenones, and (hetero)aryl bromides

A new nickel-catalyzed cyclization of ortho-chlorobenzophenone hydrazones, to afford 3-aryl-1H-indazoles, is applied in a one-pot synthesis of 1,3-diaryl-1H-indazoles.

The Influence of Bioisosteres in Drug Design: Tactical Applications to Address Developability Problems

The application of bioisosteres in drug discovery is a well-established design concept that has demonstrated utility as an approach to solving a range of problems that affect candidate optimization, progression, and durability. In this chapter, the application of isosteric substitution is explored in a fashion that focuses on the development of practical solutions to problems that are encountered in typical optimization campaigns. The role of bioisosteres to affect intrinsic potency and selectivity, influence conformation, solve problems associated with drug developability, including P-glycoprotein recognition, modulating basicity, solubility, and lipophilicity, and to address issues associated with metabolism and toxicity is used as the underlying theme to capture a spectrum of creative applications of structural emulation in the design of drug candidates.

Novel pyrazinone and pyridinone thrombin inhibitors incorporating weakly basic heterobicyclic P1-arginine mimetics

The design, synthesis and biological activity of new thrombin inhibitors with a pyridinone or pyrazinone core and different heterobicyclic P(1) arginine side-chain mimetics are described. The arginine side-chain mimetics used in this study are (+/-)-4,5,6,7-tetrahydro-2H-indazol-5-ylmethanamine and both enantiomers thereof, (+/-)-4,5,6,7-tetrahydro-1,3-benzothiazole-2,6-diamine and the corresponding R enantiomer. Compound 25, the most potent in the series of pyrazinone inhibitors, exhibited a K(i) of 41 nM in vitro and high selectivity against trypsin and factor Xa.

Novel thrombin inhibitors incorporating weakly basic heterobicyclic P1-arginine mimetics: optimization via modification of P1 and P3 moieties

Optimization of lead compounds 1 and 2 resulted in novel, selective, and potent thrombin inhibitors incorporating weakly basic heterobicyclic P(1)-arginine mimetics. The design, synthesis, and biological activity of racemic thrombin inhibitors 17-29 and enantiomerically pure thrombin inhibitors 30-33 are described. The arginine side-chain mimetics used in this study are 4,5,6,7-tetrahydro-1,3-benzothiazol-2-amine, 4,5,6,7-tetrahydro-2H-indazole, and 2-imino-4,5,6,7-tetrahydro-1,3-benzothiazol-3(2H)-ylamine.

Selective 3-amino-2-pyridinone acetamide thrombin inhibitors incorporating weakly basic partially saturated heterobicyclic P1-arginine mimetics

Novel, highly selective and potent thrombin inhibitors were identified as a result of combing the 3-benzylsulfonylamino-2-pyridinone acetamide P(2)-P(3) surrogate with weakly basic partially saturated heterobicyclic P(1)-arginine mimetics 1-8. The design, synthesis, biological activity, and the binding modes of non-covalent thrombin inhibitors featuring P(1)-4,5,6,7-tetrahydroindazole, 5,6,7,8-tetrahydroquinazoline, and 4,5,6,7-tetrahydrobenzothiazole moieties are described.

New antithrombotic drugs on the horizon

Venous and arterial thromboembolism are a major cause for morbidity and mortality. The list of established drugs for the prevention of thrombus formation and embolisation includes heparins, hirudin and derivatives, aspirin, ADP and glycoprotein IIb/IIIa receptor antagonists, as well as vitamin K antagonists. Several limitations exist for these drugs that have stimulated the search for new and better anticoagulants. A series of selective clotting factor Xa inhibitors and direct factor IIa (thrombin) inhibitors are on the horizon, two of which are getting close to broad clinical application. Additional therapeutics that are still under preclinical and clinical investigation include inhibitors of the tissue factor pathway/factor VII complex, clotting factor VIII and XIII inhibitors and modulators of the protein C pathway or of endogenous fibrinolysis, as well as novel antiplatelet drugs. This review is focused on the current status of development of novel antithrombotics and their clinical potential. Even though only a few of a broad array of antithrombotic agents have reached clinical testing, some hold the potential for significant improvement in efficacy and safety of anticoagulant therapy.

Novel thrombin inhibitors incorporating non-basic partially saturated heterobicyclic P1-arginine mimetics

The design, synthesis and biological activity of non-covalent thrombin inhibitors incorporating 4,5,6,7-tetrahydroindazole, 2-methyl-4,5,6,7-tetrahydroindazole, 4,5,6,7-tetrahydroisoindole, 5,6,7,8-tetrahydroquinazoline and 5,6,7,8-tetrahydroquinazolin-2-amine as novel, partially saturated, heterobicyclic P(1)-arginine side-chain mimetics is described. The binding mode of the most potent candidate in the series co-crystallized with human alpha-thrombin, which exhibited an in vitro K(i) of 140nM and more that 478-fold selectivity against trypsin, is discussed.