On scaffold hopping: challenges in the discovery of sulfated small molecules as mimetics of glycosaminoglycans

Asymmetric (3 + 3) and (4 + 2) Annulation Reactions of 2,3-Dioxopyrrolidines with 3-Alkylidene Oxindoles to Construct Diverse Chiral Heterocyclic Frameworks

Two substrate-controlled regiodivergent annulation protocols for 2,3-dioxopyrrolidines with 3-alkylidene oxindoles have been developed, which furnished a series of fused dihydropyrrolidone derivatives in high yields with excellent stereoselectivities. Plausible mechanistic pathways for both annulation reactions are proposed that [3 + 3] annulation reaction involves vinylogous Michael addition followed by intramolecular aldol cyclization, while [4 + 2] annulation reaction occurs through a vinylogous Michael addition and a subsequent intramolecular oxa-Michael cyclization.

Rapid synthetic approaches to libraries of diversified 1,2-dihydrochromeno[2,3-c]pyrrole-3,9-diones and 3-(2-hydroxyphenyl)-4,5-dihydropyrrolo[3,4-c]pyrazol-6(1H)-ones

An efficient and practical synthetic procedure for libraries of diversified 1,2-dihydrochromeno[2,3-c]pyrrole-3,9-diones using a multicomponent process is presented. A convenient synthetic procedure for obtaining functionalized 3-(2-hydroxyphenyl)-4,5-dihydropyrrolo[3,4-c]pyrazol-6(1H)-ones via ring-opening strategy has also been developed. This protocol was found to be compatible with a wide range of substituents and paves the way for the practical synthesis of title compounds with a broad range of substituents under mild condition. The products can be easily isolated by crystallization without the use of chromatography.

Enantioselective synthesis of pyrano[2,3-c]pyrrole via an organocatalytic [4 + 2] cyclization reaction of dioxopyrrolidines and azlactones

The present work provides a simple and efficient access to chiral pyrano[2,3-c]pyrrole via an asymmetric [4 + 2] cyclization reaction catalyzed by a cinchona-squaramide catalyst.

Catalytic Asymmetric Inverse-Electron-Demand Hetero-Diels-Alder Reaction of Dioxopyrrolidines with Hetero-Substituted Alkenes

A highly efficient enantioselective inverse-electron-demand hetero-Diels-Alder reaction of dioxopyrrolidines with heterosubstituted alkenes has been realized by using a N, N'-dioxide/Ni(II) complex as the catalyst. A series of chiral bicyclic dihydropyranes were generated in excellent yields, good dr, and excellent ee values. Besides, a catalytic cycle with a possible transition state was proposed.

Supramolecular Platform Stabilizing Growth Factors

High concentrations of supplemented growth factors can cause oversaturation and adverse effects in in vitro and in vivo studies, though these supraphysiological concentrations are often required due to the low stability of growth factors. Here we demonstrate the stabilization of TGF-β1 and BMP4 using supramolecular polymers. Inspired by heparan sulfate, sulfonated peptides were presented on a supramolecular polymer to allow for noncovalent binding to growth factors in solution. After mixing with excipient molecules, both TGF-β1 and BMP4 were shown to have a prolonged half-life compared to the growth factors free in solution. Moreover, high cellular response was measured by a luciferase assay, indicating that TGF-β1 remained highly active upon binding to the supramolecular assembly. The results demonstrate that significant lower concentrations of growth factors can be used when supramolecular polymers bearing growth factor binding moieties are implemented. This approach can also be exploited in hydrogel systems to control growth factor release.

Asymmetric synthesis of bicyclic dihydropyrans via organocatalytic inverse-electron-demand oxo-Diels–Alder reactions of enolizable aliphatic aldehydes

An unprecedented highly enantioselective amine catalyzed oxo-IEDDA reaction of cyclic enones with enolizable aldehydes including aqueous acetaldehyde has been developed.

Synthesis and biological evaluation of some dibenzofuran-piperazine derivatives

In the present paper, a novel series of dibenzofuran-piperazine derivatives were synthesized via the treatment of N-(2-methoxy-3-dibenzofuranyl)-2-chloroacetamide with substituted piperazine derivatives. The chemical structures of the compounds were elucidated by (1)H NMR, (13)C NMR, mass spectral data; elemental analysis and HPLC analysis. Each derivative was evaluated for antiplatelet activity and anticholinesterase activity. Compound 2 m with 2-furoyl moiety exhibited high percentage inhibition as much as standard drug aspirin on arachidonic acid (AA)-induced platelet aggregation. None of the compounds presented significant inhibitor effect on collagen-induced platelet aggregation. Furthermore, the anticholinesterase activity of the compounds was determined and they did not show promising inhibitor activity compared with standard drug donepezil.

A simple, general approach of allosteric coagulation enzyme inhibition through monosulfated hydrophobic scaffolds

Allosteric inhibition of coagulation enzymes offers the advantage of controlled inhibition. In this study, a small library of mono sulfated indole and benzothiazole based molecules was synthesized and screened against the panel of coagulation proteases. The results reveal that selected molecules inhibit the thrombin, factor Xa and factor XIa with moderate potency. Compound 6a was found to have an allosteric mode of inhibition against thrombin. Plasma clotting assays suggest that selected inhibitors 14b, 14c and 14d prolong both prothrombin and activated partial thromboplastin time. Overall, this work presents the newer class of allosteric inhibitors of thrombin and factor XIa with improved aqueous solubility profile.

Recent advances in employing molecular modelling to determine the specificity of glycan-binding proteins

Impressive improvements in docking performance can be achieved by applying energy bonuses to poses in which glycan hydroxyl groups occupy positions otherwise preferred by bound waters. In addition, inclusion of glycosidic conformational energies allows unlikely glycan conformations to be appropriately penalized. A method for predicting the binding specificity of glycan-binding proteins has been developed, which is based on grafting glycan branches onto a minimal binding determinant in the binding site. Grafting can be used either to screen virtual libraries of glycans, such as the known glycome, or to identify docked poses of minimal binding determinants that are consistent with specificity data. The reviewed advances allow accurate modelling of carbohydrate-protein 3D co-complexes, but challenges remain in ranking the affinity of congeners.

Allosteric inhibition of human factor XIa: discovery of monosulfated benzofurans as a class of promising inhibitors

Factor XIa (fXIa) is being recognized as a prime target for developing safer anticoagulants. To discover synthetic, small, allosteric inhibitors of fXIa, we screened an in-house, unique library of 65 molecules displaying many distinct scaffolds and varying levels of sulfation. Of these, monosulfated benzofurans were the only group of molecules found to inhibit fXIa (∼100% efficacy) and led to the identification of monosulfated trimer 24 (IC₅₀ 0.82 μM) as the most potent inhibitor. Michaelis–Menten kinetics studies revealed a classic noncompetitive mechanism of action for 24. Although monosulfated, the inhibitors did not compete with unfractionated heparin alluding to a novel site of interaction. Fluorescence quenching studies indicated that trimer 24 induces major conformational changes in the active site of fXIa. Docking studies identified a site near Lys255 on the A3 domain of fXIa as the most probable site of binding for 24. Factor XIa devoid of the A3 domain displayed a major defect in the inhibition potency of 24 supporting the docking prediction. Our work presents the sulfated benzofuran scaffold as a promising framework to develop allosteric fXIa inhibitors that likely function through the A3 domain.