Phosphorus Dendrimers for Metal-Free Ligation: Design of Multivalent Pharmacological Chaperones against Gaucher Disease

The first phosphorus dendrimers built on a cyclotriphosphazene core and decorated with six or twelve monofluorocyclooctyne units were prepared. A simple stirring allowed the grafting of N-hexyl deoxynojirimycin inhitopes onto their surface by copper-free strain promoted alkyne-azide cycloaddition click reaction. The synthesized iminosugars clusters were tested as multivalent inhibitors of the biologically relevant enzymes β-glucocerebrosidase and acid α-glucosidase, involved in Gaucher and Pompe lysosomal storage diseases, respectively. For both enzymes, all the multivalent compounds were more potent than the reference N-hexyl deoxynojirimycin. Remarkably, the final dodecavalent compound proved to be one of the best β-glucocerebrosidase inhibitors described to date. These cyclotriphosphazene-based deoxynojirimycin dendrimers were then evaluated as pharmacological chaperones against Gaucher disease. Not only did these multivalent constructs cross the cell membranes but they were also able to increase β-glucocerebrosidase activity in Gaucher cells. Notably, dodecavalent compound allowed a 1.4-fold enzyme activity enhancement at a concentration as low as 100 nM. These new monofluorocyclooctyne-presenting dendrimers may further find numerous applications in the synthesis of multivalent objects for biological and pharmacological purposes.

An Intramolecular Hydroaminomethylation-Based Approach to Pyrrolizidine Alkaloids under Microwave-Assisted Heating

A general method for the synthesis of pyrrolizidine derivatives using an intramolecular hydroaminomethylation protocol (HAM) under microwave (MW) dielectric heating is reported. Starting from a 3,4-bis(benzyloxy)-2-[(benzyloxy)methyl]-5-vinylpyrrolidine, MW-assisted intramolecular HAM in the presence of gaseous H2 and CO gave the natural alkaloid hyacinthacine A2 protected as benzyl ether. The same approach gave a lentiginosine analogue starting from the corresponding vinyl N-hydroxypyrrolidine. The nature of the reaction products and the yields were strongly influenced by the relative stereochemistry of the starting pyrrolidines, as well as by the catalyst/ligand employed. The use of ethanol as a solvent provides environmentally friendly conditions, while the ligand/catalyst system can be recovered by separating the alkaloid product with an SCX column and recycling the ethanolic solution. HAM worked up to three times with the recycled catalyst solution without any significant impact on yield.

3,4,5-Trihydroxypiperidine based multivalent glucocerebrosidase (GCase) enhancers

The synthesis of five new multivalent derivatives of a trihydroxypiperidine iminosugar was accomplished through copper catalyzed alkyne‐azide cycloaddition (CuAAC) reaction of an azido ending piperidine and several propargylated scaffolds. The resulting multivalent architectures were assayed as inhibitors of lysosomal GCase, the defective enzyme in Gaucher disease. The multivalent compounds resulted in much more potent inhibitors than a parent monovalent reference compound, thus showing a good multivalent effect. Biological investigation of these compounds as pharmacological chaperones revealed that the trivalent derivative (12) gives a 2‐fold recovery of the GCase activity on Gaucher patient fibroblasts bearing the L444P/L444P mutations responsible for neuropathies. Additionally, a thermal denaturation experiment showed its ability to impart stability to the recombinant enzyme used in therapy.

Carbohydrate supramolecular chemistry: beyond the multivalent effect

(Hetero)multivalency acts as a multichannel switch that shapes the supramolecular properties of carbohydrates in an intrinsically multifactorial biological context.

Synthesis and Glycosidase Inhibition of Broussonetine M and Its Analogues

Cross-metathesis (CM) and Keck asymmetric allylation, which allows access to defined stereochemistry of a remote side chain hydroxyl group, are the key steps in a versatile synthesis of broussonetine M (3) from the d-arabinose-derived cyclic nitrone 14. By a similar strategy, ent-broussonetine M (ent-3) and six other stereoisomers have been synthesized, respectively, starting from l-arabino-nitrone (ent-14), l-lyxo-nitrone (ent-3-epi-14), and l-xylo-nitrone (2-epi-14) in five steps, in 26%–31% overall yield. The natural product broussonetine M (3) and 10’-epi-3 were potent inhibitors of β-glucosidase (IC₅₀ = 6.3 μM and 0.8 μM, respectively) and β-galactosidase (IC₅₀ = 2.3 μM and 0.2 μM, respectively); while their enantiomers, ent-3 and ent-10’-epi-3, were selective and potent inhibitors of rice α-glucosidase (IC₅₀ = 1.2 μM and 1.3 μM, respectively) and rat intestinal maltase (IC₅₀ = 0.29 μM and 18 μM, respectively). Both the configuration of the polyhydroxylated pyrrolidine ring and C-10’ hydroxyl on the alkyl side chain affect the specificity and potency of glycosidase inhibition.

Dual targeting of PTP1B and glucosidases with new bifunctional iminosugar inhibitors to address type 2 diabetes

The diffusion of type 2 diabetes (T2D) throughout the world represents one of the most important health problems of this century. Patients suffering from this disease can currently be treated with numerous oral anti-hyperglycaemic drugs, but none is capable of reproducing the physiological action of insulin and, in several cases, they induce severe side effects. Developing new anti-diabetic drugs remains one of the most urgent challenges of the pharmaceutical industry. Multi-target drugs could offer new therapeutic opportunities for the treatment of T2D, and the reported data on type 2 diabetic mice models indicate that these drugs could be more effective and have fewer side effects than mono-target drugs. α-Glucosidases and Protein Tyrosine Phosphatase 1B (PTP1B) are considered important targets for the treatment of T2D: the first digest oligo- and disaccharides in the gut, while the latter regulates the insulin-signaling pathway. With the aim of generating new drugs able to target both enzymes, we synthesized a series of bifunctional compounds bearing both a nitro aromatic group and an iminosugar moiety. The results of tests carried out both in vitro and in a cell-based model, show that these bifunctional compounds maintain activity on both target enzymes and, more importantly, show a good insulin-mimetic activity, increasing phosphorylation levels of Akt in the absence of insulin stimulation. These compounds could be used to develop a new generation of anti-hyperglycemic drugs useful for the treatment of patients affected by T2D.

Multimerization of DAB-1 onto Au GNPs affords new potent and selective N-acetylgalactosamine-6-sulfatase (GALNS) inhibitors

Gold glyconanoparticles (Au GNPs) decorated with the natural iminosugar DAB-1 at different densities are reported.

Pyrrolizidine alkaloids: occurrence, biology, and chemical synthesis

Covering: 2013 up to the end of 2015This review covers the isolation and structure of new pyrrolizidines; pyrrolizidine biosynthesis; biological activity, including the occurrence of pyrrolizidines as toxic components or contaminants in foods and beverages; and formal and total syntheses of naturally-occurring pyrrolizidine alkaloids and closely related non-natural analogues.

C-Glycopyranosyl Arenes and Hetarenes: Synthetic Methods and Bioactivity Focused on Antidiabetic Potential

This Review summarizes close to 500 primary publications and surveys published since 2000 about the syntheses and diverse bioactivities of C-glycopyranosyl (het)arenes. A classification of the preparative routes to these synthetic targets according to methodologies and compound categories is provided. Several of these compounds, regardless of their natural or synthetic origin, display antidiabetic properties due to enzyme inhibition (glycogen phosphorylase, protein tyrosine phosphatase 1B) or by inhibiting renal sodium-dependent glucose cotransporter 2 (SGLT2). The latter class of synthetic inhibitors, very recently approved as antihyperglycemic drugs, opens new perspectives in the pharmacological treatment of type 2 diabetes. Various compounds with the C-glycopyranosyl (het)arene motif were subjected to biological studies displaying among others antioxidant, antiviral, antibiotic, antiadhesive, cytotoxic, and glycoenzyme inhibitory effects.

Amino-functionalized iminocyclitols: synthetic glycomimetics of medicinal interest

A review on the syntheses and biological activities of unnatural glycomimetics highlighting the effect of replacement of hydroxyl groups of natural iminosugars by amino functionalities is presented.

Evidence for a multivalent effect in inhibition of sulfatases involved in lysosomal storage disorders (LSDs)

New targets sensitive to multivalency: synthesis of nonavalent pyrrolidine iminosugars.

Exploring architectures displaying multimeric presentations of a trihydroxypiperidine iminosugar

The synthesis of new multivalent architectures based on a trihydroxypiperidine α-fucosidase inhibitor is reported herein. Tetravalent and nonavalent dendrimers were obtained by means of the click chemistry approach involving the copper azide-alkyne-catalyzed cycloaddition (CuAAC) between suitable scaffolds bearing terminal alkyne moieties and an azido-functionalized piperidine as the bioactive moiety. A preliminary biological investigation is also reported towards commercially available and human glycosidases.

Design, synthesis and photochemical properties of the first examples of iminosugar clusters based on fluorescent cores

The synthesis and photophysical properties of the first examples of iminosugar clusters based on a BODIPY or a pyrene core are reported. The tri- and tetravalent systems designed as molecular probes and synthesized by way of Cu(I)-catalysed azide-alkyne cycloadditions are fluorescent analogues of potent pharmacological chaperones/correctors recently reported in the field of Gaucher disease and cystic fibrosis, two rare genetic diseases caused by protein misfolding.

Gold nanoparticles are suitable cores for building tunable iminosugar multivalency

Inhibition in the low micromolar range towards amyloglucosidase.

Synthesis and biological properties of multivalent iminosugars

Clustering 1-deoxynojirimycin (DNJ), first isolated from white mulberry, and other iminosugars around various scaffolds gave strong glycosidase inhibitors.

New synthesis and biological evaluation of uniflorine A derivatives: towards specific insect trehalase inhibitors

(–)-Uniflorine A and 7-deoxy-uniflorine A are selective inhibitors of insect trehalases from C. riparius and S. littoralis.