Nucleophilic substitution at the anomeric position of furanose carbohydrates. The case of the C-allylations

Taking advantage of the locked conformation of cyclic furanose form, carbohydrate derivatives have been transformed into relevant tetrahydrofuran moieties through a chemical operation commonly known as C-glycosylation reaction. Consequently, a large number of total synthesis of naturally occurring products containing this heterocycle have been accomplished by applying this reaction. In this regard, the C-allylation reaction of furanose carbohydrates provides flexible routes for stereoselective anomeric functionalization by incorporating an allyl group, which is eventually re-functionalized into advanced natural product intermediates. Therefore, this mini review deals with the description of the origin of the stereoselectivity and synthetic applications of this type of glycosylation reaction, which can be also called as: "Nucleophilic Substitution at the Anomeric Position", conducted by various research groups including our own group.

Sugar-Based Ionic Liquids: Multifaceted Challenges and Intriguing Potential

Carbohydrates represent a promising option in transitioning from oil-based chemical resources to renewable ones, with the goal of developing chemistries for a sustainable future. Cellulose, hemicellulose, and largely available monosaccharides already provide useful chemical building blocks, so-called platform chemicals, such as levulinic acid and hydroxymethyl furfural, as well as solvents like cyrene or gamma-valerolactone. Therefore, there is great anticipation for novel applications involving materials and chemicals derived from sugars. In the field of ionic liquids (ILs), sugar-based ILs have been overlooked for a long time, mainly on account of their multistep demanding preparation. However, exploring new strategies for accessing sugar-based ILs, their study, and their exploitation, are attracting increasing interest. This is due to the growing concerns about the negative (eco)toxicity profile of most ILs in conjunction with their non-sustainable nature. In the present review, a literature survey concerning the development of sugar-based ILs since 2011 is presented. Their preparation strategies and thermal behavior analyses, sorted by sugar type, make up the first two sections with the intention to provide the reader with a useful guide. A final overview of the potential applications of sugar-based ILs and their future perspectives complement the present analysis.

Progress in the development of human carbonic anhydrase inhibitors and their pharmacological applications: Where are we today?

Carbonic anhydrases (CAs, EC 4.2.1.1) are widely distributed metalloenzymes in both prokaryotes and eukaryotes. They efficiently catalyze the reversible hydration of carbon dioxide to bicarbonate and H⁺  ions and play a crucial role in regulating many physiological processes. CAs are well-studied drug target for various disorders such as glaucoma, epilepsy, sleep apnea, and high altitude sickness. In the past decades, a large category of diverse families of CA inhibitors (CAIs) have been developed and many of them showed effective inhibition toward specific isoforms, and effectiveness in pathological conditions in preclinical and clinical settings. The discovery of isoform-selective CAIs in the last decade led to diminished side effects associated with off-target isoforms inhibition. The many new classes of such compounds will be discussed in the review, together with strategies for their development. Pharmacological advances of the newly emerged CAIs in diseases not usually associated with CA inhibition (neuropathic pain, arthritis, cerebral ischemia, and cancer) will also be discussed.

Theoretical modeling of pKa's of thiol compounds in aqueous solution

The pK_a's of different kinds of thiols (R-SH) were investigated by using the M06-2X method with a SMD_sSAS model.

Inhibition of carbonic anhydrase IX targets primary tumors, metastases, and cancer stem cells: Three for the price of one

Human carbonic anhydrase (CA) IX is a tumor-associated protein, since it is scarcely present in normal tissues, but highly overexpressed in a large number of solid tumors, where it actively contributes to survival and metastatic spread of tumor cells. Due to these features, the characterization of its biochemical, structural, and functional features for drug design purposes has been extensively carried out, with consequent development of several highly selective small molecule inhibitors and monoclonal antibodies to be used for different purposes. Aim of this review is to provide a comprehensive state-of-the-art of studies performed on this enzyme, regarding structural, functional, and biomedical aspects, as well as the development of molecules with diagnostic and therapeutic applications for cancer treatment. A brief description of additional pharmacologic applications for CA IX inhibition in other diseases, such as arthritis and ischemia, is also provided.

Synthesis of Conformationally-Locked cis- and trans-Bicyclo[4.4.0] Mono-, Di-, and Trioxadecane Modifications of Galacto- and Glucopyranose; Experimental Limiting 3JH,H Coupling Constants for the Estimation of Carbohydrate Side Chain Populations and Beyond

Hexopyranose side chains populate three staggered conformations, whose proportions can be determined from the three sets of ideal limiting 3JH5,H6R and 3JH5,H6S coupling constants in combination with the time-averaged experimental coupling constants. Literature values for the limiting coupling constants, obtained by the study of model compounds, the use of the Haasnoot-Altona and related equations, or quantum mechanical computations, can result in computed negative populations of one of the three ideal conformations. Such values arise from errors in the limiting coupling constants and/or from the population of nonideal conformers. We describe the synthesis and analysis of a series of cis- and trans-fused mono-, di-, and trioxabicyclo[4.4.0]octane-like compounds. Correction factors for the application of data from internal models (-CH(OR)-CH(OR)-) to terminal systems (-CH(OR)-CH2(OR)) are deduced from comparison of further models, and applied where necessary. Limiting coupling constants so-derived are applied to the side chain conformations of three model hexopyranosides, resulting in calculated conformer populations without negative values. Although, developed primarily for hexopyranose side chains, the limiting coupling constants are suitable, with the correction factors presented, for application to the side chains of higher carbon sugars and to conformation analysis of acyclic diols and their derivatives in a more general sense.

Design of α-S-Neoglycopeptides Derived from MUC1 with a Flexible and Solvent-Exposed Sugar Moiety

The use of vaccines based on MUC1 glycopeptides is a promising approach to treat cancer. We present herein several sulfa-Tn antigens incorporated in MUC1 sequences that possess a variable linker between the carbohydrate (GalNAc) and the peptide backbone. The main conformations of these molecules in solution have been evaluated by combining NMR experiments and molecular dynamics simulations. The linker plays a key role in the modulation of the conformation of these compounds at different levels, blocking a direct contact between the sugar moiety and the backbone, promoting a helix-like conformation for the glycosylated residue and favoring the proper presentation of the sugar unit for molecular recognition events. The feasibility of these novel compounds as mimics of MUC1 antigens has been validated by the X-ray diffraction structure of one of these unnatural derivatives complexed to an anti-MUC1 monoclonal antibody. These features, together with potential lack of immune suppression, render these unnatural glycopeptides promising candidates for designing alternative therapeutic vaccines against cancer.

Carbonic Anhydrase Glycoinhibitors belonging to the Aminoxysulfonamide Series

A general approach for the synthesis of carbonic anhydrases glycoinhibitors belonging to an aminoxysulfonamide series is presented using a Ferrier sulfonamidoglycosylation reaction on glycals. All the compounds showed good in vitro inhibitory activity against four human carbonic anhydrase isoforms, with selectivity against the cytosolic (hCA II) vs the tumor associated (hCA IX and XII) enzymes.

Carbonic Anhydrase Inhibition with Benzenesulfonamides and Tetrafluorobenzenesulfonamides Obtained via Click Chemistry

A series of novel benzene- and 2,3,5,6-tetrafluorobenzenesulfonamide was synthesized by using a click chemistry approach starting from azido-substituted sulfonamides and alkynes, incorporating aryl, alkyl, cycloalkyl, and amino-/hydroxy-/halogenoalkyl moieties. The new compounds were medium potency inhibitors of the cytosolic carbonic anhydrase (CA, EC 4.2.1.1) isoforms I and II and low nanomolar/subnanomolar inhibitors of the tumor-associated hCA IX and XII isoforms. The X-ray crystal structure of two such sulfonamides in adduct with hCA II allowed us to understand the factors governing inhibitory power.