Toward the synthesis of fine chemicals from lactose: preparation of d-xylo and l-lyxo-aldohexos-5-ulose derivatives

Formal Glycosylation of Quinones with exo-Glycals Enabled by Iron-Mediated Oxidative Radical-Polar Crossover

The intermolecular C-O coupling reaction of 1,4-quinones with exo-glycals under iron hydride hydrogen atom transfer (HAT) conditions is described. This method provides a direct and regioselective access to a wide range of phenolic O-ketosides related to biologically relevant natural products in diastereomeric ratios up to >98:2 in the furanose and pyranose series. No trace of the corresponding C-glycosylated products that might have resulted from the radical alkylation of 1,4-quinones was observed. The results of mechanistic experiments suggest that the key C-O bond-forming event proceeds through an oxidative radical-polar crossover process involving a single-electron transfer between the HAT-generated glycosyl radical and the electron-acceptor quinone.

Exploring and exploiting different catalytic systems for the direct conversion of cellulose into levulinic acid

The single step conversion of cellulose into levulinic acid has been studied under hydrothermal conditions with several catalytic systems.

Ensemble-based ADME-Tox profiling and virtual screening for the discovery of new inhibitors of the Leishmania mexicana cysteine protease CPB2.8ΔCTE

In an effort to identify novel molecular warheads able to inhibit Leishmania mexicana cysteine protease CPB2.8ΔCTE, fused benzo[b]thiophenes and β,β'-triketones emerged as covalent inhibitors binding the active site cysteine residue. Enzymatic screening showed a moderate-to-excellent activity (12%-90% inhibition of the target enzyme at 20 μm). The most promising compounds were selected for further profiling including in vitro cell-based assays and docking studies. Computational data suggest that benzo[b]thiophenes act immediately as non-covalent inhibitors and then as irreversible covalent inhibitors, whereas a reversible covalent mechanism emerged for the 1,3,3'-triketones with a Y-topology. Based on the predicted physicochemical and ADME-Tox properties, compound 2b has been identified as a new drug-like, non-mutagen, non-carcinogen, and non-neurotoxic lead candidate.

Molecular modeling studies of pseudouridine isoxazolidinyl nucleoside analogues as potential inhibitors of the pseudouridine 5'-monophosphate glycosidase

In this paper, we investigated the hypothesis that pseudouridine isoxazolidinyl nucleoside analogues could act as potential inhibitors of the pseudouridine 5'-monophosphate glycosidase. This purpose was pursued using molecular modeling and in silico ADME-Tox profiling. From these studies emerged that the isoxazolidinyl derivative 1 5'-monophosphate can be effectively accommodated within the active site of the enzyme with a ligand efficiency higher than that of the natural substrate. In this context, the poor nucleofugality of the N-protonated isoxazolidine prevents or slows down, the first mechanistic step proposed for the degradation of the pseudouridine 5'-monophosphate glycosidase, leading to the enzyme inhibition. Finally, the results of the physicochemical and ADME-Tox informative analysis pointed out that compound 1 is weakly bounded to plasma protein, only moderately permeate the blood-brain barrier, and is non-carcinogen in rat and mouse. To the best of our knowledge, this is the first paper that introduces the possibility of inhibition of pseudouridine 5'-monophosphate glycosidase by a molecule that competing with the natural substrate hinders the glycosidic C-C bond cleavage.

Adipocyte fatty acid binding protein 4 (FABP4) inhibitors. A comprehensive systematic review

Small molecule inhibitors of adipocyte fatty acid binding protein 4 (FABP4) have attracted interest following the recent publications of beneficial pharmacological effects of these compounds. FABP4 is predominantly expressed in macrophages and adipose tissue where it regulates fatty acids (FAs) storage and lipolysis and is an important mediator of inflammation. In the past years, hundreds FABP4 inhibitors have been synthesized for effective atherosclerosis and diabetes treatments, including derivatives of niacin, quinoxaline, aryl-quinoline, bicyclic pyridine, urea, aromatic compounds and other novel heterocyclic compounds. This review provides an overview of the synthesized and discovered molecules as adipocyte fatty acid binding protein 4 inhibitors (FABP4is) since the synthesis of the putative FABP4i, BMS309403, highlighting the interactions of the different classes of inhibitors with the targets.

Synthesis and conformational analysis of a simplified inositol-model of the Streptococcus pneumoniae 19F capsular polysaccharide repeating unit

Carbohydrate mimics have been studied for a long time as useful sugar substitutes, both in the investigation of biological events and in the treatment of sugar-related diseases. Here we report further evaluation of the capabilities of inositols as carbohydrate substitutes. The conformational features of an inositol-model of a simplified repeating unit corresponding to the capsular polysaccharide of Streptococcus pneumoniae 19F has been evaluated by computational analysis, and compared to the native repeating unit. The inositol mimic was synthesized, and its experimental spectroscopic data allowed for verification of the theoretical results.

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

The intramolecular aldol condensation of aldohexos-5-ulose derivatives of the D-xylo and L-ribo stereoseries has been studied. Only one of the four possible inososes was isolated from both stereoseries in reasonable yields (30–38%). The results obtained, together with the previous findings for the L-arabino and L-lyxo stereoseries, allowed for the rationalisation of a mechanism of the reaction based on open-transition-state models and electron-withdrawing inductive effects. Complementary reductions of the intermediate inososes were possible by changing the reaction conditions, and two isomeric inositol derivatives were obtained with complete stereoselection from each inosose. The presented approach permits us to control the configuration of three out of the six stereocentres of the inositol frame and gives access to seven of the nine inositols. Noteworthy, for the D-xylo derivative, the two-step sequence (condensation followed by reduction with NaBH(OAc)₃) represents the biomimetic synthesis of myo-inositol. Furthermore, the sugar-based pathway leads directly to enantiomerically pure selectively protected inositols and does not require any desymmetrisation procedure which is needed when myo-inositol and other achiral precursors are employed as starting materials. As an example of application of the method, the indirect selective protection of secondary inositols’ hydroxy functions, by placing specific protecting groups on the aldohexos-5-ulose precursor has been presented.

5'-Spiro-cyclopropanated lactose derivatives as suitable intermediates for the chain elongation: synthesis of a new 6-deoxy-6-methyl δ-eptulose

A δ-dicarbonyl heptose has been prepared through an electrophilic ring opening procedure of a 5'-spirocyclopropanated lactose derivative. The reported synthetic procedure outlines a new route for the transformation of this renewable disaccharide into new and interesting δ-dicarbonyl sugars, synthetic precursors of cyclitols, carba- and azasugars. The experimental results of the cyclopropanation process have been successfully rationalized by in silico studies.