Regioselective sulfonylation at O-2 of cyclomaltoheptaose with 1-(p-tolylsulfonyl)-(1H)-1,2,4-triazole

Cyclodextrin Inclusion Complexes for Improved Drug Bioavailability and Activity: Synthetic and Analytical Aspects

Many active pharmaceutical ingredients show low oral bioavailability due to factors such as poor solubility and physical and chemical instability. The formation of inclusion complexes with cyclodextrins, as well as cyclodextrin-based polymers, nanosponges, and nanofibers, is a valuable tool to improve the oral bioavailability of many drugs. The microencapsulation process modifies key properties of the included drugs including volatility, dissolution rate, bioavailability, and bioactivity. In this context, we present relevant examples of the stabilization of labile drugs through the encapsulation in cyclodextrins. The formation of inclusion complexes with drugs belonging to class IV in the biopharmaceutical classification system as an effective solution to increase their bioavailability is also discussed. The stabilization and improvement in nutraceuticals used as food supplements, which often have low intestinal absorption due to their poor solubility, is also considered. Cyclodextrin-based nanofibers, which are polymer-free and can be generated using environmentally friendly technologies, lead to dramatic bioavailability enhancements. The synthesis of chemically modified cyclodextrins, polymers, and nanosponges based on cyclodextrins is discussed. Analytical techniques that allow the characterization and verification of the formation of true inclusion complexes are also considered, taking into account the differences in the procedures for the formation of inclusion complexes in solution and in the solid state.

Comparison of Various Tosylating Reagents for the Synthesis of Mono-2-O-tosyl-β-cyclodextrin

Mono-2-O-tosyl-β-cyclodextrin is a key compound, as starting material, for the preparation of multifunctional systems in supramolecular chemistry. Although several methods are available in the literature for its synthesis, yields are always moderate (usually less than 42%) and reproducibility can be an issue as a result of the difficulties encountered in its preparation that are related to selectivity, monofunctionalization, solubility and purification, among others. A modification of a literature method was developed giving emphasis to simplicity and reproducibility and, for the first time, was tested with nine easily accessible tosylating reagents that differ significantly in their nature and reactivity. Product isolation was accomplished with precipitation followed by reverse-phase flash chromatography, which is easy to scale up. Interestingly, with the proposed method, all nine reagents can be successfully applied for the synthesis of the product with yields ranging from 33% to 40%. Optimum reaction times and temperatures were found and conclusions for each tosylating reagent are drawn.

Base free regioselective synthesis of α-triazolylazine derivatives

A regioselective α-heteroarylation followed by deoxygenation towards the synthesis of variety of azine triazole from simple azine N-oxides derivatives and N-tosyl-1,2,3-triazoles has been described.

Selective Secondary Face Modification of Cyclodextrins by Mechanosynthesis

α-, β-, and γ-cyclodextrins (CDs) were modified on their secondary face by mechanosynthesis at room temperature using a laboratory-scale ball-mill. Mono-2-tosylated α-, β-, and γ-CDs were obtained in good yield from mixtures of native α-, β-, and γ-CDs, respectively, N-tosylimidazole, and an inorganic base, with each of them being in the solid state. The yields appeared to be dependent upon the nature of the base and the reaction time. A kinetic monitoring by (1)H NMR spectroscopy demonstrated that the highest yields in mono-2-tosyl-CDs were measured using KOH as a base in very short reaction times (up to 65% in 80 s). Mono-(2,3-manno-epoxide) α-, β-, and γ-CDs were subsequently synthesized by ball-milling a mixture of monotosylated α-, β-, and γ-CDs, respectively, and KOH. The characterization of the modified CDs was carried out by X-ray diffraction, mass spectrometry, solid-state NMR, and diffuse reflectance UV-vis (DR UV-vis) spectroscopies. Clues to the supramolecular arrangement of the molecules in the solid state provide information on the reaction mechanism.