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We have explored the rich structural diversity provided by an α-azido ester derived from d -arabinose as the source of sugar templates with reduced conformational flexibility. Using transient α-thioureido(selenoureido) esters we have prepared spiranic thio(seleno)hydantoins at the C-3 position of the sugar moiety. In this context, the first example of a stable spiranic α-lactam (or aziridinone) was isolated as a by-product in the hydrogenolysis of the starting α-azido ester. Furthermore, using copper(I)-catalyzed azido–alkyne cycloaddition (click chemistry), we have accessed bicyclic cis-fused α-triazolyl lactones fixed in the furanose form. Spiranic thiohydantoins turned out to be moderate, though selective, inhibitors of glycosidases, whereas their selenium isosters behaved as good free radical scavengers.

The synthesis of a series of l-fuco-configured selenosugars, isosters of the potent glycosidase inhibitor isofucofagomine has been accomplished by a double nucleophilic displacement of a dimesylated derivative with selenide anion generated in situ. Se-Alkylation and oxidation of the corresponding selenane afforded a selenonium and a selenoxide, respectively. The biological activities of such compounds have been evaluated, finding a dual activity caused by the presence of the selenium atom: the selenane exerted a good glutathione peroxidase mimicry by efficiently scavenging H2O2 in the presence of thiols, whereas the stable selenoxide derivative was found to be the first example of a selenosugar acting as a good α-l-fucosidase inhibitor.

We have explored the preparation of conformationally-restricted pseudonucleosides bearing a spiranic thiohydantoin scaffold on C-3 of the sugar moiety by coupling partially protected 3-amino-3-methoxycarbonyl and 3-isothiocyanato-3-methoxycarbonyl glucofuranose derivatives with alkyl(aryl)isothiocyanates or with alkyl(aryl)amines; the key step is a spontaneous or thermal-induced intramolecular nucleophilic substitution of transient thioureas. Upon deprotection, final spiranic thiohydantoins were evaluated as glycosidase and glycogen phosphorylase inhibitors.

The complexation of the potent olive oil antioxidant hydroxytyrosol (HT) with commercial β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous solutions has been studied for the first time. The 1:1 stoichiometries of the complexes were evidenced by Job’s plot and the association constants were determined by linear regressions from Scott’s method. The geometry of the HT/β-CD complex was elucidated by 2D-ROESY experiments, suggesting insertion of the catechol moiety with the hydroxyalkyl chain directed to the primary rim. The antioxidant activity of encapsulated HT was also evaluated by scavenging of the stable DPPH radical, observing an improvement of the scavenging activity upon increase of the cyclodextrin concentration. Complexation of HT with β-CD also provided a strong photoprotection of the polyphenolic compound upon irradiation with UV (λ=254 nm).

Aryl, alkyl, and sugar-derived isoselenocyanates were prepared by a one-pot procedure starting from the corresponding formamides, using triphosgene as a dehydrating agent, triethylamine, and black selenium powder. The preparation of sugar selenoureas by coupling of O-protected sugar-derived isoselenocyanates with different amines, and by coupling of unprotected glycopyranosyl amines with phenyl isoselenocyanate was also accomplished. The synthesis of a glucopyranos-2-yl-selenazole starting from O-protected 2-amino-2-deoxy-d-glucose by coupling with benzoyl isoselenocyanate, Se-alkylation with phenacyl bromide, and acid-catalyzed dehydration is also reported. Unprotected N-(β-d-glucopyranosyl)-N′-phenylselenourea was transformed into a 1,2-trans-fused bicyclic isourea upon treatment with aqueous hydrogen peroxide; the same isourea was prepared by a one-pot three-step procedure from β-d-glycopyranosylamine by thiophosgenation, coupling with aniline, and HgO-mediated desulfurization.

1,2-cis-Fused bicyclic sugar thiocarbamates of gluco and manno configurations have been prepared by treatment of the corresponding O-unprotected amino sugars and glycopyranosyl amines with thiophosgene. The reactivity of these compounds towards amines has been studied in order to determine whether these compounds could act as latent isothiocyanates; it is shown that 1,2-cis-fused bicyclic sugar thiocarbamates are more stable than their trans analogues, and are not transformed into thioureas upon treatment with amines. An unprecedented isomerization of a peracetylated glucopyranoso[2,1-d]oxazolidine-2-thione into a glucopyranoso[2,1-d]thiazolidin-2-one in DMF is also reported. The structure of this thiazolidin-2-one was confirmed by X-ray crystallography.

We report the selective preparation of α- and β-cyclodextrins bearing one and two phosphate moieties on the primary rim. These compounds were prepared by selective O-debenzylation of fully protected derivatives, followed by phosphorylation and deprotection. The synthesis of an α-cyclodextrin with both, a carboxylic group and a phosphate moiety on primary positions is also described. Title compounds are examples of negatively charged cyclodextrins that might be of interest in studying the complexation of cationic guests.

An efficient method for the preparation of urea-bridged cyclodextrins using triphosgene in the isocyanation step in an aqueous two-phase system is reported. Per- O -acetylated glycopyranosylamines and 2-amino-2-deoxy-α and β- d -glucose were also transformed into the corresponding isocyanates using either an aqueous two-phase or an anhydrous dichloromethane medium, and converted in situ into ureas. An alternative method for the preparation of sugar-derived ureas consisting of desulfurization of sugar thioureas with mercury oxide is also presented.

A series of furan C -nucleosides having a sulfur atom in the sugar ring were synthesised. The α and β anomers of 3-ethoxycarbonyl-2-methyl-5-(4′-thio- d -erythrofuranosyl)furans 10 and 11 were obtained by acid treatment of (4′- S -acetyl-4′-thio- d - arabino -tetritol-1-yl)furan 9 . Oxidation of 10 with m -chloroperbenzoic acid gave sulfoxide 12 as one epimer at the sulfur atom whereas 11 was transformed into sulfoxide 13 as an epimeric mixture. S -Methylation of 10 and 11 with methyl triflate led to sulfonium salts 14 and 15 . The prepared compounds were found to be moderate inhibitors of α- l -fucosidase.