The first enantioselective total synthesis of scopadulcic acid A is described. The key step is a cascade intramolecular Heck reaction of a methylenecycloheptene iodide, which generates the B, C, and D rings of the scopadulan ring system in 90% yield as a single stereoisomer. A distinctive feature of these syntheses is the use of stereoselective enolization to dictate which enantiomer of the natural product is produced.

The synthesis of crystalline per-O-TBS-beta-D-galactofuranose (4beta) as a new precursor of D-Gal f units is described. Anomeric iodination by reaction with TMSI followed by in situ coupling with simple alcohols and a wide variety of glycosyl acceptors, in the absence of a promoter, was employed as a new efficient glycosylation method for the assembly of D-galactofuranosyl moieties with high beta-stereoselectivity. Under the mild conditions of this reaction labile protective groups, like acetals, and furanosyl linkages are preserved.

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Beta-D-galactofuranosidase is a good chemotherapeutic target for the design of inhibitors, since beta-D-galactofuranose is a constituent of important parasite glycoconjugates but is not present in the host mammals. With this aim, we have synthesized for the first time alkyl, benzyl and aryl 1-thio-beta-D-galactofuranosides by condensation of penta-O-benzoyl-alpha,beta-D-galactofuranose with the corresponding thiols, in the presence of SnCl4as catalyst. The complete chemical and spectroscopical characterization of these compounds showed that the reaction was stereoselective. Debenzoylation with sodium methoxide afforded the beta-S-galactofuranosides in high yield. The thioglycosides were tested as inhibitors of the beta-D-galactofuranosidase of Penicillium fellutanum, using for the first time 4-nitrophenyl-beta-D-galactofuranoside as chromogenic substrate. The 4-aminophenyl-1-thio-beta-D-galactofuranoside, obtained by catalytic hydrogenation of the nitrophenyl derivative, was the best inhibitor being then an adequate ligand for the preparation of an affinity phase aimed at the isolation of beta-d-galactofuranosidases from different sources. Also the inhibitory activity of d-galactono-1, 4-lactone was shown.

The use of biomarkers for the detection of fungal infections is of interest to complement histopathological and culture methods. Since the production of antibodies in immunocompromised patients is scarce, detection of a specific antigen could be effective for early diagnosis. D-Galactofuranose (Galf) is the antigenic epitope in glycoconjugates of several pathogenic fungi. Since Galf is not biosynthesized by mammals, it is an attractive candidate for diagnosis of infection. A monoclonal antibody that recognizes Galf is commercialized for detection of aspergillosis. The linkage of Galf in the natural glycans and the chemical structures of the synthesized Galf-containing oligosaccharides are described in this paper. The oligosaccharides could be used for the synthesis of artificial carbohydrate-based antigens, not enough exploited for diagnosis.

Keywords: Thiodisaccharides / Furanose / Glycosylation / Catalysis / Molybdenum / Michael addition Thiodisaccharides having a 1-thiopentofuranose nonreducing end were synthesized by two routes starting from per-Oacylaldofuranoses with arabino, ribo, and xylo configurations. These glycosyl donors were converted into S-glycosyl isothiourea derivatives as precursors of 1-thiofuranose units, which were generated in situ and trapped by a sugar enone to produce, by Michael addition, the thioglycosidic linkage.