Q112432486
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An approach to stereoselective synthesis of alpha- or beta-3-C-glycosylated L- or D-1,2-glucals starting from the corresponding alpha- or beta-glycopyranosylethanals is described. The key step of the approach is the stereoselective cycloaddition of chiral vinyl ethers derived from both enantiomers of mandelic acid. The preparation of 1,5-anhydro-4,6-di-O-benzyl-2,3-dideoxy-3-C-[(2,3,4,6-tetra-O-benzyl-beta-D-glucopyranosyl)methyl]-L-arabino-hex-1-enitol, 1,5-anhydro-4,6-di-O-benzyl-2,3-dideoxy-3-C-[(2,3,4,6-tetra-O-benzyl-beta-D-glucopyranosyl)methyl]-D-arabino-hex-1-enitol, and 1,5-anhydro-4,6-di-O-benzyl-2,3-dideoxy-3-C-[(2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl)methyl]-D-arabino-hex-1-enitol serves as an example of this approach.
The diastereomeric substituted 2H-dihydropyran derivatives 2b and 3b were obtained by the stereoselective cycloaddition of (E)-4-(tetra-O-benzyl-?-D-galactopyranosyl)-1-(thiazol-2-yl)but-2-en-1-one (1) with either of the enantiomeric chiral vinyl ethers (R)-4 or (S)-4. Reduction of the ester group, transformation of the thiazole ring into an aldehyde group and reaction with an excess of borane afforded the final C-(1›3)-disaccharide structures. The obtained C-(1›3)-disaccharides, containing an L- or D-deoxy-arabino-hexopyranose moiety at the reducing end, were characterized as peracetylated methyl glycosides 9a, 9b and 12a, 12b.
New types of porphyrin derivatives bearing "C-glycoside" moieties, either in 5,10,15,20- or in 5,15-meso-positions, were prepared and fully characterized. The presence of the glycosidic groups imparts to the title macrocycles, besides an amphiphilic character, a clear tendency to form chiral suprastructures upon solvent-driven self-aggregation in different aqueous-organic solvent mixtures. Supra-assembly phenomena, in terms of the size and morphology of the resulting structures, as well as their kinetics of aggregation, were studied by UV-visible, fluorescence, resonance light scattering (RLS), and CD spectroscopy, indicating that the morphology of the aggregates depends strongly on the structure of the porphyrin rings, and on the bulk conditions of aggregation.
- MeSH
- aldehydy chemie MeSH
- cirkulární dichroismus MeSH
- financování organizované MeSH
- glykosidy chemická syntéza chemie MeSH
- katalýza MeSH
- kinetika MeSH
- kyselina trifluoroctová MeSH
- porfyriny chemická syntéza chemie MeSH
- pyrroly chemie MeSH
- radiační rozptyl MeSH
- rozpouštědla chemie MeSH
- spektrofotometrie ultrafialová MeSH
- světlo MeSH
