Miklós Hornyák

University of Debrecen, Debrecen, Hajdu-Bihar, Hungary

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Publications (7)8.82 Total impact

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    ABSTRACT: The carbohydrate subunits carrying an N-O-interglycosidic bond play a very important role in the biological activity of the enediyne antibiotics. Condensation of O-(alpha- and beta-D-glucopyranosyl)hydroxylamine (5a and 5b) with the hex-3-ulopyranoside (6) furnished methyl 4,6-O-benzylidene-2,3-dideoxy-3-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyloxy)imino-alpha- and beta-D-erythro-hexopyranoside (7a and 7b). Stereoselective reduction of the Cz.dbnd6;N bond of 7a and 7b with sodium cyanoborohydride resulted in the formation of the required protected N-O-interglycosidic disaccharides (8a and 8b). Finally, catalytic hydrogenation of 8a afforded methyl 2,3-dideoxy-3-(alpha-D-glucopyranosyloxy)amino-alpha-D-ribo-hexopyranoside (9a). Under similar conditions the beta anomer 8b underwent decomposition.
    Carbohydrate Research 09/2003; 338(17):1787-92. · 2.04 Impact Factor
  • The Journal of Antibiotics 12/1999; 52(11):1050-5. · 2.19 Impact Factor
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    ABSTRACT: Acylation of amoxycillin and cephalexin with acids III, V and VII, and with isocyanate VIII furnished the corresponding beta-lactam antibiotics (X and XIII-XV, respectively). The antibacterial activity of these new antibiotic analogues against Helicobacter pylori was found to be identical with those of amoxycillin, Augmentin, erythromycin and ciprofloxacin.
    Acta pharmaceutica Hungarica 10/1999; 69(4):213-7.
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    ABSTRACT: A molecular dynamics study and solution-phase 1H and 13C chemical shift anisotropy determination of a symmetric cryogenic disaccharide, α,α-trehalose, has been performed in a temperature range between 264 and 350 K. Negligible temperature dependence of proton−carbon couplings of the asymmetrically [1-13C]-labeled trehalose suggest that the averaged conformation of the interglycosidic linkage is centered around dihedral angles φ = ψ = −41° with ±5° uncertainty. Homonuclear NOE-s in the labeled trehalose support the dominance of similar conformation. Close to the slow and fast motional regime, α,α-trehalose can be considered as a spherical top, and global correlation times can be determined easily at extreme temperatures. This allows the construction of an Arrhenius plot for the whole range of temperature. The approach, which we call “trouble-free”, yields Ea = 28.2 kJ/mol for the activation energy of molecular reorientation. The model-free analysis of 13C T1, T2, and NOE data showed a local maximum of the generalized order parameters with S2 = 0.9 around 273 K. Monte-Carlo error analysis corroborated that this effect could be real; however, effective correlation times have relatively high error limits. Thermodynamically, the S2 data can be interpreted in terms of changes in the Gibbs free energy due to increased or diminished spatial restriction of rapid CH fluctuations. Liquid state 1H and 13C chemical shift anisotropies were determined from the interference of dipole−dipole and chemical shift anisotropy relaxation. In solution, chemical shift anisotropies cannot be separated from an inherent geometrical factor, so a combined CSAg factor was used. Cross-correlated spectral densities could be well fitted for the C-1,H-1 vector over the entire temperature range with the “trouble-free” global correlation times. The resulting numerical values for CSAg were smaller compared to the model-free evaluation, due to the omission of internal fluctuations. The measured shift anisotropies were found to be independent from the selection of isotropic or anisotropic dynamical models. Apparent CSAg factors were nearly constant in the entire temperature range except C-3, H-2, and H-3. Comparison with deuterium labeled [2,4,6-2H]trehalose proved that temperature-induced changes of the ABX-type strong coupling pattern (caused by the change of differential chemical shift of vicinal H-2 and H-3 protons) interfere with asymmetric multiplet relaxation and potentially lead to misinterpretation of CSA/DD relaxation rates.
    Journal of The American Chemical Society - J AM CHEM SOC. 01/1997; 119(6):1336-1345.
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    ABSTRACT: Novel pseudodisaccharide-type aminocyclitol antibiotic models, built up from D-arabinose, D-ribose, D-glucosamine, L-ristosamine and L-acosamine have been synthesized by the glycosylation of suitably protected (azido)deoxyinosose aglycones derived by the Ferrier carbocyclic ring transformation of carbohydrate precursors. An alternative approach to related pseudodisaccharides, based on the Ferrier carbocyclization of reducing disaccharides, has also been elaborated. This latter method extends the scope of the Ferrier reaction, by demonstrating that acid-labile 2-deoxydisaccharides can also be readily transformed into the corresponding pseudodisaccharides under the slightly acidic conditions of this ring-transformation.
    The Journal of Antibiotics 08/1995; 48(7):683-95. · 2.19 Impact Factor
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    ABSTRACT: Novel non-reducing disaccharides (27–31) synthesized from L-acos- amine and L-ristosamine are reported.
    Bioorganic & Medicinal Chemistry Letters. 02/1993; 3(2):235–240.
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    ABSTRACT: The first definitive synthesis and physical data of the α-methyl glycoside (methyl α-kedarosaminide 2) of kedarosamine (1), the aminodeoxy sugar component of the antibiotic kedarcidin is presented.
    Tetrahedron Letters 01/1993; 34(25):4087-4090. · 2.40 Impact Factor