Geometry optimizations at the B3LYP level of density functional theory (DFT) are reported for methyl 4-O-acetyl-3-azido- and 3-azido-4-O-methylsulfonyl-2,3,6-trideoxy-alpha,beta-d-threo- and -beta-d-erythro-hex-5-enopyranosides. The most stable conformers for each compound are presented, along with the corresponding enthalpies and Gibbs free energies. The influence of the exocyclic double bond on the chair conformation is discussed. Conformations of the 1-OMe, 3-N3, and 4-OAc groups were examined, and delocalization in the OAc and N3 groups was demonstrated. The contributions of particular conformers to the total number of structures found for each hex-5-enopyranoside were calculated. The theoretical results are compared with assignments based on 1H NMR studies.
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Synthesis and geometry of methyl (methyl 4-O-acetyl-3-azido-2,3-dideoxy-alpha/beta-D-arabino- and -alpha/beta-D-ribo-hexopyranosid)uronates.
Carbohydr Res
February 2008
Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, PL-80-952 Gdańsk, Poland.
The synthesis of methyl (methyl 4-O-acetyl-3-azido-2,3-dideoxy-alpha/beta-D-arabino- and -alpha/beta-D-ribo-hexopyranosid)uronates is presented. High resolution (1)H and (13)C NMR spectral data for all diastereoisomers and single-crystal X-ray diffraction analysis for methyl (methyl 3-azido-2,3-dideoxy-beta-D-arabino-hexopyranosid)uronate are reported. The planarity of the 4-OAc and 5-COOMe groups as well as the orientations of the aglycone and azide groups in the crystal lattice is discussed.
View Article and Find Full Text PDFMethyl 4-O-acetyl-3-azido- and 3-azido-4-O-methylsulfonyl-2,3,6,-trideoxyhex-5- enopyranosides in DFT-level conformational studies.
J Phys Chem A
May 2007
Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, PL-80-952 Gdańsk, Poland.
Geometry optimizations at the B3LYP level of density functional theory (DFT) are reported for methyl 4-O-acetyl-3-azido- and 3-azido-4-O-methylsulfonyl-2,3,6-trideoxy-alpha,beta-d-threo- and -beta-d-erythro-hex-5-enopyranosides. The most stable conformers for each compound are presented, along with the corresponding enthalpies and Gibbs free energies. The influence of the exocyclic double bond on the chair conformation is discussed.
View Article and Find Full Text PDFSynthesis and conformational studies on methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-hex-5-enopyranosides of the L series.
Carbohydr Res
September 2005
Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, PL-80-952 Gdańsk, Poland.
Methyl 3-azido-2,3-dideoxy-alpha-D-xylo-, -alpha-D-lyxo-, and -beta-D-xylo-hexopyranosides were converted into 4-O-acetyl-3-azido-6-iodo-2,3,6-trideoxy analogues via 6-O-p-tolylsulfonyl compounds. The elimination of hydrogen iodide from 6-iodo glycosides yielded methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-beta-L-erythro-, -alpha-L-threo-, and -beta-L-threo-hex-5-enopyranosides. The configuration and conformation of all products are evaluated in depth on the basis of (1)H and (13)C NMR data.
View Article and Find Full Text PDFSynthesis of 3-azido-2,3,6-trideoxy-beta-D-arabino-hexopyranosyl pyranonaphthoquinone analogues of medermycin.
Org Biomol Chem
May 2003
Department of Chemistry, University of Auckland, 23 Symonds St., Auckland, New Zealand.
The synthesis of an isomeric mixture of 4-O-acetyl-3-azido-2,3,6-trideoxy-beta-D-arabino-hexopyranosyl analogues 6 of the C-glycosylpyranonaphthoquinone antibiotic medermycin is described. The key 3-acetyl-6-(4-O-acetyl-3-azido-2,3,6-trideoxy-beta-D-arabino- hexopyranosyl)-5-methoxy-1,4-naphthoquinone 8 was prepared via Stille coupling of 6-(3-azido-2,3,6-trideoxy-beta-D-arabino-hexopyranosyl)-3-bromo-1,4- naphthoquinone 17 with (alpha-ethoxyvinyl)tributyl-stannane followed by hydrolysis and oxidation of the resultant hydroquinone 18. Bromonaphthoquinone 17 in turn was afforded by oxidative demethylation of 6-(4-O-acetyl-3-azido-2,3,6-trideoxy-beta-D-arabino-hexopyranosyl)-3- bromo-1,4,5-trimethoxynaphthalene 16 formed by regioselective bromination of 6-(4-acetyl-3-azido-2,3,6-trideoxy- beta-D-arabino-hexopyranosyl)-1,4,5-trimethoxynaphthalene 10.
View Article and Find Full Text PDFSynthesis, the crystal structure, and high-resolution NMR spectroscopy of methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-6-iodo-alpha-D-arabino-hexopyranoside.
Carbohydr Res
February 2002
Department of Chemistry, University of Gdańsk, 18/19 Sobieski Strasse, PL-80-952 Gdańsk, Poland.
Selective tosylation followed by acetylation of methyl 3-azido-2,3-dideoxy-alpha-D-arabino-hexopyranoside (1) in pyridine at room temperature affords a mixture of methyl 4-O-acetyl-3-azido-2,3-dideoxy-6-di-O-p-tolylsulfonyl-alpha-D-arabino-hexopyranoside (4) and methyl 3-azido-2,3-dideoxy-4,6-di-O-p-tolylsulfonyl-alpha-D-arabino-hexopyranoside (3). Compound 4 undergoes nucleophilic displacement with sodium iodide in acetic anhydride to give methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-6-iodo-alpha-D-arabino-hexopyranoside (7), whose crystal structure and (1H) and (13)C NMR data are reported. This compound adopts the 4C(1) conformation.
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