| 1. |
- Bella, M., et al.
(författare)
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Reaction of selected carbohydrate aldehydes with benzylmagnesium halides: benzyl versus o-tolyl rearrangement
- 2014
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 10, s. 1942-1950
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Tidskriftsartikel (refereegranskat)abstract
- The Grignard reaction of 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside and benzylmagnesium chloride (or bromide) afforded a non-separable mixture of diastereomeric benzyl carbinols and diastereomeric o-tolyl carbinols. The latter resulted from an unexpected benzyl to o-tolyl rearrangement. The proportion of benzyl versus o-tolyl derivatives depended on the reaction conditions. Benzylmagnesium chloride afforded predominantly o-tolyl carbinols while the application of benzylmagnesium bromide led preferably to the o-tolyl carbinols only when used in excess or at higher temperatures. The structures of the benzyl and o-tolyl derivatives were confirmed unambiguously by NMR spectral data and X-ray crystallographic analysis of their 5-ketone analogues obtained by oxidation of the corresponding mixture of diastereomeric carbinols. A possible mechanism for the Grignard reaction leading to the benzyl -> o-tolyl rearrangement is also proposed.
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| 2. |
- Scholtzová, Eva, et al.
(författare)
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Crystal Structure, Infrared Spectra and DFT Study of Benzyl 2,3-Anhydro-β-D-Ribopyranoside
- 2011
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Ingår i: Journal of Chemical Crystallography. - 1074-1542 .- 1572-8854. ; 41:2, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of benzyl 2,3-anhydro-β-D-ribopyranoside is orthorhombic, P212121, Z = 4. The pyranose ring adopts the EO conformation distorted considerably to the 5HO direction. The molecules of the title compound are linked into infinite chains running along the a-axis by bifurcated O–H···O hydrogen bonds. Interaction energies of these hydrogen bonds are significantly different, ~−5.4 for the bond with the smaller and ~−1.1 kcal/mol for the bond with the larger O···O separation. The hydrogen-bond pattern is completed by the two weaker C–H···O intermolecular hydrogen bonds, aiming at the epoxy oxygen atom. IR vibrational spectrum was interpreted by means of comparison with the full list of vibrational modes predicted using DFT method in the solid state. While till 1495 cm−1 the individual bands can be reconciled with single calculated modes, the region below this limit is populated by heavily overlapped HCH, HCO, HOC, COC and HCC bending modes merged with few ν(CC) and ν(CO) modes. The respective “red” shifts of the positions of the ν(OH) bands correlate well with the size of the O···O separation.
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| 3. |
- Steiner, Bohumil, et al.
(författare)
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Cyanohydrins from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexofuranosid-4-ulose via Bucherer-Bergs and Strecker reactions
- 2013
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 369, s. 31-37
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Tidskriftsartikel (refereegranskat)abstract
- The formation of methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-alpha-L-talopyranoside (3), methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-alpha-L-mannopyranoside (4), methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-beta-D-allopyranoside (5), and methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-beta-D-gulopyranoside (7) from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexopyranosid-4-ulose (1) under Strecker amino nitrile synthesis and Bucherer-Bergs hydantoin synthesis reaction conditions, respectively, is reported. Their structures were determined on the basis of NMR and mass spectral data. The configurations of free cyanohydrins 3 and 4 and 4-O-acetylated cyanohydrins 6 and 8 (obtained by acetylation of 5 and 7, respectively) were established by single-crystal X-ray analysis. The conformations of the six-membered pyranose ring and five-membered 1,3-dioxolane ring in compounds 3, 4, 6, and 8 are also reported.
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