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| Titel: |
Applicability of the Mosher MPTA-Ester Methodology to Monosaccharides |
| Auteur: |
Adinolfi, Matteo De Castro, Cristina Iadonisi, Alfonso Lanzetta, Rosa Molinaro, Antonio |
| Verschenen in: |
Journal of carbohydrate chemistry |
| Paginering: | Jaargang 17 (1998) nr. 6 pagina's 987-992 |
| Jaar: |
1998-08-01 |
| Inhoud: |
Caryophyllose 1 is a novel twelve carbon 4-C-branched monosaccharide and a component of the polysaccharide chains found in the lypopolysaccharide fraction from Pseudormnas caryophylli bacterium.1 Its absolute stereochemistry was elucidated2 by applying the exciton chiral coupling method to two fragments obtained by NaIO4, oxidation of the polysaccharide chain. The absolute configuration of a chiral secondary alcohol can be defined by Mosher's method.3 It analyzes the signs of the differences between the chemical shifts of the protons vicinal to the chiral Center in the (S)- and (R)-α-methoxy-α-trifluoromethylphenylacetate (MPTA) esters obtained from the compound. However, the Mosher ester methodology failed to give completely reliable results when applied to the bisisopropylidene derivative 2 of caryophyllose. In fact, whereas ΔδH(δR-δS) was positive for 3'-H and negative for 5'-H, indicating R configuration for the 4' chiral centre, it was positive for 1-H but of opposite sign for the two protons at C-3 (negative for 3eq and positive for 3ax), failing to indicate the configuration at C-2. This result, however, was in line with Mosher's warning3 about circumspection in applying his correlation to molecules which “contain additional chiral centres, possess heteroatoms, or show unusual conformational restraints”. It also prompted us to an investigation of applicability of Mosher arguments to sugar MPTA esters, in view of our interest in carbohydrate structure elucidation. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 3 van 15 gevonden artikelen
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