ISSN:
0018-019X
Schlagwort(e):
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Two types of endocyclic enol-acetal forming β-elimination were investigated on synthetic model compounds. In both types the 4-O-methanesulfonyl residue was chosen as leaving group. The a,e-β-elimination was proved on 2,3-benzyl ether protected D-glucopyranosiduronate derivatives I, and the a, a-β-elimination on the analogous substituted D-galactopyranosiduronates XVII. Using a small excess of KOH in methanol at 25°, a quick elimination of a molecule of methanesulfonic acid was observed, and as reaction product the 4,5-unsaturated 4-deoxyhexopyranosiduronate derivative II was obtained. Only an unimportant stereoselectivity was found between the a,e- and a,a-mesylate β-eliminations.The 4,5-unsaturated 4-deoxyhexopyranosiduronates show a strong UV. maximum at 238 nm, and Cotton effects in the ORD. spectra. This stable ring system with an endocyclic enol-acetal linkage is present in a half-chair (H12) conformation.The structure of the unsaturated deoxyhexopyranosiduronate obtained was established by structure- and stereo-correlation with a 2-deoxy-L-xylose derivative, showing that a ring contraction during the β-elimination does not occur.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/hlca.19700530515
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