o-Xylylene protecting group in carbohydrate chemistry: application to the regioselective protection of a single vic-diol segment in cyclodextrins.
J Org Chem
; 78(4): 1390-403, 2013 Feb 15.
Article
em En
| MEDLINE
| ID: mdl-23336396
ABSTRACT
A systematic study of the suitability of α,α'-dibromo-o-xylene as a reagent for cyclic o-xylylene protection of vic-diols in different monosaccharide substrates is reported. The installation of this protecting group, formally equivalent to a di-O-benzylation reaction, proceeds with good regioselectivity toward 1,2-trans-diequatorial diol systems in pyranose and furanose rings. Initially, the benzyl ether-type derivative of the more acidic hydroxyl is preferentially formed. Subsequent intramolecular etherification toward the equatorial-oriented vicinal OH is kinetically favored. The methodology has been implemented for the simultaneous protection of the secondary O-2 and O-3 positions of a single d-glucopyranosyl unit in cyclic oligosaccharides of the cyclodextrin (CD) family (cyclomaltohexa-, -hepta-, and -octaose; α, ß, and γCD).
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MEDLINE
Idioma:
En
Ano de publicação:
2013
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Article