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Synlett 1994; 1994(1): 84-86
DOI: 10.1055/s-1994-22748
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Synthesis of Unprotected O-Glycosyl Trichloroacetimidates Structure Assignment and New Results

Roland Haeckel* , Carsten Troll, Helmut Fischer, Richard R. Schmidt
  • *Fakultät für Chemie, Universität Konstanz, Postfach 5560 M 725, D-78434 Konstanz, Germany
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Publication Date:
22 March 2002 (online)

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X-Ray analysis of crystals obtained via base-catalyzed O-deacetylation of O-glucosyl-trichloroacetimidate 1a revealed formation of amide acetal 3a. The previously assigned unprotected O-glucosyl-trichloroacetimidate structure 2a (ref. 2) was not found in the 1H-NMR as possible equilibrium product. Yet, acid-catalyzed glycosylation with amide acetal 3a follows the trichloroacetimidate route and not the orthoester route. 3,4,6-Tri-O-benzyl-D-glucose (11) gave with trichloroacetonitrile in the presence of DBU as the base amide acetal 12; however, in the presence of K2CO3 as the base 2-O-unprotected trichloroacetimidate 13 (α/β-mixture) was obtained, thus exhibiting that O-unprotected O-glycosyl-trichloroacetimidates can be obtained via direct anomeric O-trichloroacetimidoylation without subsequent 2-hydroxy group attack leading to amidacetals.

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