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An Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst : Acid-Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts

An Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst : Acid-Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts

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PENG, Peng, Richard R. SCHMIDT, 2015. An Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst : Acid-Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts. In: Journal of the American Chemical Society : JACS. 137(39), pp. 12653-12659. ISSN 0002-7863. eISSN 1520-5126

@article{Peng2015Alter-33145, title={An Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst : Acid-Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts}, year={2015}, doi={10.1021/jacs.5b07895}, number={39}, volume={137}, issn={0002-7863}, journal={Journal of the American Chemical Society : JACS}, pages={12653--12659}, author={Peng, Peng and Schmidt, Richard R.} }

Gold(III) chloride as catalyst for O-glycosyl trichloroacetimidate activation revealed low affinity to the glycosyl donor but high affinity to the hydroxy group of the acceptor alcohol moiety, thus leading to catalyst-acceptor adduct formation. Charge separation in this adduct, increasing the proton acidity and the oxygen nucleophilicity, permits donor activation and concomitant acceptor transfer in a hydrogen-bond mediated S<sub>N</sub>2-type transition state. Hence, the sequential binding between acceptor and catalyst and then with the glycosyl donor enables self-organization of an ordered transition-state. This way, with various acceptors, even at temperatures below -60 °C, fast and high yielding glycosidations in high anomeric selectivities were recorded, showing the power of this gold(III) chloride acid-base catalysis. Alternative reaction courses via hydrogen chloride or HAuCl<sub>4 </sub>activation or intermediate generation of glycosyl chloride as the real donor could be excluded. With partially O-protected acceptors, prone to bidentate ligation to gold(III) chloride, particularly high reactivities and anomeric selectivities were observed. Gold(I) chloride follows the same catalyst-acceptor adduct driven acid-base catalysis reaction course. An Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst : Acid-Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts 2016-02-29T13:35:34Z 2016-02-29T13:35:34Z Peng, Peng Schmidt, Richard R. Schmidt, Richard R. eng 2015 Peng, Peng

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