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Synlett 2002(2): 0269-0270
DOI: 10.1055/s-2002-19770
LETTER
© Georg Thieme Verlag Stuttgart · New York

Iodine/Triethylsilane as a Convenient Promoter System for the Activation of Disarmed Glycosyl Trichloro- and N-(Phenyl)trifluoroacetimidates

Matteo Adinolfi, Gaspare Barone, Alfonso Iadonisi*, Marialuisa Schiattarella
Dipartimento di Chimica Organica e Biochimica, Università degli Studi di Napoli Federico II, Via Cynthia 4, 80126 Napoli, Italy
Fax: +39(81)674393; e-Mail: iadonisi@unina.it;
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Publication History

Received 8 November 2001
Publication Date:
02 February 2007 (online)

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Abstract

Disarmed glycosyl trichoro- and N-(phenyl)trifluoroacetimidates can be efficiently activated by the combined reagent system I2/Et3SiH in the fast and high yielding glycosylation of primary and secondary saccharidic acceptors.

Key words

carbohydrates - glycosylations - iodine - neighboring-group effects - triethylsilane

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8

Use of acetonitrile as the solvent resulted in lower glycosylation yields due to concomitant side reactions of the donor. On the other hand, in dichloromethane the reactions occurred very sluggishly.

10

This donor was prepared as an anomeric mixture (α/β, 2:1) by reacting the corresponding 1-hydroxyl sugar [3] with N-(phenyl)trifluoroacetimidoyl chloride in the presence of diisopropylethylamine (overnight stirring in CH2Cl2 at r.t., yield 88%). The use of K2CO3 as the base (as reported in ref. [11] ) resulted in a very sluggish reaction.

15

Treatment of per-O-acetyl-β-d-glucose with I2 and triethylsilane (1.2 mol each) in refluxing CH2Cl2 for 20 min resulted in the high yielding synthesis of the corresponding α-glycosyl iodide in analogy to the alternative system (RSH/I2) reported in ref. [6] .