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Pastore A.,University of Naples Federico II | Valerio S.,International Chemical Industry | Adinolfi M.,University of Naples Federico II | Iadonisi A.,University of Naples Federico II
Chemistry - A European Journal | Year: 2011

The use of cheap and easy to handle reagents, such as I2 and Et3SiH, at low temperature allows the regioselective removal of benzyl protecting groups from highly O-benzylated carbohydrates. The observed regioselectivity is dependent on the nature of the precursor, the least accessible carbinol often being liberated. A mechanistic investigation reveals that in situ generated HI is the promoter of the process, whereas the regioselectivity appears to be mainly controlled by steric effects. However, the presence of an electron withdrawing acyl protecting group can switch the regioselectivity to favour deprotection of the carbinol position farthest from the ester group. The protocol is experimentally simple and provides straightforward access in useful yields to a wide range of partially protected mono- and disaccharide building blocks that are valuable for the synthesis of either biologically useful oligosaccharides or highly functionalised chiral compounds. Partially protected sugars thus obtained can also be coupled in situ with a glycosyl donor, as illustrated by the one-pot synthesis of a Lewis X mimic from fully protected precursors. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Pastore A.,University of Naples Federico II | Adinolfi M.,University of Naples Federico II | Iadonisi A.,University of Naples Federico II | Valerio S.,International Chemical Industry | Valerio S.,University of Naples Federico II
European Journal of Organic Chemistry | Year: 2010

The removal of a transient Fmoc protecting group can be simply performed by the addition of excess Et3N just after the accomplishment of a Bi(OTf)3-promoted glycosidation reaction. The obtained oligosaccharide can be directly employed as a glycosyl acceptor for further elongation of the saccharide. The preparation of biologically important, linear and branched mannans incorporated into HIV gp 120 demonstrates that the iteration of this one-pot sequence leads to a very straightforward oligosaccharide assembly. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Source


Adinolfi M.,University of Naples Federico II | D'Ischia M.,University of Naples Federico II | Iadonisi A.,University of Naples Federico II | Leone L.,University of Naples Federico II | And 2 more authors.
European Journal of Organic Chemistry | Year: 2012

A series of 3-thioglycosylated 5,6-diacetoxyindole derivatives, which are important tools for eumelanin research and application, were prepared through a practical and efficient approach exploiting a dynamic mixture of thioglycoside agents. The strategy is feasible for installing both mono- and disaccharide units and relies on the facile in situ conversion of glycosyl disulfides into the corresponding, more reactive, phenylselenenyl sulfides in the presence of diphenyl diselenide, N-bromosuccinimide (NBS) and tetrabutylammonium bromide (TBAB). An expedient thioglycosidation of 5,6-diacetoxyindole with a dynamic mixture of thioglycosides is described. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Pastore A.,International Chemical Industry | Adinolfi M.,International Chemical Industry | Iadonisi A.,International Chemical Industry | Valerio S.,International Chemical Industry
Carbohydrate Research | Year: 2010

Mannosyl trihaloacetimidate donors equipped with a 2-O-Fmoc group can be effectively activated by catalytic Bi(OTf)3 in glycosidations. Despite the expected participating effect of the Fmoc group, the reaction solvent was found to be decisive for obtaining highly selective α-mannosylations. The Fmoc 2-O-protecting group can be then simply removed from the obtained di-oligosaccharide in the same vessel where the glycosidation is conducted. The resulting oligosaccharide can thus be directly employed as a glycosyl acceptor for further elongation. The preparation of biologically important linear and branched oligomannoses incorporated into HIV gp120 demonstrates that iteration of this one-pot sequence leads to very straightforward oligosaccharide assembly. As an additional result, a rapid approach has been disclosed for accessing a 3,6-OH mannose building-block to be incorporated in branched structures. This relies on a double reductive opening of a di-O-benzylidene mannose intermediate whose regioselectivity appears to be independent of the configuration of the five-membered benzylidene. © 2010 Elsevier Ltd. All rights reserved. Source

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