2-Deoxyglycosyl 3-benzoylpropionates as novel donors for the direct and stereoselective synthesis of 2-deoxy-glycosides

Abstract

Lewis acid mediated stereoselective synthesis of 2-deoxy-O-glycosides has been demonstrated using 2-deoxyglycosyl 3-benzoylpropionates as novel glycosyl donors. These newly developed donors are easily synthesized from simple glycals, are stable at room temperature and react with ease to provide products with high stereoselectivity. These donors can be successfully utilized with all types of acceptors (primary, secondary and tertiary alcohols) for the synthesis of 2-deoxy-glycosides. Additionally, these newly developed glycosyl donors are also efficient for the synthesis of trisaccharides.

Additive‐Free Gold(III)‐Catalyzed Stereoselective Synthesis of 2‐Deoxyglycosides Using Phenylpropiolate Glycosides as Donors

“…2019, 14,4651 -4658 www.chemasianj.org On the basis of previous literaturer eports, [13,18] and DFT calculations,a na nticipated mechanism for the stereoselective synthesis of 2-deoxyglycosides have been depicted in Scheme8.A tf irst, the alkynophilic and mild Lewis acidic AuCl 3 simultaneously coordinates with triple bond and carbonyl oxygen of glycosyl phenylpropiolate 1 to facilitatet he expulsion of phenylpropiolate leaving group with the involvement of endo-cyclic oxygen atom via the intermediate A and lead to the formation of oxocarbenium ionintermediate B.I ns itu generated phenylpropiolate anion further increases the nucleophilicity of alcoholb ya bstracting the proton and allowing them for preferentially attack from bottom face to the intermediate B to form the desired CÀOb ond and eventually afford the deoxyglycoside 3 in as tereoselective manner with the regeneration of phenylpropiolicacida nd Au III salt. Asian J.…”

“…On the basis of previous literature reports, and DFT calculations, an anticipated mechanism for the stereoselective synthesis of 2‐deoxyglycosides have been depicted in Scheme . At first, the alkynophilic and mild Lewis acidic AuCl 3 simultaneously coordinates with triple bond and carbonyl oxygen of glycosyl phenylpropiolate 1 to facilitate the expulsion of phenylpropiolate leaving group with the involvement of endo ‐cyclic oxygen atom via the intermediate A and lead to the formation of oxocarbenium ion intermediate B .…”

“…Various elegant glycosyl donors such as glycosyl imidates, [11] glycosyl phosphites, [12] (2'-carboxy)benzyl-4,6-O-benzylidene-2deoxyglucoside, [13] thioglycosides, [14] and glycals [15] were employedf or the synthesis of 2-deoxyglycosides.I nt he recent time, several research groups have introduced the bifunctional moiety at the anomeric position to act as leaving groups such as S-but-3-ynyl-thioglycoside, [16] ortho-alkynylbenzoate, [17] and 3-benzoylpropionates, [18] which could be activated by remote participation of catalystu nder mild conditions (Scheme 1a-b). The major constraint with these direct approaches are (a) involvement of multi-steps for the preparation of glycosyl donors, (b) requirement of expensive additives, (c) formation of as toichiometric amount of lipophilic byproducts, and (d) mostly afford the mixtureo fa nomers.…”

Deoxy sugars. General methods for carbohydrate deoxygenation and glycosidation

“…Under scandium( iii ) triflate catalyst, glycosidations proceed via a five member intermediate, with good α-stereoselectivity (Scheme 32). 184…”