Glycal

About: Glycal is a research topic. Over the lifetime, 897 publications have been published within this topic receiving 17422 citations.

The Addition of Malonates to Glycals: A General and Convenient Method for the Synthesis of 2‐C‐Branched Carbohydrates.

Abstract: A general and convenient synthesis of carbohydrate 2-C-analogs by addition of malonates to glycals is described. The method is applicable to glycals derived from hexoses and pentoses and is characterized by easily available precursors. The reactions are mediated by manganese(III) or cerium(IV) and proceed via intermediarily generated malonyl radicals. All additions exhibit a very high degree of regioselectivity, since only 2-C-branched sugars were obtained. This result can be best rationalized by favorable orbital interactions between the SOMO of the malonyl radical and the HOMO of the double bond. Variation of the steric demand of the malonate or the glycal allows the stereoselectivities to be increased up to >98%. Highest selectivities were obtained with tri-O-acetyl-d-galactal and di-O-acetyl-d-arabinal, where the attack occurs exclusively from one face of the carbohydrate. For all cerium(IV)-mediated reactions, methyl glycosides are formed as main products in 73−89% yield, which can be isolated in ana...

Synthesis and Use of Glycosyl Phosphates as Glycosyl Donors.

Abstract: Differentially protected glycosyl phosphates prepared by a straightforward synthesis from glycal precursors are used as powerful glycosyl donors. Activation of β-glycosyl phosphates by TMSOTf at −78 °C achieves the selective formation of β-glycosidic linkages in excellent yields with complete stereoselectivity. Reaction with thiols results in the conversion of glycosyl phosphates into thioglycosides in nearly quantitative yield. An orthogonal coupling strategy using glycosyl phosphate donors and thioethyl glycoside acceptors allows for the rapid synthesis of a trisaccharide.

Synthesis of Methyl α-L-Vancosaminide.

Abstract: The synthesis of methyl α- l -vancosaminide from di- O -acetyl- l -rhamnal is described. The allylic alcohol methyl 2,3,6-trideoxy-3- C -methyl-α- l - threo -hex-2-enopyranoside was prepared from the glycal, 1,5-anhydro-1,2,6-trideoxy-3- C -methyl- l - ribo -hex-1-enitol, and converted to its N , N -dimethylisourea derivative. The cis amino alcohol functionality in vancosamine was introduced by the electrophilic cyclization of the isourea, followed by hydrolysis of the resulting oxazoline.

Direct access to various C3-substituted sialyl glycal derivatives from 3-iodo-sialyl glycals

Abstract: A new and efficient method was developed for the synthesis of C3-substituted sialyl glycals that are useful for novel sialidase inhibitor discovery. This method was based on the cross-coupling reactions of 3-iodo-sialyl glycal methyl ester with boronic acids, alkenes and alkynes to directly introduce various functional groups to the sialyl glycal C3-position. A series of C3-aryl, alkyl, alkenyl, and alkynyl derivatives of sialyl glycal were efficiently and conveniently synthesized for the first time by this method, which has demonstrated its wide application scope.