Directing/protecting groups mediate highly regioselective glycosylation of monoprotected acceptors
A directing/protecting group designed for regioselective functionalization of partially-protected glucopyrannosides has been successfully used to prepare disaccharides in high yields. Most importantly, it has been demonstrated that highly regioselective a
Lawandi, Janice,Rocheleau, Sylvain,Moitessier, Nicolas
scheme or table
p. 8411 - 8420
(2011/11/14)
Efficient acylation and sulfation of carbohydrates using sulfamic acid, a mild, eco-friendly catalyst under organic solvent-free conditions
A fast and efficient acylation of carbohydrate derivatives and free sugars using a stoichiometric quantity of acylating agents in the presence of sulfamic acid, an environmentally benign catalyst, under organic solvent-free conditions is reported. Excellent yields in the selective acylation and sulfation of carbohydrate derivatives have also been achieved using sulfamic acid as the catalyst. The reaction is fast and the yields were excellent.
Application of ball milling technology to carbohydrate reactions: I. Regioselective primary hydroxyl protection of hexosides and nucleoside by planetary ball milling
Dry ball milling of hexosides with trityl chloride in the presence of DABCO or Na2CO3 has been found to result in their complete conversion to the respective 6-O-trityl ethers. Further wet grinding of the reaction mixture with Ac2O in the presence of DMAP led to the respective fully protected hexosides in good to excellent yields after isolation. It has been found to be an effective one-pot two-step synthesis under solvent-free condition. The speed of homogenization has been shown to highly influence the rate and outcome of the reaction, and commercially available planetary ball mill has been proved to be very convenient for carrying out the reaction under standardized and reproducible conditions.
Efficient acetylation of carbohydrates promoted by imidazole
An efficient per-O-acetylation of carbohydrate derivatives and unprotected reducing sugars promoted by imidazole is reported. The reaction conditions have been successfully employed to acetylate carbohydrate derivatives containing acid-susceptible functional groups. In most of the cases the yields obtained were excellent. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
Facile conversion of O-silyl protected sugars into their corresponding formates using POCl3·DMF complex
The direct O-formylation of two selectively protected sugar derivatives using the Vilsmeier-Haack (V-H) complex POCl3·DMF was studied. Primary O-TBDMS and O-TBDPS ethers of sucrose, the most common disaccharide, underwent regio and chemoselecti
Andrade, Marta M.,Barros, M. Teresa
p. 9235 - 9243
(2007/10/03)
SIMPLE STEREOCONTROLLED SYNTHESIS OF METHYL 2-DEOXY-D-ERYTHRO-HEXOPYRANOSID-4-ULOSES, THROMBOXANE B2 (TXB2) PRECURSORS, FROM D-GALACTOSE
The stereospecific synthesis of methyl 3-O-benzoyl-6-O-(tert-butyldiphenylsilyl)-2-deoxy-α-D-erythro-hexopyranosid-4-ulose (5) - a Thromboxane B2 (TXB2) precursor - starting from D-galactose is described.Facile and established methods including selective benzoylation, oxidation-elimination and a stereocontrolled hydrogenation (Pd/charcoal) were employed effectively.
Moradei, Oscar,Mortier, Cecile du,Cirelli, Alicia Fernandez,Thiem, Joachim
p. 525 - 532
(2007/10/02)
Selective Silylation of β-D-Galactosides. A New Approach to the Synthesis of (1->6)-β-D-Galactopyranooligosaccharides.
A simple and convenient synthesis of β-D-galactopyranose derivatives selectively modified at C-1 and C-6 is described.A key feature is the selective protection of the 6-OH group of methyl-, allyl-,and (p-nitrophenyl)-β-D-galactopyranosides using tert-buty
Nashed, Eugenia M.,Glaudemans, Cornelis P.J.
p. 5255 - 5260
(2007/10/02)
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