Showing papers on "Glycal published in 1993"
TL;DR: Repeating glycosidic linkages of oligosaccharides can be synthesized by solid-phase methods using glycals attached to a polystyrene copolymer with a silyl ether bond.
Abstract: Repeating glycosidic linkages of oligosaccharides can be synthesized by solid-phase methods. Glycals were attached to a polystyrene copolymer with a silyl ether bond and were activated to function as glycosyl donors with 3,3-dimethyldioxirane. Glycosidation was performed by reactions with a solution-based acceptor (itself a glycal). Excess acceptor and promoter were removed by rinsing after each coupling, and the desired oligosaccharides were then easily obtained from the polymer by the addition of tetra-n-butylammonium fluoride. By this method, glycosidations are stereospecific and interior deletions are avoided.
273 citations
65 citations
TL;DR: O-Glycosidations of glycals 1, 8 and 9 with several alcohols by using a catalytic amount of 2,3-dichloro-5,6-dicyano-p-benzoquinone under neutral conditions proceeds smoothly to give the corresponding 2, 3-unsaturated glycosides in high yields.
Abstract: O-Glycosidations of glycals 1, 8 and 9 with several alcohols by using a catalytic amount of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) under neutral conditions proceeds smoothly to give the corresponding 2,3-unsaturated glycosides in high yields.
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TL;DR: Several fluorinated oligosaccharides, including 2-deoxy-2-fluoro derivatives of cellobiose, maltose, and maltotriose were synthesized by the action of fluorine or acetyl hypofluorite on the corresponding glycal peracetates.
48 citations
TL;DR: Anti-Markovnikov azido-phenylselenylation of diversely protected glycals affords protected phenyl 2-azido-2-deoxy-α-selenoglycopyranosides and a complete stereocontrol is observed.
45 citations
TL;DR: In this paper, the synthesis of the spiroketal II and tricyclic glycal III portions of the polyether antibiotic monensin (I) are described.
Abstract: The syntheses of the spiroketal II and tricyclic glycal III portions of the polyether antibiotic monensin (I) are described. The butyric acid side chain of spiroketal II is constructed through either Sharpless epoxidation of a cis-2-butenol residue or by Brown crotylation of an α-methylacetaldehyde unit. The spiroketal is then generated through a hetero-Diels-Alder addition between a tetrahydropyranoid methylene ketone and acrolein. Finally, [6.5] - spiroketal structure II is prepared by mild acid catalyzed rearrangement of [6.6]-spiroketal epoxide 23. Glycal III was made from the C/D subunit 44. This subunit was prepared by the ester enolate Claisen rearrangement that unites the tetrahydrofuranoid C and D rings 40 and 41 by Brown crotylation, Wittig condensation, and then cyclization to form the E ring. The synthesis of the two fragments set the stage for a final ester enolate Claisen rearrangement that will form the skeleton of the polyether monensin (I)
44 citations
TL;DR: In this paper, a 3-O-benzyl-1-(tri-n-butylstannyl)furanoid glycal was derived from the 1-phenylsulfonyl glycal using AIBN.
TL;DR: In this paper, a chiral pyrano[2,3-b] benzopyrans were synthesized by reaction of 2-C-acetoxymethylglycals 1 and 2 with phenols under Lewis acid catalysis.
TL;DR: Glycosidase-mediated coupling of glycal acceptors with galactose donors affords β 1,3-linked disaccharides that are versatile intermediates for further chemical and enzymatic manipulation.
Abstract: Glycosidase-mediated coupling of glycal acceptors with galactose donors affords β 1,3-linked disaccharides that are versatile intermediates for further chemical and enzymatic manipulation. The utility of these disaccharides is demonstrated by the elaboration of these compounds into the type I and type IV core disaccharides of carbohydrate-containing antigens. Further conversion of the type IV disaccharide to a mucin-type trisaccharide (Galβ1,6(GlcNAcβ1,6)GalNAc) was accomplished with the use of a β1,6-N-acetylglucosaminyltransferase
TL;DR: In this article, the synthesis of an advanced olivomycin A C-D disaccharide is described in which the anomeric configuration of both 2-deoxy-β-glycosidic linkages is determined by a sequential diastereoselective radical reaction at the end of the synthesis.
TL;DR: A novel and highly stereoselective method for the synthesis of allyl C-glycosides bearing C2-C3 unsaturation has been developed using glycal acetate, allyltrimethylsilane and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as a neutral activator.
Abstract: A novel and highly stereoselective method for the synthesis of allyl C-glycosides bearing C2-C3 unsaturation has been developed using glycal acetate, allyltrimethylsilane and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as a neutral activator.
TL;DR: In this paper, 2.2′-deoxynacleosides have been stereoselectively synthesized starting from glycals, using phenylselenenyl reagents.
TL;DR: In this article, a quaternary ammonium tribromides as bromine donors are used as donors for the α-1,2-trans dibromo adducts.
Abstract: Addition of bromine to glycals using quaternary ammonium tribromides as bromine donors is realized with higher stereoselectivities (α-1,2-trans configurated products) compared to bromination with molecular bromine. The reaction is neither sensitive to the solvent nor to the nature of the protecting groups (acetyl, benzoyl, benzyl) of the glycals and very slightly affected by the orientation of the substituents of the different glycals. Some of the α-1,2-trans dibromo adducts have been isolated in 60-75% yields and transformed into the corresponding α-1,2-trans-2-bromo-2-deoxyglycopyranosyl fluorides
TL;DR: In this article, enantiomeric 2,3-dideoxy glycals, (5S)- and (5R)-4,5-dihydro-5-[(triphenylmethoxy)methyl]furans and 2,4-dimethoxy-5-iodopyrimidine undergo palladium-mediated coupling by two different, complementary procedures to form enantiomeic pairs of (2',3'-dideiox-2,3]-didehydrofuranosyl)-and (2,4'-didoxy-
Abstract: Newly available enantiomeric 2,3-dideoxy glycals, (5S)- and (5R)-4,5-dihydro-5-[(triphenylmethoxy)methyl]furans and 2,4-dimethoxy-5-iodopyrimidine undergo palladium-mediated coupling by two different, complementary procedures to form enantiomeric pairs of (2',3'-dideoxy-2',3'-didehydrofuranosyl)- and (2',4'-dideoxy-3',4'-didehydrofuranosyl)pyrimidine C-nucleosides. Stereoselective reductions of the carbohydrate unsaturations produce all four enantio- and diastereoisomers of 2,4-dimethoxy-5-(2,3-dideoxy-5-O-tritylribofuranosyl)pyrimidine
TL;DR: The results show that following stereoselective sulfenylation, glycosylation of furanoid glycals, in the presence of SnCl4, proceeds both regio- and stereoselectedively.
TL;DR: In this paper, the synthesis of tri-O-benzyl-2-C-acetoxymethyl glycals and subsequent Ferrier rearangement to give 2C-methylene glycosides is described.
Abstract: Syntheis of tri-O-benzyl-2-C-acetoxymethylglycals and subsequent Ferrier rearangement to give 2-C-methylene glycosides is described.
TL;DR: In this article, the reaction of furanoid glycals with PhSCl afforded 1-chlorosugars, which were used for condensation reaction with silylated uracil in the presence of SnCl4.
Abstract: Reaction of furanoid glycals with PhSCl afforded 1-chlorosugars, which were used for condensation reaction with silylated uracil in the presence of SnCl4. These two reactions proceeded in a highly stereoselective manner
TL;DR: In this paper, the response of glycals substituted at C(1) with a tertiary cyclic carbinol was shown to vary strikingly as a function of ring size.
TL;DR: Highly stereoselective syntheses of naphthyl disaccharides 4 and 5, which correspond to the A-B disACcharide units of olivomycin A and mithramycin, are described in this paper.