Showing papers on "Glycal published in 1992"
TL;DR: The reaction of 3,4,6-tri-O-benzyl-D-glucal (2) with 3,3-dimethyldioxirane gives rise to the 2α,3α-oxirane with high stereoselection as mentioned in this paper.
Abstract: The reaction of 3,4,6-tri-O-benzyl-D-glucal (2) with 3,3-dimethyldioxirane gives rise to the 2α,3α-oxirane with high stereoselection. Reaction of this compound with various phenols under alkaline conditions affords aryl 2α-hydroxy-β-glycosides (3a-d). Oxidative coupling (I + ) of these compounds with glycals followed by deiodination gives rise to aryloxydisaccharides (6a and 6b). In addition, proton-mediated coupling of 3a and 3b with vancosamine-derived glycal 8 affords 10a and 10b, which simulate the aryloxy carbohydrate domain of vancomycin
84 citations
69 citations
66 citations
TL;DR: In this paper, the ribofuranoid glycal 1,4-anhydro-2-deoxy-3-O-[(1,1-dimenthylethyl) diphe⊇ylsilyl]-D- erythro-pent-1-enitol underwent regio-and stereospecific coupling in the presence of catalytic palladium acetate and either triphenylphosphine or triphensylarsine ligands.
Abstract: 5-Iodouracil and the ribofuranoid glycal 1,4-anhydro-2-deoxy-3-O-[(1,1-dimenthylethyl) diphe⊇ylsilyl]-D- erythro-pent-1-enitol underwent regio- and stereospecific coupling in the presence of catalytic palladium acetate and either triphenylphosphine or triphenylarsine ligands. The resulting C-glycosyl product was converted to 2'-deoxypseudouridine. In a similar way 2'-deoxyformycin B and 2',3'-dideoxyformycin B have been synthesized by reaction sequences in which the key step is a palladium-mediated regio- and stereospecific C-glycosyl bond forming reaction between this furanoid glycal and a bis(tetrahydropyranyl)-protected 3-iodopyrazolo[4,3-d]pyrimidine aglycon derivative
62 citations
TL;DR: In this article, Silylacetylenes have been shown to be sufficiently reactive for the selective introduction of acetylenic groups, usefull for organic synthesis, which is of significance for introducing carbon chains to sugar nuclei.
56 citations
TL;DR: In this paper, a series of substituted glycosyl phenyl sulfones was converted into glycals after reductive samariation with SmI 2 in the presence of hexamethylphosphoric triamide, followed by elimination of the substituent at C-2.
56 citations
TL;DR: In this paper, the Furanoid glycal 10 has been used as a key step in the synthesis of ddA and d4T antiviral nucleosides, which were used as key steps in the development of the D4T virus.
52 citations
TL;DR: It has been shown that the resulting 1-C-aryl(alkyl)-D-glucals are suited for further synthetic manipulation of the enol ether group, including stereoselective hydrogenation, hydroboration-oxidation, or epoxidation.
52 citations
TL;DR: In this article, 1,6-Anhydro-2,azido-2-deoxy-β-D-glucopyranose has been prepared by a two-step procedure from Dglucal and transformed into precursors useful in the synthesis of oligosaccharides.
Abstract: 1,6-Anhydro-2-azido-2-deoxy-β-D-glucopyranose has been prepared by a two-step procedure from D-glucal and transformed into precursors useful in the synthesis of oligosaccharides.
51 citations
TL;DR: In this article, a functionalized C-D-E trisaccharide precusors of olivomycin A were derived by employing 2-deoxy-2-(phenylthio)-α-glucotrichloroacetimidate.
Abstract: Syntheses of functionalized C-D-E trisaccharide precusors of olivomycin A are reported. A stereoselective C-D β-glycosidation was accomplished by employing 2-deoxy-2-(phenylthio)-α-glucotrichloroacetimidate. The α-D-E glycosidic linkage was introduced by using 2-deoxy-2-iodo-α-glycosyl acetate donor as the glycosyl agent
48 citations
TL;DR: In this paper, the proton-catalyzed addition of alcohols to glycals is shown not to be a trans-diaxial addition, and it is shown that the addition is not a trans diaxional addition.
Abstract: The proton-catalyzed addition of alcohols to glycals is shown not to be a trans diaxial addition
TL;DR: The left halves of norhalichondrins and homohalichondRins were synthesized from γ-lactone 1, readily available from D-galactose glycal via Ireland-Claisen rearrangement then iodolactonization.
TL;DR: O-Tributylstannyl-D-glucal undergoes allylic oxidation when treated with N-iodosucinimide (NIS) in benzene, whereas oxidative 1,6-halocyclization occurs with NIS in acetonitrile or molecular halogens in various solvents as mentioned in this paper.
TL;DR: A short review on the recent methodological progress in O-glycoside synthesis is given in this article, where the focus is on the design of newer classes of glycosyl donor, which allow the selective activation/O-Glycoside formation under specific reaction conditions.
Abstract: The present article deals with a short review on the recent methodological progress in O-glycoside synthesis. Particular stress is laid on the design of newer classes of glycosyl donor, which allow the selective activation/O-glycoside formation under specific reaction conditions. Based on the anomeric leaving group, glycosyl donors are classified into nine classes, 1) fluoride, 2) thioglycoside, 3) O-acylate, 4) O- and S-carbonate derivatives, 5) phosphate derivatives, 6) trichloroacetimidate, 7) 1-hydroxyl sugar, 8) 4-pentenyl glycoside, 9) glycal, and their selective activation methods are tabulated. Also described are the other approaches based on different principles, e.g., glycosylidene carbene, anomeric O-alkylation, internal cyclization or glycoside synthesis based on physical means;light, electric, thermal, and high pressure. Recent topics in this field are also included, 1) new protecting groups, 2) stereochemical control in manno- and 2-deoxy-sugars, and 3) the armed/disarmed concept.
Abstract: Syntheses of 8-ethenyl-1-hydrory-4-β-D-ribofuranosylbenzo[d]naphtho[1,2-b]pyran-6-one (1) and 8-ethenyl- 1-hydrory-4-(2'-deoxy-β-ribofuranosyl)benzo[d]naphtho[1,2-b]pyran-6-one (2) have been accomplished. These two compounds are the first synthetic C-glycosides structurally related to the gilvocarcin, ravidomycin, and chrysomycin antibiotic class which possess the aglycon substituents (hydroxyl at C-1 and ethenyl at C-8) considered critical for the photolytic nicking of DNA.Anthracycline C-glycoside 1 was prepared by a route involving Lewis acid-catalyzed C-glycosyl bond formation between the tetracyclic aglycon and 1,2,3,5-tetra-O-acetyl-D-ribose followed by construction of the aglycon 8-ethenyl substituent from the corresponding ethyl group by radical bromination-dehydrobromination.Synthesis of C-glycoside 2 utilized a different, complementary procedure for C-glycosyl bond formation by palladium-mediated coupling of an iodoaglycon derivative with 1,4-anhydro-2-deoxy-3-O-(tert-butyldiphenylsilyl)-D-erythro-pent-1-enitol,a furanoid glycal designed to form only β C-glycosyl bonds in this reaction
TL;DR: In this article, azasugar and glycal inhibitors were studied to map the active site of α-L-fucosidase enzyme, and the results showed that these inhibitors were effective in detecting α-Fucoside.
TL;DR: Several glycosidases have been investigated with respect to their regioselectivity in the formation of glyclosidic bonds between various donor sugars and glycal acceptors as mentioned in this paper.
TL;DR: In this paper, a formal electrophilic addition of hypoiodous acid to 3,4,6-tri0-acetyl-o-glucal'3 (1) and 3, 4,di-0,acetyl 6-0-tosyl-D-glocal'4 (2) was described, which can be used for the preparation of Brigl's anhydrides.
TL;DR: In this article, the reaction of hydrogen chloride or hydrogen bromide in glacial acetic acid with 3,4-di-O-acetyl-L-rhamnal followed by hydrolysis and acetylation of the reaction product afforded 3-chloro- or 3-bromo-2,3,6-trideoxy-Larabino-hexopyranoses.
Abstract: Reaction of hydrogen chloride or hydrogen bromide in glacial acetic acid with 3,4-di-O-acetyl-L-rhamnal followed by hydrolysis and acetylation of the reaction product afforded 3-chloro- or 3-bromo-2,3,6-trideoxy-L-arabino-hexopyranoses. These novel halosugars were further converted into various glycosides
TL;DR: The C-glycosidic alkene 21, on treatment with tributyltin hydride and a radical initiator, underwent intramolecular radical cyclisation to give the 2-oxabicyclo[3.2] octane derivative 23 which is structurally related to the sesquiterpenoid trichothecenes.
Abstract: The C-glycosidic alkene 21, on treatment with tributyltin hydride and a radical initiator, underwent intramolecular radical cyclisation to give the 2-oxabicyclo[3.2.1]octane derivative 23 which is structurally related to the sesquiterpenoid trichothecenes. The unsaturated acetals 27 and 29, formed using methods encountered in the first part of the work, permitted branch-point substituents to be introduced regio- and stereo-specifically at C-3 and at C-4 (carbohydrate numbering) of compounds of this type. Methods are thus available for the synthesis of pyranoid derivatives bearing several C-substituents.
TL;DR: Two new 3'-deamino-3'-hydroxy-2'-iodoesorubicin analogues showed cytotoxic activity similar to that of doxorubsicin in vitro and higher antitumor activity against L-1210 leukemia thanDoxorubICin in vivo.
Abstract: New 3'-deamino-3'-hydroxy-2'-iodoesorubicin analogues were synthesized using optically active 4, 6-dideoxyhex-l-enitol (7) as starting material. Direct coupling of daunomycinone (8) and 14-O-tert-butyldimethylsilyladriamycinone (9) with glycal 7 in the presence of N-iodosuccinimide gave 2'-iodo analogues 10 and 12. Deprotection of compounds 10 and 12 led to compounds 11 and 14, the 2'-iodinated, fully unblocked 4'-deoxy-3'-hydroxy congeners of daunorubicin (2) and doxorubicin (1). 2'-Iodo-3'-hydroxyesorubicin (14) showed cytotoxic activity similar to that of doxorubicin in vitro and higher antitumor activity against L-1210 leukemia than doxorubicin in vivo.
TL;DR: In this paper, the synthesis of the phenyl β-glycoside of avobiose, a disaccharide fragment present in the antibiotic avoparcin, is reported.
TL;DR: Iodonium ion treatment of 1,2-unsaturated heptadeca-O-benzylmaltohexaose and icosa-O-, O-bensyl-malto-heptaose derivatives derived from α- and β-cyclodextrins brought about their recyclization by intramolecular glycosidation, giving mono(2-deoxy-2-iodo)-α- and -β- cyclodextrin derivatives, which were converted into mono( 2 -deoxy)-α-, β-, cyclode
Abstract: Iodonium ion treatment of 1,2-unsaturated heptadeca-O-benzylmaltohexaose and icosa-O-benzylmaltoheptaose derivatives derived from α- and βcyclodextrins brought about their recyclization by intramolecular glycosidation, giving mono(2-deoxy-2-iodo)-α- and -β-cyclodextrin derivatives, which were converted into mono(2-deoxy)-α- and -β-cyclodextrins by radical reduction.
TL;DR: Two routes, the "tail" or the "head" addition are presented, both leading to the target molecule 9, a mimic of the C-B-A trisaccharide component of dihydroaclacinomycin.
TL;DR: In this article, the C-3 epimer of the glycal triacetate was separated from the reaction mixture using preparative HPLC, which was then used for HPLC analysis.
Abstract: Treatment of tri-O-acetyl-D-glycals, e.g., tri-O-acetyl-D-glucal, tri-O-acetyl-D-allal and tri-O-acetyl-D-galactal, with metal chlorides in acetic anhydride afforded the C-3 epimer of the glycal triacetate with pseudo-glycal triacetate and unreacted glycal triacetate as an equilibrium mixture. The C-3 epimer of the glycal was readily separated from the reaction mixture using preparative HPLC.
Patent•
16 Jul 1992TL;DR: An enzymatic process for the preparation of galactosyl β 1,3 glycal disaccharides such as Galβ 1, 3 Glucal, an intermediate useful in leating a preparation and an inhibitor of β-galactosidase is described in this paper.
Abstract: An enzymatic process is disclosed for the preparation of galactosylβ1,3glycal disaccharides such as Galβ1,3Glucal, an intermediate useful in Le a preparation and an inhibitor of β-galactosidase. The process utilizes β-galactosidase, an enzyme usually used for bond breaking, to form a bond between a galactoside and a glucal such as glycal, a 6-O--C 1 -C 6 acylglucal or 6-O--C 1 -C 6 acetylgalactal.