Showing papers on "Glucal published in 2008"
TL;DR: Three different series of pyrazolo[3,4-b]pyridines and their structural analogues are synthesized using novel synthetic strategy involving one-pot condensation of 5, 6-dihydro-4H-pyran-3-carbaldehyde/2-formyl-3, 4,6-tri-O-methyl-D-glucal/chromone-3
80 citations
TL;DR: A total synthesis of (+)-papulacandin D which shows an antifungal activity is reported, and was accomplished in 31 steps overall from commercial starting materials.
Abstract: A total synthesis of (+)-papulacandin D which shows an antifungal activity is reported The molecule is one of the members of C-arylglycoside isolated from Papularia spherosperma The synthetic strategy bifurcates the molecule into two nearly equal subunits, the aryl glycoside and 18-carbon fatty acid side chain The key strategic transformations are (1) the palladium catalyzed, organosilanolate-based cross-coupling of a protected glucal silanol and (2) a catalytic enantioselective allylation of a dienal using allyltrichlorosilane This highly convergent synthesis was accomplished in 31 steps overall from commercial starting materials
80 citations
TL;DR: A convenient, mild and highly stereoselective method for C-glycosidation (alkynylation) of D-glucal with various potassium alkynyltrifluoroborates, mediated by BF3x OEt2 and involving oxonium intermediates, preferentially provides the alpha-acetylene glycoside products with good yields.
69 citations
TL;DR: In this paper, a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glucosides via Ferrier rearrangement, was developed.
66 citations
TL;DR: The formal synthesis of (−)-morphine was described in this paper, where the C-ring in morphine was prepared in an optically pure form from d -glucal using Ferrier's carbocyclization reaction, and the vicinal tertiary and quaternary stereocenters in the Cring were stereoselectively generated in a one-step reaction based on the cascade sequential Claisen rearrangement of an allylic vicinal diol derivative.
61 citations
TL;DR: This protocol was applied to the syntheses of a key precursor of vineomycinone B2 methyl ester by borylation of protected D-glucals with B( 2)pin(2) to give alpha-boryl glucal followed by cross-coupling with haloarenes, benzyl bromide, and allyl b Bromide.
Abstract: Borylation of the vinylic C--H bond of 1,4-dioxene, 2,3-dihydrofuran, 3,4-dihydro-2H-pyran and their gamma-substituted analogs was carried out in the presence of bis(pinacolato)diboron (B(2)pin(2)) and a catalytic amount of Ir(I)-dtbpy (dtbpy=4,4'-di-tert-butyl-2,2'-bipyridine) complex. The two boron atoms in B(2)pin(2) participated in the coupling, thus giving two equivalents of the coupling product from one equivalent of B(2)pin(2). The borylation of 1,4-dioxene in hexane resulted in 81 % yield at room temperature. The borylation of 2,3-dihydrofurans at 80 degrees C in octane suffered from low regioselectivity, and gave a mixture of alpha- and beta-coupling products even for hindered gamma-disubstituted analogs, but gamma-substituted analogs of 3,4-dihydro-2H-pyran achieved high alpha-selectivity, giving single coupling products. This protocol was applied to the syntheses of a key precursor of vineomycinone B2 methyl ester and other C-substituted D-glucals by borylation of protected D-glucals with B(2)pin(2) to give alpha-boryl glucal followed by cross-coupling with haloarenes, benzyl bromide, and allyl bromide. A catalytic cycle that involves the oxidative addition of sp(2) C--H bond to iridium(III)-trisboryl intermediate as the rate-determining step has been proposed.
46 citations
TL;DR: In this article, the authors explored the use of Hexafluoroisopropanol (HFIP) as an effective medium for the synthesis of 2,3-unsaturated glycosides through allylic rearrangement of 3,4,6-tri-O-acetyl glucal.
33 citations
TL;DR: Indium triflate proved to be the catalyst of choice in terms of conversion and regioselectivity and Transformations using O-, S, C, and N-nucleophiles could be achieved readily under mild and scalable conditions.
25 citations
TL;DR: Biological evaluation of one migrastatin and one dorrigocin A sugar derived analogue show that they inhibit proliferation and serum-induced migration of tumour and synovial cells at higher concentrations than evodiamine.
Abstract: The synthesis of a range of analogues of the migrastatin macrolide core has been achieved from tri-O-acetyl-D-glucal in order to facilitate structure-activity studies. Efficient macrolactone formation was achieved in the presence of a reactive olefin, by increasing steric hindrance in the olefin environment. Acyclic analogues of migrastatin, structurally related to dorrigocin A, have also been prepared from D-glucal. The dorrigocin A analogues were prepared using the combination of the cross metathesis of ethyl 6-heptenoate with a glycal derivative and a subsequent allylic rearrangement-alkene isomerisation reaction (Perlin reaction). A synthetic route is thus provided that will enable dorrigocin A analogues to be prepared in parallel to migrastatin analogues in the search for novel anti-cancer and anti-arthritic therapeutics. Biological evaluation of one migrastatin and one dorrigocin A sugar derived analogue show that they inhibit proliferation and serum-induced migration of tumour and synovial cells at higher concentrations than evodiamine. Dorrigocin A analogues displayed similar potency to analogues of the migrastatin core.
20 citations
TL;DR: The role of the immobilization strategy and the effect of the presence of different moieties in the anomeric position of the substrate on the hydrolytic activities, specificities and regioselectivities of the lipases were investigated.
18 citations
TL;DR: A variety of alcohols react with 2,3,4,6-tetra-O-acetyl-1,5-anhydro-D-arabino-hex-1-enopyranose 1 in the presence of a catalytic amount of HClO(4) supported on silica gel to give the corresponding alkyl 3-deoxy-hex
Abstract: A variety of alcohols react with 2,3,4,6-tetra-O-acetyl-1,5-anhydro-D-arabino-hex-1-enopyranose 1 in the presence of a catalytic amount of HClO(4) supported on silica gel to give the corresponding alkyl 3-deoxy-hex-2-enopyranosides 2 in high yield, with short reaction times (10-45 mins) and good alpha-selectivity. Work-up merely involves filtration of the reagent, followed by chromatographic purification of the crude product. This methodology has also been employed in the synthesis of a bicyclic ether, a useful precursor for cyclic polyethers, and a 4-amino-C-glucoside.
TL;DR: The solid-state structures of C12 bola form isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key intermolecular interactions between bolaform headgroups are necessary to determine the structure in the solid state.
Abstract: Glycal-based bolaforms serve as synthetically flexible components of molecular self-assembly. The compounds are prepared in good yield by a Ferrier reaction between triacetylglucal or -galactal or diacetylxylal and a long chain α,ω-diol, followed by deacetylation under Zemplen conditions. The reactions are stereoselective and preferentially afford the α-diastereomer. The bolaforms undergo self-assembly in water or water/dioxane solution to give a variety of nanostructures. In solution, bolaforms with C8 or C10 chains between glucal headgroups form nanoscale vesicles. In contrast, bolaforms with C12 chains exhibit lower solubility and a dynamic self-assembly, forming several different nanoscale structures. However, the solid-state structures of C12 bolaform isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key interm...
TL;DR: Glycosyl azides, prepared in situ from glucal and trimethylsilyl azide via Ferrier rearrangement, undergo smooth coupling with alkynes under neutral conditions by means of "Click reactions" to furnish 1,2,3-triazole-linked glycoconjugates in high yields and with moderate stereoselectivity.
TL;DR: In this paper, the acid-resistant phenylsulfonylethylidene (PSE) acetal, d-glucal privileged the additive pathway over the Ferrier I rearrangement when confronted with protic nucleophiles.
TL;DR: Venturello's phosphotungstate complex and titanium(IV) isopropoxide [Ti(O-i-Pr) 4 ] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H 2 O 2 ].
Abstract: Venturello's phosphotungstate complex and titanium(IV) isopropoxide [Ti(O-i-Pr) 4 ] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H 2 O 2 ]. Reaction substrates included a range of variously protected glycals and different alcohols were used as solvents. Ti(O-i-Pr) 4 was only effective in methanol as solvent, but gave methyl glycosides in high yields and high selectivities. The Venturello complex proved to be a very versatile and efficient catalyst. Apart from epoxidation-alcoholysis in alcoholic solvents it also showed activity in biphasic conditions to allow for glycosylation of long-chain alcohols and was very effective in the stereoselective dihydroxylation of benzylated glucal.
TL;DR: A simple, efficient, and mild method for the synthesis of omega-aminoalkyl 2-deoxy-d-arabino/lyxo-hexopyranoside and 2,3-dideoxy-alpha-d
TL;DR: In this article, a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glucosides via Ferrier rearrangement, was developed.
Abstract: We have developed a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glycosides via Ferrier rearrangement. The reaction of the perbenzyl glucal with various alcohols catalyzed by ferric sulfate hydrate (Fe2(SO4)3·xH2O) was successfully carried out to give 2,3-unsaturated d-O-glucosides with exclusive α-selectivity and no formation of addition products 2-deoxy hexopyranosides was observed. It is the first report on peralkyl glycal efficiently undergoing Ferrier rearrangement instead of addition of alcohols catalyzed by Lewis acids. Fe2(SO4)3·xH2O is an effective, convenient, and environmentally benign heterogeneous catalyst. It has low catalytic loading and recyclable without significant loss of activity.
TL;DR: The high similarity in large-scale solid state structures between 1 and glucosamide bolaamphiphile 4 suggest a strong dependence on head group stereochemistry, and that only a few, key intermolecular interactions between head groups are necessary in controlling the ultimate structure observed.
TL;DR: Silyl and isopropylidene-O-protected chromium glucal and galactal carbenes have been synthesized from their glycal precursors according to the Fischer route.
Abstract: Silyl- and isopropylidene-O-protected chromium glucal and galactal carbenes have been synthesized from their glycal precursors according to the Fischer route. NMR studies indicate a preferred 5 H 4 or 4 H 5 conformation, depending on the nature of the protective group and the configuration at C-4. The complexes with glycal carbenes have been applied to the diastereoselective cyclopropanation of methyl crotonate and γ-crotonolactone.
TL;DR: Venturello's phosphotungstate complex and titanium(IV) isopropoxide [Ti(O-i-Pr) 4 ] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H 2 O 2 ].
Abstract: Venturello's phosphotungstate complex and titanium(IV) isopropoxide [Ti(O-i-Pr) 4 ] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H 2 O 2 ]. Reaction substrates included a range of variously protected glycals and different alcohols were used as solvents. Ti(O-i-Pr) 4 was only effective in methanol as solvent, but gave methyl glycosides in high yields and high selectivities. The Venturello complex proved to be a very versatile and efficient catalyst. Apart from epoxidation-alcoholysis in alcoholic solvents it also showed activity in biphasic conditions to allow for glycosylation of long-chain alcohols and was very effective in the stereoselective dihydroxylation of benzylated glucal.
TL;DR: Glycosyl azides, prepared in situ from glucal and trimethylsilyl azide via Ferrier rearrangement, undergo smooth coupling with alkynes under neutral conditions by means of "Click reactions" to furnish 1,2,3-triazole-linked glycoconjugates in high yields and with moderate stereoselectivity as discussed by the authors.
Abstract: Glycosyl azides, prepared in situ from glucal and trimethylsilyl azide via Ferrier rearrangement, undergo smooth coupling with alkynes under neutral conditions by means of ‘Click reactions’ to furnish 1,2,3-triazole-linked glycoconjugates in high yields and with moderate stereoselectivity. The method provides a convenient route to prepare glycoconjugates from glucals, trimethylsilyl azide, and alkynes via a three component reaction.