- Visible-Light-Mediated, Chemo- and Stereoselective Radical Process for the Synthesis of C-Glycoamino Acids
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An approach for efficient synthesis of C-glycosyl amino acids is described. Different from typical photoredox-catalyzed reactions of imines, the new process follows a pathway in which α-imino esters serve as electrophiles in chemoselective addition reactions with nucleophilic glycosyl radicals. The process is highlighted by the mild nature of the reaction conditions, the highly stereoselectivity attending C-C bond formation, and its applicability to C-glycosylations using both armed and disarmed pentose and hexose derivatives.
- Ji, Peng,Zhang, Yueteng,Wei, Yongyi,Huang, He,Hu, Wenbo,Mariano, Patrick A.,Wang, Wei
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supporting information
p. 3086 - 3092
(2019/05/01)
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- Deprotection of silyl ethers by using SO3H silica gel: Application to sugar, nucleoside, and alkaloid derivatives
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We applied a desilylation procedure using SO3H silica gel, with the surface modified by alkylsulfonic acid groups, to silylated sugar, nucleoside, and alkaloid derivatives. The treatment with SO3H silica gel provided desilylated products in good to excellent yield. In the reactions of sugar and nucleoside derivatives, no silyl residue was detected in the crude products, but the crude products of the reaction of alkaloids contained small amounts of silyl residues. Even though the sugar and nucleoside derivatives had a labile glycosyl and C–N bond, respectively, these bonds tolerated the reaction conditions. These outcomes suggested that the desilylation procedure using SO3H silica gel would be applicable to the deprotection of a variety of types of compounds protected by silyl groups. In a gram scale experiment, the desilylation procedure successfully proceeded without the observation of any silyl residue in the crude product.
- Fujii, Hideaki,Shimada, Naoyuki,Ohtawa, Masaki,Karaki, Fumika,Koshizuka, Masayoshi,Hayashida, Kohei,Kamimura, Mitsuhiro,Makino, Kazuishi,Nagamitsu, Tohru,Nagase, Hiroshi
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p. 5425 - 5429
(2017/08/11)
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- Studies on the substrate specificity of a GDP-mannose pyrophosphorylase from Salmonella enterica
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A series of methoxy and deoxy derivatives of mannopyranose-1-phosphate (Manp-1P) were chemically synthesized, and their ability to be converted into the corresponding guanosine diphosphate mannopyranose (GDP-Manp) analogues by a pyrophosphorylase (GDP-ManPP) from Salmonella enterica was studied. Evaluation of methoxy analogues demonstrated that GDP-ManPP is intolerant of bulky substituents at the C-2, C-3, and C-4 positions, in turn suggesting that these positions are buried inside the enzyme active site. Additionally, both the 6-methoxy and 6-deoxy Manp-1P derivatives are good or moderate substrates for GDP-ManPP, thus indicating that the C-6 hydroxy group of the Manp-1P substrate is not required for binding to the enzyme. When taken into consideration with other previously published work, it appears that this enzyme has potential utility for the chemoenzymatic synthesis of GDP-Manp analogues, which are useful probes for studying enzymes that employ this sugar nucleotide as a substrate.
- Zou, Lu,Zheng, Ruixiang Blake,Lowary, Todd L.
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supporting information; experimental part
p. 1219 - 1226
(2012/09/21)
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- Synthesis and structure elucidation of benzoylated deoxyfluoropyranosides
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Benzoylated deoxyfluoropyranosides have been synthesized, starting with protected, unprotected, or fluorinated precursors. Fluorination of eight derivatives was compared using DAST and Deoxo-Fluor as reagents. Deoxo-Fluor was found to be especially useful
- Esmurziev, Aslan M.,Simic, Nebojsa,Hoff, Bard Helge,Sundby, Eirik
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scheme or table
p. 348 - 367
(2011/09/30)
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- Regioselective C-6 hydrolysis of methyl O-benzoyl-pyranosides catalysed by candida rugosa lipase
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Hydrolysis of six methyl O-benzoyl-pyranosides has been investigated using Candida rugosa lipase in dioxane/buffer mixtures. The lipase catalysed the hydrolysis of all substrates in a regiospecific manner at C-6, The rate of reaction was dependent on pyra
- Esmurziev, Asian,Sundby, Eirik,Hoff, Bard Helge
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experimental part
p. 1592 - 1597
(2009/09/08)
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- Removal of acid-labile protecting groups on carbohydrates using water-tolerant and recoverable vanadyl triflate catalyst
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Acetal, trityl, and TBDMS protecting groups on saccharides were subjected to alcoholysis using a catalytic amount of vanadyl triflate in an MeOH-CH 2Cl2 solvent system. The configuration at the anomeric positions of saccharides was retained, and no glycosidic bond cleavage and oxidation of sulfides were observed. The presented method was easily implemented, compatible with diverse functional groups, and regioselective in some cases.
- Yan, Ming-Chung,Chen, Yeng-Nan,Wu, Huan-Ting,Lin, Chang-Ching,Chen, Chien-Tien,Lin, Chun-Cheng
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p. 299 - 302
(2007/10/03)
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- A facile, catalytic, and environmentally benign method for selective deprotection of teri-butyldimethylsilyl ether mediated by phosphomolybdic acid supported on silica gel
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An environmentally benign PMA supported on SiO2 is found to be an efficient catalyst for the chemoselective deprotection of TBDMS ethers under very mild conditions. Various labile functional groups such as isopropylidene acetal, OTBDPS, OTHP, Oallyl, OBn, alkene, alkyne, OAc, OBz, N-Boc, N-Cbz, N-Fmoc, mesylate, and azide are found to be stable under the reaction conditions. This "truly catalytic" heterogeneous reaction does not require aqueous workup, and the supported catalyst and the solvent can be readily recovered and recycled.
- Kishore Kumar,Baskaran, Sundarababu
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p. 4520 - 4523
(2007/10/03)
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- Detritylation of mono- and di-saccharide derivatives using ferric chloride hydrate
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Quantitative detritylation of mono- and di-saccharide derivatives of diverse structure was achieved with FeCl3 · 6H2O in CH2Cl2 at room temperature. Benzyl, isopropylidene, isopropylthio, allyl, acetyl, and benzoyl O-protecting groups were not effected under the designated conditions.
- Ding, Xianglan,Wang, Wei,Kong, Fanzuo
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p. 445 - 448
(2007/10/03)
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- Synthesis of mono- and dimannoside phosphoramidite derivatives for solid-phase conjugation to oligonucleotides
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Mannose and dimannose derivatives have been prepared with an anomerically-linked hydrophobic spacer, and converted to phoshoramidite derivatives suitable for conjugation to oligoribodeoxynucleotides on a DNA/RNA synthesizer. Synthesis of a monomannoside-linked 15-mer oligoribodeoxynucleotide is reported.
- Akhtar,Akhtar, Saghir,Routledge,Routledge, Anne,Patel,Patel, Ramila,Gardiner,Gardiner, John M.
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p. 7333 - 7336
(2007/10/02)
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- Binding studies on internal immunodeterminants: synthesis of β-(1->6)-linked oligosaccharide methyl glycosides having one to four internal D-galactopyranosyl residues flanked by gentiobiose residues
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The oligosaccharide glycosides β-D-Glcp-(1->6)-β-D-Glcp-(1->6)-6)>n-β-D-Glcp-(1->6)-β-D-Glcp-1->OMe (n=1-4) were prepared by a convergent block synthesis.Haloacetyl, tert-butyldiphenylsilyl, and dimethylthexylsilyl groups were used as tempo
- Ziegler, Thomas,Sutoris, Heinz,Glaudemans, Cornelis P. J.
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p. 271 - 292
(2007/10/02)
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- SELECTIVE BROMOACETYLATION OF ALKYL HEXOPYRANOSIDES: A FACILE PREPARATION OF INTERMEDIATES FOR THE SYNTHESIS OF (1 -> 6)-LINKED OLIGOSACCHARIDES
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Bromoacetylation of methyl β-D-galacto- (1), α-D-galacto- (6), β-D-gluco- (18), α-D-gluco- (22), and α-D-manno-pyranoside (31), and benzyl β-D-gluco-pyranoside (27), gave the corresponding 6-O-bromoacetyl derivatives 2, 7, 19, 23, 32, and 28 in 50-60perce
- Ziegler, Thomas,Kovac, Pavol,Glaudemans, Cornelis P.J.
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p. 185 - 198
(2007/10/02)
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- NOVEL D-GLUCANS OBTAINED BY DIMETHYL SULFOXIDE EXTRACTION OF THE LICHENS Letharia vulpina, Actinogyra muehlenbergii, AND AN Usnea SP.
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Extraction of certain lichens with cold dimethyl sulfoxide provided a β-D-glucan virtually free of contaminating α-D-glucan and galactomannan.Applied to Letharia vulpina, the method gave β-D-glucan, and extraction of the residue with hot water followed by cooling gave α-D-glucan.From Usnea sp. a β-D-glucan was isolated, but little α-D-glucan was present.Extraction of Actinogyra muehlenbergii provided a (16)-linked β-D-glucopyranan containing one acetyl group of every 8-9 glucosyl units, being present almost exclusively as monosubstituent at O-2, O-3, and O-4.
- Iacomini, Marcello,Gorin, Philip A. J.,Baron, Madalena,Tulloch, Alexander P.,Mazurek, Mytosk
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p. 117 - 126
(2007/10/02)
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- Oxidative Cleavage of 4,6-O-Benzylidene Ring with t-Butyl Hydroperoxide and Copper(II) Chloride. Preparation of Methyl 4-O- and 6-O-Benzoylhexopyranoside Derivatives
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Copper(II) chloride and palladium(II) acetate were found to be highly effective catalysts for oxidative cleavage of O-benzylidene ring with t-butyl hydroperoxide.Using the former catalyst 4,6-O-benzylidenehexopyranoside derivatives were converted into the
- Sato, Ken-ichi,Igarashi, Tetsutaro,Yanagisawa, Yukio,Kawauchi, Nobuya,Hashimoto, Hironobu,Yoshimura, Juji
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p. 1699 - 1702
(2007/10/02)
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- Dioxolanylium Ions Derived from Carbohydrates. IX. Rearrangement between Dioxolanylium and Dioxanylium Ions
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The formation of 4,6-acetoxonium and benzoxonium ion derivatives of methyl gluco-, manno-, galacto- and idopyranosides from the 6-azido-6-deoxy compounds on treatment with nitrosonium ion is described and the formation and rearrangement of the 3,5-benzoxonium ion derived from methyl α-d-xylofuranoside discussed.
- Jacobsen, Steffen
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p. 157 - 164
(2007/10/02)
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- A reversal in the order of H-6R and H-6S chemical shifts of some aldohexopyranose derivatives, associated with the acetylation of OH-4 and OH-6 groups. A distinction between 3- and 4-linked D-glucose residues in disaccharides
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On peracetylation of methyl α- or β-D-glucopyranose, there is a reversal in the order of the chemical shifts of the 6,6'-methylene protons, i.e., whereas the H-6S signal appears downfield of H-6R in the spectra of the glucosides, the
- Rao, Vanga S.,Perlin, Arthur S.
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p. 2688 - 2694
(2007/10/02)
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