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1.
New glycosyl donors have been developed that contained several para‐substituted O‐aryl protecting groups and their stereoselectivity for the glycosylation reaction was evaluated. A highly β‐selective glycosylation reaction was achieved by using thioglycosides that were protected by 4‐nitrophenyl (NP) groups, which were introduced by using the corresponding diaryliodonium triflate. Analysis of the stereoselectivities of several glycosyl donors indicated that the β‐glycosides were obtained through an SN2‐type displacement from the corresponding α‐glycosyl triflate. The NP group could be removed by reduction of the nitro group and acylation, followed by oxidation with ceric ammonium nitrate (CAN). 相似文献
2.
We have identified silver tetrafluoroborate (AgBF4) as an excellent promoter for the activation of various glycosyl donors including glycosyl halides, trichloroacetimidates, and thioimidates. Easy handling and no requirement for azeotropic dehydration prior to application makes AgBF4 especially beneficial in comparison to the commonly used AgOTf. Selective activation of glycosyl halides or thioimidates over thioglycosides or n-pentenyl glycosides, including simple sequential one-pot syntheses, has also been demonstrated. Versatility of glycosyl thioimidates was further explored by converting these intermediates into a variety of other classes of glycosyl donors. 相似文献
3.
Yu Bai Geert-Jan Boons Andrew Burton Matthew Johnson Michael Haller 《Journal of carbohydrate chemistry》2013,32(7):939-958
ABSTRACT An extension of the latent-active glycosylation strategy is reported whereby 3-buten-2-yl 2-deoxy-2-azidoglycosides and 3-buten-2-yl 2-deoxy-2-phthalimidoglycosides are used as building blocks for the preparation of amino sugar containing oligosaccharides. The allyl moieties of the latent substrates 5, 16 and 19 can be conveniently isomerised by treatment with a catalytic amount of (Ph3P)3RhCl/BuLi to give the active vinyl glycosides 6, 17 and 20 in high yield. These glycosyl donors were successfully used in glycosylations with acceptors 7, 9 and 11. In the case of glycosyl donor 6, the disaccharides 8, 10 and 12 could be obtained as anomeric mixtures or with high α-or β-selectivities depending on the reaction conditions selected. Glycosylations with glycosyl donors 17 and 20 in each case gave solely the β-linked products only in high yields. 相似文献
4.
Dr. Yi Wei Dr. Quanquan Wang Prof. Dr. Ming Joo Koh 《Angewandte Chemie (International ed. in English)》2023,62(5):e202214247
C-Alkyl glycosides and glycoproteins exist in natural products and are prized for their role as carbohydrate mimics in drug design. However, a practical strategy that merges glycosyl donors with readily accessible reagents, derived from abundant carboxylic acid and amine feedstocks, is yet to be conceived. Herein, we show that a nickel catalyst promotes C−C coupling between glycosyl halides and aliphatic acids or primary amines (converted into redox-active electrophiles in one step), in the presence of Hantzsch ester and LiI (or Et3N) under blue LED illumination to deliver C-alkyl glycosides with high diastereoselectivity. Mechanistic studies support the photoinduced formation of alkyl radicals that react with a glycosyl nickel species generated in situ to facilitate cross-coupling. Through this manifold, innate CO2H and NH2 motifs embedded within amino acids and oligopeptides are selectively capped and functionalized to afford glycopeptide conjugates through late-stage glycosylation. 相似文献
5.
Yang-Fan Guo Tao Luo Guang-Jing Feng Chun-Yang Liu Hai Dong 《Molecules (Basel, Switzerland)》2022,27(18)
An improved method to efficiently synthesize 2-OH thioaryl glycosides starting from corresponding per-protected glycals was developed, where 1,2-anhydro sugars were prepared by the oxidation of glycals with oxone, followed by reaction of crude crystalline 1,2-anhydro sugars with NaBH4 and aryl disulfides. This method has been further used in a one-pot reaction to synthesize glycosyl donors having both “armed” and “NGP (neighboring group participation)” effects. 相似文献
6.
A number of new glycosyl donors, O-(1-phenyl-1H-tetrazol-5-yl) glycosides, are prepared from the corresponding hemiacetals, commercially available 5-chloro-1-phenyl-1H-tetrazole ( 2 ), and tetrabutylammonium fluoride (Bu4NF) in either THF or DMF. The mild reaction conditions are compatible with a variety of protecting groups. The glycosyl donors are treated with hydrogen fluoride-pyridine complex (HF·py) to rapidly provide glycosyl fluorides in good-to-excellent yields, apparently by a (single or double) SN2 mechanism as studied by both 1H- and 19F-NMR spectroscopy. Under acidic conditions, glycosyl fluorides equilibrate partially or completely, equilibration requiring a large excess of HF · py. 相似文献
7.
Gopalsamy Sureshkumar 《Tetrahedron letters》2007,48(37):6564-6568
Propargyl 1,2-orthoesters are identified as glycosyl donors. Various glycosides and disaccharides were synthesized in a stereoselective manner using AuBr3 as the promoter. AuBr3 may activate the alkyne resulting in the formation of a 1,2-dioxolenium ion and also behaves as a Lewis acid to facilitate the attack of the glycosyl acceptor. The versatility of the protocol was demonstrated using a panel of aglycones comprising aliphatic, alicyclic, steroidal and sugar alcohols. 相似文献
8.
Saptashwa Chakraborty Dr. Bijoyananda Mishra Pratim Kumar Das Sandip Pasari Prof. Dr. Srinivas Hotha 《Angewandte Chemie (International ed. in English)》2023,62(6):e202214167
The synthesis of N-glycosides from stable glycosyl donors in a catalytic fashion is still challenging, though they exist ubiquitously in DNA, RNA, glycoproteins, and other biological molecules. Herein, silver-assisted gold-catalyzed activation of alkynyl glycosyl carbonate donors is shown to be a versatile approach for the synthesis of purine and pyrimidine nucleosides, asparagine glycosides and quinolin-2-one N-glycosides. Thus synthesized nucleosides were subjected to the oxidation–reduction sequence for the conversion of Ribf- into Araf- nucleosides, giving access to nucleosides that are otherwise difficult to synthesize. Furthermore, the protocol is demonstrated to be suitable for the synthesis of 2’-modified nucleosides in a facile manner. Direct attachment of an asparagine-containing dipeptide to the glucopyranose and subsequent extrapolation to afford the dipeptide disaccharide unit of chloroviruses is yet another facet of this endeavor. 相似文献
9.
A new approach towards the synthesis of glycosides based upon a (formal) insertion of glycosylidene carbenes into O? H bonds is presented. The synthesis and characterization of the glycosylidene-derived diazirines 25 – 28 , precursors of glycosylidene carbenes, are described. The diazirines were prepared by the rapid, high-yielding oxidation of the diaziridines 20 and 22 – 24 with I2/Et3N. The diaziridines, the first examples of C- alkoxy-diaziridines, were formed in high yields by the reaction of the [(glycosylidene)-amino]methanesulfonates 14 and 17 – 19 with a saturated solution of NH3 in MeOH. The diazirines are highly reactive compounds, losing N2 at room temperature or below. The reaction of the gluco-configurated diazirine 25 with i-PrOH yielding a mixture of the α- and β-D -glucosides 29 and 30 illustrates the potential of glycosylidene-derived diazirines as a new type of glycosyl donors. 相似文献
10.
Haijing Liang Lixia Ma Changwei Li Qiang Peng Zhaoyan Wang Zhan-xin Zhang Lan Yu Huanxiang Liu Fengli An Weihua Xue 《Tetrahedron letters》2019,60(1):84-87
Glycosylation reactions are significant as they provide access to model compounds that are useful for elucidating biochemical pathways. Herein, we describe the development of glycosyl ortho-alkynylbenzoates as novel, bench-top stable, and readily available glycosyl donors. Glycosylation is promoted by inexpensive trimethylsilyl triflate (TMSOTf) in combination with N-iodosuccinimide (NIS) under mild reaction conditions; hence, the novel glycosyl donors are promising reagents for the synthesis of glycosides. 相似文献
11.
Bis(pyridinium) iodonium(I) tetrafluoroborate (IPy2BF4), a solid and stable reagent, can be used to transform n-pentenyl orthoesters (NPOEs) and n-pentenyl glycosides (NPGs) into glycosyl fluorides. The latter pair constitutes a new set of semiorthogonal glycosyl donors that can be used in glycosylation strategies, alone or in combination with NPOEs. 相似文献
12.
Interrupted Pummerer Reaction in Latent‐Active Glycosylation: Glycosyl Donors with a Recyclable and Regenerative Leaving Group
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Penghua Shu Xiong Xiao Yueqi Zhao Yang Xu Wang Yao Jinyi Tao Hao Wang Prof. Dr. Guangmin Yao Prof. Dr. Zimin Lu Prof. Dr. Jing Zeng Prof. Dr. Qian Wan 《Angewandte Chemie (International ed. in English)》2015,54(48):14432-14436
Latent O‐glycosides, 2‐(2‐propylthiol)benzyl (PTB) glycosides, were converted into the corresponding active glycosyl donors, 2‐(2‐propylsulfinyl)benzyl (PSB) glycosides, by a simple and efficient oxidation. Treatment of the PSB donor and various acceptors with triflic anhydride provided the desired glycosides in good to excellent yields. The leaving group, which was activated by an interrupted Pummerer reaction, can be recycled (PSB‐OH) and regenerated as the precursor (PTB‐OH). A natural hepatoprotective glycoside, leonoside F, was efficiently synthesized in a convergent [3+1] manner with this newly developed method. The present total synthesis also led to a structural revision of this phenylethanoid glycoside. 相似文献
13.
Tsuyoshi Ikeda Ken Yamauchi Kenji Nakanishi Shin-ichi Ito 《Tetrahedron letters》2006,47(26):4355-4359
The aim of this study was to verify the antitumor role of the β-d-glucopyranosyl-(1→2)-O-[β-d-xylopyranosyl-(1→3)]-O-β-d-glucopyranosyl-(1→4)-d-galactopyranosyl (lycotetraosyl) moiety present in steroidal glycosides from Solanaceous plants. We explored a new chemical trans-glycosylation method using an endoglycosidase called tomatinase that is produced by the tomato pathogen, Fusarium oxysporum f. sp. lycopersici. The lycotetraose, which was prepared by enzymatic hydrolysis of α-tomatine with tomatinase, was converted to glycosyl donors such as trichloroacetimidate, fluoride, and thioglycoside. All obtained glycosyl donors were glycosylated with cholesterol to form α-lycotetraosyl cholesterols in a stereoselective manner. The obtained lycotetraosyl derivatives together with typical natural lycotetraosyl glycosides were examined for their antiproliferative activity. 相似文献
14.
15.
Regioselective and 1,2‐cis‐α‐Stereoselective Glycosylation Utilizing Glycosyl‐Acceptor‐Derived Boronic Ester Catalyst
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Akira Nakagawa Masamichi Tanaka Shun Hanamura Dr. Daisuke Takahashi Prof. Dr. Kazunobu Toshima 《Angewandte Chemie (International ed. in English)》2015,54(37):10935-10939
Regioselective and 1,2‐cis‐α‐stereoselective glycosylations using 1α,2α‐anhydro glycosyl donors and diol glycosyl acceptors in the presence of a glycosyl‐acceptor‐derived boronic ester catalyst. The reactions proceed smoothly to give the corresponding 1,2‐cis‐α‐glycosides with high stereo‐ and regioselectivities in high yields without any further additives under mild reaction conditions. In addition, the present glycosylation method was successfully applied to the synthesis of an isoflavone glycoside. 相似文献
16.
Santosh Kumar Giri 《合成通讯》2013,43(22):3378-3383
In(OTf)3 has been found to be an efficient catalyst for the direct conversion of reducing sugars to their respective acylated glycosyl halides in good yields under mild conditions. The glycosyl halides so obtained can be converted to alkyl glycosides in the same pot by reacting them with the respective alcohols in good yield. 相似文献
17.
Teruaki Mukaiyama Kazuya Takeuchi Hideki Jona Hisashi Maeshima Terunobu Saitoh 《Helvetica chimica acta》2000,83(8):1901-1918
A catalytic and stereoselective glycosylation of several glycosyl acceptors with β‐D ‐glycosyl fluoride was successfully performed in the presence of a catalytic amount of trityl tetrakis(pentafluorophenyl)borate (TrB(C6F5)4) or trifluoromethanesulfonic acid (TfOH). When TrB(C6F5)4 was used as a catalyst in the solvent pivalonitrile/(trifluoromethyl)benzene 1 : 5, the glycosylation proceeded smoothly to afford the glycosides in high yields with high β‐D ‐stereoselectivities (see Table 3). Further, the glycosylation by the armed‐disarmed strategy in the presence of this catalyst was established (see Table 4). Similarly, glycosylation catalyzed by the strong protic acid TfOH afforded the corresponding β‐D ‐glycosides in good‐to‐excellent yields on treating β‐D ‐ glycosyl fluorides having a 2‐O‐benzoyl group with various glycosyl acceptors including thioglycosides (see Tables 6 and 7). 相似文献
18.
Dr. Fuzhu Yang Wu Hou Dr. Dapeng Zhu Dr. Yu Tang Prof. Biao Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202104002
Conventional syntheses of 1,2-trans-β-d - or α-l -glycosidic linkages rely mainly on neighboring group participation in the glycosylation reactions. The requirement for a neighboring participation group (NPG) excludes direct glycosylation with (1→2)-linked glycan donors, thus only allowing stepwise assembly of glycans and glycoconjugates containing this type of common motif. Here, a robust glycosylation protocol for the synthesis of 1,2-trans-β-d - or α-l -glycosidic linkages without resorting to NPG is disclosed; it employs an optimal combination of glycosyl N-phenyltrifluroacetimidates as donors, FeCl3 as promoter, and CH2Cl2/nitrile as solvent. A broad substrate scope has been demonstrated by glycosylations with 12 (1→2)-linked di- and trisaccharide donors and 13 alcoholic acceptors including eight complex triterpene derivatives. Most of the glycosylation reactions are high yielding and exclusively 1,2-trans selective. Ten representative, naturally occurring triterpene saponins were thus synthesized in a convergent manner after deprotection of the coupled glycosides. Intensive mechanistic studies indicated that this glycosylation proceeds by SN2-type substitution of the glycosyl α-nitrilium intermediates. Importantly, FeCl3 dissociates and coordinates with nitrile into [Fe(RCN)nCl2]+ and [FeCl4]−, and the ferric cationic species coordinates with the alcoholic acceptor to provide a protic species that activates the imidate, meanwhile the poor nucleophilicity of [FeCl4]− ensures an uninterruptive role for the glycosidation. 相似文献
19.
Gold nanoparticle (Au‐NPs)‐Titanium oxide nanotube (TiO2‐NTs) electrodes are prepared by using galvanic deposition of gold nanoparticles on TiO2‐NTs electrodes as support. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy results indicate that nanotubular TiO2 layers consist of individual tubes of about 60–90 nm diameters and gold nanoparticles are well‐dispersed on the surface of TiO2‐NTs support. The electrooxidation of hydroquinone of Au‐NPs/TiO2‐NTs electrodes is investigated by different electrochemical methods. Au‐NPs/TiO2‐NTs electrode can be used repeatedly and exhibits stable electrocatalytic activity for the hydroquinone oxidation. Also, determination of hydroquinone in skin cream using this electrode was evaluated. Results were found to be satisfactory and no matrix effects are observed during the determination of hydroquinone content of the “skin cream” samples. 相似文献
20.
ABSTRACT Glycosyl esters constitute a widespread family of natural products such as anti-tumor agents,1 antibiotics,2 terpenoid glycosides,3 plant pigments4 and other substances.5 It has been shown that aromatic carboxylic acids are metabolized by humans as glycosyl esters,6 and D-glucopyranosyl fatty acid esters were found to inhibit the growth of leukemia cells7 and plant growth.8 The synthesis of a prodrug in the g form of a glycosyl ester has been reported.9 In synthetic chemistry glycosyl acetates are frequently used glycosyl donors in Lewis-acid catalyzed glycosylation reactions10 and other transformations.11 相似文献