cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• independent. The isomerization of flavanonols at C-2, C-3 is not without precedent, as it was described for taxillusin – the flavanonol glycoside from Taxillus kaempferi (Japanese mistletoe) containing the 3-hydroxy-2,3-dihydro-2-phenylchromen-4-one moiety [29]. Taxillusin (24, (2R,3R)-taxifolin 3-β-D

• -glucopyranoside 6''-gallate, Figure 6) was subjected to both, basic and acidic hydrolysis during its structure elucidation. However, under these conditions four stereoisomers of the original aglycon (2R,3R)-taxifolin were formed. Base-catalyzed isomerization of another taxifolin glycoside, (2R,3R)-2,3

Efficient carbon-Ferrier rearrangement on glycals mediated by ceric ammonium nitrate: Application to the synthesis of 2-deoxy-2-amino-C-glycoside

• Alafia A. Ansari,
• Y. Suman Reddy and
• Yashwant D. Vankar

Beilstein J. Org. Chem. 2014, 10, 300–306, doi:10.3762/bjoc.10.27

• with high selectivity. The versatility of this method has been demonstrated by applying it to differently protected glycals and by employing several nucleophiles. The obtained C-allyl glycoside has been utilized for the synthesis of a orthogonally protected 2-amino-2-deoxy-C-glycoside. Keywords: C

• -O-acetyl-D-glucal (1a) by using 3 equivalents of allyltrimethylsilane and 2 equivalents of CAN in anhydrous acetonitrile at room temperature. The reaction proceeded smoothly over 1 hour and exclusively furnished the α-C-allyl glycoside 2a in 88% yield (Table 1) [42]. We attempted the same reaction

• obtained the α-C-glycosides in an efficient manner, we explored their synthetic utility to synthesize a 2-deoxy-2-amino-α-C-glycoside. 2-Deoxy-2-amino-α-C-glycosides have received considerable attention in recent years due to their use in the synthesis of glycopeptides [50][51], glycolipids [51] and

Convergent synthesis of a tetrasaccharide repeating unit of the O-specific polysaccharide from the cell wall lipopolysaccharide of Azospirillum brasilense strain Sp7

• Pintu Kumar Mandal,
• Debashis Dhara and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2014, 10, 293–299, doi:10.3762/bjoc.10.26

• the O-specific polysaccharide of the LPS of A. brasilense Sp7 strain as its 2-aminoethyl glycoside (Figure 1) is presented herein. Results and Discussion The target tetrasaccharide 1 has been synthesized as its 2-aminoethyl glycoside (Figure 1) to facilitate its conjugation with a suitable substrate

• use of Et2O in the reaction solvent facilitated the formation of 1,2-cis glycoside as the major product. The concept of the Fraser–Reid’s “armed–disarmed” effect was successfully exploited in this glycosylation reaction [34][35]. Compound 5 acted as an activated or armed glycosyl donor because of the

• summary, a straightforward and convergent synthesis of the tetrasaccharide 1 as its 2-aminoethyl glycoside corresponding to the O-specific polysaccharide of the LPS of A. brasilense strain Sp7 has been presented. The use of thioglycosides both as glycosyl donor and acceptor according to the concept of the

Physalin H from Solanum nigrum as an Hh signaling inhibitor blocks GLI1–DNA-complex formation

• Midori A. Arai,
• Kyoko Uchida,
• Samir K. Sadhu,
• Firoj Ahmed and
• Masami Ishibashi

Beilstein J. Org. Chem. 2014, 10, 134–140, doi:10.3762/bjoc.10.10

• physalin F (5; IC50, 0.66 μM) [17], physalin B (6; IC50, 0.62 μM) [17], colubrinic acid (IC50, 38 μM) [18], caldenolides (IC50, 0.1–0.45 μM) [19], taepeenin D (IC50, 1.6 μM) [20] and a flavonoid glycoside (IC50, 0.5 μM) [21] were isolated by using this screening assay. Recently, we found that vitetrifolin

Stereoselectively fluorinated N-heterocycles: a brief survey

• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2013, 9, 2696–2708, doi:10.3762/bjoc.9.306

• ) is an inhibitor of the β-glucosidase from sweet almond, and it is thought to exert its inhibitory activity by mimicking the oxocarbenium intermediate of glycoside cleavage [49]. Several analogues of 31 have been investigated (41–44, Figure 11) [50][51][52], and on first inspection it is difficult to

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• set the stage for mesylation, and conversion of 3 to fluoride 4 with an extremely economical reagent. Acetal cleavage and peracetylation released glycoside 5 which was converted to 6 via known methods. The main disadvantages of the approach are the extensive use which must be made of protection

Synthesis of enantiopure sugar-decorated six-armed triptycene derivatives

• Paola Bonaccorsi,
• Maria Luisa Di Gioia,
• Antonella Leggio,
• Lucio Minuti,
• Teresa Papalia,
• Carlo Siciliano,
• Andrea Temperini and
• Anna Barattucci

Beilstein J. Org. Chem. 2013, 9, 2410–2416, doi:10.3762/bjoc.9.278

• oligovalent scaffold, a number of sugar moieties, and suitable spacers which link the sugar moieties to the central core. Several examples of such molecular architectures have been obtained, and it has been demonstrated that these compounds are well-suited for the binding of lectins because of the glycoside

Gold-catalyzed glycosidation for the synthesis of trisaccharides by applying the armed–disarmed strategy

• Abhijeet K. Kayastha and
• Srinivas Hotha

Beilstein J. Org. Chem. 2013, 9, 2147–2155, doi:10.3762/bjoc.9.252

• carbohydrate chemistry was first reported for the oxidation of alcohols [11][12][13][14][15][16]. However, until recently these catalysts were scarcely applied. Glycosidation is one of the key reactions in chemistry of carbohydrates, in which a nucleophile attaches to a saccharide to form a glycoside. In this

• still no universal glycosyl donor [17][18], although the first glycoside was reported by Emil Fischer more than a century ago. A series of observations in our laboratory led to the identification of a gold(III)-catalyzed glycosidation reaction that uses alkynyl glycosides as glycosyl donors [19][20][21

• ][32][33][34]. Esters at the C-2 position of the saccharide are known to impede the glycoside formation whereas ethers (–OBn) facilitate the reaction. Fraser-Reid applied the terms disarmed to deactivated glycosyl donors [e.g., esters], and armed to the activated donors [e.g., ethers] [35][36]. During

Synthesis of mucin-type O-glycan probes as aminopropyl glycosides

• David Benito-Alifonso,
• Rachel A. Jones,
• Anh-Tuan Tran,
• Hannah Woodward,
• Nichola Smith and
• M. Carmen Galan

Beilstein J. Org. Chem. 2013, 9, 1867–1872, doi:10.3762/bjoc.9.218

• access disaccharide 20b, trichloroacetimidate glycoside donor 12 was reacted with 19 in the presence of catalytic TMSOTf to yield an inseparable mixture of disaccharide product 20a and unreacted starting material. Acetal cleavage with p-TsOH in MeOH under sonication followed by acetylation of the free OH

• and higher α-selectivities than other sialosyl donors [23]. Under our reaction conditions, sialylated disaccharide 22a was prepared as a 3/1 (α/β) mixture using 1-thioadamantyl sialoside 21 as the glycoside donor upon reaction with 19, using NIS in combination with catalytic TMSOTf to activate the

Straightforward synthesis of a tetrasaccharide repeating unit corresponding to the O-antigen of Escherichia coli O16

• Manas Jana and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2013, 9, 1757–1762, doi:10.3762/bjoc.9.203

• from natural sources. Hence, the development of chemical synthetic strategies for the synthesis of oligosaccharides is essential. In this context, a straightforward synthesis of the tetrasaccharide corresponding to the O-antigen of E. coli O16 as its p-methoxyphenyl glycoside has been developed and is

• presented herein (Figure 2). Results and Discussion The target tetrasaccharide as its p-methoxyphenyl (PMP) glycoside was synthesized following a sequential glycosylation approach from the suitably functionalized monosaccharide intermediates 2 [13], 3 [14], 4 [15] and 5 [16]. These monosaccharide

• summary, a straightforward synthetic strategy was developed for the synthesis of the tetrasaccharide 1 as its p-methoxyphenyl glycoside corresponding to the O-antigen of E. coli O16. The target compound was synthesized by using a minimum number of steps and by applying recently developed elegant synthetic

Short synthesis of the common trisaccharide core of kankanose and kankanoside isolated from Cistanche tubulosa

• Goutam Guchhait and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2013, 9, 705–709, doi:10.3762/bjoc.9.80

• , H2 and I isolated from C. tubulosa thereby exploiting newly developed regio- and stereoselective glycosylation conditions (Figure 1). This straightforward synthetic strategy employs a minimum number of steps. Results and Discussion The target trisaccharide 1 in the form of its 2-phenylethyl glycoside

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• represents a model study for the total synthesis of gilvocarcin M (47), a natural C-glycoside [27]; while the latter illustrates the possibility of constructing a cyclobutane-containing tricyclic motif related to the one found in penitrem D, 50 [28]. The two-step formation of tetralone 53, starting from

• alkenes, as indicated by the two examples in Scheme 28. The first represents a one-step synthesis of a steroid C-glycoside 149 [66], while the second illustrates a modular approach where the formation of alkene 152 is associated with the initial addition–transfer of cortisone derived xanthate 150 to vinyl

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• that of the standard inhibitor methyl mannoside. These findings could be rationalised on the basis of computer-aided docking studies. The properties of the new azobenzene mannobioside have qualified this glycoside to be eventually employed on solid support, in order to fabricate photoswitchable

• process is high-yielding and the lifetime of the (Z)-form of the azobenzene glycoside is long enough, it can be employed in bacterial adhesion assays independently from the more stable (E)-isomer. Eventually, this type of azobenzene mannobioside can be further functionalised to be attached to various

• ) gave the title glycoside 5 as an orange crystalline solid (4.33 g, 8.19 mmol, 81%). Mp 53–55 °C; Rf 0.35 (cyclohexane/ethyl acetate 2:1); [α]20D +0.86 (c 0.9, DMSO); 1H NMR (500 MHz, CDCl3) δ 7.92 (d, J = 9.0 Hz, 2H, H-9, H-11), 7.89 (d, J = 8.5 Hz, 2H, H-14, H-18), 7.53–7.45 (m, 3H, H-15, H-16, H-17

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

• El Sayed H. El Ashry,
• El Sayed H. El Tamany,
• Mohy El Din Abdel Fattah,
• Mohamed R. E. Aly,
• Ahmed T. A. Boraei and
• Axel Duerkop

Beilstein J. Org. Chem. 2013, 9, 135–146, doi:10.3762/bjoc.9.16

• anomeric protons of the N-glycosides 29, 30 indicate that β-configuration is still retained here. X-ray analysis Single-crystal X-ray diffraction experiments yielded unambiguous confirmations of the structural assignments of the S-glycoside 23, the 2-N-(glycosyl)thiosemicarbazide 29, and the

Removal of benzylidene acetal and benzyl ether in carbohydrate derivatives using triethylsilane and Pd/C

• Abhishek Santra,
• Tamashree Ghosh and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2013, 9, 74–78, doi:10.3762/bjoc.9.9

• achieved under catalytic transfer hydrogenation conditions by using a combination of triethylsilane and 10% Pd/C in CH3OH at room temperature. A variety of carbohydrate diol derivatives were prepared from their benzylidene derivatives in excellent yield. Keywords: benzylidene; glycoside; Pd/C; transfer

Acylsulfonamide safety-catch linker: promise and limitations for solid–phase oligosaccharide synthesis

• Jian Yin,
• Steffen Eller,
• Mayeul Collot and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 2067–2071, doi:10.3762/bjoc.8.232

• activated by TMSOTf were conducted, and followed by Zemplén cleavage. Similarly, three equivalents of thioglycosides 17 and 19 were added three times (triple coupling) for each glycosylation employing DMTST or NIS/TfOH as an activator. In both instances, surprisingly, only N-glycoside 20 (minor product) and

• -phase oligosaccharide synthesis were discovered. The sulfamyl group can be attacked by excess glycosylating agent to give the unexpected resin-bound N-glycoside, which may block additional reaction sequences and extension of the oligosaccharide [28]. In addition, sodium methoxide can directly cleave the

Convergent synthesis of the tetrasaccharide repeating unit of the cell wall lipopolysaccharide of Escherichia coli O40

• Abhijit Sau and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2012, 8, 2053–2059, doi:10.3762/bjoc.8.230

• strategy. Results and Discussion The target tetrasaccharide 1 as its 2-aminoethyl glycoside was synthesized by a stereoselective glycosylation of a disaccharide acceptor 8 and a disaccharide thioglycoside donor 9 using a [2 + 2] block synthetic strategy. The disaccharide intermediates were synthesized from

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

Automated synthesis of sialylated oligosaccharides

• Davide Esposito,
• Mattan Hurevich,
• Bastien Castagner,
• Cheng-Chung Wang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 1601–1609, doi:10.3762/bjoc.8.183

• from commercially available Sia (Figure 1b). Compound 6 was converted in a single step into various sialylating agents, such as the N-phenyl trifluoroacetimidoyl glycoside 10, and glycosyl phosphites 8 and 1 as previously described (Table 1) [19][20][21]. Galactal 2 was identified recently as an

Interaction of cyclodextrins with pyrene-modified polyacrylamide in a mixed solvent of water and dimethyl sulfoxide as studied by steady-state fluorescence

• Akihito Hashidzume,
• Yongtai Zheng and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1312–1317, doi:10.3762/bjoc.8.150

• fluorescence; water/DMSO mixed solvent; Introduction Cyclodextrins (CDs) are cyclic oligomers composed of glucopyranose units linked through α-1,4-glycoside bonding. They bear a tapered structure with a narrower rim of primary hydroxy groups and a wider rim of secondary hydroxy groups. CDs of 6, 7, and 8

Studies on the substrate specificity of a GDP-mannose pyrophosphorylase from Salmonella enterica

• Lu Zou,
• Ruixiang Blake Zheng and
• Todd L. Lowary

Beilstein J. Org. Chem. 2012, 8, 1219–1226, doi:10.3762/bjoc.8.136

• affording 15. The benzylidene protecting group was cleaved, together with the methyl glycoside, by acetolysis giving the tetra-O-acetylated compound 16 in 81% yield. This glycosyl acetate was converted to the corresponding thioglycoside (17), which was, in turn, coupled with dibenzyl phosphate under NIS

Synthesis of 4” manipulated Lewis X trisaccharide analogues

• Christopher J. Moore and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2012, 8, 1134–1143, doi:10.3762/bjoc.8.126

• used conditions very similar to those used by Risbood et al. to prepare peracetylated trichloroethyl galactopyranoside from peracetylated galactose. Indeed, in agreement with their work [57], the ratio of α-anomer isolated here suggests a late anomerization of the β-glycoside during our extended

• displacement of the triflate by using tetrabutylammonium fluoride [62][63] gave the 4-fluoro galactoside analogue 19 in excellent yields. As described above for the preparation of donor 9 from glycoside 16, trichloroethyl galactosides 18 and 19 were, in turn, converted in two steps (Zn/AcOH then Cl3CCN/DBU) to

• ]. We applied similar conditions to prepare disaccharides 20–22 (Table 1). Glycosylation of methyl glycoside 6 with the 4-methoxy donor 9 gave the best results when the reaction was carried out at 40 °C and left to proceed for 2 hours. Under these conditions, the desired disaccharide 20 was isolated in

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• Thomas Ziegler Ulrich Heber Institute of Organic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, 72076 Tuebingen, Germany 10.3762/bjoc.8.118 Abstract A series of 15 glycoside-derived tricarbonyl(η6-arene)chromium complexes were prepared in 19–87% yield by heating fully acetylated or

• prevent the excessive sublimation of Cr(CO)6 during the formation of the arene–chromium complexes [17]. Therefore, we used method (b) for the preparation of tricarbonyl(η6-arene)chromium complexes of glycosides as follows. One equivalent of phenyl or benzyl glycoside 1 and one equivalent of Cr(CO)6 were

• sample with iodine in CHCl3 followed by measurement of the NMR spectrum of the formed glycoside. The latter showed a CH-coupling constant at the anomeric center of 173.9 Hz, which is indicative of an α-anomer [19]. As additional proof for the anomeric configuration of 2f, we also prepared β-anomer 2g

Low-generation dendrimers with a calixarene core and based on a chiral C₂-symmetric pyrrolidine as iminosugar mimics

• Marco Marradi,
• Stefano Cicchi,
• Francesco Sansone,
• Alessandro Casnati and
• Andrea Goti

Beilstein J. Org. Chem. 2012, 8, 951–957, doi:10.3762/bjoc.8.107

• [14]. Multivalent calixarenes functionalised with carbohydrate units (glycocalixarenes) [15] have been extensively reported in the literature and represent examples of sugar clustering on macrocyclic structures [16][17]. Thanks to the “glycoside cluster effect” [18][19][20], glycocalixarenes can

• enhance the avidity of interactions between glycans and lectins [15]. Some glycocalixarenes have shown remarkable inhibition properties towards galectins [21][22] or Pseudomonas Aeruginosa lectin [23], the inhibition ability being dependent on the macrocyclic conformation and presentation of the glycoside

• units. With the purpose of expanding the valency and increasing the glycoside density, glycodendrimers have also been synthesised and their properties in protein–carbohydrate interactions have been studied [24][25][26]. However, the innovative frontier of combining glycodendrimeric arrangements onto a

The use of glycoinformatics in glycochemistry

• Thomas Lütteke

Beilstein J. Org. Chem. 2012, 8, 915–929, doi:10.3762/bjoc.8.104

• glycan chain, and by glycoside hydrolases (GH) that remove specific monosaccharides [3]. For this reason there is no technique available to amplify carbohydrates comparable to Polymerase Chain Reaction (PCR) or protein expression systems. Instead, carbohydrates have to be analyzed in physiological

• the enzymes that build or degrade the glycan chains in vivo, the glycosyltransferases or glycoside hydrolases, respectively [46][47][48][49]. To plan such experiments, however, detailed knowledge of the substrate-specificity of these enzymes is required. The same applies to glycan-binding proteins

• (glycosyltransferases, glycoside hydrolases, polysaccharide lyases and carbohydrate esterases) as well as proteins that feature carbohydrate-binding modules is CAZy (Carbohydrate Active Enzymes). This database classifies proteins by sequence comparison and clusters them into families by using well-established