The effect of neighbouring group participation and possible long range remote group participation in O-glycosylation

• Rituparna Das and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2025, 21, 369–406, doi:10.3762/bjoc.21.27

• [40]. In such a case, the acceptor has the advantage of attacking from both the sides, and thus, a diastereomeric mixture of both equatorial (7) and axial (8) anomers are formed [25]. Apart from these, some cases of glycosylation reactions have also been reported to reside along a continuum between

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• of n-propyl mercaptane with subsequent addition of acetic anhydride, pyridine and KHF2 afforded indigo-N-rhamnoside 5c as a 2:1 mixture of α/β-anomers. The relatively low yield is a result of side reactions and decomposition, due to the rather unstable nature of the product. The reaction of 5c with

• cyclization of 4e with oxalyl chloride afforded yellow isatin-N-glycoside 16a as an anomeric mixture from which the pure α- and β-anomer could be separated by chromatography. Likewise, isatin-N-glycosides 16b–f were prepared which were all isolated (except from rhamnoside 16b) as the pure β-anomers. The

• -glycosyl aniline β-22b which was formylated to give 22c in 74% yield (Scheme 16) [24]. Product 22c resides as a mixture of α- and β-anomers, because an anomeric equilibrium was activated during the acid-mediated formylation. The cyclization of 22c with oxalyl chloride, carried out under forcing conditions

Synthesis and conformational analysis of pyran inter-halide analogues of ᴅ-talose

• Olivier Lessard,
• Mathilde Grosset-Magagne,
• Paul A. Johnson and
• Denis Giguère

Beilstein J. Org. Chem. 2024, 20, 2442–2454, doi:10.3762/bjoc.20.208

• , therefore we were compelled to proceed directly to the next step. Cleavage of the 1,6-anhydro bridges was achieved under acetolysis conditions providing halogenated talopyranoses 12–15 in good yield over 3 steps as α anomers. Luckily, inter-halides 13–15 were crystalline, allowing the absolute configuration

• -talose, except for the C3–C4 bond of compound 15. This can be explained by the adjacent repulsion between CF3 with the CI4 group. Next, it has been reported that the C1–O1 bond lengths are shorter than the O5–C1 for α anomers [42][46][47]. Talopyranose (18) follows this trend, but not the halogenated

Synthesis of 1,4-azaphosphinine nucleosides and evaluation as inhibitors of human cytidine deaminase and APOBEC3A

• Maksim V. Kvach,
• Stefan Harjes,
• Harikrishnan M. Kurup,
• Geoffrey B. Jameson,
• Elena Harjes and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2024, 20, 1088–1098, doi:10.3762/bjoc.20.96

• , providing a linear nucleoside 17 as a mixture of two anomers, which were successfully separated on a silica gel column. Finally, cyclisation of a linear nucleoside was accomplished in the presence of a catalytic amount of the Lewis acid TMSOTf in 64% yield. Unfortunately, cyclisation was accompanied by

• racemisation, and nucleoside 14 with the same α/β ratio of 3:2 formed from either anomerically pure 17 or from a mixture of the anomers. Catalytic hydrogenation is usually used for the removal of benzyl protecting groups. However, standard hydrogenation conditions using 10% Pd/C led to reduction of the C=C

• double bond in the nucleobase, providing nucleoside 24 (Scheme 3). To circumvent this problem, we used poisoned Pd catalyst (Lindlar’s catalyst, 5% Pd/CaCO3/3% Pb) and obtained the desired nucleoside 18. Individual anomers of nucleosides 18 and 24 were separated on a C18 column using a gradient of CH3CN

Skeletal rearrangement of 6,8-dioxabicyclo[3.2.1]octan-4-ols promoted by thionyl chloride or Appel conditions

• Martyn Jevric,
• Julian Klepp,
• Johannes Puschnig,
• Oscar Lamb,
• Christopher J. Sumby and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2024, 20, 823–829, doi:10.3762/bjoc.20.74

• ]octane, while O6 migrated when the C4–OH was axial leading to 2,4-dioxabicyclo[2.2.2]octanes. The formation of both anomers from the non-selective addition of fluoride suggested intermediates with oxocarbenium character. This work has recently been extended by Banwell and co-workers to include a set of

Elucidating the glycan-binding specificity and structure of Cucumis melo agglutinin, a new R-type lectin

• Jon Lundstrøm,
• Emilie Gillon,
• Valérie Chazalet,
• Nicole Kerekes,
• Antonio Di Maio,
• Ten Feizi,
• Yan Liu,
• Annabelle Varrot and
• Daniel Bojar

Beilstein J. Org. Chem. 2024, 20, 306–320, doi:10.3762/bjoc.20.31

• . While no direct interactions with the protein backbone were observed, we found one water molecule to mediate hydrogen bonding between the oxygen of the N-acetyl group and the Asn43 side chain oxygen (Figure 4d). Both GalNAc anomers could be observed, showing interactions through water molecule

Optimizations of lipid II synthesis: an essential glycolipid precursor in bacterial cell wall synthesis and a validated antibiotic target

• Milandip Karak,
• Cian R. Cloonan,
• Brad R. Baker,
• Rachel V. K. Cochrane and
• Stephen A. Cochrane

Beilstein J. Org. Chem. 2024, 20, 220–227, doi:10.3762/bjoc.20.22

• using established procedures from the literature, commencing with ᴅ-glucosamine and benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-ᴅ-glucopyranoside as the starting materials, respectively [40][41][42][43]. Imidate donors 1a and 1e were obtained exclusively as α-anomers, and 1b and 1g as a 1:1 α:β

• mixture which were then purified to give the desired α-anomers. Thioglycosides 1c, 1d, and 1f were isolated purely as β-anomers due to anchimeric assistance from the C2 N-acetyl or N-Troc groups. In glycosyl acceptors, the first amino acid of the lipid II pentapeptide, Ala, was incorporated as a 2

• -anomers of compound 5. It is noteworthy to mention that the benzyl ether in compound 4 exhibited successful cleavage upon treatment with sodium bromate/sodium dithionite in ethyl acetate/water, while other protecting functionalities like acetyl and phenylsulfonylethyl ester groups remained intact [45

Comparison of glycosyl donors: a supramer approach

• Anna V. Orlova,
• Nelly N. Malysheva,
• Maria V. Panova,
• Nikita M. Podvalnyy,
• Michael G. Medvedev and
• Leonid O. Kononov

Beilstein J. Org. Chem. 2024, 20, 181–192, doi:10.3762/bjoc.20.18

• the stereoselectivity of sialylation, it is important to analyze anomeric ratio values (α/β) for the disaccharide fraction separated by size-exclusion chromatography since the retention values of different disaccharide anomers on silica gel may be surprisingly large and a minor isomer may be lost

• -acetyl groups. The disaccharide fraction was isolated by gel permeation chromatography on Bio-Beads S-X3 (toluene) and analyzed by 1H NMR spectroscopy to give the anomeric ratio (α/β). Individual anomers of disaccharides were then separated by silica gel chromatography to give the yield. Model

GlAIcomics: a deep neural network classifier for spectroscopy-augmented mass spectrometric glycans data

• Thomas Barillot,
• Baptiste Schindler,
• Baptiste Moge,
• Elisa Fadda,
• Franck Lépine and
• Isabelle Compagnon

Beilstein J. Org. Chem. 2023, 19, 1825–1831, doi:10.3762/bjoc.19.134

• four monomers is shown in Figure 2. Note that both α and β-anomers coexist in the experimental conditions. The second set of experimental MS–IR spectra was acquired using different instrumental conditions on a different experimental set-up: it consists of the coupling of an alternative design of mass

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• known as (±)-BCH-189 (1c). The key oxathiolane 4, a precursor of the corresponding nucleoside, was obtained as a 1:1 mixture of anomers (60%) from benzoyloxyacetaldehyde (3a) and 2-mercapto-substituted dimethyl acetal 3na. The reaction was performed in toluene in the presence of p-toluenesulfonic acid

• , which was subsequently acetylated with acetic anhydride to afford 8 as a 2:1 mixture of anomers. Chu and co-workers [40] applied a novel strategy for the synthesis of enantiomerically pure (+)-BCH-189 (1a) using ᴅ-mannose (3c) as a starting material (Scheme 3). 1,2,3,4-Tetraacetyl-ᴅ-mannose derivative 9

• treated with acetic anhydride at room temperature. After workup by adding water and diethyl ether, the reaction mass was filtered and distilled until a residue was obtained. The colorless liquid compound 8 was obtained in 64% yield (as 6:1 mixture of anomers) after flash chromatography with 20% ethyl

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• recognition by plant cell-wall antibodies. To avoid performing the challenging 1,2-cis glycosylation that would generate a mixture of anomers in AGA, the α(1–6) linkage between glucose and xylose was pre-installed in the disaccharide BB 16 (Scheme 3, highlighted in red) [104]. The orthogonal levulinoyl (Lev

• dramatic when 2,4-di-O-acyl groups are present, sometimes leading to exclusive formation of α-anomers [128][129]. PGs like 2-O-ADMB (4-acetoxy-2,2-dimethylbutanoate) [130] or 2,2’-O-benzylidene [131] were introduced to solve this issue. Several reports highlighted the importance of the 4,6-O-benzylidene

Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide phenyl thioglycosides

• Vojtěch Hamala,
• Lucie Červenková Šťastná,
• Martin Kurfiřt,
• Petra Cuřínová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2021, 17, 1086–1095, doi:10.3762/bjoc.17.85

• and 12 under these conditions produced the expected thioglycosides 18 and 19, respectively. Difluorinated derivative 13 decomposed on reaction with the PhSTMS/ZnI2 system. The separation of the anomers of products 14–19 was attempted because of the risk of thiophenyl migration in the subsequent C6

• deoxyfluorination, which would likely occur with the β-anomers of 14–19 [41]. The complete separation of the α-anomer by conventional silica gel column chromatography was possible for thioglycosides 14, 16, 17, and 19, while the products 15 and 18 were obtainable as enriched α-anomers (α/β ≥ 3.3:1). Cleavage of the

• sulfurtrifluoride (DAST) [51], but our experiments revealed that DAST-mediated C6-deoxyfluorination of thioglycosides 14–17 and 19 proceeded satisfactorily under microwave irradiation, on condition that pure or substantially enriched α-anomers were subjected to reaction with DAST, yielding thioglycosides 22–26

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• glucosyl fluoride gave better yields (18a and 18d) than with the corresponding acylated analogues β-9 and α-11 described above. It was also found that the glycosylation stereoselectivity with glucosyl fluoride 16 did not depend on the anomeric ratio of glucosyl fluoride 16: both anomers of 16 yielded

Simulating the enzymes of ganglioside biosynthesis with Glycologue

• Andrew G. McDonald and
• Gavin P. Davey

Beilstein J. Org. Chem. 2021, 17, 739–748, doi:10.3762/bjoc.17.64

• , sugars, and are read from right to left starting with the base (reducing-end) sugar. The letters a and b are reserved for α and β-anomers, respectively, while brackets are used to delimit branches, and the letter T is used to denote the connection point to ceramide, or to another conjugate depending on

Easy access to a carbohydrate-based template for stimuli-responsive surfactants

• Thomas Holmstrøm,
• Daniel Raydan and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2020, 16, 2788–2794, doi:10.3762/bjoc.16.229

• could then be opened under acidic conditions [22] to give the acetyl pyranoside 4 as a mixture of two anomers (α:β: 1:0.5) in a 95% yield. The methyl glucoside 5 was prepared by treating acetyl glucopyranoside 4 with methanol and HCl to generate an anomeric mixture of the methyl glucopyranoside 5. By

• group has earlier been used as metal chelator [25]. At this stage, it was possible to separate both anomers of the diazide 18 using flash column chromatography. The pure α-anomer was then subjected to a CuAAC reaction using 1-heptyne and, in only two steps, the new surfactant 19 could be prepared from

• conformation as discussed earlier. Conclusion In conclusion, it was possible to convert levoglucosan into building block 5 in only five robust steps. The building block 5 could be purified to afford the two pure anomers using column chromatography. The β-anomer, 5β, proved to be a very versatile template for

Synthesis, docking study and biological evaluation of ᴅ-fructofuranosyl and ᴅ-tagatofuranosyl sulfones as potential inhibitors of the mycobacterial galactan synthesis targeting the galactofuranosyltransferase GlfT2

• Marek Baráth,
• Jana Jakubčinová,
• Zuzana Konyariková,
• Stanislav Kozmon,
• Katarína Mikušová and
• Maroš Bella

Beilstein J. Org. Chem. 2020, 16, 1853–1862, doi:10.3762/bjoc.16.152

• -tagatofuranoside 13 in satisfactory yield (Scheme 3). In the course of the thioglycosylation, only the α-anomer of 13 was detected and isolated as the product. In general, the formation of α-anomers during the thioglycosylation of di-O-isopropylidene-ᴅ-tagatofuranoses 11 and 12 was controlled by the approach of a

Synthesis of Streptococcus pneumoniae serotype 9V oligosaccharide antigens

• Sharavathi G. Parameswarappa,
• Claney L. Pereira and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2020, 16, 1693–1699, doi:10.3762/bjoc.16.140

• reducing-end monosaccharide 14 equipped with the linker in 70% yield as a mixture of anomers (α:β = 2:1) (Scheme 2). The reductive opening of the benzylidene protecting group in 14 enabled the separation of anomers and furnished acceptor 15α [28], that was reacted with thioglucoside 11 to yield exclusively

Synthesis of new asparagine-based glycopeptides for future scanning tunneling microscopy investigations

• Laura Sršan and
• Thomas Ziegler

Beilstein J. Org. Chem. 2020, 16, 888–894, doi:10.3762/bjoc.16.80

• glycosylamines 2a–f by hydrogenation with Pd on charcoal in ethyl acetate. Since an anomeric mixture of glycosylamines was obtained in most cases, with a strong predominance of the corresponding β-anomers, and TLC analysis showed no formation of other unwanted side products during hydrogenation, the latter

Regioselectivity of glycosylation reactions of galactose acceptors: an experimental and theoretical study

• Enrique A. Del Vigo,
• Carlos A. Stortz and
• Carla Marino

Beilstein J. Org. Chem. 2019, 15, 2982–2989, doi:10.3762/bjoc.15.294

• β-ᴅ-Galp was also observed [33]. For donor 3, there was no major difference between benzylated (1α/β) and benzoylated acceptors (2α/β), and the regioselectivity was higher for the α-anomers (compare Table 1, entries 1 and 2 or 3 and 4, for example). The low nucleophilic character of the OH-4 group

• in α-anomers could be associated with the lower capacity of the O-5 atom to establish hydrogen bond interactions due to the anomeric effect [34]. For donor 4, the regioselectivity observed for 1α, 1β, and 2α was lower than that observed for 3, but for 2β, the only product detected was the 1→4

• accurate prediction of the trends in selectivity could not be achieved. We have tried to explain the reduced regioselectivity of the β-anomers through hydrogen bonding interactions of the OH-3 and OH-4 groups of the model acceptors. Doutheau and co-workers proposed that such a reduced regioselectivity

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

• Sara Tejera,
• Giada Caniglia,
• Rosa L. Dorta,
• Andrea Favero,
• Javier González-Platas and
• Jesús T. Vázquez

Beilstein J. Org. Chem. 2019, 15, 2881–2888, doi:10.3762/bjoc.15.282

• (10), forming gels much easier than their corresponding β-anomers (trans). This showed that their ability to form gels was critically dependent on the cis/trans configuration present in the molecule. To confirm this result, the supramolecular properties of trans- and cis-1,2-bis(4-(4-bromophenyl)-1H

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• -acetylation was conducted leading to a mixture of all four species, indicated by NMR analysis (Scheme 3). In the case of 2-syn the β-pyranose species 5-syn-β was obtained as the main product, besides α-pyranose (5-syn-α) as well as both anomers of the furanoid form (Scheme 4). The overall yield obtained over

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

• dried over MgSO4 and the solvent removed under reduced pressure. The crude product was purified by column chromatography (petroleum ether/ethyl acetate 1:1) to yield Ac4ManNCp(H2) (302 mg, 34%) as a mixture of anomers as a colorless solid. Whereas the α-anomer could be partially separated by column

• chromatography (petroleum ether/ethyl acetate 1:1) to yield Ac4ManNCyc(H2) (473 mg, 52%) as a mixture of isomers (anomers as well as cyclopropane isomers indicated as a and b) as a colorless solid. Whereas the α-anomers could be partially separated by column chromatography, semi-preparative RP-HPLC (50–55% B

• over 20 min) was required to obtain β-anomers (tR = 12.3 min). Rf = 0.54 (petroleum ether/ethyl acetate 1:2); α-isomer: 1H NMR (400 MHz, CDCl3) δ 6.07 (d, J = 1.8 Hz, 1H, H-1a), 6.04 (d, J = 1.9 Hz, 1H, H-1b), 5.86–5.72 (m, 1H, NH), 5.36–5.28 (m, 1H, H-3), 5.28–5.12 (m, 1H, H-4), 4.69–4.57 (m, 1H, H-2

Low-budget 3D-printed equipment for continuous flow reactions

• Jochen M. Neumaier,
• Amiera Madani,
• Thomas Klein and
• Thomas Ziegler

Beilstein J. Org. Chem. 2019, 15, 558–566, doi:10.3762/bjoc.15.50

•  1 shows the detailed reaction conditions for methanol, propargyl alcohol and 4-pentynol. The two-step reaction starting from pyranose 4 gave overall yields in the range from 43% to 69%. Due to the neighbouring group participation of the acetyl group at C-2, only β-anomers of the respective

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• modifications which have been undertaken on the nicotinoyl riboside scaffold. Keywords: anomers; glycosylation; isotopologues; isotopomeres; nicotinamide riboside; Review 1. Introduction 1-(β-D-Ribofuranosyl)nicotinamide (also referred to as nicotinamide riboside, NR+) is one of the multiple precursors of

• riboside anomers were synthesized, with the best β/α-anomer stereoselectivity obtained when the chloride form of the sugars were used as precursors. Thus, the reaction between Nam (1a) and 2,3,5-tri-O-acetyl-D-ribofuranosyl chloride (3a) in acetonitrile at 0 °C yielded the triacetylated product 4a mainly

• yield. The anomeric purity of the acylated intermediates 4a and 4b was not reported in [20]. However, these triesters must have contained some admixture of α-anomers as evidenced by the optical rotation of the final product NR+Cl−. The corresponding nicotinamide mononucleotide (NMN) was prepared from NR