Synthesis of type 1 Lewis b hexasaccharide antigen structures featuring flexible incorporation of l-[U-13C6]-fucose for NMR binding studies

Article abstract of DOI:10.1039/d0ob00426j

While 13C-labelled proteins are common tools in NMR studies, lack of access to 13C-labelled carbohydrate structures has restricted their use. l-Fucose is involved in a wide range of physiological and pathophysiological processes in mammalian organisms. He

Full text of DOI:10.1039/d0ob00426j

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Biomolecular Chemistry
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Synthesis of type 1 Lewis b hexasaccharide antigen
structures featuring flexible incorporation of
L-[U-13C6]-fucose for NMR binding studies†
Cite this: DOI: 10.1039/d0ob00426j
Mark Long,a Aisling Ní Cheallaigh, b Mark Reihill, b Stefan Oscarson b and
a
Martina Lahmann
*
While 13C-labelled proteins are common tools in NMR studies, lack of access to 13C-labelled carbohydrate
structures has restricted their use. L-Fucose is involved in a wide range of physiological and pathophysio-
logical processes in mammalian organisms. Here, L-[U-13C6]-Fuc labelled type I Lewis b (Leb) structures
have been synthesised for use in NMR binding studies with the Blood-group Antigen Binding Adhesin
(BabA), a membrane-bound protein from the bacterium Helicobacter pylori. As part of this work, an
efficient synthesis of a benzylated L-[U-13C6]-Fuc thioglycoside donor from L-[U-13C6]-Gal has been
developed. The design and synthesis of an orthogonally protected tetrasaccharide precursor enabled
controlled introduction of one or two 13C-labelled or non-labelled fucosyl residues prior to global de-
protection. NMR analysis showed that it is straightforward to assign the anomeric centres as well as the
H-5 positions to the individual fucosyl residues which are relevant for NMR binding studies.
Received 26th February 2020,
Accepted 27th May 2020
DOI: 10.1039/d0ob00426j
rsc.li/obc
cosylation patterns which permits Helicobacter pylori to adapt
Introduction
to its host and to maintain persistent colonisation.10–12
Helicobacter pylori is a spiral-shaped Gram-negative bacterium,
A
crystal structure of the carbohydrate-binding
which causes gastric and duodenal ulcers and is a major cause domain of BabA has been obtained while bound to a syn-
of stomach cancer. The bacterium selectively colonises the thetic Lewis b structure. Analysis has revealed that the
gastric epithelium.1–5 Unlike other pathogens, Helicobacter anchoring point for the binding of the glycan is the term-
pylori has evolved to survive the highly acidic environment by inal disaccharide D-Galα(1 → 2) L-Fuc motif of the Leb
metabolising urea to ammonia and carbon dioxide by a nickel hexasaccharide.13,14
depending urease.6–8 The bacterium expresses at least five
Detailed knowledge of these carbohydrate–protein inter-
types of adhesins9 which enable adherence to the stomach epi- actions of Helicobacter pylori is crucial for understanding the
thelium and concomitant production of several cytotoxins that structural and molecular basis for resulting diseases. While
destroy stomach epithelial cells, creating painful ulcers. The 13C-labelled proteins are common tools in NMR studies, lack
resulting chronic inflammation promotes cell proliferation, of access to 13C-labelled carbohydrate structures has limited
and thus predisposes the host to stomach cancer. One of the their use. Despite the difficulties arising from the need to
five adhesins expressed by Helicobacter pylori is the mem- synthesise the 13C-labelled material, 13C-enriched glycans are
brane-bound protein “Blood-group Antigen Binding Adhesin” gaining traction as valuable tools for structure determi-
(BabA). BabA binds to type I Lewis b (Leb) antigens expressed nation15 and conformational analysis.16 Conformational ana-
on the surface of gastric epithelial cells. Analyses of binding lysis of a ligand bound to a lectin can be carried out by
specificities of Helicobacter pylori strains from across the world Saturation Transfer Difference (STD) and Transfer Nuclear
suggest that BabA has evolved in response to host mucosal gly- Overhauser Effect (NOE) NMR experiments and do not
require isotopically enriched material.17 Intramolecular NOE
uses a combination of unlabelled carbohydrates and labelled
proteins to extrapolate ligand–protein interactions,18,19 while
aSchool of Natural Sciences, Bangor University, Bangor, Gwynedd, LL57 2UW, UK.
13C-filtered NOESY can be used for identifying the confor-
mation of bound ligands.20,21 More recently, a combination
E-mail: m.lahmann@bangor.ac.uk
bCentre for Synthesis and Chemical Biology, University College Dublin, Belfield,
of 13C-labelled carbohydrates and 15N (or 13C/15N) labelled
Dublin 4, IE
proteins has been used to detail contact sites on the carbo-
†Electronic supplementary information (ESI) available: DETAILS. See DOI:
hydrate and the protein simultaneously.22 Availability of 13C-
10.1039/d0ob00426j
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labelled Leb structures would provide access to valuable tools
for probing the interactions with BabA and other Leb binding
proteins.
Results and discussion
The easiest access to isotopically enriched monosaccharides is
Several strategies for the synthesis of type 1 Lewis struc- via biosynthesis, which provides 100% uniformly [U-13C]
tures have been reported. Danishefsky and co-workers have labelled material when the carbon source in the growth media
synthesised the Leb tetrasaccharide and hexasaccharide using is 13C labelled.31
a polymer-based oligosaccharide preparation method with
In previous syntheses of Leb hexasaccharide structures, a
glycals as glycosyl donors.23,24 Chernyak et al. have also per-O-benzylated fucosyl thioglycoside donor has been used
reported the synthesis of the Leb hexasaccharide using a con- successfully, and therefore the analogous L-[U-13C6]-Fuc 4
vergent synthesis involving a tetrasaccharide thioglycoside (Scheme 1) was envisioned as a suitable labelled donor. Since
donor and a spacer-equipped 3′,4′-diol lactoside acceptor.25 L-[U-13C6]-Fuc is prohibitively expensive, the less costly L-
Furthermore, Lahmann et al. have reported the synthesis of [U-13C6]-Gal was selected as starting material. The synthetic
the Leb hexasaccharide, forming a tetrasaccharide acceptor route was elaborated using unlabelled D-Gal (S-24–S-29, ESI†)
via a [2 + 2] glycosylation which was then di-fucosylated.26 and then applied to L-[U-13C6]-Gal (Scheme 2). Thus, after a
Fournière et al. reported the synthesis of the Leb pentasac- near quantitative conversion of L-[U-13C6]-Gal into its pentaace-
charide by first preparing the trisaccharide backbone, fol- tate 9,32,33 a thiotolyl group was introduced at the anomeric
lowed by di-fucosylation.27 The Leb tetrasaccharide was syn- position using p-thiocresol in the presence of BF3·Et2O (98%
thesised in addition to the Lea trisaccharides by Ryzhov yield).34 Deacetylation of 10, followed by protection of the
et al.28 and Yan et al.29 An enzymatic approach was also 6-position as TBDMS silyl ether and subsequent benzylation of
adopted by Chen and co-workers towards the truncated Leb the remaining free hydroxy groups, furnished L-galactoside 11
and Lea structures.30
in a 75% yield over 3 steps. The silyl ether was removed with
Herein, we report the synthesis of a uniformly 13C labelled TBAF (12, 96% yield) and the 6-position was tosylated, produ-
fucosyl donor as a general building block and an improved cing a 94% yield of compound 13. Reduction with LiAlH4 in
preparation of Lewis b structures via a linear approach. The THF (61% yield) gave the desired L-[U-13C6]-fucosyl donor 4 in
flexibility of this approach allows access to novel mono and di an overall yield of 41% from L-[U-13C6]-Gal.
L-[U-13C6]-fucose labelled Leb hexasaccharide structures, exem-
As expected, complex coupling patterns due to 13C–1H and
plified by the mono L-[U-13C6]-Fuc-labelled Leb hexasaccharide 13C–13C couplings were observed for the labelled L-Fuc donor 4
1 and the di L-[U-13C6]-Fuc-labelled Leb hexasaccharide 2 in the 1H and 13C NMR spectra respectively but decoupling
(Scheme 1).
produced the matching spectra for the literature known
unlabelled donor L-Fuc 535 (ESI Fig. 1†).
The corresponding unlabelled L-Fuc 5,35 the D-GlcNH2
7,36the D-Gal 8 37 thioglycoside donors, and the D-Lac acceptor
6 38 (Scheme 1) were prepared according to literature
procedures.
The assembly of the tetrasaccharide backbone 15 started
with the NIS/AgOTf-mediated glycosylation at room tempera-
ture with D-Lac acceptor 6 and D-GlcNH2 donor 7 to give the
Scheme 1 The target structures and the building blocks shown in a
simplified retrosynthesis scheme: mono L-[U-13C6]-Fuc-labelled Leb
hexasaccharide 1, di L-[U-13C6]-Fuc-labelled Leb hexasaccharide 2 and
the unlabelled Leb hexasaccharide 3 were prepared from the labelled
and unlabelled building blocks 4–8.
Scheme 2 Reagents and conditions: (a) 1. NaOAc, Ac2O, 140 °C,
30 min, 99% (9); 2. MePhSH, BF3·Et2O, CH2Cl2, rt, 2 h, 98% (10); (b) 1.
NaOMe, MeOH, rt, 30 min, 99%; 2. TBDMSCl, pyridine, 0 °C to rt, 4 h,
95%; 3. BnBr, NaH, DMF, 0 °C to rt, 2 h, 79% (11); (c) Bu4NF, THF, rt, 16 h,
96%; (d) TsCl, pyridine, rt, 3 h, 94%; (e) LiAlH4, THF, reflux, 61%.
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corresponding 1,2-trans linked trisaccharide 14 38 (58%) asaccharide 22 was obtained in a 79% yield. A similar reac-
(Scheme 3). The phthalimido and acetyl protecting groups tion sequence with stepwise introduction of the fucosyl resi-
were removed simultaneously with EDA in EtOH. Subsequent dues was also carried out with acceptor 18 to give the
selective N-acetylation was performed with Ac2O in MeOH or unlabelled
2′′′-fucosylated
pentasaccharide
(73%).
toluene/MeOH (2 : 1, v/v), furnishing 3″-OH acceptor 15 (76%). Subsequent reductive ring-opening of the benzylidene acetal
In previous studies, we observed orthoester formation as a (66%) and a repeated fucosylation with unlabelled L-Fuc
common side product during the glycosylation of acceptor 15 donor 4 provided the fully protected, unlabelled Leb hexa-
with the 2-O-acetyl analogue of donor 8. 2-Benzoate protected saccharide 24, demonstrating the feasibility of this approach
glycosyl donors are less prone to orthoester formation.39,40 The to access also the 4″-mono L-[U-13C6]-Fuc labelled Leb
2-OBz thioglycoside donor 8 was successfully trialled and hexasaccharide.
underwent glycosylation with acceptor 15 promoted by NIS
and AgOTf (cat.) to furnish tetrasaccharide 16 in an 81% yield.
The di-L-[U-13C6]-Fuc labelled hexasaccharide 23 and
unlabelled Leb hexasaccharide 24 are also accessible from diol
The orthogonal protecting group pattern of tetrasaccharide acceptor 19 obtained from tetrasaccharide 17 by debenzoyla-
16 permits the preparation of three different acceptors, and tion (88%, Scheme 4). Interestingly, this transesterification
thus provides flexibility with respect to the position and was even slower than the corresponding reaction on the mono
number of L-[U-13C6]-Fuc residues to be incorporated. One step fucosylated pentasaccharide 21. As above, the unlabelled L-Fuc
deprotection exposes either the 4″-OH group when using donor 5 was converted into the corresponding bromide in the
reductive ring opening conditions (acceptor 17) or the 2′′′-OH presence of acceptor diol 19, with the glycosylation facilitated
position under Zemplén conditions (acceptor 18), whilst by Et4NBr to give the protected unlabelled hexasaccharide 24
sequential deprotection of both positions provides the corres- in an 80% yield (Scheme 4). The same halide-assisted glycosy-
ponding diol acceptor 19.
lation conditions were applied to the L-[U-13C6]-Fuc donor 4
For the synthesis of the fully protected 2′′′-mono L- and diol acceptor 19 to produce the di-L-[U-13C6]-Fuc labelled
[U-13C6]-Fuc labelled Leb hexasaccharide 22 (Scheme 3), tet- hexasaccharide 23 in a moderate yield (52%).
rasaccharide 16 was subjected to reductive ring-opening
The three hexasaccharides 22, 23 and 24 were globally
conditions with NaBH3CN and HCl/Et2O in THF to reveal deprotected by Pd-catalysed hydrogenolysis to give targets 1, 2
the 4″-OH, giving acceptor 17 (85%).41,42 Acceptor 17 under-
went glycosylation with L-Fuc donor 5 using Lemieux’s
halide-assisted methodology to ensure α-selectivity.43 This
produced pentasaccharide 20 in a moderate yield of 45%.
The removal of the 2′′′-benzoyl group under Zemplén con-
ditions required extended reaction times and a slightly elev-
ated temperature in order to unmasked the second fucosyla-
tion site (21, 93%). The L-[U-13C6]-Fuc residue was installed
using donor 4 and Lemieux’s halide-assisted glycosylation
conditions, and the 2′′′-mono L-[U-13C6]-Fuc labelled Leb hex-
Scheme 4 Reagents and conditions: (a) NaBH3CN, 2 M HCl/Et2O, 3 Å
molecular sieves, THF, rt, 40 min, 85%; (b) Br2, Et4NBr, 4 Å molecular
Scheme 3 Reagents and conditions: (a) 7, NIS, AgOTf (cat.), 4 Å mole-
cular sieves, CH2Cl2, rt, 20 min, 58%; (b) 1. EDA, EtOH, reflux, 16 h; 2.
Ac2O, MeOH/toluene (2 : 1, v/v), rt, 30 min; 76% over 2 steps; (c) 8, NIS,
AgOTf (cat.), 4 Å molecular sieves, CH2Cl2, rt, 20 min – 2 h, 81%.
sieves, CH2Cl2/DMF (9 : 1, v/v), rt, 16 h (donor 5: 20, 45%; donor 4: 22,
79%; 4: 23, 52%; 5: 24, 80%); (c) 1 M NaOMe/MeOH, MeOH, rt to 40 °C
(21, 26 h, 93%) and 1 M NaOMe/MeOH, MeOH/CH2Cl2 7 : 1, rt to 40 °C
(18, 48 h, 73%) and (19, 64 h, 88%).
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Scheme 5 Reagents and conditions: (a) H2, Pd/C, 0.1 M aq. HCl, 1,4-
dioxane/H2O (3 : 1, v/v), rt, 2 d, (1, 87%; 2, 30%; 3, 96%).
and 3 respectively (Scheme 5). A variety of hydrogenolysis con-
ditions were attempted. The presence of aqueous HCl was
found to be crucial for efficient progression of the reaction in
all cases, while a range of solvents were tolerated. The use of a
mixture of heterogeneous catalysts (Pd/C and Pd(OH)2/C) was
found to be beneficial in similar unpublished work but not for
the compounds presented here. Applying optimised con-
ditions, the deprotections proceeded very well for both the 2′′
′-mono L-[U-13C6]-Fuc hexasaccharide 22 and the unlabelled
hexasaccharide 24, giving the mono-labelled (1, 87%) and
unlabelled (3, 96%) Leb hexasaccharides in excellent yields.
After deprotection of 23, a low yield of the di-L-[U-13C6]-Fuc
labelled hexasaccharide 2 (30%) was recorded.
1
1H NMR and H–13C-HSQC was used to assign most of the
signals and a CLIP-HSQC experiment confirmed the presence
of two α-Fuc linkages and β-linkages for the remaining four
glycosidic bonds of the known unlabelled Leb hexasaccharide
3 (Fig. 1A and B). 1D TOCSY spectra were generated by selective
excitation of each of the six H-1 signals individually (Fig. 1C).
In combination with the NMR data obtained for the mono-
labelled hexasaccharide 1 (vide infra), this enabled us, to
assign undoubtedly the anomeric and the H-5 signals – which
appeared in the same region occupied by the anomeric
signals, to the individual 2′′′ and the 4″ fucosyl residues. There
Fig. 1 (A) 1H NMR spectrum of the unlabelled Leb hexasaccharide 3; (B)
CLIP-HSQC of 3; (C) 1D TOCSY experiments for 3. The anomeric signals
were selectively excitated to generate spectra for each individual residue
and then compared to the overall 1H NMR spectrum (bottom).
was no substantial difference in the chemical shift between makes it a convenient experiment to verify the incorporation of
the methyl groups of the two fucosyl residues which are other- labelled material (Fig. 2B).
wise distinct signals. The ability to distinguish between the
individual fucosyl residues is of importance for NMR binding ide 1 shows again the expected 13C–1H couplings from the 2′′
experiments with the labelled material.
′-α-L-[U-13C6] Fuc residue, while the 13C–1H decoupled spec-
The 1H NMR spectrum of the mono-labelled hexasacchar-
1
The H NMR spectrum of di-13C-labelled hexasaccharide 2 trum overlays with the unlabelled hexasaccharide 3. The pres-
shows the expected additional 13C–1H couplings corres- ence of the 13C–1H couplings makes the identification of the
ponding to the labelled fucosyl residues (Fig. 2A) which col- anomeric proton and the H-5 for the 2′′′-α-1 connected Fuc
lapsed in the 13C–1H decoupled experiments, reassembling the residue straightforward (Fig. 2D). This information can also be
corresponding spectrum of the unlabelled hexasaccharide 3. A obtained by comparing the 13C NMR data of di-labelled com-
standard 13C NMR experiment displays only the 13C enriched pound 2 to the 13C NMR data for the 2′′′ mono labelled com-
fucosyl residues, clearly showing the 13C–13C couplings, and pound 1, which shows the anomeric carbon of the α-L-[U-13C6]
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Fig. 2 (A) 1H NMR spectrum of di-α-L-[U-13C6] fucosylated 2 with 13C–1H couplings visible (bottom, red), 13C–1H decoupled spectrum of 2 (middle,
blue), and for comparison the 1H NMR spectrum of the unlabelled hexasaccharide 3 (top, green); (B) 13C NMR spectrum of the di-α-L-[U-13C6] fuco-
sylated hexasaccharide 2. Only the signals from the uniformly labelled fucosyl residues are visible; (C) direct comparison of the 13C NMR spectrum
of mono 2’’’-α-L-[U-13C6] fucosylated hexasaccharide 1 (bottom, red) with the 13C NMR spectrum of the di labelled hexasaccharide 2 (top, blue)
allows unambiguous identification of the anomeric carbons of the fucosyl residues. There is no significant difference in the C-6 shifts between the
fucosyl residues; (D) the coupled (bottom, red) and 13C–1H decoupled (top, blue) 1H NMR spectra of the 2’’’-α-L-[U-13C6] fucosylated hexasaccharide
1. The stacked view allows unambiguous assignment of the anomeric and H-5 signals for the individual fucosyl residues.
Fuc-(1 → 2)-β-D-Gal linkage to appear downfield to the α-L- labelled type I Lewis b (Leb) structures have been synthesised for
[U-13C6] Fuc-(1 → 4)-β-D-GlcNAc bond (Fig. 2C).
use in NMR binding studies with BabA, a membrane-bound
protein from the bacterium Helicobacter pylori. An orthogonally
protected tetrasaccharide 16 allowed the regioselective introduc-
tion of one or two 13C labelled fucose residues producing the pro-
tected 13C labelled hexasaccharides 22 and 23. Subsequent hydro-
genolysis afforded the differently 13C labelled hexasaccharides
1–3. NMR analysis showed that it is straightforward to dis-
tinguish between the differently positioned fucosyl residues in
the oligosaccharides. Making those and related structures a valu-
able tool for NMR protein-carbohydrate binding studies.
Experimental
All experimental data are available in the ESI.†
Conclusions
In this work, an efficient synthesis of a 13C-labelled L-fucosyl
donor was developed from L-[U-13C6]-Gal. The synthesis of the L-
[U-13C6]-fucose donor 4 was carried out on a 500 mg scale in a
yield of 41% over 8 steps. This uniformly 13C labelled fucosyl
donor is a valuable building block for the preparation of labelled
Conflicts of interest
oligosaccharides for NMR binding studies. Thus, L-[U-13C6]-Fuc There are no conflicts to declare.
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15 C. Fontana, H. Kovacs and G. Widmalm, J. Biomol. NMR,
2014, 59, 95–110.
Acknowledgements
Financial support from the European Social Fund (KESS 16 M. D. Battistel, M. Shangold, L. Trinh, J. Shiloach and
80300, PhD scholarship for Mark Long) and Science D. I. Freedberg, J. Am. Chem. Soc., 2012, 134, 10717–10720.
Foundation Ireland Awards 13/IA/1959 and 16/RC/3889 is 17 B. Meyer and T. Peters, Angew. Chem., Int. Ed. Engl., 2003,
gratefully acknowledged (Aisling Ní Cheallaigh, Mark Reihill).
42, 864–890.
18 C. A. Bewley, Structure, 2001, 9, 931–940.
19 M. Schubert, S. Bleuler-Martinez, A. Butschi, M. A. Walti,
P. Egloff, K. Stutz, S. Yan, M. Collot, J. M. Mallet,
I. B. Wilson, M. O. Hengartner, M. Aebi, F. H. Allain and
M. Kunzler, PLoS Pathog., 2012, 8, e1002706.
References
1 J. Parsonnet, G. D. Friedman, D. P. Vandersteen, Y. Chang,
J. H. Vogelman, N. Orentreich and R. K. Sibley, N. 20 A. Canales, J. Angulo, R. Ojeda, M. Bruix, R. Fayos,
Engl. J. Med., 1991, 325, 1127–1131.
2 A. Dubois, Emerging Infect. Dis., 1995, 1, 79–85.
3 N. Uemura, S. Okamoto, S. Yamamoto, N. Matsumura,
R. Lozano, G. Gimenez-Gallego, M. Martin-Lomas,
P. M. Nieto and J. Jimenez-Barbero, J. Am. Chem. Soc., 2005,
127, 5778–5779.
S. Yamaguchi, M. Yamakido, K. Taniyama, N. Sasaki and 21 L. Nieto, A. Canales, G. Gimenez-Gallego, P. M. Nieto and
R. J. Schlemper, N. Engl. J. Med., 2001, 345, 784–789. J. Jimenez-Barbero, Chemistry, 2011, 17, 11204–11209.
4 S. Suerbaum and P. Michetti, N. Engl. J. Med., 2002, 347, 22 G. Nestor, T. Anderson, S. Oscarson and A. M. Gronenborn,
1175–1186.
J. Am. Chem. Soc., 2017, 139, 6210–6216.
23 V. Behar and S. J. Danishefsky, Angew. Chem., Int. Ed. Engl.,
1994, 33, 1468–1470.
24 S. J. Danishefsky, V. Behar, J. T. Randolph and K. O. Lloyd,
J. Am. Chem. Soc., 1995, 117, 5701–5711.
5 C. Y. Kao, B. S. Sheu and J. J. Wu, Biomed. J., 2016, 39, 14–23.
6 D. L. Weeks, S. Eskandari, D. R. Scott and G. Sachs, Science,
2000, 287, 482–485.
7 E. F. Miller and R. J. Maier, J. Bacteriol., 2014, 196, 3074–
3081.
25 A. Chernyak, S. Oscarson and D. Turek, Carbohydr. Res.,
2000, 329, 309–316.
8 M. Campanale, E. Nucera, V. Ojetti, V. Cesario, T. A. Di
Rienzo, G. D’Angelo, S. Pecere, F. Barbaro, G. Gigante, 26 M. Lahmann, L. Bülow, P. Teodorovic, H. Gybäck and
T. De Pasquale, A. Rizzi, G. Cammarota, D. Schiavino, S. Oscarson, Glycoconjugate J., 2004, 21, 251–256.
F. Franceschi and A. Gasbarrini, Dig. Dis. Sci., 2014, 59, 27 V. Fournière, L. Skantz, F. Sajtos, S. Oscarson and
1851–1855. M. Lahmann, Tetrahedron, 2010, 66, 7850–7855.
9 D. J. Evans Jr. and D. G. Evans, Helicobacter, 2000, 5, 183– 28 I. M. Ryzhov, E. Y. Korchagina, A. B. Tuzikov, I. S. Popova,
195.
T. V. Tyrtysh, G. V. Pazynina, S. M. Henry and N. V. Bovin,
Carbohydr. Res., 2016, 435, 83–96.
29 L. Yan and D. Kahne, J. Am. Chem. Soc., 1996, 118, 9239–
9248.
10 T. Boren, P. Falk, K. A. Roth, G. Larson and S. Normark,
Science, 1993, 262, 1892–1895.
11 D. Ilver, A. Arnqvist, J. Ogren, I. M. Frick, D. Kersulyte,
E. T. Incecik, D. E. Berg, A. Covacci, L. Engstrand and 30 H. Yu, Y. Li, Z. Wu, L. Li, J. Zeng, C. Zhao, Y. Wu, N. Tasnima,
T. Boren, Science, 1998, 279, 373–377.
J. Wang, H. Liu, M. R. Gadi, W. Guan, P. G. Wang and
12 M. Aspholm-Hurtig, G. Dailide, M. Lahmann, A. Kalia,
X. Chen, Chem. Commun., 2017, 53, 11012–11015.
D. Ilver, N. Roche, S. Vikstrom, R. Sjostrom, S. Linden, 31 F. V. Filipp, N. Sinha, L. Jairam, J. Bradley and S. J. Opella,
A. Backstrom, C. Lundberg, A. Arnqvist, J. Mahdavi, J. Magn. Reson., 2009, 201, 121–130.
U. J. Nilsson, B. Velapatino, R. H. Gilman, M. Gerhard, 32 M. L. Wolfrom and H. B. Wood, J. Am. Chem. Soc., 1949, 71,
T. Alarcon, M. Lopez-Brea, T. Nakazawa, J. G. Fox, 3175–3176.
P. Correa, M. G. Dominguez-Bello, G. I. Perez-Perez, 33 M. Lahmann and J. Thiem, Carbohydr. Res., 1997, 299, 23–
M. J. Blaser, S. Normark, I. Carlstedt, S. Oscarson, 31.
S. Teneberg, D. E. Berg and T. Boren, Science, 2004, 305, 34 R. J. Ferrier and R. H. Furneaux, Carbohydr. Res., 1976, 52,
519–522. 63–68.
13 N. Hage, T. Howard, C. Phillips, C. Brassington, 35 Z. Zhang, I. R. Ollmann, X.-S. Ye, R. Wischnat, T. Baasov
R. Overman, J. Debreczeni, P. Gellert, S. Stolnik, and C.-H. Wong, J. Am. Chem. Soc., 1999, 121, 734–753.
G. S. Winkler and F. H. Falcone, Sci. Adv., 2015, 1, 36 Q. Wang, J. Xue and Z. Guo, Chem. Commun., 2009, 5536–
e1500315–e1500315. 5537.
14 K. Moonens, P. Gideonsson, S. Subedi, J. Bugaytsova, 37 Z. Wang, L. Zhou, K. El-Boubbou, X.-S. Ye and X. Huang,
E. Romaõ, M. Mendez, J. Nordén, M. Fallah, L. Rakhimova, J. Org. Chem., 2007, 72, 6409–6420.
A. Shevtsova, M. Lahmann, G. Castaldo, K. Brännström, 38 A. Sundgren, M. Lahmann and S. Oscarson, Beilstein J. Org.
F. Coppens, A. W. Lo, T. Ny, J. V. Solnick, Chem., 2010, 6, 704–708.
G. Vandenbussche, S. Oscarson, L. Hammarström, 39 P. J. Garegg, P. Konradsson, I. Kvarnstroem, T. Norberg,
A. Arnqvist, D. E. Berg, S. Muyldermans, T. Borén and
H. Remaut, Cell Host Microbe, 2016, 19, 55–66.
S. C. T. Svensson and B. Wigilius, Acta Chem. Scand., Ser. B,
1985, B39, 569–577.
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2020

View Article Online
Organic & Biomolecular Chemistry
Paper
40 P. J. Garegg and T. Norberg, Acta Chem. Scand., Ser. B, 1979, 42 P. J. Garegg and H. Hultberg, Carbohydr. Res., 1982, 110,
B33, 116–118. 261–266.
41 P. J. Garegg and H. Hultberg, Carbohydr. Res., 1981, 93, 43 R. U. Lemieux and H. Driguez, J. Am. Chem. Soc., 1975, 97,
C10–C11.
4069–4075.
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