Stereo- And regioselective hydroboration of 1-exo-methylene pyranoses: Discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

Article abstract of DOI:10.3762/bjoc.15.102

Galectins are carbohydrate recognition proteins that bind carbohydrates containing galactose and are involved in cell signaling and cellular interactions, involving them in several diseases. We present the synthesis of (aryltriazolyl)methyl galactopyranos

Full text of DOI:10.3762/bjoc.15.102

Stereo- and regioselective hydroboration of 1-exo-methylene
pyranoses: discovery of aryltriazolylmethyl C-galactopyrano-
sides as selective galectin-1 inhibitors
Alexander Dahlqvist1, Axel Furevi‡1, Niklas Warlin‡1, Hakon Leffler2 and Ulf J. Nilsson*1
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2019, 15, 1046–1060.
1Centre for Analysis and Synthesis, Department of Chemistry, Lund
University, Box 124, SE-221 00 LUND, Sweden and 2Division of
Microbiology, Immunology and Glycobiology, Lund University, BMC
C12, SE-221 84 LUND, Sweden
doi:10.3762/bjoc.15.102
Received: 07 February 2019
Accepted: 21 April 2019
Published: 07 May 2019
Email:
Ulf J. Nilsson* - ulf.nilsson@chem.lu.se
Associate Editor: S. Flitsch
* Corresponding author ‡ Equal contributors
© 2019 Dahlqvist et al.; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
C-galactoside; galectin-1; hydroboration; inhibition; selective; triazole
Abstract
Galectins are carbohydrate recognition proteins that bind carbohydrates containing galactose and are involved in cell signaling and
cellular interactions, involving them in several diseases. We present the synthesis of (aryltriazolyl)methyl galactopyranoside
galectin inhibitors using a highly diastereoselective hydroboration of C1-exo-methylene pyranosides giving inhibitors with fourfold
or better selectivity for galectin-1 over galectin-3, -4C (C-terminal CRD), -4N (N-terminal CRD), -7, -8C, -8N, -9C, and -9N and
dissociation constants down to 170 µM.
Introduction
Galectins are defined by a typically about 130 amino acid variety of tissues. Galectin-3 is almost ubiquitously expressed
carbohydrate recognition domain (CRD) that binds to carbo- while galectin-1 is mainly expressed by immune cells, muscle
hydrates with at least one β-galactose subunit within a binding cells, kidney cells and neurons [2,3]. Galectin-1 has a marked
pocket large enough to accommodate a tetrasaccharide se- preference for binding N-linked glycans, while galectin-3 binds
quence of larger glycans [1-3]. Some galectins contain one both O-linked and N-linked glycans [5]. Galectins play many
CRD and occur as monomers or dimers, including galectins -1, biological roles in the body and one important and well-under-
-2, -7, -10 and -13 in humans. Others contain 2 different CRDs stood function is the cross-linking of cell-surface glycoproteins
within the same peptide sequence and include galectins -4, -8, through binding to O and N-linked glycans on the cell surface.
-9 and -12. Galectin-3 contains one CRD and a long N-terminal Surface proteins such as integrins [6,7], vascular endothelial
Pro/Gly-rich intrinsically disordered sequence [3,4]. The two growth factor receptor [8], and lysosome-associated membrane
most studied galectins, galectin-1 and -3, are present in a wide proteins [9] are known to be crosslinked by galectins, giving
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galectins a modulating role in cell adhesion, blood vessel resulted in no conversion of 2 and an almost complete recovery
growth and cellular uptake and breakdown, respectively. The of starting material in repeated experiments, although 9-BBN is
association of galectins to cell signaling and adhesion gives known to convert the gluco analog 6 to β-7 in high yield and
them roles in several different pathological processes, such as with excellent stereoselectivity [31]. In none of the reaction
pulmonary fibrosis [6,10], pathological lymphangiogenesis conditions 1-methyl glycopyranoside side products were formed
[11], inflammation [12] and cancer [13], with galectin inhibi- (Scheme 1).
tors demonstrated to attenuate such processes [3,10,11,14]. Ex-
perimental galectin inhibitors have often been developed with a
close resemblance to natural disaccharide ligands, such as
lactose and N-acetyllactosamine (lacNAc) [15] via thiodigalac-
tosides [16-19], as adding a second monosaccharide unit to the
anomeric position of the minimal D-galactose ligand allows for
an additional affinity-enhancing hydrogen bond according to
structural and affinity analyses [20,21]. A complementary
strategy has been to, instead of a second saccharide unit, add
non-natural structural elements to a monogalactoside scaffold,
as such derivatives have been hypothesized to allow for tuning
of galectin selectivities and to be designed to have improved
pharmacokinetic properties over natural saccharide fragments.
Early reports along this strategy involved C-galactosides that
were shown to reach affinities approaching those of lactose and
LacNAc for galectin-3 and also to have selectivity over other
galectin-1 [22,23]. Later, combining non-natural thiophenyl
aglycons with C3-triazole groups at D-galactose led to the
discovery of high affinity and selective galectin-3 inhibitors
Scheme 1: Diastereoselective hydroboration of glycopyranosyl
exomethylene enol ethers 2, 4, and 6: a) BH3-DMS, THF, 0 °C, 2 h;
b) H2O2, NaOH, THF/water, 0 °C, 2 h.
[24]. In this work, we present a synthesis pathway involving a Continuing the synthesis towards (aryltriazolyl)methyl galac-
diastereoselective hydroboration towards (aryltriazolyl)methyl topyranosyl derivatives, the 2-deoxygalactoheptulose 3 was
galactopyranosyl derivatives and determined the viability of this mesylated with mesyl chloride in pyridine at 0 °C to give
as a scaffold for galectin inhibitors by screening a library of 2-deoxy-1-mesylgalactoheptulose 8 (91%), followed by a
fourteen different products against galectins -1, -3, -4C (C-ter- nucleophilic substitution reaction with sodium azide in
minal CRD), -4N (N-terminal CRD), -7, -8C, -8N, -9C, and dimethylformamide to give the azide 9 in good yield (90%)
-9N.
[26]. The azide 9 was reacted with a panel of substituted
ethynyl arenes to give (aryltriazolyl)methyl galactopyranosyls
10a–n in fair to good yields (42–78% yields) via a copper-cata-
lyzed Huisgen cycloaddition [17,32]. The resulting (aryltria-
Results and Discussion
Chemistry
The synthesis starts from the known enol ethers 2, 4, and 6 pre- zolyl)methyl galactopyranosyls 10a–n were debenzylated using
pared using published methods [25,26]. Hydroborations of enol palladium hydroxide on carbon in a 2:1 cyclohexene and
ethers have been known to give good to excellent regio- and ethanol mixture to give 1a–n in yields varying from poor to
stereoselectivity and are thus a possible route to 2-deoxyhepu- good (10–87% yields, Scheme 2). The transfer hydrogenation
loses 3, 5 and 7 [27-30]. The hydroboration of enol ethers 2, 4, was selected as common hydrogenation using conditions with
and 6 with borane dimethyl sulfide in THF, followed by oxida- hydrogen gas and palladium on carbon lead to very low yields
tion using hydrogen peroxide and sodium hydroxide gave or no recovered product during the synthesis of 1a,b. Unfortu-
2-deoxygalactoheptulose 3 and 2-deoxymannoheptulose 5 in nately, no arenes bearing halogen substituents other than fluo-
good yields (89% and 78%) and with excellent diastereoselec- rine could be prepared, as they were dehalogenated during the
tivities (1:19 and 1:99 α:β ratio, respectively). Hydroboration of final debenzylation.
the glucose enol ether 6 afforded a mixture of both diastereo-
mers (1:2.3 α:β ratio) in good yield (43% β and 18% α isolated Galectin binding
yields, respectively). Identification of the diastereomers was Galectin-1, -3, -4C (C-terminal CRD), -4N (N-terminal CRD),
accomplished by NOESY experiments using deuterated pyri- -7, -8C, -8N, -9C, and -9N affinities for (aryltriazolyl)methyl
dine as a shift reagent solvent. Other hydroboration reagents, galactopyranosyls 1a–n were determined in a competitive fluo-
such as 9-borabicyclo[3.3.1]nonane (9-BBN) or pinacolborane, rescence polarization titration assay [6,15-18,33]. Compounds
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Scheme 2: Synthesis of (aryltriazolyl)methylene galactopyranosides 1a–n. Conditions: a) 3, MsCl, pyridine, 0 °C, 2 h; b) NaN3, DMF, 95 °C, 12 h; c)
alkyne, CuI, Et3N, MeCN, 12 h; d) Pd(OH)2/C, cyclohexene/EtOH, reflux, 12 h.
1a–n had millimolar or higher affinities for all galectins except the 3-fluoro and 2-fluoro derivatives 1c and 1d, respectively
for galectins-1 and -3. Generally, compounds based on the also show a reversed galectin selectivity, but with only about
(aryltriazolyl)methyl galactopyranoside scaffold were selective twofold selectivity and poor affinity. The most potent galectin-1
for galectin-1, with the best ligand (4-fluorophenyltriazol- inhibitor 1b has at least fiftyfold better affinity than the refer-
yl)methyl galactopyranoside 1b having an affinity of ence monosaccharide methyl β-D-galactoside (11) and a simi-
170 ± 2 µM and fourfold better than for galectin-3 (Table 1). lar affinity as the reference disaccharide methyl β-lactoside
The (4-(trifluoromethyl)phenyltriazolyl)methyl galactopyrano- (12). Hence, the 4-fluorophenyltriazol moiety of 1b efficiently
side 1k displayed a comparable affinity of 240 ± 61 µM, but replaces the galectin-1-interacting glucose unit in methyl
slightly lower selectivity over galectin-3. (1-Naphthyl- β-lactoside (12) and at the same time induces a significantly
triazolyl)methyl galactopyranoside 1l also displayed a good better selectivity than that of methyl β-lactoside (12). Taken
affinity of 180 ± 20 µM for galectin-1 with a threefold selec- together, the 4-fluorophenyltriazole 1b represents the most po-
tivity over galectin-3. Methyl substituents gave ligands (1h,i) tent mono-galactoside-derived galectin-1 inhibitor, albeit with
with poor galectin-1 affinity and undetectable galectin-3 an apparently lower selectivity than reported C-galactosides
binding, rendering them ineffective as galectin inhibitors. The [22,23]. Monosaccharide derivatives with somewhat higher
contrast between the 4-methylphenyl 1h and the 4-trifluoro- affinity for galectin-1 are known; dissociation constants down
methylphenyl 1k is interesting, suggesting that the affinity of 1k to 62 µM and selectivity of 8 over galectin-3 [34]. However,
may be explained by fluorine interaction(s) and/or solvation these inhibitors are larger and carry double modifications with
effects. Of particular interest is the different difluorinated aryls an anomeric thiophenyl aglycon combined with a heteroaryltria-
1e–g, which show a reversed selectivity pattern. They display zole moiety at galactose C3 that both form affinity and selec-
twofold preference for galectin-3 (1g), but their poor affinities tivity-enhancing interactions with galectin-1. Unfortunately,
limit their use as effective galectin-3 inhibitors. Furthermore, attempts to combine the anomeric 4-fluorophenyltriazolyl-
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Beilstein J. Org. Chem. 2019, 15, 1046–1060.
methyl moiety of compound 1b with such a galactose C3-thia- may also explain the weaker affinity by the corresponding
zolyltriazole substituent reported to enhance affinity for 2-fluorophenyltriazole analogue 1d, because in the favored
galectin-1 [34] failed in our hands, why other additional substit- complex geometry of 1b introduction of a 2-fluoro atom would
uents to combine with the 4-fluorophenyltriazolylmethyl moiety lead to this atom being close to either the Glu71 carboxylate or
of compound 1b remain to be discovered.
the triazole N3 lone pair.
Table 1: Dissociation constants (KD ± SEM in µM) and selectivities of
1a–n and references methyl β-D-galactopyranoside (11) and methyl
β-lactoside (12) binding to galectin-1 and -3 determined in a competi-
tive fluorescence polarization assay [33].
Galectin-
3
Selectivity
1
Galectin-1/3
1a
600 ± 48
170 ± 2
870 ± 37
1.5
4.2
0.6
1.3
0.7
0.7
0.4
>3
1b
710 ± 36
720 ± 64
500 ± 23
610 ± 160
790 ± 48
490 ± 55
>3000
1c
1200 ± 120
390 ± 38
860 ± 150
1100 ± 43
1100 ± 16
1000 ± 130
990 ± 23
500 ± 59
240 ± 61
180 ± 20
710 ± 12
1500 ± 290
>10000
1d
1e
1f
1g
1h
1i
>3000
>3
1j
700 ± 52
830 ± 38
470 ± 95
1200 ± 11
1700 ± 190
4400
1.4
3.5
2.6
1.7
1.1
0.4
1.2
1k
1l
1m
1n
Figure 1: Galectin-1 in complex with 1b derived by energy-minimizing
a representative snapshot from a 200 ns molecular dynamic simula-
tion. The distance between the triazole hydrogen and the Glu71
carboxylate is depicted with a yellow dashed line. The image was
generated using PyMOL v1.7 (Schrodinger LLC).
11 [35]
12 [35]
190
220
Molecular modelling
MD simulations with 1b positioned in a similar manner in the
In order to gain understanding of the affinity-enhancing effects complex with galectin-3 converged to a similar complex geom-
of the aryltriazolyl C-galactoside aglycons, we performed a etry with the 4-fluorophenyltriazole rings extending along a
200 ns molecular dynamic simulation of 1b in the complex with shallow, but somewhat wider groove formed by the correspond-
galectin-1 and galectin-3. Starting conformations were selected ing galectin-3 side chains Trp181-Gly182-Arg183-Glu184,
with the galactopyranose of 1b positioned overlapping with the which may explain why several of the aryltriazoles 1 also pos-
positions of the lactose or N-acetyllactosamine galactopyra- sess enhanced affinity for galectin-3 as compared to the refer-
noses in galectin-1 (pdb id 1GZW) and galectin-3 (pdb id ence methyl galactoside (11). Although the binding groove
1KJL), respectively, and with the 4-fluorophenyltriazol ring interacting with the ligand 4-fluorophenyl moiety is somewhat
protruding away from the protein. The simulations with 1b and wider in galectin-3, analyses of factors underlying the 4-fold
galectin-1 converged toward a complex geometry in which the galectin-1 selectivity remain inconclusive.
4-fluorophenyltriazole extended along a shallow groove formed
by Trp68-Gly69-Thr70-Glu71, while complex geometries in Conclusion
which the 1b 4-fluorophenyltriazole interacted with the His52 Hydroboration of 1-exo-methylene pyranosides 2 and 4 gives
that is situated above the β-face of the bound galactopyranose 3,4,5,7-tetra-O-benzyl-2-deoxy-D-galactoheptulose (3) and
ring were less populated (Figure 1). The preferred complex ge- 3,4,5,7-tetra-O-benzyl-2-deoxy-D-mannoheptulose (5) in good
ometry with the 4-fluorophenyltriazole extending along the yields and with excellent diastereoselectivities. This opens a
Trp68-Gly69-Thr70-Glu71 groove may, in addition to a more quick, high-yielding route to (aryltriazolyl)methyl galactopyra-
favorable steric complementarity, benefit from the electron- nosyls 1a–n, a majority of which are galectin-1 selective with
poor triazole hydrogen sampling positions close to the Glu71 dissociation constants down to 170 ± 2 µM (1b) and fourfold or
carboxylate and the electron-rich triazole nitrogens sampling better selectivity for galectin-1 over other galectins. This is
positions close to the rim of Trp68 side chain. This hypothesis comparable to or better than known C-galactoside based
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galectin-1 inhibitors with almost a factor of two [22,23]. Hence, hydroxide on charcoal (17 mg, 20 wt %) was added and the
one monosaccharide moiety, glucose/N-acetylglucosamine of mixture refluxed overnight at 80 °C. The reaction mixture was
the common disaccharide ligands lactose/N-acetyllactosamine diluted with methanol (15 mL), filtered through Celite, evapo-
has effectively been replaced with an aryltriazole motif, which rated, purified by column chromatography (5:1, dichloro-
is chemically wholly dissimilar and more selective. This opens methane/methanol), and then preparative HPLC (gradient from
a route towards galectin inhibitors with improved selectivities 10% acetonitrile/90% water with 0.1% formic acid to 100%
and potentially better pharmacokinetic properties than existing acetonitrile over 20 min, followed by 3 min of 100% aceto-
inhibitors based on lactose- and thiodigalactoside or other disac- nitrile) to give 1a (14 mg, 71%) as a white powder. [α]D20 24 (c
charide core structures.
0.6, methanol); 1H NMR (400 MHz, CD3OD) δ 8.42 (s, 1H),
7.86–7.81 (m, 2H), 7.48–7.42 (m, 2H), 7.38–7.33 (m, 1H),
4.98–4.95 (m, 1H), 4.57 (dd, J = 14.4 Hz, 7.5 Hz, 1H, H1),
3.91–3.88 (m, 1H, H5), 3.78 (dd, J = 10.8 Hz, 7.35 Hz, 1H,
Experimental
General procedures
Chemicals were obtained from Sigma-Aldrich unless otherwise H7), 3.70 (dd, J = 12.1 Hz, 4.8 Hz, 1H, H7), 3.60–3.48 (m,
stated and used without further purification, unless stated in the 4H); 13C NMR (100 MHz, CD3OD) δ 128. 5, 127.9, 125.3,
procedure. NMR spectra were collected on a Bruker Ultra- 122.3, 78.9, 78.7, 74.7, 69.5, 68.4, 61.5, 51.5; HRMS (m/z):
shield Plus/Avance II 400 MHz spectrometer. 1H NMR spectra [M + H]+ calcd for 322.1403; found, 322.1402; purity by
were recorded at 400 MHz and 13C NMR spectra at 100 MHz HPLC, UV–vis detection: 98.4%.
with residual solvent signals as references. 19F NMR spectra
were recorded at 376 MHz. Stereochemistry was assigned 1,2-Dideoxy-1-[4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl]-β-
through NOESY using pyridine-d5 as a shift reagent solvent. D-galactoheptulose (1b): Compound 10b (50 mg, 0.147 mmol)
All final compounds were purified using preparative HPLC on was dissolved in cyclohexene/ethanol 2:1 (3 mL), palladium(II)
an Agilent 1260 Infinity system with a SymmetryPrep C18 hydroxide on charcoal (40 mg, 20 wt %) was added, and the
5 µM 19 × 100 mm column using a gradient (water with 0.1% mixture refluxed overnight at 80 °C. The reaction mixture was
formic acid and acetonitrile); 0–20 min 10–100% acetonitrile, diluted with methanol (15 mL), filtered through Celite, evapo-
20–23 min 100% acetonitrile. Monitoring and collection based rated, purified by column chromatography (dichloromethane/
on UV–vis absorbance at 210 nm and 254 nm, respectively. methanol 5:1), and then preparative HPLC (gradient from 10%
Purity analysis was performed using UPLC–MS with UV–vis acetonitrile/90% water with 0.1% formic acid to 100% aceto-
detection on a Waters Acquity UPLC + Waters XEVO-G2 nitrile over 20 min, followed by 3 min of 100% acetonitrile) to
system using a Waters Acquity CSH C18, 1.7 µm, give 1b (9 mg, 37%) as a white powder. [α]D20 17 (c 0.7,
2.1 × 100 mm column. Samples were run using a gradient with CD3OD); 1H NMR (400 MHz, CD3OD) δ 8.43 (s, 1H),
water (0.1% formic acid) and acetonitrile using a flow rate of 7.88–7.82 (m, 2H), 7.24–7.16 (m, 2H), 4.95 (dd, J = 14.36 Hz,
0.50 mL/min and a column temperature 60 °C. Gradient param- 2.0 Hz, 1H, H1), 4.58 (dd, J = 13.6, 7.2 Hz, H1), 3.89 (dd, J =
eters: 0–0.7 min: 40% acetonitrile, 0.7–10.0 min: 40–99% 2.9 Hz, 0.9 Hz, 1H, H5), 3.78 (dd, J = 11.4 Hz, 7.2 Hz, 1H,
acetonitrile, 10.0–11.0 min 99% acetonitrile, 11.0–11.1 min H7), 3.69 (dd, J = 11.5 Hz, 4.6 Hz, 1H, H7), 3.60–3.49 (m,
99–40% acetonitrile, 11.1–13 min 40% acetonitrile, 3 or 6 µL 4H); 13C NMR (100 MHz, CD3OD) δ 161.6, 146.2, 127.4,
injection, detection 190–300 nm. MS parameters: Cap voltage 127.3, 126.6, 122.4, 115.5, 115.3, 79.0, 78.6, 74.7, 69.4, 68.4,
3.0 kV, cone voltage 40 kV, Ext 4, source temperature 120 °C, 61.5, 51.6; 19F NMR (376 MHz, CD3OD) δ −115.54; HRMS
desolvation temperature 500 °C, cone gas 50, desolvation gas (m/z): [M + H]+ calcd for 340.1306; found, 340.1309; purity by
800, centroid resolution mode, m/z interval 50–1200, lockspray. HPLC, UV–vis detection: 95.6%.
Calibration: Leu-enkephalin m/z 556.2771, 0.25 s every 30 s,
average 3. For optical rotation measurements, samples were dis- 1,2-Dideoxy-1-[4-(3-fluorophenyl)-1H-1,2,3-triazol-1-yl]-β-
solved in an appropriate solvent to a concentration of D-galactoheptulose (1c): Compound 10c (71 mg, 0.102 mmol)
2–10 mg/mL. Polarimetry was performed on a PerkinElmer was dissolved in cyclohexene/ethanol 2:1 (4.5 mL), 27 mg of
Model 341 Polarimeter using a sodium lamp and measuring at 20 wt % palladium(II) hydroxide on charcoal was added, and
589 nM with a 90 mm long 1 mL cell at 20 °C. For infrared the mixture refluxed overnight at 80 °C. The reaction mixture
spectroscopy, samples were pelleted with potassium bromide was diluted with methanol (15 mL), filtered through Celite,
and analyzed on a Shimadzu FTIR-84005.
evaporated, and purified by column chromatography (dichloro-
methane/methanol 5:1), and then preparative HPLC (gradient
1,2-Dideoxy-1-(4-phenyl-1H-1,2,3-triazol-1-yl)-β-D-galacto- from 10% acetonitrile/90% water with 0.1% formic acid to
heptulose (1a): Compound 10a (42 mg, 0.062 mmol) was dis- 100% acetonitrile over 20 min, followed by 3 min of 100%
solved in cyclohexene/ethanol 2:1 (1.5 mL), palladium(II) acetonitrile) to give 1c (16 mg, 46%) as a white powder. [α]D20
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Beilstein J. Org. Chem. 2019, 15, 1046–1060.
19 (c 0.6, CD3OD); 1H NMR (400 MHz, CD3OD) δ 8.47 (s, 4.94 (dd, J = 14.3 Hz,1.9 Hz, 1H, H1), 4.57 (dd, J = 14.5 Hz,
1H), 7.68–7.64 (m, 1H), 7.62–7.57 (m, 1H), 7.50–7.43 (m, 1H), 7.3 Hz, 1H, H1), 3.89 (dd, J = 2.9 Hz, 1.1 Hz, 1H, H5), 3.78
7.12–7.06 (m, 1H), 4.95 (dd, J = 14.4 Hz, 1.9 Hz, 1H, H1), 4.58 (dd, J = 11.3 Hz, 7.4 Hz, 1H, H7), 3.70 (dd, J = 11.6 Hz,
(dd, J = 14.2 Hz, 7.7 Hz, 1H, H1), 3.90 (dd, J = 2.9 Hz, 0.9 Hz, 4.7 Hz, 1H, H7), 3.59–3.49 (m, 4H); 13C NMR (100 MHz,
1H, H5), 3.79 (dd, J = 11.2 Hz, 6.9 Hz, 1H, H7), 3.70 (dd, J = CD3OD) δ 163.6, 157.1, 151.6, 151.1, 145.4, 128.1, 122.7,
11.6 Hz, 4.71 Hz, 1H, H7), 3.60–3.48 (m, 4H); 13C NMR 121.9, 121.81, 121.79, 121.75, 117.6, 117.5, 114.3, 114.1, 79.0,
(100 MHz, CD3OD) δ 164.5, 146.2, 132.9, 130.5, 122.9, 121.1, 78.7, 74.7, 69.4, 68.4, 61.5, 51.5; 19F NMR (376 MHz,
114.4, 111.9, 78.9, 78.7, 74.7 69.4, 68.4, 61.5, 51.5; 19F NMR CD3OD) δ −139.97, −140.03, −141.26, −141.31; HRMS (m/z):
(376 MHz, CD3OD) δ −114.83; HRMS (m/z): [M + H]+ calcd [M + H]+ calcd for 358.1212; found, 358.1215; purity by
for 340.1314; found, 340.1309; purity by HPLC, UV–vis detec- HPLC, UV–vis detection: 98.2%.
tion: 99.6%.
1,2-Dideoxy-1-[4-(3,5-difluorophenyl)-1H-1,2,3-triazol-1-yl]-
1,2-Dideoxy-1-[4-(2-fluorophenyl)-1H-1,2,3-triazol-1-yl]-β- β-D-galactoheptulose (1f): Compound 10f (81 mg,
D-galactoheptulose (1d): Compound 10d (66 mg, 0.095 mmol) 0.113 mmol) was dissolved in cyclohexene/ethanol 2:1 (6 mL)
was dissolved in cyclohexene/ethanol 2:1 (4.5 mL), with 2 drops of acetic acid, palladium(II) hydroxide on char-
palladium(II) hydroxide on charcoal (25 mg, 20 wt %) was coal (30 mg, 20 wt %) was added and the mixture refluxed
added, and the mixture refluxed overnight at 80 °C. The reac- overnight at 80 °C. The reaction mixture was diluted with
tion mixture was diluted with methanol (15 mL), filtered 15 mL methanol, filtered through Celite, evaporated, purified
through Celite, evaporated, purified by column chromatogra- by column chromatography (dichloromethane/methanol 5:1),
phy (dichloromethane/methanol 5:1), and then preparative and then preparative HPLC (gradient from 10% acetonitrile/
HPLC (gradient from 10% acetonitrile/90% water with 0.1% 90% water with 0.1% formic acid to 100% acetonitrile over
formic acid to 100% acetonitrile over 20 min, followed by 20 min, followed by 3 min of 100% acetonitrile) to give 1f
3 min of 100% acetonitrile) to give 1d (8 mg, 23%) as a white (7 mg, 18%) as a white powder. [α]D20 22 (c 0.8, CD3OD);
powder. [α]D20 27 (c 0.5, CD3OD); 1H NMR (400 MHz, 1H NMR (400 MHz, CD3OD) δ 8.51 (s, 1H), 7.51–7.44 (m,
CD3OD) δ 8.41 (d, J = 3.74 Hz, 1H), 8.11 (td, J = 7.6 Hz, 2H), 6.98–6.91 (tt, J = 9.1 Hz, 2.3 Hz, 1H, phenyl H4), 4.95
1.9 Hz, 1H), 7.43–7.37 (m, 1H), 7.30 (td, J = 7.6 Hz, 1.3 Hz, (dd, J = 14.4 Hz, 2.0 Hz, 1H, H1), 4.57 (dd, J = 14.2 Hz,
1H), 7.24 (ddd, J = 11.4 Hz, 8.3 Hz, 1.1 Hz, 1H), 4.97 (dd, J = 7.5 Hz, 1H, H1), 3.89 (dd, J = 2.7 Hz, 1.2 Hz, 1H, H5), 3.79
14.4 Hz, 2.1 Hz, 1H, H1), 4.60 (dd, J = 13.9 Hz,7.6 Hz, 1H, (dd, J = 11.2 Hz, 7.3 Hz, 1H, H7), 3.70 (dd, J = 11.3 Hz,
H1), 3.92–3.89 (m, 1H), 3.75 (J = 11.3 Hz, 6.7 Hz, 1H, H7), 4.7 Hz, 1H, H7), 3.59–3.47 (m, 4H); 13C NMR (100 MHz,
3.70 (dd, J = 11.3 Hz, 5.1 Hz, 1H, H7), 3.62–3.49 (m, 4H); CD3OD) δ 164.9, 162.3, 145.2, 123.4, 108.1, 107.8, 102.8,
13C NMR (100 MHz, CD3OD) δ 158.0, 140.7, 129.5, 129.4, 102.6, 102.0, 79.0, 78.6, 74.7, 69.4, 68.4, 61.5, 51.5; 19F NMR
127.3, 127.3, 124.9, 124.8, 124.38, 124.35, 118.4, 115.6, 115.4, (376 MHz, CD3OD) δ −111.27; HRMS (m/z): [M + H]+ calcd
78.8, 78.7, 74.7, 69.3, 68.4, 61.2, 51.4; 19F NMR (376 MHz, for 358.1219; found, 358.1215; purity by HPLC, UV–vis detec-
CD3OD) δ −116.16; HRMS (m/z): [M + H]+ calcd for tion: 99.6%.
340.1304; found, 340.1309; purity by HPLC, UV–vis detection:
98.5%.
1,2-Dideoxy-1-[4-(2,4-difluorophenyl)-1H-1,2,3-triazol-1-yl]-
β-D-galactoheptulose (1g): Compound 10g (88 mg,
1,2-Dideoxy-1-[4-(3,4-difluorophenyl)-1H-1,2,3-triazol-1-yl]- 0.123 mmol) was dissolved in cyclohexene/ethanol 2:1 (6 mL),
β-D-galactoheptulose (1e): Compound 10e (66 mg, palladium(II) hydroxide on charcoal (69 mg, 20 wt %) was
0.092 mmol) was dissolved in cyclohexene/ethanol 2:1 added and the mixture refluxed overnight at 80 °C. The reac-
(4.5 mL), palladium(II) hydroxide on charcoal (24 mg, tion mixture was diluted with 15 mL methanol, filtered through
20 wt %) was added, and the mixture refluxed overnight at Celite, evaporated, purified by column chromatography
80 °C. The reaction mixture was diluted with methanol (dichloromethane/methanol 5:1), and then preparative HPLC
(15 mL), filtered through Celite, evaporated, purified by column (gradient from 10% acetonitrile/90% water with 0.1% formic
chromatography (dichloromethane/methanol 5:1), and then acid to 100% acetonitrile over 20 min, followed by 3 min of
preparative HPLC (gradient from 10% acetonitrile/90% water 100% acetonitrile) to give 1g (40 mg, 87%) as a clear solid.
with 0.1% formic acid to 100% acetonitrile over 20 min, fol- [α]D20 7 (c 0.7, methanol); 1H NMR (400 MHz, CD3OD) δ 8.36
lowed by 3 min of 100% acetonitrile) to give 1e (17 mg, 52%) (d, J = 3.6 Hz, 1H), 8.14–8.07 (m, 1H), 7.13–7.05 (m, 2H), 4.95
as a white powder. [α]D20 16 (c 0.8, CD3OD); 1H NMR (dd, J = 14.2 Hz, 2.0 Hz, 1H, H1), 4.60 (dd, J = 14.2 Hz,
(400 MHz, CD3OD) δ 8.44 (s, 1H), 7.76 (ddd, J = 11.7 Hz, 7.6 Hz, 1H, H1), 3.91 (dd, J = 2.7 Hz,1.0 Hz, 1H, H5),
7.8 Hz, 2.2 Hz, 1H), 7.67–7.62 (m, 1H), 7.39–7.31 (m, 1H), 3.77–3.67 (m, 2H), 3.61–3.48 (m, 4H); 13C NMR (100 MHz,
1051

Beilstein J. Org. Chem. 2019, 15, 1046–1060.
CD3OD) δ 163.6, 163.5, 161.6, 161.5, 160.3, 160.2, 158.3, 336.1553; found, 336.1559; purity by HPLC, UV–vis detection:
158.2, 139.91, 139.89, 128.5, 128.44, 128.40, 128.36, 124.5, 97.3%.
124.4, 115.0, 114.9, 114.84, 114.81, 111.58, 111.55, 111.40,
111.37, 103.9, 103.7, 103.5, 78.7, 78.6, 74.6, 70.6, 69.2, 68.3, 1,2-Dideoxy-1-[4-(4-trifluoromethoxyphenyl)-1H-1,2,3-
61.2, 60.7, 51.4; 19F NMR (376 MHz, CD3OD) δ −111.90, triazol-1-yl]-β-D-galactoheptulose (1j): Compound 10j
−112.17; HRMS (m/z): [M + H]+ calcd for 358.1211; found, (77.3 mg, 0.101 mmol) was dissolved in cyclohexene/ethanol
358.1215 calculated. Purity by HPLC, UV–vis detection: 2:1 (4.5 mL), palladium(II) hydroxide on charcoal (28 mg,
96.6%.
20 wt %) was added, and the mixture was refluxed overnight at
80 °C. The reaction mixture was diluted with methanol
1,2-Dideoxy-1-[4-(4-methylphenyl)-1H-1,2,3-triazol-1-yl]-β- (15 mL), filtered through Celite, evaporated, purified by column
D-galactoheptulose (1h): Compound 10h (71 mg, 0.102 mmol) chromatography (dichloromethane/methanol 5:1), and then
was dissolved in cyclohexene/ethanol 2:1 (4.5 mL), preparative HPLC (gradient from 10% acetonitrile/90% water
palladium(II) hydroxide on charcoal (27 mg, 20 wt %) was with 0.1% formic acid to 100% acetonitrile over 20 min, fol-
added, and the mixture refluxed overnight at 80 °C. The reac- lowed by 3 min of 100% acetonitrile) to give 1j (40 mg, 89%)
tion mixture was diluted with methanol (15 mL), filtered as a white solid. [α]D20 7 (c 0.9, MeOH); 1H NMR (400 MHz,
through Celite, evaporated, purified by column chromatogra- CD3OD) δ 8.46 (s, 1H), 7.96–7.91 (m, 2H), 7.39–7.34 (m, 2H),
phy (dichloromethane/methanol 5:1), and then preparative 4.95 (dd, J = 14.1 Hz, 2.0 Hz, 1H, H1), 4.57 (dd, J = 14.0 Hz,
HPLC (gradient from 10% acetonitrile/90% water with 0.1% 7.5 Hz, 1H, H1), 3.90–3.88 (m, 1H, H5), 3.78 (dd, J = 11.4 Hz,
formic acid to 100% acetonitrile over 20 min, followed by 7.3 Hz, 1H, H7), 3.70 (dd, J = 11.5 Hz, 4.9 Hz, 1H, H7),
3 min of 100% acetonitrile) to give 1h (18 mg, 53%) as a white 3.60–3.49 (m, 4H); 13C NMR (100 MHz, CD3OD) δ 148.8,
powder. [α]D20 19 (c 0.9, CD3OD); 1H NMR (400 MHz, 145.9, 129.8, 126.9, 122.7, 121.2, 78.9, 78.7, 74.7, 69.4, 68.4,
CD3OD) δ 8.37 (s, 1H), 7.74–7.69 (m, 2H), 7.29–7.25 (m, 2H), 61.5, 51.5; 19F NMR (376 MHz, CD3OD) δ −59.49; HRMS
4.94 (dd, J = 14.2 Hz, 1.8 Hz, 1H, H1), 4.56 (dd, J = 14.1 Hz, (m/z): [M + H]+ calcd for 406.1234; found, 406.1226; purity by
7.4 Hz, 1H, H1), 3.91–3.88 (m, 1H, H5), 3.78 (dd, J = 10.8 Hz, HPLC, UV–vis detection: 99.8%.
7.3 Hz, 1H, H7), 3.70 (dd, J = 11.4 Hz, 4.8 Hz, 1H, H7),
3.60–3.48 (m, 4H), 2.39 (s, 3H); 13C NMR (100 MHz, CD3OD) 1,2-Dideoxy-1-[4-(4-trifluoromethylphenyl)-1H-1,2,3-
δ 147.4, 137.9, 129.1, 127.6, 125.3, 121.9, 78.9, 78.8, 74.7, triazol-1-yl]-β-D-galactoheptulose (1k): Compound 10k
69.4, 68.4, 61.5, 51.4, 19.9; HRMS (m/z): [M + H]+ calcd for (51 mg, 0.067 mmol) was dissolved in cyclohexene/ethanol 2:1
336.1558; found, 336.1559; purity by HPLC, UV–vis detection: (4.5 mL), palladium(II) hydroxide on charcoal (38 mg,
99.6%.
20 wt %) was added, and the mixture refluxed overnight at
80 °C. The reaction mixture was diluted with methanol
1,2-Dideoxy-1-[4-(3-methylphenyl)-1H-1,2,3-triazol-1-yl]-β- (15 mL), filtered through Celite, evaporated, purified by column
D-galactoheptulose (1i): Compound 10i (71 mg, 0.102 mmol) chromatography (dichloromethane/methanol 5:1), and then
was dissolved in cyclohexene/ethanol 2:1 (4.5 mL), preparative HPLC (gradient from 10% acetonitrile/90% water
palladium(II) hydroxide on charcoal (27 mg, 20 wt %) was with 0.1% formic acid to 100% acetonitrile over 20 min, fol-
added, and the mixture refluxed overnight at 80 °C. The reac- lowed by 3 min of 100% acetonitrile) to give 1k (17 mg, 63%)
tion mixture was diluted with methanol (15 mL), filtered as a white solid. [α]D20 8 (c 0.7, MeOH); 1H NMR (400 MHz,
through Celite, evaporated, purified by column chromatogra- CD3OD) δ 8.55 (s, 1H), 8.06–8.01 (m, 2H), 7.78–7.73 (m, 2H),
phy (dichloromethane/methanol 5:1), and then preparative 4.97 (dd, J = 14.3 Hz, 2.0 Hz, 1H, H1), 4.59 (dd, J = 14.3 Hz,
HPLC (gradient from 10% acetonitrile/90% water with 0.1% 7.6 Hz, 1H, H1), 3.91–3.88 (m, 1H, H5), 3.78 (dd, J = 11.8 Hz,
formic acid to 100% acetonitrile over 20 min, followed by 7.2 Hz, 1H, H7), 3.70 (dd, J = 11.8 Hz, 4.9 Hz, 1H, H7),
3 min of 100% acetonitrile) to give 1i (20 mg, 60%) as a white 3.60–3.49 (m, 4H); 13C NMR (100 MHz, CD3OD) δ 145.8,
powder. [α]D20 16 (c 1, CD3OD); 1H NMR (400 MHz, 125.6, 125.50, 125.46, 123.3, 79.0, 78.7, 74.7, 69.4, 68.4, 61.5,
CD3OD) δ 8.40 (s, 1H), 7.66 (s, 1H), 7.62 (d, J = 7.8 Hz, 1H), 51.5; 19F NMR (376 MHz, CD3OD) δ −64.13; HRMS (m/z):
7.32 (t, J = 7.6 Hz, 1H), 7.18 (d, J = 7.6 Hz, 1H), 4.94 (dd, J = [M + H]+ calcd for 390.1279; found, 390.1277; purity by
14.3 Hz, 1.8 Hz, 1H, H1), 4.56 (dd, J = 14.3 Hz, 7.4 Hz, 1H, HPLC, UV–vis detection: 99.8%.
H1), 3.90–3.88 (m, 1H, H5), 3.78 (dd, J = 11.5 Hz, 7.3 Hz, 1H,
H7), 3.70 (dd, J = 11.3 Hz, 4.6 Hz, 1H, H7), 3.60–3.50 (m, 1,2-Dideoxy-1-(4-naphth-1-yl-1H-1,2,3-triazol-1-yl)-β-D-
4H), 2.41 (s, 3H); 13C NMR (100 MHz, CD3OD) δ 147.4, galactoheptulose (1l): Compound 10l (12 mg, 0.016 mmol)
138.4, 130.3, 128.6, 128.5, 125.9, 122.5, 122.2, 78.9, 78.8, 74.7, was dissolved in cyclohexene/ethanol 2:1 (4.5 mL),
69.4, 68.4, 61.5, 51.5, 20.1; HRMS (m/z): [M + H]+ calcd for palladium(II) hydroxide on charcoal (10 mg, 20 wt %) was
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Beilstein J. Org. Chem. 2019, 15, 1046–1060.
added, and the mixture refluxed overnight at 80 °C. The reac- give 1n (26 mg, 54%) as a clear solid. [α]D20 12 (c 0.7, MeOH);
tion mixture was diluted with methanol (15 mL), filtered 1H NMR (400 MHz, CD3OD) δ 8.54 (s, 1H), 8.32 (s, 1H),
through Celite, evaporated, purified by column chromatogra- 7.97–7.85 (m, 4H), 7.54–7.47 (m, 2H), 4.98 (dd, J = 14.2 Hz,
phy (dichloromethane/methanol 5:1), and then preparative 2.0 Hz, 1H, H1), 4.60 (dd, J = 14.2 Hz, 7.5 Hz, 1H, H1), 3.91
HPLC (gradient from 10% acetonitrile/90% water with 0.1% (dd, J = 2.8 Hz, 1.0 Hz, 1H, H5), 3.81 (dd, J = 12.0 Hz, 7.3 Hz,
formic acid to 100% acetonitrile over 20 min, followed by 1H, H7), 3.72 (dd, J = 12.0 Hz, 4.9 Hz, H7), 3.63–3.51 (m,
3 min of 100% acetonitrile) to give 1l (5 mg, 79%) as a clear 4H); 13C NMR (100 MHz, CD3OD) δ 147.3, 133.6, 133.2,
solid. [α]D20 22 (c 0.5, MeOH); 1H NMR (400 MHz, CD3OD) δ 128.3, 127.80, 127.75, 127.4, 126.2, 125.9, 123.9, 123.4, 122.6,
8.43 (s, 1H), 8.32–8.26 (m, 1H), 7.98–7.93 (m, 2H), 7.73 (d, 79.0, 78.8, 74.8, 69.5, 68.4, 61.5, 51.5; HRMS (m/z): [M + H]+
J = 7.1 Hz, 1H), 7.60–7.53 (m, 3H), 5.02 (dd, J = 14.4 Hz, calcd for 372.1557; found, 372.1559; purity by HPLC, UV–vis
1.2 Hz, 1H, H1), 4.69 (dd, J = 14.2 Hz, 7.6 Hz, 1H, H1), 3.91 detection: 99.5%.
(dd, J = 2.7 Hz,1.0 Hz, 1H, H5), 3.81 (dd, J = 11.8 Hz, 7.5 Hz,
1H, H7), 3.71 (dd, J = 11.4 Hz, 4.8 Hz, 1H, H7), 3.67–3.61 (m, 3,4,5,7-Tetra-O-benzyl-2-deoxy-β-D-galactoheptulose (3):
1H, HX), 3.59–3.52 (m, 3H); 13C NMR (100 MHz, CD3OD) δ Compound 2 (3.66 g, 6.82 mmol) was dissolved in dry tetra-
133.8, 131.2, 128.6, 128.1, 126.9, 126.3, 125.7, 125.3, 124.98, hydrofuran (130 mL) under nitrogen and cooled to 0 °C. Borane
124.95, 78.9, 78.6, 74.8, 69.5, 68.3, 61.6, 51.4; HRMS (m/z): dimethyl sulfide complex in dry tetrahydrofuran (4.78 mL,
[M + H]+ calcd for 372.1563; found, 372.1559; purity by 9.55 mmol, 2 M) was added slowly, and the reaction was kept
HPLC, UV–vis detection: 96.3%.
at 0 °C for 2 h. The reaction mixture went from light yellow to
colorless during the addition of the borane dimethyl sulfide
1,2-Dideoxy-1-[4-(4-biphenyl)-1H-1,2,3-triazol-1-yl]-β-D- complex. Upon complete consumption of 2, distilled water
galactoheptulose (1m): Compound 10m (69 mg, 0.085 mmol) (15 mL) was added to the reaction mixture slowly (dropwise at
was dissolved in cyclohexene/ethanol 2:1 (4.5 mL), first) while vigorous gas evolution was observed. After comple-
palladium(II) hydroxide on charcoal (9 mg, 20 wt %) was tion of the gas evolution, sodium hydroxide (14 mL,
added, and the mixture refluxed overnight at 80 °C. The reac- 14.00 mmol, 1 M) and hydrogen peroxide (33%, 2 mL,
tion mixture was diluted with methanol (15 mL), filtered 20.5 mmol) were added, and the reaction mixture left for 2 h.
through Celite, evaporated, purified by column chromatogra- Upon completion of the reaction, 1 M hydrochloric acid was
phy (dichloromethane/methanol 5:1), and then preparative added to the reaction mixture until the pH was approximately 7.
HPLC (gradient from 10% acetonitrile/90% water with 0.1% The reaction mixture was poured into brine (150 mL), extracted
formic acid to 100% acetonitrile over 20 min, followed by with dichloromethane (3 × 150 mL) after which the organic
3 min of 100% acetonitrile) to give 1m (3 mg, 10%) as a white phases were pooled, dried with anhydrous sodium sulfate,
powder. [α]D20 45 (c 0.7, MeOH); 1H NMR (400 MHz, filtered, and evaporated. The crude was purified with column
CD3OD) δ 8.47 (s, 1H), 7.95–7.90 (m, 2H), 7.75–7.65 (m, 4H), chromatography (heptane/ethyl acetate 1:1) to give 3 (3.38 g,
7.50–7.44 (m, 2H), 7.37 (tt, J = 7.4 Hz, 1.2 Hz, 1H), 4.97 (dd, 89%) as a clear, viscous oil. The diastereoselectivity was deter-
J = 14.2 Hz, 1.9 Hz, 1H, H1), 4.58 (dd, J = 14.0 Hz, 7.5 Hz, mined to be α:β 1:19 by HPLC, using the same protocol as is
1H, H1), 3.92–3.89 (m, 1H, H5), 3.87–3.68 (m, 2H), 3.62–3.49 used for purity determinations. The stereochemistry of the β
(m, 4H); 13C NMR (100 MHz, CD3OD) δ 147.0, 140.9, 140.4, diastereomer, the only one isolated, was assigned using
128.5, 127.2, 127.1, 126.5, 125.7, 122.3, 78.9, 78.8, 74.7, NOESY. [α]D20 31 (c 1, CH2Cl2); 1H NMR (400 MHz, CDCl3)
69.4, 68.4, 61.5, 51.5; HRMS (m/z): [M + H]+ calcd for δ 7.41–7.24 (m, 20H), 4.97 (d, J = 9.2 Hz, 1H), 4.94 (d, J =
398.1717; found, 398.1716; purity by HPLC, UV–vis detection: 8.4 Hz, 1H), 4.78 (d, J = 11.9 Hz, 1H), 4.71 (d, J = 11.9 Hz,
99.7%.
1H), 4.67 (d, J = 10.9 Hz, 1H), 4.62 (d, J = 11.6 Hz, 1H), 4.49
(d, J = 11.6 Hz, 1H), 4.43 (d, J = 11.9 Hz, 1H), 3.99 (d, J =
1,2-Dideoxy-1-(4-naphth-2-yl-1H-1,2,3-triazol-1-yl)-β-D- 2.7 Hz, 1H, H5), 3.95 (d, J = 9.4 Hz, 1H, H3), 3.87 (dd, J =
galactoheptulose (1n): Compound 10n (96 mg, 0.131 mmol) 11.9 Hz, 2.7 Hz, 1H, H1), 3.71 (dd, J = 11.7 Hz, 5.2 Hz, 1H,
was dissolved in cyclohexene/ethanol 2:1 (6 mL), palladium(II) H1), 3.65 (dd, J = 9.4 Hz, 2.7 Hz, 1H, H4), 3.62–3.50 (m, 3H),
hydroxide on charcoal (73 mg, 20 wt %) was added, and the 3.40–3.33 (m, 1H, H2); 13C NMR (100 MHz, CDCl3) δ 138.7,
mixture refluxed overnight at 80 °C. The reaction mixture was 138.32, 138.26, 137.8, 128.5, 128.5, 128.3, 128.2, 128.1, 128.0,
diluted with methanol (15 mL), filtered through Celite, evapo- 127.89, 127.85, 127.72, 127.65, 127.6, 84.7, 79.6, 77.0, 75.4,
rated, purified by column chromatography (dichloromethane/ 75.3, 74.6, 73.8, 73.6, 72.4, 69.0, 62.6; 1H NMR (400 MHz,
methanol 5:1), and then preparative HPLC (gradient from 10% pyridine-d5) δ 7.60–7.20 (m, 20H), 5.19 (d, J = 11.1 Hz, 1H),
acetonitrile/90% water with 0.1% formic acid to 100% aceto- 5.13 (d, J = 11.1 Hz, 1H), 4.94–4.86 (m, 2H), 4.79 (d, J =
nitrile over 20 min, followed by 3 min of 100% acetonitrile) to 11.1 Hz, 2H), 4.60–4.48 (m, 3H), 4.43 (t, J = 9.1 Hz, 1H, H2),
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Beilstein J. Org. Chem. 2019, 15, 1046–1060.
4.32–4.25 (m, 2H), 4.14 (dd, J = 11.7 Hz, 4.6 Hz, 1H, H3), 71.8, 62.9; HRMS (m/z): [M + H]+ calcd for 555.2743; found,
3.95–3.85 (m, 3H), 3.77 (dd, J = 7.6 Hz, 4.3 Hz, 1H, H1), 555.2747.
3.70–3.64 (m, 1H); 13C NMR (100 MHz, pyridine-d5) δ 139.6,
139.5, 139.2, 138.8, 132.53, 132.46, 130.0, 128.57, 128.55, 3,4,5,7-Tetra-O-benzyl-2-deoxy-β-D-glucoheptulose (7):
128.5, 128.4, 128.3, 128.2, 128.11, 128.06, 128.04, 127.99, Compound 6 (67 mg, 0.125 mmol) was dissolved in dry tetra-
127.8, 127.7, 127.6, 127.5, 85.0, 81.7, 77.1, 75.8, 75.1, 75.0, hydrofuran (3 mL) under nitrogen and cooled to 0 °C. Borane
75.1, 73.3, 72.0, 69.5, 62.1; HRMS (m/z): [M + Na]+ calcd for dimethyl sulfide complex in dry tetrahydrofuran (75 µL,
577.2526; found, 577.2566.
0.150 mmol, 2 M) was added slowly and the reaction was kept
at 0 °C for 2 h. The reaction mixture went from light yellow to
3,4,5,7-Tetra-O-benzyl-2-deoxy-β-D-mannoheptulose (5): colorless during the addition of the borane dimethyl sulfide
Compound 4 (35 mg, 0.065 mmol) was dissolved in dry tetra- complex. Upon complete consumption of the starting material,
hydrofuran (3 mL) under nitrogen and cooled to 0 °C. Borane distilled water (0.66 mL) was added to the reaction mixture
dimethyl sulfide complex in dry tetrahydrofuran (40 µL, slowly (dropwise at first) while vigorous gas evolution was ob-
0.078 mmol, 2 M) was added slowly and the reaction was kept served. After completion of the gas evolution, sodium hydrox-
at 0 °C for 2 h. The reaction mixture went from light yellow to ide (250 µL, 0.251 mmol, 1 M) and hydrogen peroxide (33%,
colorless during the addition of the borane dimethyl sulfide 25 µL, 0.251 mmol) were added, and the reaction mixture left
complex. Upon complete consumption of the starting material, for 2 h. Upon completion of the reaction, 1 M hydrochloric acid
distilled water (0.66 mL) was added to the reaction mixture was added to the reaction mixture until the pH was approxi-
slowly (dropwise at first) while vigorous gas evolution was ob- mately 7. The reaction mixture was poured into brine (30 mL),
served. After completion of the gas evolution, sodium hydrox- extracted with dichloromethane (3 × 30 mL) after which the
ide (131 µL, 0.131 mmol, 1 M) and hydrogen peroxide (33%, organic phases were pooled, dried with anhydrous sodium
13 µL, 0.131 mmol) were added, and the reaction mixture left sulfate, filtered and evaporated. The crude was purified with
for 2 h. Upon completion of the reaction, 1 M hydrochloric acid column chromatography (heptane/ethyl acetate 1:1) to give 7
was added to the reaction mixture until the pH was approxi- (31 mg, 45%) as a diastereomeric mixture. Three consecutive
mately 7. The reaction mixture was poured into brine (30 mL), preparative HPLC purifications gave 3 mg of pure α-7, 17 mg
extracted with dichloromethane (3 × 30 mL) after which the of pure β-7, and 11 mg of 7 α/β-mixture as clear and viscous
organic phases were pooled, dried with anhydrous sodium oils. The diastereoselectivity was determined to be α:β 1:2.3 by
sulfate, filtered and evaporated. The crude was purified with HPLC using the same protocol as is used for purity determina-
column chromatography (heptane/ethyl acetate 1:1) to give 5 tions. The stereochemistry was assigned using NOESY. Data
(28 mg, 78%) as a clear, viscous oil. The diastereoselectivity for α-7: [α]D20 52 (c 0.2, CH3CN); 1H NMR (400 MHz, ace-
was determined to be α:β 1:99 by HPLC, using the same tone-d6) δ 7.44–7.24 (m, 20H), 4.93 (d, J = 11.5 Hz, 1H), 4.84
protocol as is used for purity determinations. The stereochemis- (d, J = 11.0 Hz, 1H), 4.81 (d, J = 11.3 Hz, 1H), 4.76 (m, 2H),
try of the β diastereomer, the only one isolated, was assigned 4.66–4.53 (m, 3H), 4.18–4.12 (m, 1H), 4.08–4.00 (m, 1H),
using NOESY. [α]D20 −37 (c 0.1, CH3CN); 1H NMR 3.93–3.69 (m, 5H), 3.64–3.56 (m, 2H); 13C NMR (100 MHz,
(400 MHz, CDCl3) δ 7.43–7.26 (m, 18H), 7.22–7.18 (m, 2H), acetone-d6) δ 139.3, 139.0, 138.9, 138.8, 128.3, 128.2, 128.13,
5.00 (d, J = 12.0 Hz, 1H), 4.91 (d, 10.7 Hz, 1H), 4.83–4.74 (m, 128.11, 127.8, 127.7, 127.6, 127.5, 127.32, 127.29, 127.2, 82.4,
2H), 4.72–4.54 (m, 4H), 3.95 (t, J = 9.8 Hz, 1H, H5), 3.90 (d, 79.5, 78.3, 74.6, 74.6, 74.3, 72.9, 72.6, 72.4, 69.6, 57.9, 57.8;
2.6 Hz, 1H, H3), 3.87–3.70 (m, 3H), 3.65 (dd, J = 9.4 Hz, 1H NMR (400 MHz, pyridine-d5) δ 7.51–7.23 (m, 20H),
2.7 Hz, 1H, H6), 3.54–3.47 (m, 2H), 3.44 (t, J = 5.7 Hz, 1H, 5.09–5.01 (m, 2H), 5.00–4.91 (m, 2H, obstructed by solvent),
H2); 13C NMR (100 MHz, CDCl3) δ 138.4, 138.2, 128.53, 4.81–4.75 (m, 3H), 4.69–4.53 (m, 3H), 4.48 (t, J = 8.1 Hz, 1H,
128.45, 128.37, 128.35, 128.1, 127.94, 127.89, 127.8, 127.7, H3), 4.37 (ddd, J = 9.9 Hz, 4.0 Hz, 1.9 Hz, 1H, H6), 4.34–4.27
127.62, 127.59, 85.0, 79.6, 78.6, 75.4, 75.3, 74.1, 73.5, 73.3, (m, 2H), 4.04 (dd, J = 8.9 Hz, 5.9 Hz, 1H, H2), 3.98–3.88 (m,
72.7, 69.6, 62.5; 1H NMR (400 MHz, pyridine-d5) δ 7.43–7.22 2H), 3.85 (dd, J = 10.8 Hz,2.2 Hz, 1H, H7); 13C NMR
(m, 20H), 5.23 (d, J = 11.2 Hz, 1H), 5.10 (d, J = 11.2 Hz, 1H), (100 MHz, pyridine-d5) δ 141.1, 140.8, 140.6, 140.4, 130.01,
4.93–4.87 (partially obscured by solvent), 4.80–4.64 (m, 3H), 129.99, 129.97, 129.95, 129.52, 129.49, 129.45, 129.40, 129.3,
4.56 (d, J = 4.56 Hz, 1H), 4.48 (d, J = 2.9 Hz, 1H, H3), 4.32 (t, 129.12, 129.10, 84.4, 81.6, 80.3, 77.1, 76.3, 76.1, 74.8, 74.7,
J = 9,5 Hz, 1H, H4), 4.27 (m, 1H, H1), 4.18 (m, 1H, H1), 74.5, 71.5, 60.2; HRMS (m/z): [M + H]+ calcd for 555.2755;
3.95–3.88 (m, 4H), 3.76 (dt, J = 9.5 Hz, 3.4 Hz, 1H, H5); found, 555.2747. Data for β-7: [α]D20 20 (c 1.1, CH3CN);
13C NMR (100 MHz, pyridine-d5) δ 141.3, 140.9, 140.7, 1H NMR (400 MHz, acetone-d6) δ 7.43–7.24 (m, 20H), 4.93 (s,
140.6, 130.1, 129.90, 129.86, 129.49, 129.45, 129.2, 129.1, 2H), 4.89 (d, J = 7.8 Hz, 1H), 4.86 (d, J = 7.6 Hz, 1H), 4.75 (d,
128.99, 128.95, 86.7, 81.4, 81.3, 77.4, 76.5, 76.4, 74.8, 73.3, J = 11.1 Hz, 1H), 4.67 (d, J = 10.9 Hz, 1H), 3.87 (m, 1H),
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Beilstein J. Org. Chem. 2019, 15, 1046–1060.
3.80–3.68 (m, 4H), 3.60 (td, J = 9.3 Hz, 2.2 Hz, 2H), 3.51 (ddd, (heptane/ethyl acetate 1:1) to give 9 (2.90 g, 90%) as a clear,
J = 9.7 Hz, 3.8 Hz, 2.3 Hz, 1H), 3.36 (ddd, J = 9.7 Hz, 4.2 Hz, viscous oil that after about two weeks crystallized into a grey-
2.2 Hz, 1H); 13C NMR (100 MHz, acetone-d6) δ 139.2, 139.0, white sticky solid. [α]D20 −5 (c 1.1, CH2Cl2); IR ν: 2101 cm−1,
138.9, 138.8, 128.20, 128.17, 128.15, 127.73, 127.71, 127.69, azide; 1H NMR (400 MHz, CDCl3) δ 7.45–7.25 (m, 20H), 5.00
127.5, 127.4, 127.34, 127.26, 87.1, 80.1, 78.9, 78.6, 78.4, 74.9, (d, J = 3.3 Hz, 1H), 4.97 (d, J = 2.5 Hz, 1H), 4.80 (d, J = 11.7
74.43, 74.36, 73.0, 69.4, 61.4, 61.3; 1H NMR (400 MHz, pyri- Hz, 1H), 4.71 (d, J = 12.0 Hz, 1H), 4.68–4.61 (m, 2H), 4.52 (d,
dine-d5) δ 7.52–7.41 (m, 6H), 7.40–7.23 (m, 14H), 5.10–4.94 J = 11.7 Hz, 1H), 4.56 (d, J = 11.7 Hz, 1H), 4.04 (d, J =
(m, partially solvent obstructed), 4.77 (d, J = 11.2 Hz, 1H), 4.63 2.6 Hz, 1H, H5), 3.90 (t, J = 9.4 Hz, 1H, H3), 3.67–3.58 (m,
(d, J = 11.9 Hz, 1H), 4.55 (d, J = 12.0 Hz, 1H), 4.27 (d, J = 4H), 3.53–3.46 (m, 2H), 3.39 (dd, J = 12.4 Hz, 7.2 Hz, 1H,
12.1 Hz, 1H, H1), 4.11 (dd, J = 11.6 Hz, 4.1 Hz, 1H, H1), H1); 13C NMR (100 MHz, CDCl3) δ 138.7, 138.2, 138.1, 137.9,
4.04–3.85 (m, 5H), 3.73 (dt, J = 9.4 Hz, 2.9 Hz, 1H, H6), 3.65 128.50, 128.46, 128.3, 128.2, 127.97, 127.96, 127.9, 127.8,
(m, 1H, H2); 13C NMR (100 MHz, pyridine-d5) δ 139.5, 139.3, 127.8, 127.6, 84.6, 79.1, 77.2, 75.7, 75.4, 74.5, 73.62, 73.55,
139.1, 138.8, 128.51, 128.48, 128.47, 127.97, 127.95, 127.8, 72.2, 69.0, 51.5; HRMS (m/z): [M + Na]+ calcd for 602.2634;
127.7, 127.62, 127.55, 87.4, 81.2, 79.1, 78.81, 78.75, 75.2, 74.7, found, 602.2631.
73.3, 69.9, 61.5; HRMS (m/z): [M + H]+ calcd for 555.2745;
found, 555.2747.
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-phenyl-1H-1,2,3-
triazol-1-yl]-β-D-galactoheptulose (10a): Compound 9
3,4,5,7-Tetra-O-benzyl-2-deoxy-1-methanesulfonyl-β-D- (100 mg, 0.184 mmol) and copper(I) iodide (4 mg, 0.035 mmol)
galactoheptulose (8): Compound 3 (3.38 g, 6.08 mmol) was were dissolved in dry acetonitrile (3 mL) under nitrogen, tri-
dissolved in dry pyridine (16.5 mL) under nitrogen and cooled ethylamine (52 μL, 0.368 mmol) and ethynylbenzene (22 μL,
to 0 °C. Methanesulfonyl chloride (1.55 mL, 20.10 mmol) was 0.194 mmol) were added, and the reaction was left at 55 °C
added slowly. The reaction mixture turns yellow/orange upon overnight. Upon completion, the reaction mixture was poured
addition. The reaction was left for 2 h, after which the reaction into ethyl acetate (20 mL) and washed with brine (20 mL). The
mixture was poured into brine (200 mL with 20 mL 5% hydro- brine was extracted with ethyl acetate (2 × 20 mL), the organic
chloric acid), extracted with dichloromethane (3 × 200 mL) phases pooled, dried with anhydrous sodium sulfate, and evapo-
after which the organic phases were pooled. The organic phases rated. The crude product was purified with column chromatog-
were washed once with brine, dried with anhydrous sodium raphy (heptane/ethyl acetate 2:1) to give 10a (96.8 mg, 77%) as
sulfate, filtered and evaporated. The crude was purified with a viscous clear oil. [α]D20 −10 (c 1.9, CH2Cl2); 1H NMR
column chromatography (heptane/ethyl acetate 1:1) to give 8 (400 MHz, CDCl3) δ 8.01 (s, 1H), 7.81–7.75 (m, 2H),
(3.51 g, 91%) as a cream white solid. [α]D20 7 (c 1.1, CH2Cl2); 7.45–7.14 (m, 23H), 4.97 (d, J = 7.4 Hz, 1H), 4.94 (d, J =
1H NMR (400 MHz, CDCl3) δ 7.52–7.25 (m, 20H), 5.06 (d, J = 6.2 Hz, 1H), 4.81 (d, J = 11.7 Hz, 1H), 4.76–4.68 (m, 4H), 4.57
4.0 Hz, 1H), 5.04 (d, J = 4.6 Hz, 1H), 4.88 (d, J = 11.6 Hz, (d, J = 11.7 Hz, 1H), 4.51–4.48 (m, 2H), 4.00 (s, 1H, H5),
1H), 4.80 (d, J = 12.2 Hz, 1H), 4.75 (d, J = 10.7 Hz, 1H), 3.75–3.55 (m, 6H); 13C NMR (100 MHz, CDCl3) δ 138.5,
4.67–4.61 (m, 2H), 4.58–4.52 (m, 2H), 4.47 (dd, J1 = 12.2 Hz, 138.01, 137.95, 137.8, 132.80, 132.2, 131.0, 129.2, 128.8,
4.9 Hz, H1), 4.09 (d, J = 2.7 Hz, 1H, H5), 4.03 (t, J = 9.7 Hz, 128.7, 128.6, 128.54, 128.50, 128.4, 128.3, 128.0, 127.91,
1H, H3), 3.73 (dd, J1 = 9.1, 2.7 Hz, 1H, H4), 3.71–3.54 (m, 127.87, 127.85, 127.7, 127.6, 127.54, 127.52, 125.8, 121.4,
4H), 2.99 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 138.5, 138.1, 84.5, 77.7, 77.2, 75.4, 74.8, 74.6, 73.8, 73.6, 72.2, 69.1, 51.1;
138.0, 137.8, 128.63, 128.60, 128.4, 128.3, 128.16, 128.04, HRMS (m/z): [M + H]+ calcd for 682.3288; found, 682.3281.
128.02, 127.92, 127.86, 127.7, 84.5, 77.7, 77.2, 75.5, 74.8, 74.2,
73.7, 73.6, 72.3, 69.9, 68.8, 38.0; HRMS (m/z): [M + Na]+ 3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(4-fluorophenyl)-
calcd for 655.2343; found, 655.2342.
1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10b): Com-
pound 9 (113 mg, 0.198 mmol), 1-ethynyl-4-fluorobenzene
1-Azido-3,4,5,7-tetra-O-benzyl-1,2-dideoxy-β-D-galactohep- (29 mg, 0.238 mmol), and copper(I) iodide (4 mg, 0.035 mmol)
tulose (9): Compound 8 (3.51 g, 5.55 mmol) was dissolved in were dissolved in dry acetonitrile (3 mL) under nitrogen, tri-
dry DMF (40 mL) and sodium azide (791 mg, 12.17 mmol) was ethylamine (55 μL,0.397 mmol) was added, and the reaction left
added. The reaction mixture was heated to 95 °C and left at room temperature overnight. Upon completion, the reaction
overnight. Upon completion, the reaction mixture was poured mixture was poured into ethyl acetate (20 mL) and washed with
into distilled water (500 mL) and washed with dichloromethane brine (20 mL). The brine was extracted with ethyl acetate
(3 × 150 mL). The organic phases were pooled and washed with (2 × 20 mL), the organic phases pooled, dried with anhydrous
brine (450 mL), dried with anhydrous sodium sulfate, and evap- sodium sulfate, and evaporated. The crude product was purified
orated. The crude was purified with column chromatography with column chromatography (heptane/ethyl acetate 3:1) to give
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Beilstein J. Org. Chem. 2019, 15, 1046–1060.
10b (97 mg, 70%) as a viscous lightly yellow oil. [α]D20 −13 (c 2:1) to give 10d (78 mg, 63%) as a viscous lightly yellow oil.
0.7, CH2Cl2); 1H NMR (400 MHz, CDCl3) δ 7.95 (s, 1H), 7.73 [α]D20 −10 (c 0.8, CH2Cl2); 1H NMR (400 MHz, CDCl3) δ 8.32
(m, 2H), 7.44–7.15 (m, 20H), 7.10–7.03 (m, 2H), 4.96 (d, J = (td, J1 = 7.6 Hz, 2.0 Hz, 1H), 8.18 (d, J = 3.9 Hz, 1H),
9.2 Hz, 1H), 4.94 (d, J = 8.2 Hz, 1H), 4.81 (d, J = 11.6 Hz, 7.45–7.09 (m, 22H), 4.96 (d, J = 10.5 Hz, 1H), 4.93 (d, J =
1H), 4.76–4.68 (m, 4H), 4.56 (d, J = 11.4 Hz, 1H), 4.52–4.49 11.7 Hz, 1H), 4.81–4.59 (m, 6H), 4.57 (d, J = 11.5 Hz, 1H),
(m, 2H), 4.00 (d, J = 1.8 Hz, 1H, H5), 3.74–3.55 (m, 6H); 4.49 (d, J = 11.7 Hz, 1H), 4.43 (d, J = 11.7 Hz, 1H), 3.98 (d,
13C NMR (100 MHz, CDCl3) δ 163.8, 161.4, 147.0, 138.6, J = 0.8 Hz, 1H, H5), 3.74–3.65 (m, 3H), 3.65–3.52 (m, 3H);
138.1, 138.0, 137.8, 128.7, 128.62, 128.60, 128.58, 128.4, 13C NMR (100 MHz, CDCl3) δ 158.0, 141.1, 138.5, 138.02,
128.1, 128.02, 127.95, 127.9, 127.69, 127.67, 127.6, 127.5, 137.96, 137.8, 129.1, 129.0, 128.53, 128.46, 128.4, 128.3,
127.24, 127.21, 84.6, 77.7, 77.3, 75.5, 74.7, 73.9, 73.7, 72.4, 128.2, 128.0, 127.9, 127.8, 127.7, 127.6, 127.4, 124.8, 124.6,
69.2, 51.2; 19F NMR (376 MHz, CD3OD) δ −114.11; HRMS 124.5, 115.8, 115.6, 84.5, 77.7, 77.2, 75.4, 74.9, 74.5, 73.6,
(m/z): [M + H]+ calcd for 700.3195; found, 700.3187.
73.5, 73.2, 72.2, 69.0, 51.1; 19F NMR (376 MHz, CD3OD) δ
−114.53; HRMS (m/z): [M + H]+ calcd for 700.3186; found,
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(3-fluorophenyl)- 700.3187.
1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10c): Com-
pound 9 (107 mg, 0.185 mmol) and copper(I) iodide (4 mg, 3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(3,4-difluoro-
0.035 mmol) were dissolved in dry acetonitrile (3 mL) under phenyl)-1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10e):
nitrogen, triethylamine (51 μL (0.369 mmol) and 1-ethynyl-3- Compound 9 (103 mg, 0.176 mmol) and copper(I) iodide (4 mg,
fluorobenzene (26 μL, 0.221 mmol) were added, and the reac- 0.035 mmol) were dissolved in dry acetonitrile (3 mL) under
tion was left at room temperature overnight. Upon completion, nitrogen, triethylamine (49 μL, 0.352 mmol) and 1-ethynyl-3,4-
the reaction mixture was poured into ethyl acetate (20 mL) and difluorobenzene (25 μL, 0.211 mmol) were added, and the reac-
washed with brine (20 mL). The brine was extracted with ethyl tion was left at room temperature overnight. Upon completion,
acetate (2 × 20 mL), the organic phases pooled, dried with an- the reaction mixture was poured into ethyl acetate (20 mL) and
hydrous sodium sulfate, and evaporated. The crude product was washed with brine (20 mL). The brine was extracted with ethyl
purified with column chromatography (heptane/ethyl acetate acetate (2 × 20 mL), the organic phases pooled, dried with an-
2:1) to give 10c (81 mg, 63%) as a viscous clear oil. [α]D20 −10 hydrous sodium sulfate, and evaporated. The crude product was
(c 1.0, CH2Cl2); 1H NMR (400 MHz, CDCl3) δ 17.98 (s, 1H), purified with column chromatography (heptane/ethyl acetate
7.53–7.46 (m, 2H), 7.43–7.14 (m, 21H), 7.06–6.99 (m, 1H), 2:1) to give 10e (86 mg, 68%) as a viscous lightly yellow oil.
4.95 (d, J = 1.9 Hz, 1H), 4.92 (s, 1H), 4.80 (d, J = 11.6 Hz, [α]D20 −9 (c 1.0, CH2Cl2); 1H NMR (400 MHz, CDCl3) δ 7.93
1H), 4.73 (d, J = 2.3 Hz, 1H), 4.71–4.67 (m, 3H), 4.54 (d, J = (s, 1H), 7.59–7.52 (m, 1H), 7.46–7.02 (m, 22H), 4.95 (d, J =
11.6 Hz, 1H), 4.50–4.47 (m, 2H), 3.99 (d, J = 1.8 Hz, 1H, H5), 2.9 Hz, 1H), 4.92 (d, J = 2.1 Hz, 1H), 4.80 (d, J = 11.6 Hz,
3.73–3.52 (m, 6H); 13C NMR (100 MHz, CDCl3) δ 164.5, 1H), 4.75–4.66 (m, 4H), 4.54 (d, J = 11.6 Hz, 1H), 4.51–4.47
162.1, 147.0, 138.4, 138.0, 137.9, 137.7, 130.4, 130.3, 128.54, (m, 2H), 3.99 (d, J = 2.0 Hz, 1H, H5), 3.73–3.53 (m, 6H);
128.53, 128.49, 128.46, 128.2, 128.0, 127.93, 127.87, 127.85, 13C NMR (100 MHz, CDCl3) δ 138.4, 137.93, 137.86, 137.7,
127.58, 127.55, 121,8, 121.3, 114.8, 114.5, 112.7, 112.5, 84.5, 128.6, 128.54, 128.50, 128.46, 128.2, 127.99, 127.96, 127.9,
77.6, 77.2, 75.4, 74.8, 74.6, 73.7, 73.6, 72.2, 69.0, 51.1; 127.6, 121.7, 121.5, 117.7, 117.5, 114.8, 114.6, 84.5, 77.5, 77.2,
19F NMR (376 MHz, CD3OD) δ −112.85; HRMS (m/z): 75.4, 74.7, 74.6, 73.7, 73.6, 72.3, 69.1, 51.2; 19F NMR
[M + H]+ calcd for 700.3185; found, 700.3187.
(376 MHz, CD3OD) δ −137.34, −137.40, −138.89, −138.95;
HRMS (m/z): [M + H]+ calcd for 718.3102; found, 718.3093.
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(2-fluorophenyl)-
1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10d): Com- 3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(3,5-difluoro-
pound 9 (102 mg, 0.179 mmol) and copper(I) iodide (4 mg, phenyl)-1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10f):
0.035 mmol) were dissolved in dry acetonitrile (3 mL) under Compound 9 (106 mg, 0.183 mmol) and copper(I) iodide (4 mg,
nitrogen, triethylamine (49 μL, 0.352 mmol) and 1-ethynyl-2- 0.035 mmol) were dissolved in dry acetonitrile (3 mL) under
fluorobenzene (24 μL, 0.211 mmol) were added, and the reac- nitrogen, triethylamine (51 μL, 0.366 mmol) and 1-ethynyl-3,5-
tion was left at room temperature overnight. Upon completion, difluorobenzene (26 μL, 0.220 mmol) was added, and the reac-
the reaction mixture was poured into ethyl acetate (20 mL) and tion was left at room temperature overnight. Upon completion,
washed with brine (20 mL). The brine was extracted with ethyl the reaction mixture was poured into ethyl acetate (20 mL) and
acetate (2 × 20 mL), the organic phases pooled, dried with an- washed with brine (20 mL). The brine was extracted with ethyl
hydrous sodium sulfate, and evaporated. The crude product was acetate (2 × 20 mL), the organic phases pooled, dried with an-
purified with column chromatography (heptane/ethyl acetate hydrous sodium sulfate, and evaporated. The crude product was
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Beilstein J. Org. Chem. 2019, 15, 1046–1060.
purified with column chromatography (heptane/ethyl acetate (2 × 20 mL), the organic phases pooled, dried with anhydrous
2:1) to give 10f (88 mg, 67%) as a viscous lightly yellow oil. sodium sulfate, and evaporated. The crude product was purified
[α]D20 −12 (c 1.1, CH2Cl2); 1H NMR (400 MHz, CDCl3) δ 7.96 with column chromatography (heptane/ethyl acetate 2:1) to give
(s, 1H), 7.44–7.17 (m, 22H), 6.78 (tt, J = 8.9 Hz, 2.3 Hz, 1H), 10h (79 mg, 64%) as viscous clear oil. [α]D20 −12 (c 0.7,
4.95 (d, J = 4.0 Hz, 1H), 4.92 (d, J = 4.8 Hz, 1H), 4.80 (d, J = CH2Cl2); 1H NMR (400 MHz, CDCl3) δ 7.95 (s, 1H),
11.8 Hz, 1H), 4.75–4.66 (m, 4H), 4.53 (d, J = 11.6 Hz, 1H), 7.69–7.64 (m, 2H), 7.44–7.14 (m, 22H), 4.96 (d, J = 5.1 Hz,
4.51–4.48 (m, 2H), 3.98 (d, J = 2.1 Hz, 1H, H5), 3.72–3.52 (m, 1H), 4.93 (d, J = 4.3 Hz, 1H), 4.79 (d, J = 11.6 Hz, 1H),
6H); 13C NMR (100 MHz, CDCl3) δ 164.6, 164.5, 162.2, 162.0, 4.75–4.61 (m, 4H), 4.56 (d, J = 11.6 Hz, 1H), 4.50–4.45 (m,
138.3, 137.9, 137.9, 137.6, 128.56, 128.55, 128.50, 128.46, 2H), 3.99 (s, 1H, H5), 3.75–3.52 (m, 6H), 2.41 (s, 3H);
128.2, 128.0, 127.91, 127.87, 127.60, 127.58, 127.57, 122.2, 13C NMR (100 MHz, CDCl3) δ 138.5, 138.0, 137.9, 137.7,
108.6, 108.3, 103.3, 103.0, 102.8, 84.5, 77.5, 77.2, 75.4, 74.7, 137.6, 129.4, 128.54, 128.52, 128.49, 128.3, 128.1, 128.0,
74.6, 73.7, 73.6, 72.2, 69.0, 51.2; 19F NMR (376 MHz, 127.9, 127.8, 127.6, 127.5, 125.7, 121.0, 84.5, 77.8, 77.2, 75.4
CD3OD) δ −109.45; HRMS (m/z): [M + H]+ calcd for 74.9, 74.6, 73.7, 73.5, 72.2, 69.0, 51.1, 21.3; HRMS (m/z):
718.3097; found, 718.3093.
[M + H]+ calcd for 696.3450; found, 696.3437.
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(2,4-difluoro- 3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(3-methylphenyl)-
phenyl)-1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10g): 1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10i): Com-
Compound 9 (150 mg, 0.259 mmol), 1-ethynyl-2,4-difluoroben- pound 9 (106 mg, 0.183 mmol) and copper(I) iodide (4 mg,
zene (40 mg, 0.285 mmol), and copper(I) iodide (10 mg, 0.035 mmol) were dissolved in dry acetonitrile (3 mL) under
0.052 mmol) were dissolved in dry acetonitrile (4 mL) under nitrogen, triethylamine (50 μL, 0.366 mmol) and 3-ethynyl-
nitrogen, triethylamine (72 μL, 0.518 mmol) was added, and the toluene (27 μL, 0.214 mmol) were added, and the reaction was
reaction left at 60 °C overnight. Upon completion, the reaction left at 50 °C overnight. Upon completion, the reaction mixture
mixture was poured into ethyl acetate (20 mL) and washed with was poured into ethyl acetate (20 mL) and washed with brine
brine (20 mL). The brine was extracted with ethyl acetate (20 mL). The brine was extracted with ethyl acetate
(2 × 20 mL), the organic phases pooled, dried with anhydrous (2 × 20 mL), the organic phases pooled, dried with anhydrous
sodium sulfate, and evaporated. The crude product was purified sodium sulfate, and evaporated. The crude product was purified
with column chromatography (heptane/ethyl acetate 3:1) to give with column chromatography (heptane/ethyl acetate 2:1) to give
10g (136 mg, 73%) as a sticky clear solid. [α]D20 −10 (c 1.6, 10i (83 mg, 65%) as a viscous lightly yellow oil. [α]D20 −7.8 (c
CH3CN); 1H NMR (400 MHz, CDCl3) δ 8.31–8.25 (m, 2H), 0.8, CH2Cl2); 1H NMR (400 MHz, CDCl3) δ 7.97 (s, 1H), 7.69
8.11 (d, J = 4.0 Hz, 1H), 7.45–7.17 (m, 20H), 7.01 (td, J = (s, 1H), 7.52 (d, J = 7.63 Hz, 1H), 7.44–7.11 (m, 22H), 4.96 (d,
8.6 Hz, 2.3 Hz, 1H), 6.89–6.83 (m, 1H), 4.98–4.90 (m, 2H), J = 3.2 Hz, 1H), 4.93 (d, J = 1.6 Hz, 1H), 4.79 (d, J = 11.7 Hz,
4.81–4.69 (m, 4H), 4.68–4.60 (m, 1H), 4.56 (d, J = 11.3 Hz, 1H), 4.75–4.59 (m, 4H), 4.56 (d, J = 11.7 Hz, 1H), 4.50–4.45
1H), 4.51–4.42 (m, 2H), 3.98 (s, 1H, H5), 3.72–3.54 (m, 6H); (m, 2H), 3.98 (d, J = 1.1 Hz, 1H, H5), 3.76–3.52 (m, 6H), 2.40
13C NMR (100 MHz, CDCl3) δ 163.3, 163.2, 160.1, 160.0, (s, 3H); 13C NMR (100 MHz, CDCl3) δ 147.7, 138.5, 138.4,
158.1, 158.0, 140.3, 138.4, 137.91, 137.85, 137.7, 128.73, 138.0, 137.9, 137.7, 130.7, 128.7, 128.54, 128.52, 128.48,
128.66, 128.62, 128.56, 128.44, 128.35, 128.3, 128.2, 128.1, 128.0, 127.9, 127.8, 127.57, 127.55, 127.5, 126.5, 122.9, 121.4,
127.9, 127.7, 127.6, 127.52, 127.49, 127.4, 124.2, 124.1, 115.3, 84.5, 77.7, 77.2, 75.4, 74.9, 74.5, 73.7, 73.5, 72.2, 69.0, 51.1,
111.9, 111.8, 111.7, 104.2, 103.9, 103.7, 84.4, 77.5, 77.1, 75.3, 21.5; HRMS (m/z): [M + H]+ calcd for 696.3442; found,
74.8, 74.4, 73.51, 73.47, 72.1, 69.0, 51.1; 19F NMR (376 MHz, 696.3437.
CD3OD) δ −110.77, −110.96; HRMS (m/z): [M + H]+ calcd for
718.3091; found, 718.9093.
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(4-trifluo-
romethoxyphenyl)-1H-1,2,3-triazol-1-yl]-β-D-galactoheptu-
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(4-methylphenyl)- lose (10j): Compound 9 (100 mg, 0.173 mmol), 4-(trifluo-
1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (10h): Com- romethoxy)ethynylbenzene (34 mg, 0.181 mmol), and copper(I)
pound 9 (103 mg, 0.178 mmol) and copper(I) iodide (4 mg, iodide (7 mg, 0.035 mmol) were dissolved in dry acetonitrile
0.035 mmol) were dissolved in dry acetonitrile (3 mL) under (3 mL) under nitrogen, (50 μL, 0.356 mmol) triethylamine was
nitrogen, triethylamine (50 μL, 0.356 mmol) and 4-ethynyl- added, and the reaction left at room temperature overnight.
toluene (27 μL, 0.214 mmol) were added, and the reaction was Upon completion, the reaction mixture was poured into ethyl
left at 50 °C overnight. Upon completion, the reaction mixture acetate (20 mL) and washed with brine (20 mL). The brine was
was poured into ethyl acetate (20 mL) and washed with brine extracted with ethyl acetate (2 × 20 mL), the organic phases
(20 mL). The brine was extracted with ethyl acetate pooled, dried with anhydrous sodium sulfate, and evaporated.
1057

Beilstein J. Org. Chem. 2019, 15, 1046–1060.
The crude product was purified with column chromatography with column chromatography (heptane/ethyl acetate 3:1) to give
(heptane/ethyl acetate 2:1) to give 10j (103 mg, 78%) as a clear 10l (120 mg, 42%) as a sticky clear solid. [α]D20 −11 (c 1.1,
solid. [α]D20 −19 (c= 0.8, CHCl3); 1H NMR (400 MHz, CDCl3) CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.40 (d, J = 8.5 Hz,
δ 8.00 (s, 1H), 7.76–7.71 (m, 2H), 7.44–7.15 (m, 22H), 1H), 8.04 (s, 1H), 7.94–7.88 (m, 2H), 7.66 (dd, J = 7.2 Hz,
4.98–4.91 (m, 2H), 4.81 (d, J = 11.8 Hz, 1H), 4.77–4.66 (m, 1.1 Hz, 1H), 7.54–7.12 (m, 23H), 5.00 (d, J = 10.9 Hz, 1H),
4H), 4.55 (d, J = 11.8 Hz, 1H), 4.52–4.49 (m, 2H), 4.00 (d, J = 4.94 (d, J = 11.8 Hz, 1H), 4.85–4.77 (m, 3H), 4.76–4.68 (m,
2.3 Hz, 1H, H5), 3.75–3.55 (m, 6H); 13C NMR (100 MHz, 3H), 4.59 (d, J = 11.8 Hz, 1H), 4.47–4.44 (m, 2H), 4.01 (s, 1H,
CDCl3) δ 148.7, 146.5, 138.4, 138.0, 137.9, 137.7, 129.7, H5), 3.77–3.69 (m, 3H), 3.68–3.56 (m, 3H); 13C NMR
128.56, 128.54, 128.51, 128.48, 128.4, 128.2, 128.0, 127.93, (100 MHz, CDCl3) δ 146.6, 138.4, 138.04, 137.95, 137.7,
127.87, 127.8, 127.59, 127.55, 127.5, 127.1, 121.8, 121.6, 133.9, 131.2, 128.63, 128.55, 128.52, 128.46, 128.4, 128.3,
121.4, 84.5, 77.6, 77.2, 75.4, 74.7, 74.6, 73.8, 73.6, 72.3, 69.2, 128.2, 128.0, 127.9, 127.8, 127.61, 127.55, 127.2, 126.5, 125.9,
51.1; 19F NMR (376 MHz, CD3OD) δ −57.78; HRMS (m/z): 125.6, 125.4, 124.5, 84.6, 77.7, 77.2, 75.4, 74.9, 74.6, 73.8,
[M + H]+ calcd for 766.3108; found, 766.3104.
73.6, 72.3, 69.0, 51.1; HRMS (m/z): [M + H]+ calcd for
732.3442; found, 732.3437.
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(4-trifluoromethyl-
phenyl]-1H-1,2,3-triazol-1-yl)-β-D-galactoheptulose (10k): 3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-[4-(4-biphenyl)-1H-
Compound 9 (100 mg, 0.178 mmol), 4-(trifluoro- 1,2,3-triazol-1-yl]-β-D-galactoheptulose (10m): Compound 9
methane)ethynylbenzene (31 mg, 0.181 mmol), and copper(I) (103 mg, 0.178 mmol), 4-ethynylbiphenyl (38 mg
iodide (7 mg, 0.035 mmol) were dissolved in dry acetonitrile (0.213 mmol), and copper(I) iodide (4 mg, 0.035 mmol) were
(3 mL) under nitrogen, triethylamine (50 μL, 0.356 mmol) was dissolved in dry acetonitrile (3 mL) under nitrogen, triethyl-
added, and the reaction left at room temperature overnight. amine (50 μL, 0.356 mmol) was added, and the reaction left at
Upon completion, the reaction mixture was poured into ethyl room temperature overnight. Upon completion, the reaction
acetate (20 mL) and washed with brine (20 mL). The brine was mixture was poured into ethyl acetate (20 mL) and washed with
extracted with ethyl acetate (2 × 20 mL), the organic phases brine (20 mL). The brine was extracted with ethyl acetate
pooled, dried with anhydrous sodium sulfate, and evaporated. (2 × 20 mL), the organic phases pooled, dried with anhydrous
The crude product was purified with column chromatography sodium sulfate, and evaporated. The crude product was purified
(heptane/ethyl acetate 2:1) to give 10k (94 mg, 73%) as a white with column chromatography (heptane/ethyl acetate 2:1) to give
solid. [α]D20 −22 (c 1.0, CHCl3); 1H NMR (400 MHz, CDCl3) δ 10m (72 mg, 53%) as a white solid. [α]D20 −45 (c 1.0, CH2Cl2);
8.08 (s, 1H), 7.85–7.80 (m, 2H), 7.65–7.60 (m, 2H), 7.46–7.15 1H NMR (400 MHz, CDCl3) δ 8.03 (s, 1H), 7.86–7.80 (m. 2H),
(m, 20H), 4.98 (d, J = 7.1 Hz, 1H), 4.95 (d, J = 6.1 Hz, 1H), 7.69–7.58 (m, 4H), 7.53–7.46 (m, 2H), 7.44–7.15 (m, 21H),
4.82 (d, J = 11.6 Hz, 1H), 4.77–4.69 (m, 4H), 4.56 (d, J = 11.4 4.97 (d, J = 7.1 Hz, 1H), 4.94 (d, J = 6.1 Hz, 1H), 4.80 (d, J =
Hz, 1H), 4.54–4.51 (m, 2H), 4.02 (d, J = 2.4 Hz, 1H, H5), 11.7 Hz, 1H), 4.76–4.69 (m, 4H), 4.56 (d, J = 11.5 Hz, 1H),
3.78–3.56 (m, 6H); 13C NMR (100 MHz, CDCl3) δ 146.3, 4.52–4.48 (m, 2H), 4.00 (d, J = 1.9 Hz, 1H, H5), 3.77–3.55 (m,
138.4, 138.0, 137.9, 137.7, 134.3, 132.9, 129.8, 129.4, 129.1, 6H); 13C NMR (100 MHz, CDCl3) δ 147.4, 140.8, 140.6, 138.5,
128.7, 128.58, 128.56, 128.53, 128.49, 128.4, 128.02, 127.96, 138.0, 137.9, 137.7, 129.9, 128.8, 128.54, 128.53, 128.50,
127.9, 127.84, 127.75, 127.6, 127.5, 125.8, 122.2, 84.5, 77.5, 128.3, 128.0, 127.90, 127.85, 127.58, 127.55, 127.51, 127.48,
77.2, 75.5, 74.72, 74.66, 73.8, 73.6, 72.3, 69.2, 51.2; 19F NMR 127.4, 127.0, 126.11, 121.4, 84.5, 77.7, 772, 75.4, 74.8, 74.6,
(376 MHz, CD3OD) δ −62.48; HRMS (m/z): [M + H]+ calcd for 73.7, 73.6, 72.2, 69.1, 51.1; HRMS (m/z): [M + H]+ calcd for
750.3162; found, 750.3155.
758.3600; found, 758.3594.
3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-(4-naphth-1-yl-1H- 3,4,5,7-Tetra-O-benzyl-1,2-dideoxy-1-(4-napht-2-yl-1H-
1,2,3-triazol-1-yl)-β-D-galactoheptulose (10l): Compound 9 1,2,3-triazol-1-yl)-β-D-galactoheptulose (10n): Compound 9
(228 mg, 0.393 mmol), 1-ethynylnaphtalene (63 mg, (150 mg, 0.259 mmol), 2-ethynylnaphthalene (43 mg,
0.413 mmol), and copper(I) iodide (15 mg, 0.079 mmol) were 0.285 mmol), and copper(I) iodide (10 mg, 0.052 mmol) were
dissolved in dry acetonitrile (4 mL) under nitrogen, triethyl- dissolved in dry acetonitrile (4 mL) under nitrogen, triethyl-
amine (110 μL, 0.786 mmol) was added, and the reaction left at amine (72 μL, 0.518 mmol) was added, and the reaction left at
60 °C overnight. Upon completion, the reaction mixture was 60 °C overnight. Upon completion, the reaction mixture was
poured into ethyl acetate (20 mL) and washed with brine poured into ethyl acetate (20 mL) and washed with brine
(20 mL). The brine was extracted with ethyl acetate (20 mL). The brine was extracted with ethyl acetate
(2 × 20 mL), the organic phases pooled, dried with anhydrous (2 × 20 mL), the organic phases pooled, dried with anhydrous
sodium sulfate, and evaporated. The crude product was purified sodium sulfate, and evaporated. The crude product was purified
1058

Beilstein J. Org. Chem. 2019, 15, 1046–1060.
with column chromatography (heptane/ethyl acetate 3:1) to give ring in an orientation identical to that in lactose and with the
10n (143 mg of product with a yield of, 75%) as a sticky clear phenyl triazole rings extending into bulk between the Trp68-
solid. [α]D20 −25 (c 1.6,CH3CN); 1H NMR (400 MHz, CDCl3) Gly69-Thr70 and His52 was subjected to a 200 ns molecular
δ 8.33 (s, 1H), 8.11 (s, 1H), 7.90–7.84 (m, 4H), 7.55–7.48 (m, dynamics simulation. Non-minimized conformations of 1b were
2H), 7.47–7.27 (m, 15H), 7.26–7.21 (m, 2H), 7.18–7.13 (m, positioned to replace lactose in the binding site of galectin-3
3H), 4.98 (d, J = 3.6 Hz, 1H), 4.95 (d, J = 4.7 Hz, 1H), (pdb id 1KJL) with the galactose ring in an orientation identical
4.83–4.71 (m, 5H), 4.57 (d, J = 11.7 Hz, 1H), 4.51 (s, 2H), 4.01 to that in N-acetyllactosamine and with the phenyl triazole rings
(d, J = 0.9 Hz, 1H, H5), 3.75–3.58 (m, 6H); 13C NMR extending into bulk between the Trp68-Gly69-Thr70 and His52
(100 MHz, CDCl3) δ 147.7, 138.5, 138.0, 137.9, 137.8, 133.6, was subjected to a 200 ns molecular dynamics simulation.
133.1, 128.7, 128.54, 128.49, 128.34, 128.28, 128.2, 128.0, Energy minimizations of four different MD snapshots of 1b in
127.9, 127.8, 127.7, 127.59, 127.57, 127.5, 126.3, 126.0, 124.4, complex with galectin-1 and with galectin-3 were performed
124.0, 121.7, 84.6, 77.8, 77.2, 75.4, 74.9, 74.6, 73.7, 73.6, 73.3, with the OPLS3 force field in MacroModel (performed with the
72.3, 69.1, 51.2; HRMS (m/z): [M + H]+ calcd for 732.3443; OPLS3 force field in MacroModel (Schrödinger Release 2017-
found, 732.3443.
3: MacroModel, Schrödinger, LLC, New York, NY, 2017)
using default settings.
Fluorescence polarization experiments
Human galectin-1 [36] and galectin-3 [37] were expressed and
purified as earlier described. Fluorescence polarization experi-
ments were performed on a PheraStarFS plate reader with soft-
ware PHERAstar Mars version 2.10 R3 (BMG, Offenburg,
Germany). Specific experimental conditions were a galectin-1
concentration of 0.5 µM together with the fluorescent probe
(3,3’-dideoxy-3-[4-(fluorescein-5-ylcarbonylaminomethyl)-1H-
1,2,3-triazol-1-yl]-3’-(3,5-dimethoxybenzamido)-1,1’-
sulfanediyl-di-β-D-galactopyranoside [36]) concentration of
20 nM and a galectin-3 concentration of 0.2 µM together with
the fluorescent probe (3,3’-dideoxy-3-[4-(fluorescein-5-ylcar-
bonylaminomethyl)-1H-1,2,3-triazol-1-yl]-3’-(3,5-dimethoxy-
benzamido)-1,1’-sulfanediyl-di-β-D-galactopyranoside) concen-
tration of 20 nM, respectively. Inhibitors were dissolved in
dimethyl sulfoxide (analytical grade) to a concentration of
20 mM, diluted with PBS to 3–6 different concentrations, and
tested in duplicate twice for galectin affinity using a competi-
tive fluorescence polarization assay as earlier described [33].
The highest inhibitor concentrations tested were 1.5 mM due to
solubility limitations at higher concentration. Dissociation con-
stants average and SEM were calculated from two to eight
single point measurements showing between 20–80% inhibi-
tion.
Supporting Information
Supporting Information File 1
Copies of 1H NMR and 13C NMR spectra for compounds
1–10.
[https://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-15-102-S1.pdf]
Acknowledgements
The authors thank Sofia Essén for assistance with HRMS and
UPLC/MS-measurements and Barbro Kahl-Knutson for the
fluorescence polarization assay. The Swedish Research Council
(Grant No. 621-2012-2978 and 621-2016-03667), the Royal
Physiographic Society, Lund, Sweden, a project grant awarded
by the Knut and Alice Wallenberg Foundation (KAW
2013.0022), and Galecto Biotech AB, Sweden.
ORCID® iDs
Alexander Dahlqvist - https://orcid.org/0000-0002-1767-2503
Axel Furevi - https://orcid.org/0000-0002-0904-9498
Niklas Warlin - https://orcid.org/0000-0001-8041-370X
Hakon Leffler - https://orcid.org/0000-0003-4482-8945
Ulf J. Nilsson - https://orcid.org/0000-0001-5815-9522
Molecular modelling
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2005, 15, 3344–3346. doi:10.1016/j.bmcl.2005.05.084
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Kahl-Knutson, B.; Öberg, C. T.; Sundin, A.; Nilsson, R.;
Nordberg-Karlsson, E.; Nilsson, U. J.; Karlsson, A.; Rini, J. M.;
Leffler, H. J. Biol. Chem. 2010, 285, 35079–35091.
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19.Cumpstey, I.; Sundin, A.; Leffler, H.; Nilsson, U. J.
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