α-D-Mannoside ligands with a valency ranging from one to three: Synthesis and hemagglutination inhibitory properties

Article abstract of DOI:10.1016/j.carres.2021.108396

Six mono-, di-, and trivalent α-D-mannopyranosyl conjugates built on aromatic scaffolds were synthesized in excellent yields by Cu(I) catalyzed azide-alkyne cycloaddition reaction (CuAAC). These conjugates were designed to have unique, flexible tails that combine a mid-tail triazole ring, to interact with the tyrosine gate, with a terminal phenyl group armed with benzylic hydroxyl groups to avoid solubility problems as well as to provide options to connect to other supports. Biological evaluation of the prepared conjugates in hemagglutination inhibition (HAI) assay revealed that potency increases with valency and the trivalent ligand 6d (HAI = 0.005 mM) is approximately sevenfold better than the best meta-oriented monovalent analogues 2d and 4d (HAI ≈ 0.033 mM) and so may serve as a good starting point to find new lead ligands.

Full text of DOI:10.1016/j.carres.2021.108396

Carbohydrate Research 508 (2021) 108396
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Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
α
-D-Mannoside ligands with a valency ranging from one to three: Synthesis
and hemagglutination inhibitory properties
Hussein Al-Mughaid*, Maha Khazaaleh
Department of Chemistry, Jordan University of Science and Technology, PO Box 3030, Irbid 22110, Jordan
A R T I C L E I N F O
A B S T R A C T
Keywords:
Six mono-, di-, and trivalent α-D-mannopyranosyl conjugates built on aromatic scaffolds were synthesized in
Click chemistry
FimH
excellent yields by Cu(I) catalyzed azide-alkyne cycloaddition reaction (CuAAC). These conjugates were designed
to have unique, flexible tails that combine a mid-tail triazole ring, to interact with the tyrosine gate, with a
terminal phenyl group armed with benzylic hydroxyl groups to avoid solubility problems as well as to provide
options to connect to other supports. Biological evaluation of the prepared conjugates in hemagglutination in-
hibition (HAI) assay revealed that potency increases with valency and the trivalent ligand 6d (HAI = 0.005 mM)
is approximately sevenfold better than the best meta-oriented monovalent analogues 2d and 4d (HAI ≈ 0.033
mM) and so may serve as a good starting point to find new lead ligands.
Multivalency
Triazolyl α-D-mannosides
1. Introduction
FimH has an adjacent extended hydrophobic region, compounds
designed to bind to this site are poorly recognized by the many other
The interactions between carbohydrates and their protein receptors
play a key biological role in cell recognition and adhesion [1]. At the
monosaccharide level these interactions are usually weak with dissoci-
ation constants in the millimolar to micromolar range [2]. Biological
ligands present multiple copies of the monosaccharide to multiple
binding sites on the protein to achieve sufficient binding strength. To
displace or compete with the natural multivalent ligands [3,4], synthetic
ligands need to combine better binding per unit with multivalent
presentation.
mannose-binding receptors in humans [17]. Initial weak binding is
followed by a conformational change in FimH to a state that gives the
strong binding “catch-bond binding” that is critical for attachment in the
high-sheer environment of the urinary tract [18,19]. Following binding,
a conformational change in the cell surfaces [20], allows the bacteria to
enter and establish sub-surface colonies that are difficult to eradicate.
Previous studies have shown that FimH-mediated adhesion could be
inhibited by natural or synthetic ligands. Since the discovery that phenyl
α
-D-mannopyranosides, particularly the 2-chloro-4-nitro derivative,
Urinary tract infections (UTIs), are one of the most common bacterial
infections [5–7], are mainly caused by strains of the gram negative
uropathogenic bacteria, Escherichia coli (UPEC) [8,9]. UPEC bind to the
urinary tract endothelial surface through the adhesin protein FimH at
the tip of Type 1 fimbriae or pili [10], complex proteinacious hair-like
structures which extend from the surfaces of the bacterial cells. FimH
bound FimH effectively [21], most research in this area has focused on
the synthesis of multivalent mannosides to try to obtain potent FimH
antagonists [22–29]. In this strategy, mannosides are grafted in multiple
copies onto common scaffolds, particularly aromatic ones [30].
During the last three decades, several families of monovalent α-D-
mannoside ligands with diverse mannosyl lipophilic aglycones have
been synthesized to evaluate the utility of anti-adhesion strategies
is a lectin that recognizes terminal α-linked D-mannopyranoside oligo-
saccharides of the N-linked glycoprotein Uroplakin Ia (UPIa) on the
endothelial surface [11]. The mannose-binding pocket of FimH is
adjacent to a hydrophobic area known as the tyrosine gate that is
bordered by two tyrosines (Tyr48 and Tyr137) and one isoleucine
(Ile52) [12]. The non-polar faces of the non-terminal mannopyranoses
of the UPI oligosaccharides have binding interactions with the tyrosines
in the tyrosine gate [13–16]. Because the mannose-binding pocket of
against E. coli, such as alkyl
α
-D-mannoside [31], biphenyl
α
-D-manno-
-D-mannosides
α-D-mannosides [39],
sides [32–36], indolinylphenyl and (aza)indolylphenyl
α
[37], thiazolylaminomannosides [38], branched
isoquinolone-based mannosides [40], squaric acid monoamide manno-
sides [41], mannosyl triazoles [42], and others [43–47].
Since the nature of the mannosyl aglycone which could be elongated
alkyl, substituted aromatic, or extended aromatic plays a crucial role in
* Corresponding author.
E-mail address: al-mughaid@just.edu.jo (H. Al-Mughaid).
https://doi.org/10.1016/j.carres.2021.108396
Received 17 May 2021; Received in revised form 29 June 2021; Accepted 6 July 2021
Available online 8 July 2021
0008-6215/© 2021 Published by Elsevier Ltd.

H. Al-Mughaid and M. Khazaaleh
Carbohydrate Research 508 (2021) 108396
determining the binding affinity, altering its structure will influence the
inhibitory potency toward type 1 fimbriated E. coli. The Cu(I)-catalyzed
azide-alkyne [1,3] dipolar cycloaddition (CuAAC) reaction has become
a powerful tool in the regioselective formation of 1,4-disubstituted
1,2,3-triazoles. Therefore, this highly efficient reaction has emerged as
an effecient conjugation strategy for the synthesis of 1,2,3- triazole-
containing glycoconjugates [48].
benzyl alcohols 1b, 2b, and 3b in yields of 69%, 72%, and 77%,
respectively.
In the second series, the methyl esters 4, 5, and 6, prepared under
conventional conditions (H2SO4, (cat.), MeOH, reflux) from their
hydroxy-acids, were first O-alkylated at the phenolic position as for 1b,
2b, and 3b to give the alkynyl-terminated esters 4a, 5a, and 6a in good
yields. Subsequent treatment with LiAlH4 in refluxing THF provided the
alkynyl-terminated benzyl alcohols 4b, 5b [51], and 6b in yields of 93%,
88% and 93%, respectively (Scheme 2).
Following our interest in using click chemistry for the synthesis of
mannoside ligands [49,50], we describe the synthesis of α-D-mannoside
ligands using Cu(I)-catalyzed click reaction here. These mannosides
have a flexible aglycone that combines a triazole ring positioned
midway between the anomeric oxygens and the terminal phenyl groups
that bear benzylic hydroxyl groups to ensure water solubility, to take
advantage of polar interactions (H-bonds with the hydroxyl groups of
Thr51 or Tyr137), and to provide options for additional connections to
other supports. FimH ligands where the linker between the anomeric
oxygen and the triazole ring is two methylene groups showed 2- to 4-fold
higher affinity compared to their counterparts with one methylene
group, while reduction in affinity up to 8-fold was observed when the
triazole ring is directly attached to the anomeric center [42]. On the
basis of these findings and also because X-ray studies suggested that
stronger interactions could be achieved if this linkage was longer, we
investigated whether moving from two methylene groups to three in the
linker between the anomeric oxygen and the triazole ring was beneficial
for binding. The next aim was to explore the effect of stepwise increases
in valency, from mono-to trivalency. To this end, we prepared six
mannosyl conjugates (Fig. 1) with valencies ranging from one to three
and with similar distances between the binding epitopes. The binding
potencies of these conjugates were evaluated by a hemagglutination
inhibition (HAI) assay.
2.2. Synthesis of mannosyl ligands (1d-6d) via click chemistry
The efficient CuAAC click reaction [52,53] was implemented to
tether alkynyl armed benzyl alcohols (1b-4b) to mannosyl azide 7 [54].
Thus, CuAAC conjugation of 7 and the various synthesized terminal
alkynes was easily realized under the promotion of sodium ascorbate,
copper (II) sulphate pentahydrate in a mixture of THF and H2O at room
temperature, affording the desired acetylated α-D-mannosides 1c-4c in
yields of 86%, 88%, 90% and 88%, respectively. Subsequent removal of
´
acetyl groups under Zemplen conditions (MeONa, MeOH, rt) gave the
acetyl free mannosides 1d-4d in excellent yields as shown in Scheme 3.
Similarly, the dimer 5c was also obtained by reacting terminal
alkyne 5b with two equivalents of azide 7 under the same conditions
described for the synthesis of 1c-4c in a yield of 82%. Removal of acetyl
groups as above furnished dimer 5d in 88% yield as illustrated in
Scheme 4.
While compound 6c, the trimer resulting from three simultaneous
click reactions between azide 7 and terminal alkyne 6b was then ob-
tained in 76% yield. Removal of acetyl groups as for dimer 5c yielded
the desired acetyl free trimer 6d in 84% yield as shown in Scheme 5.
The proposed structures of acetyl-protected mannosides 1c-6c were
confirmed by the appearance of the signals of triazolyl protons at 7.39,
7.42, 7.32, 7.42, 7.39, and 7.48 ppm, respectively, in their 1H NMR
spectra. In the 13C NMR spectra, the triazolyl carbons appeared at 147.1
and 121.5 ppm for 1c, 147.4 and 121.4 ppm for 2c, 147.1 and 121.3
ppm for 3c, 147.3 and 121.5 ppm for 4c, 147.2 and 121.3 ppm for 5c,
147.8, 147.1 ppm and 121.3 and 121.2 ppm for 6c, further confirming
their structures. While removal of the acetates from mannosides 1c-6c to
give 1d-6d ligands was confirmed by the disappearance of methyl pro-
tons in 1H NMR spectra and the methyl carbons as well as the carbonyl
2. Results and discussion
2.1. Synthesis of terminal alkynes
Two series of alkynyl-terminated benzyl alcohols were envisioned for
the installation of mannose moiety. As shown in Scheme 1, the first
series was prepared by NaBH4 reduction of the commercially available
hydroxy-aldehydes 1, 2, and 3 to the corresponding hydroxy-benzyl
alcohols 1a, 2a, and 3a. Selective O-alkylation at the phenolic posi-
tion using 5-chloropent-1-yne, K2CO3, and a catalytic amount of (Bu)4NI
in refluxing acetone furnished the corresponding alkynyl-terminated
carbons (C O) in 13C NMR spectra.
–
–
Fig. 1. Structures of mannosyl conjugates (1d-6d).
2

H. Al-Mughaid and M. Khazaaleh
Carbohydrate Research 508 (2021) 108396
Scheme 1. Reaction conditions: (a) NaBH4, MeOH, 0 ◦C-r.t.; (b) 5-chloropent-1-yne, K2CO3, (Bu)4NI (cat.), acetone, reflux (48 h).
Scheme 2. Reaction conditions: (a) 5-chloropent-1-yne, K2CO3, (Bu)4NI (cat.), acetone, reflux (48 h), (b) LiAlH4, THF, reflux (4 h).
2.3. Biological assay results
guinea pig erythrocytes. The inhibition titer is then compared to methyl
α
-D-mannoside (MeαMan) as a reference inhibitor and therefore, leading
Mannosylated ligands (1d-6d) were evaluated as inhibitors of the
hemagglutination [44,50,55] of guinea pig erythrocytes by type 1 pili-
ated E. coli strain HB101 (pPKI4). The result of the hemagglutination
(HA) test is expressed as inhibition titer (HAI) that indicates the lowest
concentration required to prevent UPEC FimH from agglutinating
to relative inhibition titer (RIT) as shown in Table 1.
The inhibitory potency of mannosylated ligands (1d-6d) was found
to be much higher than that of the respective MeαMan. In the series of
monovalent derivatives, of the three positional isomers (1d-3d), the
meta (2d) exhibited the highest activity and showed a 118-fold
3

H. Al-Mughaid and M. Khazaaleh
Carbohydrate Research 508 (2021) 108396
Scheme 3. Reaction conditions: (a) CuSO4⋅5H2O, sodium ascorbate, H2O-THF (1:1), rt, overnight, (b) MeONa, MeOH, rt, (4h).
Scheme 4. Reaction conditions: (a) CuSO4⋅5H2O, sodium ascorbate, H2O-THF (1:1), rt, overnight, (b) MeONa, MeOH, rt, (4h).
Scheme 5. Reaction conditions: (a) CuSO4⋅ 5H2O, sodium ascorbate, H2O-THF (1:1), rt, overnight, (b) MeONa, MeOH, rt, (4h).
4

H. Al-Mughaid and M. Khazaaleh
Carbohydrate Research 508 (2021) 108396
improvement in activity relative to the reference ligand Me
αMan. It
3. Conclusions
could be hypothesized that ligand 2d more readily interacted with the
tyrosine gate. On the other hand, addition of a second methyl alcohol
moiety in the other meta positions of ligand (2d) such as ligand (4d)
displayed similar reactivity as observed for 2d. Presumably, the agly-
cone of ligand 4d adopt a conformation in which the second meta-ori-
ented hydroxymethyl group does not interact with the tyrosine gate. As
expected, a significant enhancement was observed for multimers 5d and
6d through multivalency or cluster effect. The enhancement in activity
that can be achieved with appropriate synthetic multivalent ligands as
compared to the corresponding monovalent ligands is known as the
“glycoside cluster effect” [2]. Clearly, multivalent ligands are more
advantageous than monovalent ones because of their enormous binding
strength. In other words, a multivalent ligand can bind to one or a
number of receptors with enhanced functional affinity and can promote
receptor clustering. Thus, inhibitory potency increases with valency and
In this report, we have described an efficient and experimentally
simple synthesis of -D-mannoside ligands built on aromatic platforms
with a valency ranging from one to three. The flexible and unique
triazole-containing linker to the -mannosides presented on these li-
gands was generated through Cu(I)-catalyzed click reaction between 3-
α
α
azidopropyl
α-D-mannopyranoside and various alkyne-terminated
benzyl alcohols. Binding potencies of the obtained mannosylated li-
gands (1d-6d) listed in Table 1 toward type 1 fimbriated E. coli were
determined using a hemagglutination assay. All tested ligands showed
improved affinity (HAI values of 0.12–0.005 mM) as compared to
MeαMan. Unlike their monovalent analogues, the dimer 5d (HAI =
0.023 mM) and the trimer 6d (HAI = 0.005 mM) displayed an increase
in binding potencies (cluster effect). The results obtained in this study,
along with other triazolyl mannosides reported in the literature, show
that the distance between the anomeric oxygen and the triazole ring was
a critical factor for affinity. Work in varying positions of a triazole ring
and O-substitution of the terminal methyl alcohol moiety with various
functionalities in the aglycone backbone is currently underway in our
laboratory and will be reported in the near future.
the trivalent ligand 6d is 800-fold better inhibitor than Me
means 267-fold improvement when reported on a mannose molar basis.
In a direct comparison, heptyl -D-mannopyranoside (HM), was found to
be 29 times more effective than Me Man [42]. Triazolyl mannosides
αMan, which
α
α
with N-substituents on the triazole rings being substituted on the inner
phenyl ring in the biphenyl systems have been evaluated before but none
surpass the inhibitory potency of the monovalent HM. In particular,
those containing a triazolyl-ethyl moiety showed 2- to 4-fold reduction
in affinity when compared to HM and up to 17-fold improvement in
4. Experimental section
4.1. Hemagglutination tests
affinity when compared to MeαMan (Fig. 2).
The best monovalent ligands prepared here 2d and 4d (almost
A recombinant type 1 fimbriated E. coli strain, E. coli HB 101 (pPKl4),
used was cultured according to the protocol reported in the litera-
ture.[44,50,55] Guinea pig erythrocytes were isolated and used as described
[44,50,55]. Hemagglutination tests were performed in V-shaped 96-well
microtitre plates (Nunc). The ligands were suspended in distilled
identical in performance) were found to be approximately 120 times
better than the reference ligand MeαMan and 4 times better than HM
according to the data reported by Schwardt et al. [42] But found less
inhibiting than the best ortho-substituted biphenyl derivatives being
substituted with electronegative substituents on the remote ring or
phenyl mannosides terminated with extended planar substituents [40,
56]. Our results indicate that attempts should be made to determine the
best position of N-substituted triazole ring in the aglycone backbone as
well as the best chemical structure for the N-substituents on the triazole
rings.
deionized water and serially diluted solutions (10
μl) were thoroughly
mixed with bacteria suspension (10 l) in wells. After 10 min, guinea pig
μ
erythrocytes (10 μl) were added and hemagglutination was read after
approximately 10 min at room temperature.
4.2. Synthesis
Table 1
4.2.1. General information
HAI of MeαMan and synthetic mannosylated ligands 1d-6d.
All chemicals were obtained from commercial sources and used as
received without further purification, unless stated otherwise.
Dichloromethane (DCM) was first dried with calcium chloride, and
refluxed over calcium hydride for 1 h followed by distillation over
activated 4 Å molecular sieves. Tetrahydrofuran (THF) was distilled
from sodium/benzophenone ketyl prior to use. Melting points were
determined with a SMP3 melting point apparatus and are uncorrected
[1].H and[13]C NMR spectra were recorded at 300 K in 5 mm NMR
tubes on Bruker Avance 400 MHz spectrometer operating at 400 MHz
and 100 MHz for[1]H NMR spectra and[13]C NMR spectra, respec-
tively. CDCl3 was used as a solvent with TMS as internal reference unless
otherwise indicated. The carbon and hydrogen atoms were assigned
Tested ligand
Valency
HAI titera (mM)
RITb
RIT/Manc
Me
1d
2d
3d
4d
5d
6d
αMan
1
1
1
1
1
2
3
4.0
1
1
0.12
33
33
0.034
0.091
0.033
0.023
0.005
118
44
118
44
121
174
800
121
87
267
[a]
[b]
[c]
Based on the average value from three independent experiments.
Based on the reference ligand MeαMan.
Man = mannose.
Fig. 2. Chemical structures of some previously reported mannosides containing triazolyl-methyl and ethyl moieties [42].
5

H. Al-Mughaid and M. Khazaaleh
Carbohydrate Research 508 (2021) 108396
following analysis of their one dimensional (1H, 13C) and two dimen-
sional (COSY, HSQC, and HMBC) NMR spectral data. Chemical shifts are
given in parts per million (ppm) ( ±0.01 ppm). Data are presented as
follows: chemical shift, multiplicity (s = singlet, bs = broad singlet, d =
doublet, t = triplet, q = quartet, m = multiplet, dd = doublet of dou-
blets), coupling constant (J) in Hertz (Hz). ESI high-resolution mass
spectra were recorded on a Bruker Micro-TOF mass spectrometer using
electrospray ionization. MALDI mass spectra were obtained using an
chromatography (EtOAc:Hexane, 2:1, Rf = 0.9) yielded the title com-
pound 4a as yellow oil (5.25 g, 80%); 1H NMR: δ = 8.25, 7.74 (2s, 3H,
phenyl-H), 4.16 (t, J = 6 Hz, 2H, PhOCH2), 3.93 (s, 6H, 2 x OCH3), 2.43
(t, J = 4 Hz, 2H, propargylic-CH2), 2.06–2.00 (m, 3H, CH2CH2CH2,
13
–
acetylenic-H); C NMR: δ = 166.2 (2 x C O), 159.0, 131.8, 123.0,
–
119.9 (phenyl-C), 83.2 (HCC), 69.2 (HCC), 66.8 (PhOCH2), 52.4 (2 x
OCH3), 28.1 (CH2CH2CH2), 15.2 (propargylic-CH2). HRMS (ESI): m/z
calcd for C15H16NaO5 [M+Na]+ 299.0895, found: m/z 299.0903.
α
-cyano-4-hydroxycinnamic acid matrix with acquisition in the reflec-
tron mode. Calibration was done with a peptide mixture. The reactions
were monitored by thin layer chromatography (TLC) on Merk silica gel
60 F254 plates. Compounds were visualized by UV light (λ = 254 nm) and
were located by spraying the plate with a solution of 2% ceric sulphate
in 1 M H2SO4 followed by heating on a hot plate until color developed.
Compounds were purified on silica gel (70–230 mesh) by column
chromatography using specified eluents.
4.2.2.5. Methyl 3,4,5-tris(pent-4-ynyloxy)benzoate (6a). According to
the general procedure described above, from compound 6 (2.68 g, 14.6
mmol), K2CO3 (20.0 g, 10 equiv.), 5-chloropent-1-yne (4.6 mL, 43.68
mmol, 3 equiv.), and 120 mg of 18-crown-6 in 500 mL of acetone.
Column chromatography (EtOAc:Hexane, 1:4, Rf = 0.33) yielded the
title compound 6a as brown oil (4.18 g, 75%); 1H NMR: δ = 7.28 (s, 2H,
phenyl-H), 4.13 (t, J = 6 Hz, 6H, 3 x PhOCH2), 3.93 (s, 3H, OCH3), 2.43
(t, J = 7 Hz, 6H, propargylic-CH2), 2.05–1.92 (m, 9H, 3 x CH2CH2CH2, 3
x acetylenic-H); 13C NMR: δ = 166.4 C O), 152.4, 141.6, 124.9, 107.9
–
–
4.2.2. General procedure for alkylation of benzyl alcohols (1a, 2a, and
3a)
(phenyl-C), 83.8, 83.1 (3 x HCC), 71.5, 69.1 (3 x HCC), 68.6, 67.2 (3 x
PhOCH2), 52.0 (OCH3), 29.2, 28.0 (3 x CH2CH2CH2), 15.1, 15.0 (3 x
propargylic-CH2). HRMS (ESI): m/z calcd for C23H26NaO5 [M+Na]+
405.1678, found: m/z 405.1695.
To a stirred solution of hydroxy-benzyl alcohols (1a, 2a, and 3a) in
acetone (200 mL), 5-chloropent-1-yne (1 equiv.), K2CO3 (3 equiv.) and a
catalytic amount of (Bu)4NI were added. The resulting reaction mixture
was refluxed for 60 h and cooled down to room temperature, filtered and
concentrated to dryness. Purification was then achieved by column
chromatography (EtOAc:Hexane, 2:1).
4.2.3. General procedure for reduction by Lithium Aluminum hydride
(LAH)
◦
To a suspension of LAH in anhydrous THF precooled to 0 C was
4.2.2.1. 2-(Pent-4-ynyloxy)phenylmethanol (1b). From compound 1a
(1.00 g, 8.06 mmol), 5-chloropent-1-yne (0.85 mL, 8.06 mmol), pale
yellow oil (1.05 g, 69%), Rf = 0.9 (EtOAc/Hexane, 2:1); 1H NMR: δ =
7.32–6.86 (m, 4H, phenyl-H), 4.67 (s, 2H, CH2OH), 4.07 (t, J = 5.9 Hz,
2H, PhOCH2), 2.40 (t, J = 4.8 Hz, 2H, propargylic-CH2), 2.04–1.99 (m,
3H, CH2CH2CH2, acetylenic-H); 13C NMR: δ = 156.2, 129.2, 128.5,
128.2, 120.5, 110.9 (phenyl-C), 83.3 (HCC), 69.1 (HCC), 66.0
(PhOCH2), 61.0 (CH2OH), 27.9 (CH2CH2CH2), 15.1 (propargylic- CH2).
HRMS (ESI): m/z calcd for C12H14NaO2 [M+Na]+ 213.0891, found: m/z
213.0894.
added a THF solution of the ester dropwise. Once the addition is com-
plete, the solution was allowed to warm up to rt and refluxed for 4 h
before being left to cool down. The reaction mixture was then acidified
by the addition of 10% H2SO4. The solvent was evaporated under vac-
uum and the resulting solution was extracted with CH2Cl2 (3 × 50 mL).
The combined organic extracts were dried over Na2SO4, filtered, and
concentrated.
4.2.3.1. 5-(Pent-4-ynyloxy)-1,3-benzenedimethanol (4b). The reaction
mixture of 4a (3.60 g, 13 mmol) and LAH (0.39 g, 10.4 mmol) in 200 mL
THF afforded the title compound 4b as a pale yellow oil (2.76 g, 93%)
after column chromatography (EtOAc, Rf = 0.7). 1H NMR: δ = 6.89, 6.79
(2s, 3H, Ar–H), 4.59 (2 x CH2OH), 4.05 (t, J = 6 Hz, 2H, PhOCH2), 2.37
(t, J = 4 Hz, 2H, propargylic-CH2), 1.99–1.95 (m, 3H, CH2CH2CH2,
acetylenic-H); 13C NMR: δ = 159.4, 142.9, 117.7, 112.3 (phenyl-C), 83.6
4.2.2.2. 3-(Pent-4-ynyloxy)phenylmethanol (2b). From compound 2a
(1.00 g, 8.06 mmol), 5-chloropent-1-yne (0.85 mL, 8.06 mmol), pale
brown oil, (1.11 g, 72%), Rf = 0.8 (EtOAc/Hexane, 2:1); 1H NMR: δ =
7.27–6.81 (m, 4H, phenyl-H), 4.59 (s, 2H, CH2OH), 4.05 (t, J = 6 Hz, 2H,
PhOCH2), 2.38 (t, J = 2.5 Hz, 2H, propargylic-CH2), 2.02–1.95 (m, 3H,
CH2CH2CH2, acetylenic-H); 13C NMR: δ = 159.1, 142.6, 129.6, 119.2,
113.7, 112.9 (phenyl-C), 83.6 (HCC), 69.0 (HCC), 66.1 (PhOCH2), 65.0
(CH2OH), 28.2 (CH2CH2CH2), 15.2 (propargylic-CH2). HRMS (ESI): m/z
calcd for C12H14NaO2 [M+Na]+ 213.0891, found: m/z 213.0897.
(HCC), 69.1 (HCC), 66.4 (PhOCH2), 65.1 (2
x CH2OH), 28.3
(CH2CH2CH2), 15.3 (propargylic-CH2). HRMS (ESI): m/z calcd for
C
13H16NaO3 [M+Na]+ 243.0997, found: m/z 243.1002.
4.2.3.2. (3,4,5-Tris(pent-4-ynyloxy)phenyl)methanol (6b). The reaction
mixture of 6a (6.27 g, 16.4 mmol) and LAH(0.49 g, 13 mmol) in 200 mL
THF afforded the title compound 6b as a pale yellow oil (5.39 g, 93%)
after column chromatography (EtOAc/Hexane, 1:1, Rf = 0.53). 1H NMR:
δ = 6.59 (s, 2H, phenyl-H), 4.57 (s, 2H, CH2OH), 4.08 (t, J = 4 Hz, 6H, 3
x PhOCH2), 2.45 (t, J = 8 Hz, 6H, propargylic-CH2), 2.07–1.96 (m, 9H, 3
x CH2CH2CH2, 3 x acetylenic-H); 13C NMR: δ = 152.7, 136.7, 136.5,
105.0 (phenyl-C), 84.1, 83.4 (3 x HCC), 71.6, 69.0 (3 x HCC), 68.5, 67.1
(3 x PhOCH2), 64.9 (CH2OH), 29.2, 28.1 (3 x CH2CH2CH2), 15.1 (3 x
propargylic-CH2). HRMS (ESI): m/z calcd for C22H26NaO4 [M+Na]+
377.1729, found: m/z 377.1746.
4.2.2.3. 4-(Pent-4-ynyloxy)phenylmethanol (3b). From compound 3a
(1.00 g, 8.06 mmol), 5-chloropent-1-yne (0.85 mL, 8.06 mmol), pale
yellow solid (1.18 g, 77%); m.p 53–56 ◦C; Rf = 0.7 (EtOAc/Hexane, 2:1);
1H NMR: δ = 7.26 (d, J = 8 Hz, 2H, phenyl-H), 6.88 (d, J = 8 Hz, 2H,
phenyl-H), 4.57 (s, 2H, CH2OH), 4.06 (t, J = 8 Hz, 2H, PhOCH2), 2.40 (t,
J = 4 Hz, 2H, propargylic-CH2), 2.02–1.98 (m, 3H, CH2CH2CH2,
acetylenic-H); 13C NMR δ = 158.5, 133.3, 128.7, 114.6 (phenyl-C), 83.6
(HCC), 69.0 (HCC), 66.2 (PhOCH2), 65.0 (CH2OH), 28.2 (CH2CH2CH2),
15.2 (propargylic-CH2). HRMS (ESI): m/z calcd for C12H14NaO2
[M+Na]+ 213.0891, found: m/z 213.0898.
4.2.4. General procedure for the synthesis of mannosides (1c-6c) by click
chemistry
4.2.2.4. Dimethyl 5-(pent-4-ynyloxy)isophthalate (4a). According to the
general procedure described above, from compound 4 (5.25 g, 25.0
mmol), 5-chloropent-1-yne (2.6 mL, 25 mmol). Column
To a stirred solution of alkynyl-terminated benzyl alcohol and azido
mannoside (1 equiv. for 1c-4c, 2 equiv. for 5c, and 3 equiv. for 6c) in
6

H. Al-Mughaid and M. Khazaaleh
Carbohydrate Research 508 (2021) 108396
THF (40 mL) was added sodium ascorbate (154 mg) followed by copper
(II) sulphate pentahydrate (77 mg, in 40 mL of H2O) in one portion and
the resulting heterogeneous mixture was stirred vigorously for 24 h. THF
was then removed under reduced pressure and CH2Cl2 (50 mL) was
added. The organic layer was separated, dried over MgSO4 and filtered.
The filtrate was then concentrated and the resulting residue was purified
by column chromatography.
J = 12.3, 5.1 Hz, 1H, H-6a), 4.12 (dd, J = 12.2, 2 Hz, 1H, H-5), 3.99 (t, J
= 6 Hz, 2H, Ph-OCH2), 3.78–3.73 (m, 1H, OCH2), 3.47–3.42 (m, 1H,
OCH2), 2.88 (t, J = 7.5 Hz, 2H, allylic-CH2), 2.86–2.05 (m, 16H,
CH2CH2CH2, COCH3). 13C NMR: δ = 170.8, 170.2, 170.1, 169.8 (4 x
–
–
–
C
O), 159.2 (phenyl-C), 147.3 (CH C), 143.0 (phenyl-C), 121.5
–
–
(CH C), 117.5, 111.8 (phenyl-C), 97.7 (C-1), 69.4 (C-5), 69.1 (C-2),
–
68.7 (C-3), 66.8 (PhOCH2), 66.0 (C-4), 64.6 (OCH2, CH2OH), 62.4 (C-6),
46.9 (NCH2), 29.9, 28.8, (2 x CH2CH2CH2), 22.0 (allylic-CH2), 20.9,
20.7, 20.7 (4 x COCH3). HRMS (ESI): m/z calcd for C30H41N3NaO13
[M+Na]+ 674.2537, found: m/z 674.2542.
4.2.4.1. Mannoside (1c). From compound 1b (0.50 g, 2.63 mmol),
azide 7 (1.13 g, 2.62 mmol), purification by column chromatography
(EtOAc/Hexane, 2:1, Rf = 0.2) afforded the title mannoside 1c as a pale
yellow viscous oil (1.31 g, 86%).1H NMR: δ = 7.39 (s, 1H, triazole-H),
7.30–6.85 (m, 4H, phenyl-H), 5.33–5.23 (m, 3H, H-2, H-3, H-4), 4.77
(s, 1H, H-1), 4.70 (s, 2H, CH2OH), 4.49–4.40 (m, 2H, CH2N), 4.29 (dd, J
= 12.2, 5.2 Hz, 1H, H-6a), 4.11–3.97 (m, 4H, H-5, H6b, Ph-OCH2),
3.75–3.70 (m, 1H, OCH2), 3.43–3.37 (m, 1H, OCH2), 2.94 (t, J = 7.4 Hz,
4.2.4.5. Dimer (5c). From compound 5b (0.30 g, 1.1 mmol), azide 7
(0.95 g, 2.2 mmol, 2 equiv.), purification by column chromatography
(EtOAc/Hexane, 4:1, Rf=0.1) afforded the title mannoside 5c as a
colorless viscous oil (1.02 g, 82%).1H NMR: δ = 7.39 (s, 2H, triazole-H),
6.51 (s, 2H, phenyl-H), 6.35 (s, 1H, phenyl-H), 5.34–5.25 (m, 6H, H-2,
H-3, H-4), 4.79 (s, 2H, H-1), 4.62 (s, 2H, CH2OH), 4.49–4.43 (m, 4H,
CH2N), 4.29 (dd, J = 12, 8 Hz, 2H, H-6a), 4.11–3.97 (m, 10H, H-5, H-6b,
Ph-OCH2), 3.77–3.73 (m, 2H, OCH2), 3.46–3.41 (m, 2H, OCH2), 2.89 (t,
J = 8 Hz, 4H, allylic-CH2), 2.33–1.85 (m, 32H, CH2CH2CH2, COCH3).
2H, allylic-CH2), 2.28–2.01 (m, 16H, CH2CH2CH2, COCH3).13C NMR: δ
–
= 170.7, 170.3, 170.1, 169.8 (4 x C O), 156.8 (phenyl-C), 147.1
–
–
–
–
–
(CH C), 129.5, 129.0, 128.9 (phenyl-C), 121.5 (CH C), 120.7, 111.3
(phenyl-C), 97.8 (C-1), 69.5 (C-5), 69.1 (C-2), 68.8 (C-3), 66.8
(PhOCH2), 66.0 (C-4), 64.7 (CH2OH), 62.5 (OCH2), 61.8 (C-6), 46.9
(NCH2), 29.9, 28.8, (2 x CH2CH2CH2), 22.2 (allylic- CH2), 21.0, 20.8 (4 x
COCH3). HRMS (ESI): m/z calcd for C29H39N3NaO12 [M+Na]+
644.2431, found: m/z 644.2434.
13
–
C NMR: δ = 170.6, 170.0, 169.9, 169.6 (8 x C O), 160.1 (phenyl-C),
–
–
–
–
–
147.2 (2 x CH C), 143.8 (phenyl-C), 121.3 (2 x CH C), 104.9, 100.3
(phenyl-C), 97.6 (2 x C-1), 69.3 (2 x C-5), 69.0 (2 x C-2), 68.6 (2 x C-3),
66.8 (2 x PhOCH2), 65.9 (2 x C-4), 64.7 (CH2OH), 64.6 (2 x OCH2), 62.3
(2 x C-6), 46.7 (2 x NCH2), 29.8, 28.7, (4 x CH2CH2CH2), 22.0 (2 x
allylic- CH2), 20.8, 20.6, 20.6 (8 x COCH3). HRMS (ESI): m/z calcd for
C51H70N6NaO23 [M+Na]+ 1157.4390, found: m/z 1157.4406.
4.2.4.2. Mannoside (2c). From compound 2b (0.50 g, 2.63 mmol),
azide 7 (1.13 g, 2.62 mmol), purification by column chromatography
(EtOAc/Hexane, 2:1, Rf = 0.3) afforded the title mannoside 2c as a
yellow viscous oil (1.34 g, 88%). 1H NMR: δ = 7.42 (s, 1H, triazole-H),
7.40–6.87 (m, 4H, phenyl-H), 5.38–5.31 (m, 3H, H-2, H-3, H-4), 4.84 (s,
1H, H-1), 4.73 (s, 2H, CH2OH), 4.55–4.47 (m, 2H, CH2N), 4.36 (dd, J =
12.1, 5.2 Hz, 1H, H-6a), 4.18–4.07 (m, 4H, H-5, H6b, Ph-OCH2),
3.81–3.78 (m, 1H, OCH2), 3.50–3.47 (m, 1H, OCH2), 2.98 (t, J = 7.5 Hz,
4.2.4.6. Trimer (6c). From compound 6b (0.31 g, 0.87 mmol), azide 7
(1.13 g, 2.61 mmol, 3 equiv.), purification by column chromatography
(EtOAc/CH3OH, 4:1, Rf=0.74) afforded the title mannoside 6c as a pale
yellow viscous oil (1.09 g, 76%).1H NMR: δ = 7.48 (s, 3H, triazole-H),
6.60 (s, 2H, phenyl-H), 5.32–5.27 (m, 9H, H-2, H-3, H-4), 4.82 (s, 3H,
H-1), 4.61 (s, 2H, CH2OH), 4.52–4.43 (m, 6H, CH2N), 4.31 (dd, J = 12.3,
5 Hz, 3H, H-6a), 4.13–4.04 (m, 12H, H-5, H-6b, Ph-OCH2), 3.77–3.74
(m, 3H, OCH2), 3.48–3.44 (m, 3H, OCH2), 3.01 (t, J = 7.7 Hz, 2H, allylic-
CH2), 2.93 (t, J = 7.3 Hz, 4H, allylic-CH2), 2.38–2.02 (m, 48H,
CH2CH2CH2, COCH3). 13C NMR: δ = 170.5, 169.9, 169.8, 169.6 (12 x
2H, allylic-CH2), 2.31–1.99 (m, 16H, CH2CH2CH2, COCH3). 13C NMR: δ
–
= 170.8, 170.3, 170.2, 169.8 (4 x C O), 159.3 (phenyl-C), 147.4
–
–
–
–
–
(CH C), 142.9, 129.6 (phenyl-C), 121.4 (CH C), 119.2, 113.8, 112.9
(phenyl-C), 97.8 (C-1), 69.5 (C-5), 69.1 (C-2), 68.8 (C-3), 66.8
(PhOCH2), 66.1 (C-4), 65.2 (CH2OH), 64.7 (OCH2), 62.5 (C-6), 46.9
(NCH2), 30.0, 28.8, (2 x CH2CH2CH2), 22.2 (allylic-CH2), 21.0, 20.8 (4 x
COCH3). HRMS (ESI): m/z calcd for C29H39N3NaO12 [M+Na]+
644.2431, found: m/z 644.2439.
–
–
–
C
–
O), 152.7 (phenyl-C), 147.8, 147.1 (3 x CH C), 136.9, 136.8
–
–
(phenyl-C), 121.3, 121.2 (3 x CH C), 105.1 (phenyl-C), 97.6 (3 x C-1),
72.5 (PhOCH2), 69.3 (3 x C-5), 69.0 (3 x C-2), 68.6 (3 x C-3), 67.8 (2 x
PhOCH2), 65.9 (3 x C-4), 64.6 (CH2OH), 64.8 (3 x OCH2), 62.3 (3 x C-6),
46.7 (3 x NCH2), 29.9, 29.8, 28.9, (6 x CH2CH2CH2), 22.3, 22.0 (3 x
allylic- CH2), 20.7, 20.6, 20.6, 20.5 (12 x COCH3). MALDI MS m/z calcd
for C73H101N9O34Na 1670.63, found: 1670.65.
4.2.4.3. Mannoside (3c). From compound 3b (1.00 g, 5.20 mmol),
azide 7 (2.30 g, 5.30 mmol), purification by column chromatography
(EtOAc/Hexane, 2:1, Rf = 0.3) afforded the title mannoside 3c as a pale
brown viscous oil (1.37 g, 90%).1H NMR: δ = 7.32 (s, 1H, triazole-H),
7.24 (d, J = 8.2 Hz, 2H, phenyl-H), 6.83 (d, J = 8.2 Hz, 2H, phenyl-
H), 5.27–5.21 (m, 3H, H-2, H-3, H-4), 4.74 (s, 1H, H-1), 4.57 (s, 2H,
CH2OH), 4.48–4.35 (m, 2H, CH2N), 4.26 (dd, J = 12.2, 5.2 Hz, 1H, H-
6a), 4.07–3.95 (m, 4H, H-5, H6b, Ph-OCH2), 3.72–3.67 (m, 1H, OCH2),
3.40–3.35 (m, 1H, OCH2), 2.88 (t, J = 7.4 Hz, 2H, allylic-CH2),
2.13–1.98 (m, 16H, CH2CH2CH2, COCH3). 13C NMR δ 170.6, 170.0,
4.2.5. General procedure for De-O-acetylation of mannosides (1c-6c)
To a stirred solution of a given acetylated mannoside in CH3OH (10
mL) and THF (10 mL) was added sodium methoxide (0.5 M in CH3OH, 1
mL), the reaction mixture was stirred overnight at room temperature
and neutralized with Amberlite IR-120 (H+), filtered and concentrated.
The resulting residue was then purified by column chromatography.
–
–
–
169.9, 169.9 (4 x C O), 158.2 (phenyl-C), 147.2 (CH C), 133.4, 128.4
–
–
–
(phenyl-C), 121.3 (CH C), 114.3 (phenyl-C), 97.5 (C-1), 69.3 (C-5),
4.2.5.1. Ligand (1d). From mannoside 1c (1.5 g, 2.4 mmol), column
chromatography (EtOAc/CH3OH, 2:1, Rf = 0.4) afforded ligand 1d as a
pale yellow viscous oil (90%).1H NMR(CD3OD): δ = 7.78 (s, 1H, triazole
H), 7.37–6.89 (m, 4H, Phenyl H), 4.71 (s, 1H, H-1), 4.65 (s, 2H, CH2OH),
4.47 (t, J = 8 Hz, 2H, NCH2), 4.03 (t, J = 6 Hz, 2H, PhOCH2), 3.84–3.58
(m, 6 H, H-2, H-3, H-4, H-5, H-6), 3.53–3.49 (m, 1H, OCH2), 3.42–3.37
(m, 1H, OCH2), 2.92 (t, J = 7.4 Hz, 2H, allylic CH2), 2.19–2.14 (m, 4H,
68.9 (C-2), 68.5 (C-3), 66.7 (PhOCH2), 65.8 (C-4), 64.5 (CH2OH) 64.4
(OCH2), 62.3 (C-6), 46.7 (NCH2), 29.7, 28.7, (2 x CH2CH2CH2), 21.9
(allylic-CH2), 20.7, 20.6, 20.5 (4 x COCH3). HRMS (ESI): m/z calcd for
C
29H39N3NaO12 [M+Na]+ 644.2431, found: m/z 644.2448.
4.2.4.4. Mannoside (4c). From compound 4b (0.36 g, 1.63 mmol),
azide 7 (0.70 g, 1.63 mmol), purification by column chromatography
(EtOAc, Rf = 0.2) afforded the title mannoside 4c as colorless viscous oil
(0.93 g, 88%).1H NMR: δ = 7.42 (s, 1H, triazole-H), 6.91 (s, 1H, phenyl-
H), 6.81 (s, 2H, phenyl-H), 5.34–5.28 (m, 3H, H-2, H-3, H-4), 4.82 (s,
1H, H-1), 4.62 (s, 2H, CH2OH), 4.50–4.45 (m, 3H, H6b, CH2N), 4.32 (dd,
CH2CH2CH2); 13C NMR(CD OD): δ = 157.6 (phenyl-C), 148.5 (CH C),
–
–
3
–
–
130.8, 129.5, 129.1 (phenyl-C), 123.6 (CH C), 121.5, 112.2 (phenyl-
C), 101.8 (C-1), 74.8 (C-5), 72.6 (C-3), 72.0 (C-2), 68.6 (PhOCH2), 67.9
(C-4), 65.2 (OCH2), 62.9 (HOCH2), 60.3 (C-6), 48.5 (NCH2), 31.2, 30.1,
(2 x CH2CH2CH2), 23.0 (allylic- CH2). HRMS (ESI): m/z calcd for
7

H. Al-Mughaid and M. Khazaaleh
Carbohydrate Research 508 (2021) 108396
C21H31N3NaO8 [M+Na]+ 476.2009, found: m/z 476.2016.
2H, allylic-CH2), 2.86 (t, J = 7 Hz, 4H, allylic-CH2), 2.13–2.02 (m, 12H,
6 x CH2CH2CH2); 13C NMR(CD3OD): δ = 154.0 (phenyl-C), 148.3 (3 x
–
–
–
CH C), 138.8, 137.7 (phenyl-C), 123.7, 123.5 (3 x CH C), 106.3,
–
4.2.5.2. Ligand (2d). From mannoside 2c (1.5 g, 2.4 mmol), column
chromatography (EtOAc/CH3OH, 2:1, Rf = 0.4) afforded ligand 2d as
colorless oil (90%). 1H NMR(CD3OD): δ = 7.77 (s, 1H, triazole H),
7.24–6.78 (m, 4H, Phenyl H), 4.71 (s, 1H, H-1), 4.56 (s, 2H, CH2OH),
4.47 (t, J = 6.6 Hz, 2H, NCH2), 3.99 (t, J = 5.8 Hz, 2H, PhOCH2),
3.78–3.58 (m, 6 H, H-2, H-3, H-4, H-5, H-6), 3.52–3.41 (m, 1H, OCH2),
3.40–3.31 (m, 1H, OCH2), 2.89 (t, J = 7.5 Hz, 2H, allylic CH2),
2.15–2.10 (m, 4H, CH2CH2CH2); 13C NMR(CD3OD): δ = 160.5 (phenyl-
101.7 (3 x C-1), 74.7 (3 x C-5), 72.6 (3 x C-3), 72.0 (3 x C-2), 69.0 (3 x
PhOCH2), 68.5 (3 x C-4), 65.2 (3 x OCH2), 65.1 (CH2OH), 62.8 (3 x C-6),
48.5 (3 x NCH2), 31.2, 31.0, 30.2, (6 x CH2CH2CH2), 23.2, 23.0 (3 x
allylic-CH2). MALDI MS m/z calcd for C49H77N9NaO22 1143.52, found:
1143.50.
–
–
–
Declaration of competing interest
C), 148.5 (CH C), 144.4, 130.4 (phenyl-C), 123.6 (CH C), 120.2,
–
114.4, 113.9 (phenyl-C), 101.8 (C-1), 74.8 (C-5), 72.6 (C-3), 72.0 (C-2),
68.6 (PhOCH2), 67.9 (C-4), 65.2 (OCH2), 65.0 (HOCH2), 62.9 (C-6), 48.5
(NCH2), 31.2, 30.1, (2 x CH2CH2CH2), 22.9 (allylic-CH2). HRMS (ESI):
m/z calcd for C21H31N3NaO8 [M+Na]+ 476.2009, found: m/z 476.2012.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgments
4.2.5.3. Ligand (3d). From mannoside 3c (1.5 g, 2.4 mmol), column
chromatography (EtOAc/CH3OH, 2:1, Rf = 0.4) afforded ligand 3d as a
white solid (92%), mp 102–105 ◦C. 1H NMR(CD3OD): δ = 7.76 (s, 1H,
triazole H), 7.24 (d, J = 8 Hz, 2H, Phenyl H), 6.87 (d, J = 8 Hz, 2H,
Phenyl H), 4.51 (s, 1H, H-1), 4.47 (s, 2H, CH2OH), 4.46 (t, J = 6.8 Hz,
2H, NCH2), 3.99 (t, J = 6 Hz, 2H, PhOCH2), 3.83–3.71 (m, 6 H, H-2, H-3,
H-4, H-5, H-6), 3.69–3.39 (m, 2H, OCH2), 2.88 (t, J = 7.6 Hz, 2H, allylic
CH2), 2.17–2.10 (m, 4H, CH2CH2CH2); 13C NMR(CD3OD): δ = 159.7
The authors thank Jordan University of Science and Technology
(Jordan) for Financial Support and T. B. Grindley (Dalhousie University/
Canada) for helpful discussions.
Appendix A. Supplementary data
–
–
–
(phenyl-C), 148.4 (CH C), 134.8, 129.6 (phenyl-C), 123.5 (CH C),
–
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.carres.2021.108396.
115.4 (phenyl-C), 101.7 (C-1), 74.8 (C-5), 72.6 (C-3), 72.0 (C-2), 68.5
(PhOCH2), 67.4(C-4), 65.2 (OCH2), 64.9 (HOCH2), 62.9 (C-6), 48.5
(NCH2), 31.2, 30.1, (2 x CH2CH2CH2), 22.9 (allylic-CH2). HRMS (ESI):
m/z calcd for C21H31N3NaO8 [M+Na]+ 476.2009, found: m/z 476.2011.
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4.2.5.4. Ligand (4d). From mannoside 4c (1.00 g, 1.53 mmol), column
chromatography (EtOAc/CH3OH, 2:1, Rf = 0.3) afforded ligand 4d as
colorless viscous oil (90%). 1H NMR(CD3OD): δ = 7.76 (s, 1H, triazole
H), 6.90, 6.82 (2s, 3H, Phenyl H), 4.71 (s, 1H, H-1), 4.57 (s, 4H,
CH2OH), 4.46 (t, J = 6.8 Hz, 2H, NCH2), 4.01 (t, J = 6 Hz, 2H, PhOCH2),
3.84–3.60 (m, 6 H, H-2, H-3, H-4, H-5, H-6), 3.53–3.50 (m, 1H, OCH2),
3.39–3.37 (m, 1H, OCH2), 2.88 (t, J = 7.6 Hz, 2H, allylic CH2),
2.86–2.13 (m, 4H, CH2CH2CH2); 13C NMR(CD3OD): δ = 160.6 (phenyl-
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–
–
–
C), 148.4 (CH C), 144.3 (phenyl-C), 123.5 (CH C), 118.6, 112.7
–
[11] G.R. Nielubowicz, H.L.T. Mobley, Nat. Rev. Urol. 7 (2010) 430–441.
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(phenyl-C), 101.6 (C-1), 74.7 (C-5), 72.5 (C-3), 72.0 (C-2), 68.5
(PhOCH2), 67.9 (C-4), 65.1 (OCH2), 65.0 (HOCH2), 62.8 (C-6), 48.5
(NCH2), 31.1, 30.0, (2 x CH2CH2CH2), 22.9 (allylic-CH2). HRMS (ESI):
m/z calcd for C22H33N3NaO9 [M+Na]+ 506.2114, found: m/z 506.2131.
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4.2.5.5. Ligand (5d). From mannoside 5c (0.60 g, 0.53 mmol), column
chromatography (EtOAc/CH3OH, 2:1, Rf = 0.2) afforded ligand 5d as
colorless viscous oil (88%).1H NMR(CD3OD): δ = 7.78 (s, 2H, 2 x triazole
H), 6.50, 6.34 (2s, 3H, Phenyl H), 4.71 (s, 2H, 2 x H-1), 4.52 (s, 2H,
CH2OH), 4.47 (t, J = 5.5 Hz, 4H, 2 x NCH2), 3.98 (t, J = 5.9 Hz, 4H, 2 x
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9