Synthesis of Neu5Ac-α-C-galactopyranosyl-functionalized magnetic nanoparticles via click chemistry

Article abstract of DOI:10.1016/j.tet.2013.06.086

A new type of glyco-nanoparticle has been accomplished through Cu(I)-catalyzed 1,3-dipolar cycloaddition of 6-azidohexyl Neu5Ac-α-C- galactoside and N-propargyl derivative, which was attached on a silica-wrapping magnetic nanoparticle. Neu5Ac-α-C-galactos

Full text of DOI:10.1016/j.tet.2013.06.086

Tetrahedron 69 (2013) 7300e7307
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Tetrahedron
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Synthesis of Neu5Ac-
a-C-galactopyranosyl-functionalized magnetic
nanoparticles via click chemistry
,
,b,
Chaoli Zhang a b, Xing Ma b, Yuguo Du a
*
a State Key Laboratory of Environmental Chemistry and Eco-toxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,
Beijing 100085, China
b School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 April 2013
Received in revised form 14 June 2013
Accepted 21 June 2013
Available online 29 June 2013
A new type of glyco-nanoparticle has been accomplished through Cu(I)-catalyzed 1,3-dipolar cycload-
dition of 6-azidohexyl Neu5Ac-
a-C-galactoside and N-propargyl derivative, which was attached on
a silica-wrapping magnetic nanoparticle. Neu5Ac-
a
-C-galactoside was stereo-selectively synthesized in
11 steps from isopropyl thiogalactopyranoside and per-acetylated Neu5Ac phenylsulfone using
samarium-mediated reductive desulfonylation as the key step. Magnetic nanoparticles were prepared
with one-step hydrothermal method and a subsequent coating with (N,N0-di-propargyl-3-aminopropyol)
triethoxysilane derivative.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Neu5Ac-containing compounds are thus of particular interest for
their potential pharmaceutical applications with respect to im-
The interaction between cell surface carbohydrates and their
protein receptors is implicated in many important biological
events.1e3 Due to the poor availability of carbohydrate probes in
glycobiology, synthetic carbohydrate derivatives are potentially
useful tools to study cellular interactions, the biosynthesis of gly-
coproteins, the catabolism of glycoconjugates, and the mechanism
of their enzymatic processing.4,5 One major research orientation in
glycoscience is the sialic acids and the related neuraminidases. Si-
alic acids, especially the most common N-acetylneuraminic acid
(Neu5Ac), appear in a wide range of biologically important glyco-
conjugates, and involve in cell recognition and interactions, neu-
ronal transmission, reproduction, differentiation, epitope masking,
and also pathological processes.6 Neuraminidases are hydrolases,
obtained from diverse species and tissues that bind to sialic acid
present on the outer space of cell membranes and evoke catabo-
lism.7 This de-sialation has dramatic consequence for infection,
adhesion, and recognition events. Inhibitors of the neuraminidases
may represent potent antiviral,8e10 antibacterial,11 and anticancer
proved enzymatic hydrolytic stability and exoanomeric conforma-
tional similarity to the corresponding O-glycosides.15
Recently, glyco-nanotechnology is growing fast enabling the
development of nanoparticles (NPs) with specific functional prop-
erties that address the shortcomings of traditional clinic diagnoses
and therapeutic agents.16 Magnetic nanoparticles (MNPs) have
attracted more interests due to their potential applications in
nanobiotechnology, such as magnetic resonance imaging (MRI),
bio-separation, immuassay, antitumor therapy, and so on.17e19 The
application of MNPs as drug delivery carriers has also been dem-
onstrated to be a new solution for in vivo site-specific magnetic
targeting to the liver, spleen, lymph nodes, and bone marrow,20e24
allowing them to function either as an MRI contrast agent or as
a drug carrier. However, to the best of our knowledge, seldom re-
search has been reported regarding the synthesis and application of
Neu5Ac-containing MNPs.25 Herein, we report for the first time the
synthesis of silica-coating MNPs functionalized with Neu5Ac-a-
(2/6)-C-Gal residue through Huisgen reaction (Fig. 1).
agents.12,13 In most cases, natural Neu5Ac are terminally
or -(2/6)-O-linked to a galactose of the oligosaccharide cell
epitope, or polymerized in the form of -(2/8) or a-(2/9) link-
a-(2/3)
a
2. Results and discussion
a
ages.14 The replacement of the interglycosidic oxygen atom with
a carbon atom provides C-linked analogues that are stable toward
hydrolysis fulfill the requirement for drug development. C-linked
Except for several elegant methods for direct CeC bond for-
mation at the anomeric center of carbohydrates, few advances have
been reported in the synthesis of Neu5Ac C-glycosides.26 The major
problem confounding such preparation is the CeC bond formation
generating a quaternary carbon atom. Following our co-authored
Neu5Ac-C-glycosylation procedure under Barbier conditions,27 we
* Corresponding author. E-mail address: duyuguo@rcees.ac.cn (Y. Du).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.06.086

C. Zhang et al. / Tetrahedron 69 (2013) 7300e7307
7301
Fig. 1. Neu5Ac-a-C-galactopyranoside coated magnetic nanoparticles.
explored a way toward the designed compound through SmI2-
mediated coupling of the 6-aldehyde galactose derivative with N-
acetylneuraminic acid phenylsulfone derivative.
Modification of galactose aldehyde started from per-acetylated
isopropyl galactoside (1) as shown in Scheme 1. Glycosylation of
1 and 6-benzyloxy-hexan-1-ol in the presence of NIS and TMSOTf
yield. Oxidation of 7 with 2-iodoxybenzoic acid (IBX) in DMSO
afforded the desired galactosyl aldehyde (8) in 81% yield, which
could be used for the next step without further purification.28
Barbier coupling of 8 with the known Neu5Ac sulfone 9 in the
presence of freshly prepared SmI2 in dry THF furnished the corre-
sponding C-disaccharides 10 (S) and 10 (R) (Scheme 2) in approx-
imately 1:1 ratio and in 80% total yield.29 Spectra of 1H, 13C NMR,
and 1He1H COESY for these two stereo-isomers were obtained,
respectively, and the absolute configurations were identified based
on 1H NMR and NOESY analyses. In 10 (S), the chemical shift of H-4
for Neu5Ac residue appeared at 4.78 ppm, the coupling constant of
J7,8 was 9.6 Hz, and the shift differentiation of H-9a and H-9b was
in CH2Cl2 obtained 6-benzyloxy-hexyl 2,3,4,6-tetra-O-acetyl-
galactopyranoside (2), which was fully deacetylated with NaOMe in
MeOH to afford 6-benzyloxy-hexyl -galactopyranoside (3).
b-D-
b-D
Treatment of 3 with tert-butyldimethylsilyl chloride (TBSCl) in
CH2Cl2 using catalytic amount of triethylamine (TEA) blocked the
primary hydroxyl group (/4), and the subsequent ketalation with
2,2-dimethoxypropane in the presence of toluene sulfonic acid,
provided 5 in 50% yield over four steps. Acetylation of 5 with acetic
anhydride in pyridine (/6), followed by chemoselective removal of
TBS using tetrabutylammonium fluoride (TBAF) gave 7 in excellent
less than 0.3 ppm. These characteristic data confirmed the a-con-
figuration of Neu5Ac in 10 (S). A strong NOE between H-6 of ga-
lactose and H-3ax of Neu5Ac observed in 10 (R) also supported the
assignment for 10 (R). Besides, the bridge hydroxyl group points to
Scheme 1. Synthesis of galactose aldehyde 8.
Scheme 2. Synthesis of Neu5Ac-a-C-galactopyranoside 13.

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C. Zhang et al. / Tetrahedron 69 (2013) 7300e7307
H-3eq in 10 (R) resulting in downfield chemical shift of H-3eq,
while in 10 (S), the bridge hydroxyl group resulting in downfield
chemical shift of H-3ax.29 Debenzylation of the diastereoisomeric
mixture 10 (S) and 10 (R) afforded the corresponding disaccharides
11 (S) and 11 (R) in 95% yield. Selective transformation of the chain-
end hydroxy to azide was carried out smoothly under the Mitsu-
nobu conditions to give a mixture of 12 (S) and 12 (R) in 85% yield.30
Global saponification of 12 with NaOMe in MeOH, and subsequent
core-shell nanostructure (Fig. 2b). The shell thickness could be
controlled by variation of the TEOS concentration and the reaction
time. The resulting silica-coated MNPs were then modified by di-
propargyl derivative 14, which was prepared from the reaction of
(3-aminopropyol) triethoxysilane and propargyl bromide in the
presence of TEA in THF, to graft silica surface with alkynyl group
(alkyneeMNPs). The coupling reaction did not generate significant
change to the size and appearance of nanoparticles (Fig. 2c).
To confirm the presence and demonstrate the activity of prop-
argyl groups on nanoparticles, we synthesized a fluorescent mol-
ecule 16 from rhodamine B in two steps (Scheme 4). The fluorescent
molecule, having azido tag, was bound covalently to the MNPs by
click chemistry in adequate reaction conditions.33 As a result, the
solution color of the alkyne-coated particles in methanol switched
from deep-yellow to brownish-red (Fig. 3b). The confocal fluores-
cence micrograph (CFM) image (Fig. 4a) showed the nanoparticles
emitting green fluorescence (green spots on the black background).
The fluorescence spectrum of rhodamineeMNPs (0.1 mg/mL in
MeOH) was also examined with the corresponding alkyneeMNPs
(0.1 mg/mL in MeOH) as a control (Fig. 4b), showing a significant
HþeNaþ exchanging with acidic resin, afforded Neu5Ac-
a-C-gal-
actopyranosides 13 (S) and 13 (R) in an isolated overall yield of 90%.
The synthesis of alkyne modified magnetic nanoparticles was
depicted in Scheme 3. The process started from the synthesis of
super-paramagnetic Fe3O4 nanoparticles through
a
high-
temperature hydrolysis and reduction of FeCl3 in diethylene gly-
col (DEG) and ethylene glycol (EG) under the presence of sodium
acrylate.31 TEM images of the prepared Fe3O4 nanoparticles
(Fig. 2a) indicated that the average size of the nanoparticles was
approximately 70 nm and every single particle was composed of
€
tiny primary nanocrystals. A modified Stober reaction associated
with the hydrolysis of tetraethylorthosilicate (TEOS) was employed
to cover the Fe3O4 nanoparticles with an amorphous silica layer.32
TEM images of silica-coated MNPs indicated the well-defined
fluorescence signal at lex
/lem¼574/530 nm in emission spectrum,
which is similar to that of rhodamine B chromophore.34 These re-
sults indicated that terminal alkynyl groups have been successfully
incorporated onto the MNPs surface and shown good activity under
click chemistry environment.
Next, Neu5Ac-a-C-glycosides 13 was covalently bound to the
MNPs surface under the same click chemistry conditions as de-
scribed in the preparation of rhodamineeMNPs, to give Neu5-
AceMNPs (Scheme 4). The methanol solution of the resulting
nanoparticles (0.1 mg/mL) showed deep-yellow color, and also has
good response to external magnetic field (Fig. 3c). FTIR analyses of
alkyneeMNPs, Neu5Ac-a-C-glycosides 13, and the synthetic
Neu5AceMNPs (Fig. 5) were in good accordance with the corre-
sponding structures. The FTIR spectrum of 13 (Fig. 5a) presented
characteristic asymmetric stretching of the azido at around
2103 cmꢀ1, and the absorptions at 1632 and 1600 cmꢀ1 ascribing to
the carboxyl and amide groups in the molecule. In Fig. 5c, the bands
appearing at 580 cmꢀ1 were related to the FeeO vibration, and
1558, 1406 cmꢀ1 to the asymmetric and symmetric eCeO vibration
of eCOOH. In addition, the peaks at 1091, 954 cmꢀ1 correspond to
Scheme 3. Synthesis of alkyneeMNPs.
Fig. 2. TEM images of (a) MNPs; (b) silica-coated MNPs; (c) alkyneeMNPs.

C. Zhang et al. / Tetrahedron 69 (2013) 7300e7307
7303
Scheme 4. Synthesis of rhodamineeMNPs and Neu5AceMNPs.
3. Conclusions
We have developed a strategy for the synthesis of magnetic
Neu5Ac- -C-galactosyl nanoparticles, where the magnetic cores of
a
the nanoparticles were wrapped with a silica-layer coating with C-
glycoside residues at the outer space. The presence of alkynyl groups
on MNPs was confirmed by the fluorescent-labeled approach, the
confocal fluorescence micrograph, and fluorescence spectra. The
designed Neu5Ac-a-C-galactosyl MNPs were characterized by FTIR
and TGA, and shown good magnetic property to the external field,
demonstrating the successful grafting of Neu5Ac C-glycosides to
magnetic nanoparticles. Our results should be applicable to the
detection of carbohydrate-related diseases via magnetic resonance
imaging (MRI), or as inhibitors for the related remediation.35
4. Experimental section
4.1. General methods
Anhydrous solvents were distilled prior to use: THF from Na and
benzophenone; CH2Cl2 from CaH2; MeOH from Mg. Commercial
reagents were used without purification. Thin-layer chromatogra-
phy (TLC) was performed using glass-packed silica gel plates
(0.15e0.2 mm thickness). Column chromatography was carried out
by using silica gel (100e200 mesh). Optical rotations were recorded
on
a
digital polarimeter at ambient temperature. 1H NMR
Fig. 3. (a) AlkyneeMNPs; (b) RhodamineeMNPs; (c) Neu5AceMNPs.
(400 MHz) and 13C NMR (100 MHz) spectra were recorded on
a Bruker (400 MHz) spectrometer using CDCl3, CD3OD or D2O as
the symmetric and asymmetric stretching vibrations of SieO
bonds. The FTIR spectrum of the Neu5Ac-MNPs (Fig. 5b), comparing
with the one for alkyneeMNPs, possessed not only the similar
characteristic signals at 580, 954, 1091, 1406, 1558 cmꢀ1, but also
two new distinct signals at 1631 and 631 cmꢀ1 corresponding to the
bands of C-glycoside. From thermogravimetric analysis (TGA), the
weight losses exhibited 83.8% for alkyneeMNPs and 76.7% for
Neu5AceMNPs (Fig. 6). Based on this calculation, the quantity for
immobilized C-glycosides on MNPs was approximately 0.07 mg/mg
(carbohydrates/solid). These observations confirmed that Neu5Ac-
C-glycoside 13 has been incorporated successfully onto the MNPs
surface.
solvent, and chemical shifts were reported as d values in parts per
million based on internal (CH3)4Si (0.00 ppm, 1H) or solvent peak.
FTIR transmission spectra were recorded using a Spectrum GX FTIR
spectrometer at a resolution of 4 cmꢀ1 using the KBr pellet tech-
nique. Transmission electron microscopy (TEM) images were
recorded on a Hitachi H-7500 field-emission transmission electron
microscope. Confocal fluorescence microscopy images were cap-
tured using a Leica TCS SP5 confocal laser scanning microscope.
HRMS spectra were taken in ESI (TOF) mode.
4.1.1. 6-Benzyloxyhexyl 2,3,4,6-tetra-O-acetyl-b-D-galactopyranoside
(2). A mixture of 1 (15 g, 37 mmol), 6-(benzyloxy)hexan-1-ol

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C. Zhang et al. / Tetrahedron 69 (2013) 7300e7307
Fig. 4. (a) Confocal fluorescence micrograph (CFM) image of rhodamineeMNPs; (b) Fluorescence spectra of rhodamineeMNPs.
1H, H-4), 5.18 (dd, J¼10.4, 8.0 Hz, 1H, H-2), 4.99 (dd, J¼10.4, 3.6 Hz,
1H, H-3), 4.47 (s, 2H, CH2Ph), 4.43 (d, J¼8.0 Hz, 1H, H-1), 4.18e4.08
(m, 2H, H-6a,b), 3.89e3.84 (m, 2H, H-5, eCH2O), 3.46e3.42 (m,
3H, eCH2O), 2.12 (s, 3H, OAc), 2.02 (s, 3H, OAc), 2.01 (s, 3H, OAc),1.96
(s, 3H, OAc),1.61e1.54 (m, 4H, CH2),1.38e1.30 (m, 4H, CH2); 13C NMR
(100 MHz, CDCl3)
127.8,101.6, 77.7, 77.4, 77.0, 73.2, 71.3, 70.9, 70.6, 70.4, 69.2, 67.4, 61.6,
d
¼170.7, 170.6, 170.5, 169.6, 138.9, 128.6, 127.9,
30.0, 29.6, 26.2, 26.0, 21.0, 20.9, 20.8; HRMS (ESI) calcd m/z for
C
27H38O11Na [(MþNa)þ] 561.2312, found m/z 561.2319.
4.1.2. 6-Benzyloxyhexyl b-D-galactopyranoside (3). To a solution of 2
(12 g, 22.3 mmol) in anhydrous methanol (25 mL) under nitrogen
was added 1 N NaOMe to keep pH 9.5. The reaction mixture was
stirred at rt for 3 h, at the end of which time TLC indicated a com-
plete consumption of 2, neutralized with Amberlite IR-120 (Hþ),
filtered, and evaporated in vacuo to give 3 (8.25 g, 100%) as a col-
Fig. 5. FTIR spectra of (a) Neu5Ac C-glycosides 13; (b) Neu5AceMNPs; (c)
AlkyneeMNPs.
orless solid. TLC Rf¼0.23 (EtOAc/MeOH¼6:1); [
a
]
18 ꢀ31 (c 1, CHCl3);
D
1H NMR (400 MHz, CD3OD):
d
¼7.34e7.29 (m, 5H, Ph), 4.52 (s, 2H,
CH2Ph), 4.24 (d, J¼7.2 Hz, 1H, H-1), 3.96e3.90 (m, 1H, eCH2O), 3.86
(dd, J¼3.0, 0.8 Hz, 1H, H-4), 3.78e3.76 (m, 2H, H-6a,b), 3.60e3.47
(m, 6H, H-2, H-3, H-5, eCH2O), 1.68e1.62 (m, 4H, CH2), 1.46e1.44
(m, 4H, CH2); 13C NMR (100 MHz, CDCl3)
d
¼138.3,127.9, 127.4, 127.1,
103.5, 75.1, 73.5, 72.3, 71.1, 69.9, 69.2, 68.8, 61.0, 29.3, 29.2, 25.6,
25.4; HRMS (ESI) calcd m/z for C19H30O7Na [(MþNa)þ] 393.1889,
found m/z 393.1880.
4.1.3. 6-Benzyloxyhexyl 6-O-tert-butyldimethylsilyl-b-D-galactopyr-
anoside (4). To a solution of 3 (8 g, 21.6 mmol) in anhydrous CH2Cl2
(20 mL) were added triethylamine (9 mL, 64.8 mmol) and TBSCl
(9.76 g, 64.8 mmol). The resulting mixture was stirred at rt for 3 h,
then quenched with saturated aqueous NH4Cl, and extracted with
EtOAc. The organic layer was washed with brine, dried over Na2SO4,
filtered, and concentrated. The residue was purified by silica gel
column chromatography to afford 4 (9.95 g, 95%) as a colorless oil.
12
TLC Rf¼0.12 (Petroleum ether/EtOAc¼1:1); [
a
]
ꢀ55 (c 1, CHCl3);
D
1H NMR (400 MHz, CDCl3):
d
¼7.33e7.26 (m, 5H, Ph), 4.48 (s, 2H,
CH2Ph), 4.19 (d, J¼7.6 Hz, 1H, H-1), 3.95 (d, J¼3.2 Hz, 1H, H-4)
3.89e3.78 (m, 3H, H-5, H-6a, eCH2O), 3.63 (dd, J¼9.2, 7.6 Hz, 1H, H-
2), 3.3.54e3.43 (m, 5H, H-3, H-6b, eCH2O), 1.66e1.57 (m, 4H, CH2),
1.37e1.36 (m, 4H, CH2), 0.89 (s, 9H, Si-tert-butyl), 0.10 (s, 6H,
Fig. 6. TGA curve of (a) AlkyneeMNPs; (b) Neu5AceMNPs.
ꢀ
(9.22 g, 44.3 mmol), and 4 A molecular sieves (1 g) in anhydrous
SieCH3); 13C NMR (100 MHz, CDCl3)
d
¼138.9, 128.7, 128.0, 127.8,
CH2Cl2 (50 mL) was stirred for 10 min under nitrogen at 0 ꢁC, then
NIS (12.46 g, 55.4 mmol) was added, followed immediately by
dropwise addition of TMSOTf (1 mL, 0.54 mmol). The reaction
completed in 1 h, then neutralized with TEA, and filtered. The filtrate
was evaporated under vacuo, and the syrup was purified by silica gel
103.4, 75.0, 73.9, 73.2, 71.8, 70.7, 70.3, 69.0, 62.7, 30.0, 29.7, 26.3,
26.2, 18.6, ꢀ5.0, ꢀ5.1; HRMS (ESI) calcd m/z for C25H44O7SiNa
[(MþNa)þ] 507.2754, found m/z 507.2764.
4.1.4. 6-Benzyloxyhexyl
3,4-O-isopropylidene-6-O-tert-butyldime-
solution of (9 g,
column chromatography to give 2 (13.9 g, 70%), as colorless oil. TLC
thylsilyl- -galactopyranoside (5). To
b-
D
a
4
12
Rf¼0.24 (Petroleum ether/EtOAc¼2:1); [
a
]
D
ꢀ69 (c 1, CHCl3); 1H
18.6 mmol) in anhydrous CH2Cl2 (20 mL) were added 2,2-
dimethoxypropane (4.57 mL, 37.2 mmol) and toluene sulfonic
NMR (400 MHz, CDCl3):
d
¼7.32e7.24 (m, 5H, Ph), 5.36 (d, J¼2.8 Hz,

C. Zhang et al. / Tetrahedron 69 (2013) 7300e7307
7305
acid (0.35 g, 1.86 mmol). The reaction mixture was stirred at rt for
4 h, quenched by triethylamine (1 mL), and evaporated under di-
minished pressure. The syrup was purified by silica gel column
CH2); 13C NMR (100 MHz, CDCl3)
127.4, 111.2, 100.2, 73.6, 72.8, 72.1, 70.2, 69.8, 29.6, 29.3, 27.3, 26.2,
25.8, 25.6, 20.8; HRMS (ESI) calcd m/z for C24H34O8Na [(MþNa)þ]
473.2151, found m/z 473.2147.
d
¼198.2, 169.4, 138.5, 128.3, 127.5,
chromatography to give 5 (7.4 g, 76%) as colorless oil. TLC Rf¼0.70
18
(Petroleum ether/EtOAc¼1:1); [
a]
þ13 (c 1, CHCl3); 1H NMR
D
(400 MHz, CDCl3):
d
¼7.33e7.26 (m, 5H, Ph), 4.49 (s, 2H, CH2Ph),
4.1.8. Methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2,6-anhydro-3,5-
dideoxy-2-C-{(S,R)-hydroxy-[6-(6-benzyloxyhexyl 2-O-acetyl-3,4-O-
isopropylidene-b-D-galactopyranosidyl)]-methyl}-D-erythro-L-
4.18 (dd, J¼5.6, 2.0 Hz, 1H, H-4), 4.13 (d, J¼8.0 Hz, 1H, H-1), 4.04 (dd,
J¼7.2, 5.6 Hz, 1H, H-3) 3.93e3.78 (m, 4H, H-5, H-6a,b, eCH2O),
3.54e3.43 (m, 4H, H-2, eCH2O), 1.65e1.58 (m, 4H, CH2), 1.51 (s, 3H,
isopropylidene CH3), 1.40e1.33 (m, 7H, isopropylidene CH3, CH2),
0.89 (s, 9H, Si-tert-butyl), 0.10 (s, 6H, SieCH3); 13C NMR (100 MHz,
manno-nononate (10). To a solution of 9 (1.23 g, 2 mmol) and 8
(1.08 g, 2.4 mmol) in anhydrous THF (8 mL) under nitrogen was
added a solution of freshly prepared SmI2 (1 M, 10 mL), and the re-
action mixture was stirred at rt for 15 min. The reaction mixture was
then diluted with CH2Cl2, washed successively with Na2S2O3, 1 N
HCl, and H2O. The combined organic layers were dried over anhy-
drous Na2SO4, and filtered, and the solvents were evaporated. The
residue was purified by silica gel column chromatography to give 10
(1.3 g, 76%) as a colorless oil. For 10R: TLC Rf¼0.6 (EtOAc); 1H NMR
CDCl3)
d
¼138.9, 128.6, 127.9, 127.8, 110.2, 102.7, 79.0, 74.2, 74.1,
73.4, 73.2, 70.6, 70.1, 62.3, 29.9, 29.8, 28.5, 26.6, 26.3, 26.2, 26.1,
18.5, ꢀ5.1, ꢀ5.2; HRMS (ESI) calcd m/z for C28H48O7SiNa [(MþNa)þ]
547.3067, found m/z 547.3062.
4.1.5. 6-Benzyloxyhexyl 2-O-acetyl-3,4-O-isopropylidene-6-O-tert-
butyldimethylsilyl-
b
-D-galactopyranoside (6). To a solution of 5
(400 MHz, CDCl3):
d
¼7.34e7.26 (m, 5H, Ph), 5.41e5.29 (m, 2H, H-7,
(6.5 g, 12.4 mmol) in pyridine (10 mL) was added Ac2O (2.4 mL,
24.8 mmol). The reaction mixture was stirred at rt for 2 h and then
evaporated under vacuo to give a yellow oil. It was purified by silica
gel column chromatography to give 6 (6.47 g, 92%) as colorless oil.
H-8), 5.10 (d, J¼9.2 Hz,1H, NH), 4.92 (t, J¼8.0 Hz 1H, H-20), 4.80e4.75
(m, 1H, H-4), 4.49 (s, 2H, CH2Ph), 4.39 (d, J¼8.4 Hz, 1H, H-10),
4.27e4.20 (m, 4H, H-6, H-9a, H-30, H-40), 4.06e4.00 (m, 3H, H-5, H-
9b, H-50), 3.87 (d, J¼6.0 Hz, 1H, H-60), 3.84e3.79 (m, 1H, eCH2O),
3.75 (s, 3H, COOMe), 3.47e3.43 (m, 3H, eCH2O), 3.06 (d, J¼6.0 Hz,
1H, C60-OH), 2.91 (dd, J¼13.2, 4.4 Hz, 1H, H-3eq), 2.16 (s, 3H, OAc),
2.13 (s, 3H, OAc), 2.08 (s, 3H, OAc), 2.06 (s, 3H, OAc), 2.03 (s, 3H, OAc),
1.88 (s, 3H, OAc), 1.81 (t, J¼13.2 Hz 1H, H-3ax), 1.61e1.48 (m, 7H,
isopropylidene CH3, CH2), 1.39e1.30 (m, 7H, isopropylidene CH3,
TLC Rf¼0.45 (Petroleum ether/EtOAc¼4:1); [
a
]
18 þ37 (c 1, CHCl3); 1H
D
NMR (400 MHz, CDCl3):
d
¼7.38e7.30 (m, 5H, Ph), 4.99 (t, J¼8.0 Hz,
1H, H-2), 4.54 (s, 2H, CH2Ph), 4.32 (d, J¼8.4 Hz, 1H, H-1), 4.25 (dd,
J¼5.6, 2.0 Hz,1H, H-4), 4.17 (dd, J¼7.6, 5.2 Hz,1H, H-3) 3.96e3.83 (m,
4H, H-5, H-6a,b, eCH2O), 3.51e3.43 (m, 3H, eCH2O), 2.11 (s, 3H,
OAc),1.66e1.57 (m, 7H, isopropylidene CH3, CH2), 1.42e1.35 (m, 7H,
isopropylidene CH3, CH2), 0.94 (s, 9H, Si-tert-butyl), 0.12 (s, 6H,
CH2); 13C NMR (100 MHz, CDCl3)
d
¼171.1, 170.6, 170.1, 170.0, 169.9,
169.6, 138.5, 128.3, 127.5, 127.4, 110.8, 100.1, 79.3, 72.8, 72.5, 72.3,
70.4, 70.2, 69.9, 67.5, 67.1, 66.9, 62.5, 52.4, 49.6, 36.7, 29.7, 29.5, 27.6,
26.4, 25.9, 25.7, 23.1, 21.3, 20.9, 20.8, 20.7; HRMS (ESI) calcd m/z for
SieCH3); 13C NMR (100 MHz, CDCl3)
d
¼169.5, 138.6, 128.3, 127.5,
127.4, 110.2, 100.4, 73.4, 73.2, 73.1, 72.8, 70.3, 69.3, 61.9, 29.6, 29.3,
27.7, 26.3, 25.8, 25.7, 25.6, 20.9,18.2, ꢀ5.5, ꢀ5.6; HRMS (ESI) calcd m/
z for C30H50O8SiNa [(MþNa)þ] 589.3173, found m/z 589.3181.
C
44H63NO20Na [(MþNa)þ] 948.3841, found m/z 948.3834. For 10S:
18
TLC Rf¼0.56 (EtOAc); [
a]
þ6 (c 0.5, CHCl3); 1H NMR (400 MHz,
D
CDCl3):
d¼7.34e7.26 (m, 5H, aromatic protons), 5.45e5.41 (m,1H, H-
4.1.6. 6-Benzyloxyhexyl
2-O-acetyl-3,4-O-isopropylidene-
b-
D-gal-
8), 5.29 (dd, J¼9.6,1.6 Hz,1H, H-7), 5.12 (d, J¼10.4 Hz,1H, NH), 4.91 (t,
J¼8.0 Hz, 1H, H-20), 4.80 (dt, J¼11.2, 4.8 Hz, 1H, H-4), 4.49 (s, 2H,
CH2Ph), 4.38 (dd, J¼5.2, 2.0 Hz, 1H, H-40), 4.29e4.15 (m, 4H, H-6, H-
9a, H-10, H-30), 4.08e4.00 (m, 3H, H-5, H-9b, H-60), 3.92 (dd, J¼9.2,
1.6 Hz, 1H, H-50), 3.83e3.77 (m, 1H, eCH2O), 3.71 (s, 3H, COOMe),
3.46e3.38 (m, 3H, eCH2O), 2.65 (d, J¼8.8 Hz, 1H, C60-OH), 2.46 (dd,
J¼13.2, 4.8 Hz, 1H, H-3eq), 2.38 (t, J¼13.2 Hz 1H, H-3ax), 2.14 (s, 3H,
OAc), 2.13 (s, 3H, OAc), 2.06 (s, 3H, OAc), 2.05 (s, 3H, OAc), 2.02 (s, 3H,
OAc), 1.89 (s, 3H, OAc), 1.61e1.48 (m, 7H, isopropylidene CH3, CH2),
1.37e1.28 (m, 7H, isopropylidene CH3, CH2); 13C NMR (100 MHz,
actopyranoside (7). To a solution of 6 (6.4 g, 11.3 mmol) in hydrous
tetrahydrofuran (10 mL) was added TBAF (8.35 g, 22.6 mmol). The
reaction mixture was stirred at rt for 1.5 h, then evaporated under
vacuo, and the residue was purified by silica gel column chroma-
tography to give 7 (4.9 g, 96%) as colorless oil. TLC Rf¼0.36 (Petro-
leum ether/EtOAc¼1:1); [
CDCl3):
a
]
18 þ11 (c 1, CHCl3); 1H NMR (400 MHz,
D
d
¼7.34e7.24 (m, 5H, Ph), 4.94 (dd, J¼8.0, 6.8 Hz, 1H, H-2),
4.48 (s, 2H, CH2Ph), 4.30 (d, J¼8.4 Hz, 1H, H-1), 4.18e4.13 (m, 2H, H-
4, H-3), 3.98e3.92 (m, 1H, H-5), 3.88e3.79 (m, 3H, H-6a,b, eCH2O),
3.46e3.39 (m, 3H, eCH2O), 2.06 (s, 3H, OAc), 1.61e1.54 (m, 7H,
isopropylidene CH3, CH2), 1.37e1.32 (m, 7H, isopropylidene CH3,
CDCl3)
d
¼171.1, 170.6, 170.1, 169.9, 169.8, 169.6, 138.5, 128.2, 127.5,
127.4, 110.2, 100.4, 80.2, 73.8, 73.4, 72.8, 72.7, 72.5, 70.6, 70.3, 70.2,
69.5, 67.3, 67.2, 62.6, 52.2, 49.4, 34.6, 29.7, 29.5, 27.6, 26.4, 25.9, 25.7,
23.1, 21.1, 21.0, 20.9, 20.8, 20.7; HRMS (ESI) calcd m/z for
CH2); 13C NMR (100 MHz, CDCl3)
d
¼169.5, 138.5, 128.2, 127.5, 127.4,
110.6, 100.3, 73.9, 73.2, 73.0, 72.7, 70.2, 69.5, 62.1, 29.6, 29.3, 27.6,
26.3, 25.8, 25.6, 20.9; HRMS (ESI) calcd m/z for C24H36O8Na
[(MþNa)þ] 475.2308, found m/z 475.2303.
C
44H63NO20Na [(MþNa)þ] 948.3841, found m/z 948.3834.
4.1.9. Methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2,6-anhydro-3,5-
dideoxy-2-C-{(S,R)-hydroxy-[6-(6-hydroxyhexyl 2-O-acetyl-3,4-O-
4.1.7. 6-Benzyloxy-hexyl 2-O-acetyl-3,4-O-isopropylidene-6-deoxy-
6-oxo-b-
D-galactopyranoside (8). To a solution of 7 (4 g, 8.8 mmol)
isopropylidene-b-D-galactopyranosidyl)]-methyl}-D-erythro-L-
in DMSO (10 mL) was added IBX (6.16 g, 22 mmol). The reaction
mixture was stirred at rt for 24 h and then ether (20 mL) and sat-
urated NaHCO3 (10 mL) were added. The aqueous phase was
extracted with ether (20ꢂ3). The combined organic layers were
washed with H2O, dried over anhydrous Na2SO4, and filtered, and
the solvents were evaporated under vacuo to give 8 (3.2 g, 81%)
manno-nononate (11). To a solution of 10 (0.884 g, 1 mmol) in
MeOH (10 mL) was added Pd(OH)2/C (0.08 g) and the resulting
mixture was stirred vigorously under a hydrogen atmosphere
(1 atm) for 3 h. Then the mixture was filtered and concentrated
under reduced pressure to afford a colorless oil. The oil was purified
by flash chromatography to give 11 (0.754 g, 95%) as white oil. For
without further purification. TLC Rf¼0.6 (Petroleum ether/
11R: TLC Rf¼0.24 (EtOAc); 1H NMR (400 MHz, CDCl3):
¼5.39e5.35
d
18
EtOAc¼1:1); [
a]
þ28 (c 1, CHCl3); 1H NMR (400 MHz, CDCl3):
(m, 1H, H-8), 5.29 (dd, J¼9.6, 1.0 Hz, 1H, H-7), 5.21 (d, J¼9.6 Hz, 1H,
NH), 4.91 (t, J¼8.0 Hz, 1H, H-20), 4.80e4.74 (m, 1H, H-4), 4.38 (d,
J¼8.4 Hz, 1H, H-10), 4.27e4.20 (m, 4H, H-6, H-9a, H-30, H-40),
4.04e4.00 (m, 3H, H-5, H-9b, H-50), 3.87 (d, J¼2.8 Hz, 1H, H-60),
3.85e3.80 (m, 1H, eCH2O), 3.75 (s, 3H, COOMe), 3.62 (t,
J¼6.4 Hz, 2H, CH2OH), 3.49e3.43 (m, 1H, eCH2O), 3.07 (d, J¼5.2 Hz,
D
d
¼9.73 (s, 1H, eCHO), 7.37e7.30 (m, 5H, Ph), 5.06 (t, J¼7.6 Hz,1H, H-
2), 4.53 (s, 2H, CH2Ph), 4.50e4.44 (m, 2H, H-1, H-4), 4.27 (t,
J¼6.4 Hz, 1H, H-3), 4.19 (s, 1H, H-5), 3.99e3.94 (m, 1H, eCH2O),
3.54e3.48 (m, 3H, eCH2O), 2.13 (s, 3H, OAc), 1.65e1.59 (m, 7H,
isopropylidene CH3, CH2), 1.41e1.36 (m, 7H, isopropylidene CH3,

7306
C. Zhang et al. / Tetrahedron 69 (2013) 7300e7307
1H, C60-OH), 2.91 (dd, J¼13.2, 4.4 Hz, 1H, H-3eq), 2.16 (s, 3H, OAc),
2.13 (s, 3H, OAc), 2.09 (s, 3H, OAc), 2.05 (s, 3H, OAc), 2.03 (s, 3H,
OAc), 1.87 (s, 3H, OAc), 1.80 (t, J¼13.2 Hz 1H, H-3ax), 1.56e1.51 (m,
7H, isopropylidene CH3, CH2), 1.38e1.30 (m, 7H, isopropylidene
21.2, 20.9, 20.8, 20.7, 20.6; HRMS (ESI) calcd m/z for C37H56N4O19Na
[(MþNa)þ] 883.3436, found m/z 883.3430.
4.1.11. 5-Acetamido-2,6-anhydro-3,5-dideoxy-2-C-{(S,R)-hydroxy-
CH3, CH2); 13C NMR (100 MHz, CDCl3)
d¼171.1, 170.7, 170.2, 170.1,
[6-(6-azidohexyl
b-D-galactopyranosid-yl)]-methyl}-D-erythro-L-
170.0, 169.7, 110.8, 100.1, 79.4, 77.4, 72.5, 72.3, 70.3, 69.9, 67.5, 67.3,
67.0, 62.6, 62.5, 52.3, 49.6, 36.7, 32.5, 29.4, 27.7, 26.5, 25.6, 25.4, 23.1,
20.9, 20.8, 20.7, 20.6; HRMS (ESI) calcd m/z for C37H57NO20Na
manno-nononate (13). To a solution of 12 (366 mg, 0.43 mmol) in
MeOH (10 mL) was added 1 N NaOMe until Ph¼9.5. The reaction
mixture was stirred at rt for 10 h, then Amberlite IR-120 (Hþ)
(30 mg) was added. The reaction mixture was stirred vigorously for
another 24 h followed by filtering. The filtrate was evaporated and
the dried residue was dissolved in 0.1 N NaOH and stirred for
overnight. The resulting mixture was neutralized with Amberlite
IR-120 (Hþ) and filtered and solvent was evaporated to dryness. The
residue was purified with Sephadex G-15 and desired fractions
were lyophilized to give 13 (217 mg, 90%) as white powder. TLC
Rf¼0.27 (CH3Cl/MeOH/H2O/TEA¼2:1:0.2:0.04); 1H NMR (400 MHz,
[(MþNa)þ] 858.3372, found m/z 858.3367. For 11S: TLC Rf¼0.24
(EtOAc); [
d
a]
þ7 (c 0.5, CHCl3); 1H NMR (400 MHz, CDCl3):
18
D
¼5.43e5.40 (m, 1H, H-8), 5.29e5.26 (m, 2H, H-7, NH), 4.90 (t,
J¼8.0 Hz, 1H, H-20), 4.79 (dt, J¼11.6, 4.4 Hz, 1H, H-4), 4.38 (dd, J¼5.2,
2.0 Hz, 1H, H-40), 4.29e4.15 (m, 4H, H-6, H-9a, H-10, H-30),
4.07e3.96 (m, 3H, H-5, H-9b, H-60), 3.90 (dd, J¼9.2,1.6 Hz,1H, H-50),
3.82e3.76 (m, 1H, eCH2O), 3.70 (s, 3H, COOMe), 3.61 (t, J¼6.4 Hz,
2H, CH2OH), 3.43e3.38 (m, 1H, eCH2O), 2.44 (dd, J¼13.2, 4.8 Hz,1H,
H-3eq), 2.36 (t, J¼13.2 Hz 1H, H-3ax), 2.13 (s, 3H, OAc), 2.12 (s, 3H,
OAc), 2.06 (s, 3H, OAc), 2.04 (s, 3H, OAc), 2.00 (s, 3H, OAc), 1.87 (s,
3H, OAc), 1.55e1.50 (m, 7H, isopropylidene CH3, CH2), 1.35e1.33 (m,
D2O):
d
¼4.21 (d, J¼8.0 Hz, 1H), 4.06 (d, J¼8.0 Hz, 1H), 3.95 (d,
J¼3.2 Hz, 1H), 3.88e3.79 (m, 4H), 3.74e3.31 (m, 23H), 3.19 (t,
J¼6.8 Hz, 4H), 2.60 (dd, J¼13.2, 4.4 Hz, 1H), 2.38 (dd, J¼13.2, 4.4 Hz,
1H), 1.98e1.84 (m, 7H), 1.61 (t, J¼12.0 Hz 1H), 1.51e1.47 (m, 8H),
7H, isopropylidene CH3, CH2); 13C NMR (100 MHz, CDCl3)
d¼171.1,
170.6, 170.1, 170.0, 169.9, 169.8, 169.7, 110.2, 100.4, 80.3, 73.8, 73.4,
72.8, 72.5, 70.6, 70.2, 69.5, 67.3, 62.6, 52.2, 49.4, 34.6, 32.5, 29.4,
27.6, 26.4, 25.6, 25.4, 23.1, 21.1, 20.9, 20.8; HRMS (ESI) calcd m/z for
1.28e1.27 (m, 8H); 13C NMR (100 MHz, CDCl3)
d¼176.5, 175.6, 174.9,
102.7, 102.3, 83.7, 82.3, 75.3, 73.6, 73.1, 73.0, 72.8, 72.7, 72.6, 72.1,
71.9, 71.8, 71.6, 71.0, 70.5, 70.4, 70.2, 69.0, 68.9, 68.5, 68.2, 62.7, 62.5,
52.1, 52.0, 51.1, 37.2, 36.2, 28.5, 28.4, 27.9, 25.7, 25.6, 24.7, 24.6, 22.0;
HRMS (ESI) calcd m/z for C23H40N4O14Na [(MþNa)þ] 619.2439,
found m/z 619.2447.
C
37H57NO20Na [(MþNa)þ] 858.3372, found m/z 858.3367.
4.1.10. Methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2,6-anhydro-3,5-
dideoxy-2-C-{(S,R)-hydroxy-[6-(6-azidohexyl 2-O-acetyl-3,4-O-iso-
propylidene-
nononate (12). To a solution of PPh3 (262 mg,1 mmol) in anhydrous
THF (10 mL) under nitrogen were added DIAD (198 L, 1 mmol) and
DPPA (225 L, 1 mmol), the resulting mixture was stirred at rt for
0.5 h, then the solution of 11 (418 mg, 0.5 mmol) in THF (2 mL) was
added. The reaction mixture was stirred for another 1 h at same
temperature. Then MeOH (0.5 mL) was added to the mixture and
which was evaporated under vacuo to give a yellow oil. The oil was
purified by flash chromatography to give 12 (S,R) (366 mg, 85%) as
white oil. For 12R: TLC Rf¼0.58 (EtOAc); 1H NMR (400 MHz, CDCl3):
b
-
D
-2galactopyranosidyl)]-methyl}-
D
-erythro-
L
-manno-
4.1.12. Synthesis of Fe3O4 magnetic nanoparticles (MNPs). FeCl3$6H2O
(0.54 g) and sodium acrylate (1.5 g) were dissolved in ethylene
glycol (5 mL) and diethylene glycol (15 mL) under magnetic stirring.
The obtained homogeneous yellow solution was transferred to
a Teflon-lined stainless-steel autoclave and sealed to heat 200 ꢁC.
After reaction for 10 h, the autoclave was cooled to rt. The obtained
magnetic particles were washed with MeOH and water several
times and dried in a vacuum for 12 h.
m
m
4.1.13. Synthesis of silica-coated magnetic nanoparticles (silica-
coated MNPs). The prepared MNPs (25 mg) was mixed with water
(3 mL) and EtOH (20 mL). The mixture was homogenized by ultra-
sonication for 30 min prior to the addition of an ammonia solution
(1 mL). After that, TEOS (0.2 mL) was injected into the solution. After
2 h, the products were collected with the help of a magnet and
washed with EtOH and water several times. Finally, the product was
dried in vacuum for 12 h to obtain the silica-coated MNPs.
d
¼5.42e5.38 (m, 1H, H-8), 5.33e5.29 (m, 2H, H-7, NH), 4.94 (t,
J¼8.0 Hz 1H, H-20), 4.83e4.77 (m, 1H, H-4), 4.41 (d, J¼8.4 Hz, 1H, H-
10), 4.29e4.23 (m, 4H, H-6, H-9a, H-30, H-40), 4.07e4.01 (m, 3H, H-5,
H-9b, H-50), 3.89 (d, J¼2.8 Hz, 1H, H-60), 3.87e3.82 (m, 1H, eCH2O),
3.77 (s, 3H, COOMe), 3.51e3.45 (m, 1H, eCH2O), 3.27 (t, J¼6.8 Hz,
2H, CH2N3), 3.08 (d, J¼5.2 Hz, 1H, C60-OH), 2.93 (dd, J¼13.2, 4.0 Hz,
1H, H-3eq), 2.19 (s, 3H, OAc), 2.15 (s, 3H, OAc), 2.11 (s, 3H, OAc), 2.07
(s, 3H, OAc), 2.05 (s, 3H, OAc),1.89 (s, 3H, OAc),1.82 (t, J¼13.2 Hz 1H,
H-3ax), 1.62e1.53 (m, 7H, isopropylidene CH3, CH2), 1.41e1.32 (m,
4.1.14. N-(Prop-2-yn-1-yl)-N-(3-(triethoxysilyl)propyl)prop-2-yn-1-
amine (14). To a solution of 3-aminopropyltriethoxysilane (2.3 mL,
10 mmol) in CH2Cl2 (20 mL) were added propargyl bromide
(2.2 mL, 25 mmol) and TEA (4.2 mL, 30 mmol). The reaction mixture
was stirred at rt for 3 h and evaporated under vacuo to give a yellow
oil. The oil was purified by flash chromatography to give 14 (2.77 g,
93%) as colorless oil. TLC Rf¼0.25 (Petroleum ether/EtOAc¼10:1);
7H, isopropylidene CH3, CH2); 13C NMR (100 MHz, CDCl3)
d
¼171.0,
170.6, 170.2, 170.1, 170.0, 169.9, 169.6, 110.8, 100.0, 79.3, 77.4, 77.1,
76.9, 72.5, 72.3, 70.1, 69.9, 67.5, 67.2, 67.0, 62.5, 52.3, 51.2, 49.6, 36.7,
29.4, 28.7, 27.7, 26.5, 26.4, 25.3, 23.1, 21.3, 20.9, 20.8, 20.7, 20.6;
HRMS (ESI) calcd m/z for C37H56N4O19Na [(MþNa)þ] 883.3436,
18
found m/z 883.3430. For 12S: TLC Rf¼0.55 (EtOAc); [
a
]
D
þ5 (c 0.5,
CHCl3); 1H NMR (400 MHz, CDCl3):
d
¼5.44e5.40 (m, 1H, H-8), 5.28
1H NMR (400 MHz, CDCl3):
d
¼3.77 (q, J¼6.8 Hz, 6H), 3.39 (d,
(dd, J¼9.6, 2.0 Hz, 1H, H-7), 5.16 (d, J¼10.0 Hz, 1H, NH), 4.89 (t,
J¼8.0 Hz 1H, H-20), 4.78 (dt, J¼11.6, 4.4 Hz, 1H, H-4), 4.37 (dd, J¼5.2,
2.0 Hz, 1H, H-40), 4.29e4.13 (m, 4H, H-6, H-9a, H-10, H-30),
4.06e3.96 (m, 3H, H-5, H-9b, H-60), 3.91 (dd, J¼9.2, 2.0 Hz, 1H, H-
50), 3.83e3.77 (m, 1H, eCH2O), 3.70 (s, 3H, COOMe), 3.44e3.38 (m,
1H, eCH2O), 3.24 (t, J¼6.8 Hz, 2H, CH2N3), 2.66 (d, J¼8.8 Hz, 1H, C60-
OH), 2.45 (dd, J¼13.2, 4.8 Hz, 1H, H-3eq), 2.37 (t, J¼13.2 Hz 1H, H-
3ax), 2.13 (s, 3H, OAc), 2.12 (s, 3H, OAc), 2.06 (s, 3H, OAc), 2.04 (s, 3H,
OAc), 2.01 (s, 3H, OAc), 1.88 (s, 3H, OAc), 1.58e1.48 (m, 7H, iso-
propylidene CH3, CH2), 1.36e1.30 (m, 7H, isopropylidene CH3, CH2);
J¼2.4 Hz, 4H), 2.48 (t, J¼7.6 Hz, 2H), 2.18 (t, J¼2.4 Hz, 2H), 1.59e1.51
(m, 2H), 1.18 (t, J¼7.2 Hz, 9H), 0.62e0.57 (m, 2H); 13C NMR
(100 MHz, CDCl3)
d
¼78.7, 72.7, 58.2, 55.7, 41.8, 20.7, 18.2, 7.7; HRMS
(ESI) calcd m/z for C15H27NO3SiNa [(MþNa)þ] 320.1658, found m/z
320.1650.
4.1.15. Synthesis of magnetic nanoparticles functionalized with al-
kyne (alkyneeMNPs). The prepared silica-coated MNPs (25 mg) was
mixed with water (3 mL) and EtOH (20 mL). The mixture was ho-
mogenized by ultrasonication for 30 min prior to the addition of an
ammonia solution (1 mL). After that, 14 (100 mg) was injected into
the solution. After 3 h, the products were collected with the help of
a magnet and washed with EtOH and water several times. Finally,
13C NMR (100 MHz, CDCl3)
169.6, 110.2, 100.4, 80.2, 73.8, 73.3, 72.8, 72.5, 70.6, 70.1, 69.5, 67.3,
67.2, 62.6, 52.2, 51.2, 49.4, 34.6, 29.4, 28.7, 27.6, 26.4, 26.3, 25.4, 23.1,
d
¼171.1, 170.6, 170.1, 169.9, 169.8, 169.7,

C. Zhang et al. / Tetrahedron 69 (2013) 7300e7307
7307
the product was dried in vacuum for 12
alkyneeMNPs.
h
to obtain the
Innovative Drug Foundation (Project 2012ZX09502001), and NNSF
of China (Project 21072217).
4.1.16. N-(9-(2-((3-Azidopropoxy)carbonyl)phenyl)-6-(dieth-
ylamino)-3H-xanthen-3-ylidene)-N-ethylethanaminium (16). To
References and notes
a solution of rhodamine B (4.79 g, 10 mmol) in CH2Cl2 (30 mL) with
a trace of DMF (0.5 mL) was added oxalyl chloride (0.86 mL,
20 mmol), and the resulting mixture was stirred at rt for 3 h the
reaction mixture was concentrated in vacuo and further dried
azeotropically with benzene. The residue was dissolved in anhy-
drous CH2Cl2 (30 mL) under nitrogen and to the solution were
added 6-azidohexan-1-ol (2.86 g, 20 mmol) and TEA (4.18 mL,
30 mmol). The resulting mixture was stirred at rt for 2 h and then
evaporated under vacuo to give a yellow oil. The oil was purified by
flash chromatography to give 16 (3.58 g, 68%) as red oil. TLC Rf¼0.36
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d
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7.29 (d, J¼6.4 Hz, 1H), 7.07 (d, J¼9.6 Hz, 2H), 6.92 (dd, J¼9.6, 2.0 Hz,
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This work was supported in partial by the National Basic
Research Program of China (Grant 2012CB822101), National
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