Synthesis of glycoaminooxy acid and N-oxyamide-linked glycolipids

Article abstract of DOI:10.1039/c5ob02328a

Aminooxyl sugar derivatives are versatile building blocks for the generation of various glycoconjugates with interesting bioactivities. We report herein a synthetic method for the preparation of orthogonally protected glycoaminooxy acid from methyl α-d-gl

Full text of DOI:10.1039/c5ob02328a

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Synthesis of glycoaminooxy acid and N-oxyamide-
linked glycolipids†
Cite this: DOI: 10.1039/c5ob02328a
N. Chen and J. Xie*
Aminooxyl sugar derivatives are versatile building blocks for the generation of various glycoconjugates
with interesting bioactivities. We report herein a synthetic method for the preparation of orthogonally
protected glycoaminooxy acid from methyl α-D-glycopyranoside in 7 steps. The key steps involve the
selective protection, O-alkylation and Mitsunobu reaction. Fully deprotected N-oxyamide-linked novel
glycolipids can be easily generated from the glycoaminooxy ester or from the 2-hydroxy free sugar in 5 or
6 steps.
Received 12th November 2015,
Accepted 27th November 2015
DOI: 10.1039/c5ob02328a
www.rsc.org/obc
synthesized as glycopeptide mimics.23,24 Glycoaminooxy acids,
with both aminooxyl and carboxyl functions on the sugar
Introduction
Oligosaccharides and their conjugates like glycolipids and frame, have also been developed as multifunctional building
glycopeptides are involved in a variety of important biological, blocks for the synthesis of N-oxyamide-linked oligosaccharide
physiological and pathological processes, such as cell–cell and glycopeptide mimics.25–28 Our previously developed benzyl-
interactions, viral and bacterial infections, immune response, protected 2,6-functionalized pyranoid glucoaminooxy acid has
cancer progression, etc.1–5 Recently, synthesis of glycoconju- been used for the construction of oligosaccharide mimics.28
gates and their mimics has attracted increasing research inter- However, due to the sensitivity of the N–O bond towards the
est for biological and pharmaceutical applications, especially hydrogenation conditions, removal of benzyl groups appeared
in diagnostics, vaccines and therapeutics.6–9 Diversely functio- to be not possible. With continuing interest in the development
nalized carbohydrate building blocks could provide a versatile of N-oxyamide-modified biomolecules,29–33 we reported herein
platform for the generation of carbohydrate mimics and the synthesis of para-methoxybenzyl (PMB) protected glyco-
various conjugates. Recent studies on aminooxy acids showed aminooxy ester and its use for the preparation of fully deprotected
that aminooxy acid derived peptides can easily organize into glycolipid derivatives (Fig. 1).
turns and helical structures through intramolecular hydrogen
bond formation.10 This unique property makes the N-oxyamide
linkage attractive for the modification of biomolecules.
Results and discussion
Synthesis of glycoaminooxy acid
Furthermore, the N-oxyamide linkage is resistant to chemical
and enzymatic hydrolysis,11 and the N-oxyamide bond could
In order to functionalise the 2,6-position of the sugar skeleton,
be readily formed using classical amide formation methods.
selective desilylation was first performed on the methyl
α-D-glucopyranoside, by using 2.8 equiv. of TBSCl in pyridine
Carbohydrates bearing the oxyamine group can be found in N-
or O-glycosyl hydroxylamines and O-amino sugar derivatives.
N-Glycosyl hydroxylamines have become a powerful tool in
in the presence of a catalytic amount of DMAP to give
the known 2,6-di-O-silylated compound 134 in 86% yield
glycobiology and drug discovery for generating a large neoglyco-
side-based library through chemoselective neoglycosylation12–14
(Scheme 1). Subsequent introduction of the PMB group on the
and neoglycorandomization.15–17 O-Glycosyl hydroxylamines
have been widely employed to prepare various oxime-linked
glycolipids,18 glycopeptides,19 glycocyclopeptides20 and glyco-
proteins.21,22 Glycosyl aminooxy acids containing an aminooxyl
function instead of an amino one have been recently
PPSM, ENS Cachan, CNRS, Université Paris-Saclay, Cachan, 94235 France.
E-mail: joanne.xie@ens-cachan.fr
†Electronic supplementary information (ESI) available: Copies of 1H and 13C
Fig. 1 Structure of target glycoaminooxy ester and N-oxyamide-linked
NMR spectra of all described compounds. See DOI: 10.1039/c5ob02328a
glycolipids.
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Table 1 2-O-Alkylation of compound 4 in DMF
NaHa Timeb BrCH2CO2Et
Additive
(equiv.) (equiv.)
(min)
(equiv.)
Conversionc
1
2
3
5
10
10
30
30
30
5
10
10
0
20
30
Imidazole (0.2)
Bu4NBr (0.2)
Bu4NI (3)
Bu4NI (3)
Bu4NI (3)
Bu4NI (3)
Bu4NI (3)
Bu4NI (3)
4
5
6
7
8
9
10
10
10
5
2
5
30
120
120
120
120
10
10
10
10
10
5
40
50
64d
40
30
20e
a All the reactions were performed by adding NaH (and additive) to a
solution of 4 (50 mg) in DMF (1 mL) at 0 °C, followed by dropwise
addition (10 min) of electrophile for 15 h reaction at RT. b Reaction
time with NaH (and additive if used). c The conversion was determined
by TLC except for entry 6 where the conversion rate was calculated
after purification. d BrCH2CO2Et was introduced over 30 min.
e Microwave conditions: T = 150 °C, P = 2.1–2.3 bar, 45 min.
Scheme 1 Synthesis of orthogonally protected glycoaminooxy ester 7.
3- and 4-positions appeared to be not trivial. Treatment of
compound 1 with NaH (6 equiv.) followed by dropwise
addition of PMBCl (4 equiv.) led to a mixture of several pro-
ducts. Alternate addition of NaH (4 × 1.5 equiv.) and PMBCl (4
× 1 equiv.) over 40 min at 0 °C followed by reaction at room
temperature gave 50% isolated yield of 2. The best yield (80%)
was obtained by simultaneous addition of 1.5 equiv. NaH and
1 equiv. PMBCl every 20 min (for a total amount of 6 equiv.
NaH and 4 equiv. PMBCl) under vigorous stirring under argon.
It is to be noted that the PMB group has been previously intro-
duced into the 3,4-positions of methyl 2,6-di-O-benzoyl-α-D-gluco-
pyranoside, by using PMB trichloroacetimidate/TfOH in
Et2O,35 or by heating with PMBCl/DIPEA at 150 °C.36
Removal of the TBS group in 5 with TBAF furnished the
alcohol 6. We then employed the Mitsunobu reaction to introduce
the phthalimidooxyl function on the 6-position, leading to the
target orthogonally protected glycoaminooxy ester 7 in 85% yield.
Synthesis of N-oxyamide-linked glycolipids
With the glycoaminooxy ester 7 in hand, we envisioned the syn-
thesis of the glycolipid 12 bearing the lipid chains on the 2-
and 6-positions of the sugar ring (Scheme 2). The phthaloyl
group was firstly removed under hydrazinolysis conditions. The
obtained oxyamine 8 was then acylated with palmitic acid to
afford the glycolipid 9 in 86% yield. The proton of the N-oxya-
1
mide bond appeared at 8.04 ppm in the H NMR spectrum in
Desilylation of 2 followed by selective silylation on the
primary alcohol furnished compound 4 which underwent the
O-alkylation reaction with ethyl bromoacetate. In our previous
work, this reaction worked well with the corresponding 3,4-di-O-
benzyl derivative (1.5 equiv. each of NaH and BrCH2CO2tBu in
DMF in 75% yield).28 In the present case, no reaction occurred
when treating compound 4 with up to 5 equiv. each of NaH and
BrCH2CO2Et (Table 1, entry 1). Similar difficulty in the O-alkyl-
ation has been encountered by Xing and Gleason.37 Hopefully,
increasing the amount of reagents resulted in 20% conversion
(entry 2). Addition of catalytic imidazole and Bu4NBr according
to Tomaszewski et al.38 improved the conversion to around 30%
(entry 3). The use of Bu4NI as an additive with a prolonged
reaction time (2 h) before introduction of the electrophile
improved further the conversion (entries 4 and 5). The best
conversion (64%) was obtained by very slow addition of
BrCH2CO2Et (30 min) after formation of alcoholate (entry 6).
36% of 4 was recovered after column chromatography, which
led to a corrected yield of 93% for the desired compound 5.
Further investigation with less NaH decreased the conversion
ratio (entries 7 and 8). Reaction with 5 equiv. each of NaH and
BrCH2CO2Et in the presence of 3 equiv. Bu4NI under microwave
conditions led only to 20% conversion (entry 9).
CDCl3. Deprotection of the carboxylic acid followed by coupling
with 1-dodecanol furnished the protected glycolipid 11 in 34%
total yield from 7. The PMB group can be readily removed with
5% TFA in CH2Cl2, leading to the deprotected glycolipid 12.
Scheme 2 Synthesis of glycolipid 12 from glycoaminooxy ester 7.
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tion and removal of the phthaloyl group) and acylation readily
gave the protected glycolipid 22 which could be deprotected to
the glycolipid 23 in 29% total yield in 6 steps.
Conclusions
The para-methoxybenzyl protected glycoaminooxy ester 7 has
been synthesized from the methyl α-D-glycopyranoside in 7
steps. Conditions for the introduction of the PMB group on
the 3,4-positions and 2-O-alkylation reaction have been opti-
mized. Fully deprotected N-oxyamide-linked glycolipids could
be readily obtained from the glycoaminooxy ester in 6 steps in
20% total yield. We have also demonstrated that N-oxyamide-
linked glycolipids with the lipid chains on the 2,6-positions
can be easily prepared from the orthogonally protected glyco-
pyranoside 4. We are convinced that the orthogonally pro-
tected glycoaminooxy ester could be useful for the generation
of various new glycoconjugates.
Scheme 3 Alternative synthesis of glycolipid 11 from glucoside 4.
Experimental
General
The glycolipid 11 can also be prepared from the intermedi-
ate 4, by introducing the first lipid chain on the 2-position
(Scheme 3). Due to the previously encountered difficulty
during the O-alkylation, we decided to realise the O-carboxy-
methylation under phase transfer conditions in 50% aqueous
NaOH/toluene in the presence of 0.5 equiv. Bu4NI,39,40 which
led to the carboxylic acid 13 with a corrected yield of 74%
(33% of the compound 4 was recovered). Esterification with
1-dodecanol, followed by desilylation, the Mitsunobu reaction
with PhthNOH, hydrazinolysis and coupling with palmitic acid
furnished the glycolipid 11 in 25% total yield from 4.
All commercially available reagents were used without further
purification. Column chromatography was performed on Silica
gel 60 (40–60 μm). The solvents for column chromatography
were used without purification. The reactions carried out
under anhydrous conditions are performed under argon in
glassware previously dried in an oven. Methanol is dried over
molecular sieves of 3 Å. THF, DMF, dichloromethane and
toluene were previously dried through an alumina cartridge
using a solvent purifier MBRAUN SPS-800. Reactions were
monitored by TLC on Silica Gel 60F-254 plates with detection
by UV (254 nm or 365 nm) or by spraying with 10% H2SO4 in
EtOH and heating for about 30 s at 400–600 °C. Melting points
were determined with a Kofler melting point apparatus.
Optical rotations were measured using a Jasco P-2000 polari-
meter at room temperature in a 10 cm, 1 mL cell. NMR spectra
were recorded on a JOEL ESC-400 spectrometer in CDCl3 solu-
tion. The chemical shift was given in units of parts per million
related to TMS or solvent protons as internal reference. High-
resolution mass spectra (HRMS) were recorded on a Q-TOF
MaXis using standard conditions or Bruker Microflex™
MALDI-TOF mass spectrometry.
The lipid chain could also be introduced directly to the
alcohol function of compound 4 (Scheme 4). Esterification of 4
with palmitic acid followed by introduction of the aminooxyl
group on the 6-position (by desilylation, the Mitsunobu reac-
General procedure for desilylation
To a solution of silylated compound (1 eq.) in anhydrous THF
(15 mL per mmol substrate) under argon was added TBAF
(3 eq.). After stirring at room temperature overnight, the
solvent was removed under vacuum. The residue was diluted
with EtOAc (25 mL per mmol substrate), washed with saturated
aq. NH4Cl (10 mL per mmol substrate), H2O (10 mL per mmol
substrate) and brine (10 mL per mmol substrate), dried over
MgSO4, filtered, evaporated, and purified by column chromato-
graphy over silica gel to afford the silylated compound.
Scheme 4 Synthesis of glycolipid 23 from glucoside 4.
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General procedure for the Mitsunobu reaction
extracted with CH2Cl2 (2 × 50 mL). The combined organic
layers were dried over MgSO4, filtered, concentrated, and puri-
fied by column chromatography over silica gel (petroleum
ether/EtOAc: 10/1) to afford compound 1 (1.82 g, 86.3%) as a
colourless paste: Rf = 0.66 (petroleum ether–EtOAc 5/1);
1H NMR (400 MHz, CDCl3): δ 4.60 (d, J = 3.7 Hz, 1H, H-1),
3.87–3.74 (m, 3H, H-3,6), 3.63–3.57 (m, 1H, H-5), 3.55–3.45
(m, 2H, H-2,4), 3.37 (s, 3H, OCH3), 2.78 (s, 2H, 2 × OH), 0.88,
0.89 (2 × s, 18H, 2 × tBu), 0.12–0.04 (m, 12H, 2 × Si(CH3)2);
13C NMR (100 MHz, CDCl3): δ 100.0 (C-1), 74.1 (C-3), 73.6 (C-2),
71.8 (C-4), 70.8 (C-5), 64.1 (CH2), 55.3 (OCH3), 26.0, 25.9 (CH3,
tBu); 18.5, 18.3 (Cq, tBu); −4.4, −4.5, −5.3, −5.3 (CH3, Si(CH3)2).
To a solution of alcohol (1 eq.), Ph3P (3 eq.) and PhthNOH
(3 eq.) in toluene (20 mL per mmol substrate) at 0 °C under
argon was added DIAD (3 eq.) dropwise. The resulting mixture
was stirred at room temperature for 1 h and then extracted
with EtOAc (3 × 30 mL per mmol substrate). The combined
organic layers were washed with saturated aq. NaHCO3
(3 × 30 mL per mmol substrate), H2O (30 mL per mmol sub-
strate) and brine (30 mL per mmol substrate), dried over
MgSO4, filtered, evaporated and purified by column chromato-
graphy over silica gel to afford the O-phthalimido compound.
General procedure for hydrazinolysis
Methyl 3,4-di-O-(4-methoxybenzyl)-2,6-di-O-tert-
butyldimethylsilyl-α-D-glucopyranoside (2)
To a solution of O-phthalimido compound (1 eq.) in MeOH
(20 mL per mmol substrate) was added N2H4·H2O (2 eq.). The
mixture was stirred at room temperature for 2 h and then
extracted with CH2Cl2 (3 × 50 mL per mmol substrate). The
combined organic layers were washed with saturated aq.
NaHCO3 (50 mL per mmol substrate), H2O (50 mL per mmol
substrate) and brine (50 mL per mmol substrate), dried over
MgSO4, filtered, evaporated, and purified by column chromato-
graphy over silica gel to afford the O-amino compound.
To a solution of compound 1 (4.5 g, 10.6 mmol) in anhydrous
DMF (50 ml) under argon at 0 °C were added NaH (60%,
2.55 g, 63.8 mmol) and PMBCl (5.8 ml, 42.4 mmol) in portions
over 1 h (NaH and PMBCl were added at the same time, 1/4
total amount every 20 min). After addition, the solution was
stirred at room temperature for 16 h. Ice was added to destroy
the excess NaH, and then the solution was concentrated. The
residue was diluted with EtOAc (200 mL), washed with
saturated aq. NH4Cl (100 mL), H2O (100 mL) and brine
(100 mL), dried over MgSO4, filtered, evaporated, and purified
by column chromatography over silica gel (petroleum ether/
EtOAc: 20/1) to afford compound 2 (5.64 g, 80%) as a colour-
less paste: Rf = 0.48 (petroleum ether–EtOAc 10/1); [α]D + 36.3
General procedure for N-oxyamide formation
To a solution of carboxylic acid (1 eq.) in anhydrous CH2Cl2
(15 mL per mmol substrate) were added HOBt (2 eq.),
EDC·HCl (2 eq.) and Et3N (2 eq.) under argon at 0 °C. After stir-
ring for 20 min, the oxyamine derivative (1 eq.) was added. The
resulting mixture was stirred at room temperature overnight.
The solution was diluted with EtOAc (100 mL per mmol sub-
strate), washed with aq. HCl (1 N, 2 × 40 mL per mmol sub-
strate), saturated aq. NaHCO3 (2 × 40 mL per mmol substrate)
and brine (40 mL per mmol substrate), dried over MgSO4, fil-
tered, evaporated, and purified by column chromatography
over silica gel to give the N-oxyamide.
1
(c 0.1, CHCl3); H NMR (400 MHz, CDCl3): δ 7.33–7.20 (m, 4H,
PMB), 6.90–6.82 (m, 4H, PMB), 4.79–4.40 (m, 4H, 2 × OCH2),
4.33 (d, J = 3.6 Hz, 1H, H-1), 3.96 (t, J = 8.9 Hz, 1H, H-3), 3.80,
3.78 (2 × s, 6H, 2 × OCH3), 3.72–3.59 (m, 2H, H-6), 3.53–3.46
(m, 1H, H-5), 3.31–3.19 (m, 5H, H-2,4, OCH3), 0.94, 0.85 (2 × s,
18H, 2 × tBu), 0.13–0.02 (m, 12H, 2 × Si(CH3)2); 13C NMR
(100 MHz, CDCl3): δ 159.4, 159.1, 130.8, 130.6 (Cq); 130.0,
129.3, 113.8 (CH); 98.0 (C-1), 80.1 (C-2), 79.2 (C-4), 74.6 (CH2),
74.1 (C-3), 73.3 (CH2), 71.4 (C-5), 62.6 (CH2), 55.4, 54.8 (OCH3);
26.0 (CH3, tBu); 18.4, 18.3 (Cq, tBu); −3.7, −4.1, −5.0, −5.3
(CH3, Si(CH3)2); HRMS (ESI) m/z 685.3562, Calcd for
C35H58NaO8Si2 [M + Na]+ 685.3568.
General procedure for esterification
To a solution of carboxylic acid (1 eq.) in anhydrous CH2Cl2
(15 mL per mmol substrate) were added EDC·HCl (2 eq.), DMAP
(2 eq.) and Et3N (2 eq.) under argon at 0 °C. After the mixture was
stirred for 20 min, the alcohol (1 eq.) was added. The resulting
mixture was stirred at room temperature overnight. The solution
was diluted with CH2Cl2 (50 mL per mmol substrate), washed
with aq. HCl (1 N, 2 × 40 mL per mmol substrate), saturated aq.
NaHCO3 (2 × 40 mL per mmol substrate) and brine (40 mL per
mmol substrate), dried over MgSO4, filtered, evaporated, and pur-
ified by column chromatography over silica gel to give the ester.
Methyl 3,4-di-O-(4-methoxybenzyl)-α-D-glucopyranoside (3)35,36
Desilylation of compound 2 (5.64 g, 8.52 mmol) according to
the general procedure and purification by column chromato-
graphy over silica gel (petroleum ether/EtOAc: 1/1) afforded
compound 3 (2.53 g, 68.4%) as a white solid: Rf = 0.23
(petroleum ether–EtOAc 1/1); 1H NMR (400 MHz, CDCl3):
δ 7.33–7.25 (m, 4H, PMB), 6.92–6.85 (m, 4H, PMB), 4.82 (d, J =
11.0 Hz, 1H, OCH), 4.67–4.57 (m, 3H, OCH, OCH2), 4.54 (d, J =
3.7 Hz, 1H, H-1), 4.05 (t, J = 9.2 Hz, 1H, H-3), 3.81, 3.80 (2 × s,
Methyl 2,6-di-O-tert-butyldimethylsilyl-α-D-glucopyranoside (1)34
To a solution of methyl α-D-glucopyranoside (0.97 g, 5 mmol) 6H, 2 × OCH3), 3.79–3.67 (m, 2H, H-6), 3.62–3.57 (m, 1H, H-5),
in pyridine (10 mL) under argon at 0 °C were added TBSCl 3.42 (t, J = 9.4 Hz, 1H, H-4), 3.36–3.27 (m, 4H, H-2, OCH3), 2.43
(2.1 g, 14 mmol) and DMAP (0.12 g, 1 mmol). After stirring at (s, 1H, OH), 1.67 (s, 1H, OH); 13C NMR (100 MHz, CDCl3):
room temperature for 16 h, the solvent was removed under δ 159.7, 159.5, 130.5, 130.1 (Cq); 129.9, 129.9, 114.1, 114.0
vacuum, and the concentrated mixture was partitioned between (CH); 97.7 (C-1), 79.4 (C-2), 77.0 (C-4), 74.3 (CH2), 73.5 (C-3),
CH2Cl2 (50 mL) and H2O (50 mL). The aqueous layer was 72.9 (CH2), 70.3 (C-5), 62.1 (CH2), 55.4, 55.3 (OCH3).
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Methyl 3,4-di-O-(4-methoxybenzyl)-6-O-tert-butyldimethylsilyl-
α-D-glucopyranoside (4)
Methyl 2-O-ethoxycarbonylmethyl-3,4-di-O-(4-methoxybenzyl)-
α-D-glucopyranoside (6)
To a solution of compound 3 (2.53 g, 5.82 mmol) in pyridine Desilylation of compound 5 (0.50 g, 0.79 mmol) according to
(40 mL) under argon at 0 °C were added TBSCl (1.09 g, the general procedure and purification by column chromato-
7.27 mmol) and DMAP (0.18 g, 1.46 mmol). After stirring at graphy over silica gel (petroleum ether/EtOAc: 1/1) afforded
room temperature for 16 h, the solvent was removed under compound 6 (0.3 g, 73%) as a colourless paste: Rf = 0.48
vacuum, and the concentrated mixture was partitioned (petroleum ether–EtOAc 1/2); [α]D + 34.7 (c 0.1, CHCl3); 1H NMR
between CH2Cl2 (100 mL) and H2O (50 mL). The aqueous layer (400 MHz, CDCl3): δ 7.39–7.25 (m, 4H, PMB), 6.95–6.84 (m,
was extracted with CH2Cl2 (2 × 50 mL). The combined organic 4H, PMB), 4.88 (d, J = 11.0 Hz, 1H, OCH), 4.74–4.36 (m, 6H,
layers were dried over MgSO4, filtered, concentrated, and OCH, 2 × OCH2, H-1), 4.21 (q, J = 7.0 Hz, 2H, OCH2), 3.92–3.77
purified by column chromatography over silica gel (petroleum (m, 7H, 2 × OCH3, H-3), 3.76–3.62 (m, 2H, H-6), 3.60–3.46 (m,
ether/EtOAc: 4/1) to afford compound 4 (3.15 g, 98.7%) as 3H, H-2,4,5), 3.29 (s, 3H, OCH3), 1.27 (t, J = 7.1 Hz, 3H, CH3);
a colourless paste: Rf = 0.55 (petroleum ether–EtOAc 2/1); [α]D 13C NMR (100 MHz, CDCl3): δ 170.3 (CvO), 159.6, 159.5,
1
+ 58.7 (c 0.1, CHCl3); H NMR (400 MHz, CDCl3): δ 7.32–7.24 130.5, 130.2 (Cq); 130.0, 129.8, 114.0 (CH); 98.1 (C-1), 83.4,
(m, 4H, PMB), 6.92–6.84 (m, 4H, PMB), 4.80 (d, J = 11.0 Hz, 79.7, 76.5 (CH); 74.7, 73.0, 70.9 (CH2); 70.5 (CH), 62.0, 60.9
1H, OCH), 4.66–4.56 (m, 4H, OCH, OCH2, H-1), 4.04 (t, J = 9.2 (CH2); 55.4, 55.2 (OCH3); 14.3 (CH3). HRMS (ESI) m/z 543.2201,
Hz, 1H, H-3), 3.84–3.73 (m, 8H, 2 × OCH3, H-6), 3.55 (ddd, J = Calcd for C27H36NaO10 [M + Na]+ 543.2206.
9.9, 4.3, 2.1 Hz, 1H, H-5), 3.41 (t, J = 9.4 Hz, 1H, H-4),
3.36–3.27 (m, 4H, H-2, OCH3), 2.40 (broad s, 1H, OH), 0.90 (s, Methyl 2-O-ethoxycarbonylmethyl-3,4-di-O-(4-methoxybenzyl)-
9H, tBu), 0.65–0.45 (m, 6H, Si(CH3)2); 13C NMR (100 MHz, 6-O-phthalimido-α-D-glucopyranoside (7)
CDCl3): δ 159.6, 159.4, 130.9, 130.3 (Cq); 129.8, 129.7, 114.1,
114.0 (CH); 97.4 (C-1), 79.6 (C-2), 77.4 (C-4), 74.3 (CH2), 73.7
The phthalimido group was introduced at the 6-position of
compound 6 (0.3 g, 0.58 mmol) using the Mitsunobu reaction
(C-3), 72.8 (CH2), 71.2 (C-5), 62.5 (CH2), 55.4, 55.0 (OCH3); 26.1
according to the general procedure. Purification by column
(CH3, tBu), 18.5 (Cq, tBu), −5.0, −5.2 (CH3, Si(CH3)2); HRMS
chromatography over silica gel (petroleum ether/EtOAc: 3/1)
(ESI) m/z 571.2698, Calcd for C29H44NaO8Si [M
+
Na]+
afforded compound 7 (0.33 g, 85%) as a colourless paste: Rf =
0.47 (petroleum ether–EtOAc 1/1); [α]D + 47.3 (c 0.1, CHCl3); 1H
NMR (400 MHz, CDCl3): δ 7.86–7.72 (m, 4H, Phth), 7.35–7.26
(m, 4H, PMB), 6.90–6.82 (m, 4H, PMB), 4.98 (d, J = 10.1 Hz,
1H, OCH), 4.81 (d, J = 10.5 Hz, 1H, OCH), 4.70 (d, J = 11.9 Hz,
1H, OCH), 4.56 (d, J = 9.6 Hz, 1H, OCH), 4.55–4.35 (m, 5H,
OCH2, H-1,6), 4.21 (q, J = 7.0 Hz, 2H, OCH2), 3.87–3.72 (m, 9H,
2 × OCH3, H-3,4,5), 3.57 (dd, J = 9.3, 3.5 Hz, 1H, H-2), 3.35 (s,
3H, OCH3), 1.27 (t, J = 7.1 Hz, 3H, CH3); 13C NMR (100 MHz,
CDCl3): δ 170.2, 163.3 (CvO); 159.5, 159.4 (Cq); 134.5 (CH),
130.6, 130.2 (Cq); 130.1, 129.9 (CH); 129.0 (Cq), 123.6, 114.0,
113.9 (CH); 98.2 (C-1), 83.4, 79.2 (CH); 76.5 (CH2), 76.1 (CH),
74.9, 73.1, 71.0 (CH2); 69.2 (CH), 60.8 (CH2), 55.6, 55.3 (OCH3);
14.3 (CH3); HRMS (ESI) m/z 688.2374, Calcd for C35H39NaO12
[M + Na]+ 688.2370.
571.2703.
Methyl 2-O-ethoxycarbonylmethyl-3,4-di-O-(4-methoxybenzyl)-
6-O-tert-butyldimethylsilyl-α-D-glucopyranoside (5)
To a solution of compound 4 (200 mg, 0.36 mmol) in DMF
(5 mL) under argon at 0 °C, were added NaH (60%, 144 mg,
3.6 mmol) and TBAI (386 mg, 1.1 mmol). After stirring at 0 °C
for 2 h, ethyl bromoacetate (0.4 mL, 3.6 mmol) was added
dropwise over 30 min, and the resulting mixture was stirred at
room temperature for 15 h. The reaction was quenched with
ice, and the mixture was extracted with EtOAc (3 × 20 mL). The
combined organic layers were washed with saturated aq.
NH4Cl (20 mL) and brine (20 mL), dried over MgSO4, filtered,
evaporated, and purified by column chromatography over
silica gel (petroleum ether/EtOAc: 4/1) to afford compound
4 (72 mg, conversion: 64%) and compound 5 (135 mg,
corrected yield: 92.5%) as a colourless paste: Rf = 0.55
Methyl 6-O-amino-2-O-ethoxycarbonylmethyl-3,4-di-O-(4-
methoxybenzyl)-α-D-glucopyranoside (8)
(petroleum ether–EtOAc 3/1); [α]D + 27.3 (c 0.1, CHCl3); 1H Hydrazinolysis of compound 7 (67 mg, 0.1 mmol) according to
NMR (400 MHz, CDCl3): δ 7.35–7.23 (m, 4H, PMB), 6.94–6.83 the general procedure and purification by column chromato-
(m, 4H, PMB), 4.86 (d, J = 10.5 Hz, 1H, OCH), 4.71–4.47 (m, graphy over silica gel (petroleum ether/EtOAc: 1/1) afforded
6H, OCH, 2 × OCH2, H-1), 4.22 (q, J = 7.0 Hz, 2H, OCH2), compound 8 (40 mg, 75%) as a colourless paste: Rf = 0.25
3.88–3.72 (m, 9H, 2 × OCH3, H-3,6), 3.59–3.47 (m, 3H, H-2,4,5), (petroleum ether–EtOAc 1/1); [α]D + 30.3 (c 0.1, CHCl3);
3.29 (s, 3H, OCH3), 1.27 (t, J = 7.1 Hz, 3H, CH3), 0.96–0.86 (m, 1H NMR (400 MHz, CDCl3): δ 7.38–7.22 (m, 4H, PMB),
9H, tBu), 0.09–0.02 (m, 6H, Si(CH3)2); 13C NMR (100 MHz, 6.97–6.82 (m, 4H, PMB), 4.91–4.35 (m, 7H, 3 × OCH2, H-1),
CDCl3): δ 170.4 (CvO), 159.5, 159.3, 130.9, 130.4 (Cq); 129.8, 4.20 (q, J = 7.0 Hz, 2H, OCH2), 3.93–3.72 (m, 9H, 2 × OCH3,
114.0, 113.9 (CH); 97.8 (C-1), 83.7, 79.8, 77.4 (CH); 74.8, 73.0 H-3,6), 3.72–3.65 (m, 1H, H-5), 3.57–3.45 (m, 2H, H-2,4), 3.31
(CH2); 71.4 (CH), 71.1, 62.4, 60.8 (CH2); 55.4, 54.9 (OCH3); 26.0 (s, 3H, OCH3), 1.26 (t, J = 7.1 Hz, 3H, CH3); 13C NMR
(CH3, tBu), 18.4 (Cq, tBu), 14.4 (CH3), −5.0, −5.2 (CH3, (100 MHz, CDCl3):
δ
170.3 (CvO), 159.5, 159.4,
Si(CH3)2); HRMS (ESI) m/z 657.3065, Calcd for C33H50NaO10Si 130.6, 130.2 (Cq); 130.0, 129.9, 114.0, 113.9 (CH); 98.0 (C-1),
[M + Na]+ 657.3071.
83.5, 79.5, 76.8 (CH); 74.8, 74.4, 73.0, 70.9 (CH2); 69.5 (CH),
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60.8 (CH2), 55.4, 55.3 (OCH3); 14.3 (CH3); HRMS (ESI) m/z from compound 16 (20 mg, 0.03 mmol) and palmitic acid
574.2057, Calcd for C27H37KNO10 [M + K]+ 574.2055.
according to the general procedure for N-oxyamide formation.
Purification by column chromatography over silica gel
(petroleum ether/EtOAc: 2/1) afforded compound 11 (24 mg,
Methyl 2-O-ethoxycarbonylmethyl-3,4-di-O-(4-methoxybenzyl)-
6-O-palmitoylamino-α-D-glucopyranoside (9)
88%): Rf = 0.56 (petroleum ether–EtOAc 1/1); [α]D + 27.3 (c 0.1,
1
Compound 9 was prepared from compound 8 (70 mg, CHCl3); mp 70 °C; H NMR (400 MHz, CDCl3): δ 8.01 (s, 1H,
0.13 mmol) and palmitic acid according to the general pro- NH), 7.37–7.20 (m, 4H, PMB), 6.96–6.82 (m, 4H, PMB),
cedure for N-oxyamide formation. Purification by column 4.95–4.36 (m, 7H, 3 × OCH2, H-1), 4.13 (t, J = 6.8 Hz, 2H,
chromatography over silica gel (petroleum ether/EtOAc: 3/2) OCH2), 4.09–3.89 (m, 2H, H-6), 3.86–3.75 (m, 7H, 2 × OCH3,
afforded compound 9 (86 mg, 86%) as a white solid: Rf = 0.48 H-3), 3.74–3.67 (m, 1H, H-5), 3.60–3.44 (m, 2H, H-2,4), 3.30 (s,
(petroleum ether–EtOAc 1/1); [α]D + 39.7 (c 0.1, CHCl3); mp 3H, OCH3), 2.41–1.93 (m, 2H, CH2), 1.69–1.53 (m, 4H, 2 ×
75 °C; 1H NMR (400 MHz, CDCl3): δ 8.04 (s, 1H, NH), CH2), 1.40–1.19 (m, 42H, 21 × CH2), 0.93–0.83 (m, 6H, 2 ×
7.39–7.21 (m, 4H, PMB), 6.97–6.81 (m, 4H, PMB), 4.95–4.35 CH3); 13C NMR (100 MHz, CDCl3): δ 170.6, 170.3 (CvO); 159.5,
(m, 7H, 3 × OCH2, H-1), 4.20 (q, J = 7.0 Hz, 2H, OCH2), 159.4, 130.5, 130.1 (Cq); 130.4, 129.8, 114.0, 113.9 (CH); 98.1
4.11–3.99 (m, 2H, H-6), 3.88–3.68 (m, 8H, 2 × OCH3, H-3,5), (C-1), 83.4, 79.4, 76.2 (CH); 74.7, 73.1, 70.8 (CH2); 69.5 (CH),
3.61–3.46 (m, 2H, H-2,4), 3.31 (s, 3H, OCH3), 2.43–1.92 (m, 2H, 65.1 (CH2), 55.5, 55.4 (OCH3); 33.4, 32.0, 29.8, 29.6, 29.5, 29.4,
CH2), 1.66–1.54 (m, 2H, CH2), 1.45–1.17 (m, 27H, 12 × CH2, 28.7, 26.0, 25.5, 22.8 (CH2); 14.3 (CH3); HRMS (ESI) m/z
CH3), 0.88 (t, J = 6.4 Hz, 3H, CH3); 13C NMR (100 MHz, CDCl3): 936.6179, Calcd for C53H87NaNO11 [M + Na]+ 936.6177.
δ 170.7, 170.2 (CvO); 159.6, 159.4, 130.3, 130.2 (Cq); 129.8,
Methyl 2-O-dodecyloxycarbonylmethyl-6-O-palmitoylamino-
α-D-glucopyranoside (12)
114.0, 113.9 (CH); 98.1 (C-1), 83.4, 79.5, 76.3 (CH); 74.7, 73.0,
70.9 (CH2); 69.5 (CH), 60.9 (CH2), 55.5, 55.4 (OCH3); 33.4, 32.0,
29.8, 29.6, 29.5, 25.5, 22.8 (CH2); 14.3, 14.2 (CH3); HRMS (ESI) To a solution of compound 11 (29 mg, 0.03 mmol) in CH2Cl2
m/z 812.4353, Calcd for C43H67KNO11 [M + K]+ 812.4351.
(1 mL) was added TFA (0.05 mL, 5% in CH2Cl2). The mixture
was stirred at room temperature for 1 h under argon and then
extracted with CH2Cl2 (3 × 10 mL). The combined organic
layers were washed with brine, dried over MgSO4, filtered,
Methyl 2-O-carboxymethyl-3,4-di-O-(4-methoxybenzyl)-6-O-
palmitoylamino-α-D-glucopyranoside (10)
To a solution of compound 9 (74 mg, 0.096 mmol) in MeOH evaporated and purified by column chromatography over silica
(2 mL) was added LiOH (23 mg, 0.96 mmol). The mixture was gel (petroleum ether/EtOAc: 1/1) to afford compound 12
stirred at room temperature for 48 h and then extracted with (12 mg, 60%) as a white solid: Rf = 0.44 (petroleum ether–
CH2Cl2 (3 × 10 mL). The combined organic layers were washed EtOAc 1/1); [α]D + 80.0 (c 0.1, CHCl3); mp 70 °C; 1H NMR
with aq. HCl (1 N, 10 mL) and brine (10 mL), dried over (400 MHz, CDCl3): δ 8.74 (s, 1H, NH), 4.80 (d, J = 3.2 Hz, 1H,
MgSO4, filtered, evaporated, and purified by column chromato- H-1), 4.48 (s, 2H, OCH2), 4.21–4.08 (m, 4H, OCH2, H-6), 3.88
graphy over silica gel (CH2Cl2/MeOH: 25/1) to afford (t, J = 9.3 Hz, 1H, H-4), 3.76–3.63 (m, 2H, H-2,5), 3.51 (t, J =
compound 10 (59 mg, 83%) as a white solid: Rf = 0.33 9.0 Hz, 1H, H-3), 3.42 (s, 3H, OCH3), 2.09 (t, J = 7.4 Hz, 2H,
(CH2Cl2–MeOH 25/1); [α]D + 62.0 (c 0.1, CHCl3); mp 115 °C; CH2), 1.70–1.56 (m, 4H, 2 × CH2), 1.38–1.19 (m, 42H, 21 ×
1H NMR (400 MHz, CDCl3): δ 8.14 (s, 1H, NH), 7.35–7.15 (m, CH2), 0.92–0.82 (m, 6H, 2 × CH3); 13C NMR (100 MHz, CDCl3):
4H, PMB), 6.95–6.77 (m, 4H, PMB), 4.82–4.52 (m, 5H, 2 × δ 173.8, 171.8 (CvO); 99.7 (C-1), 83.8 (CH), 75.9 (CH2), 71.8,
OCH2, H-1), 4.44 (d, J = 17.4 Hz, 1H, OCH), 4.36 (d, J = 17.4 Hz, 70.3 (CH); 69.3, 65.9 (CH2); 55.6 (OCH3), 33.3, 32.1, 29.8, 29.7,
1H, OCH), 4.20–3.93 (m, 2H, H-6), 3.81 (s, 3H, OCH3) 3.79 (s, 29.6, 29.5, 29.4, 29.3, 28.6, 25.9, 25.4, 22.8 (CH2); 14.3 (CH3);
3H, OCH3), 3.76–3.57 (m, 3H, H-3,4,5), 3.49 (dd, J = 9.5, 3.1 Hz, HRMS (ESI) m/z 696.5025, Calcd for C37H71NaNO9 [M + Na]+
1H, H-2), 3.30 (s, 3H, OCH3), 2.43–1.95 (m, 2H, CH2), 696.5027.
1.68–1.52 (m, 2H, CH2), 1.36–1.06 (m, 24H, 12 × CH2), 0.88 (t,
Methyl 2-O-carboxymethyl-3,4-di-O-(4-methoxybenzyl)-6-O-tert-
J = 6.4 Hz, 3H, CH3); 13C NMR (100 MHz, CDCl3): δ 172.1,
butyldimethylsilyl-α-D-glucopyranoside (13)
171.0 (CvO); 160.0, 159.7 (Cq, PMB); 130.4, 130.2 (CH); 129.5,
128.5 (Cq); 114.2, 114.1 (CH); 97.2 (C-1), 82.2, 78.0, 77.4 (CH); To a mixture of compound 4 (0.31 g, 0.57 mmol), aqueous
74.9, 74.3, 72.6, 70.5 (CH2); 69.5 (CH), 55.6, 55.4 (OCH3); 33.4, NaOH (5 mL, 50%) and TBAI (104 mg, 0.28 mmol) in toluene
32.0, 29.8, 29.6, 29.5, 25.4, 22.8 (CH2); 14.3 (CH3); HRMS (ESI) (10 mL) was added dropwise ethyl bromoacetate (0.13 mL,
m/z 768.4297, Calcd for C41H63NaNO11 [M + Na]+ 768.4299.
1.14 mmol). After stirring at room temperature for 3 days, the
solution was concentrated under vacuum. The residue was
diluted with EtOAc (50 mL), washed with saturated aq. HCl
(1 N, 3 × 20 mL), H2O (20 mL) and brine (20 mL), dried over
Methyl 2-O-dodecyloxycarbonylmethyl-3,4-di-O-(4-
methoxybenzyl)-6-O-palmitoylamino-α-D-glucopyranoside (11)
Esterification of compound 10 (52 mg, 0.07 mmol) with MgSO4, filtered, evaporated, and purified by column chromato-
1-dodecanol according to the general procedure and graphy over silica gel (CH2Cl2/MeOH: 100/3) to afford
purification by column chromatography over silica gel compound 4 (103 mg, conversion: 67%) and compound 13
(petroleum ether/EtOAc: 2/1) afforded compound 11 (40 mg, (170 mg, corrected yield: 74%) as a white powder: Rf = 0.25
63%) as a white solid. Compound 11 could also be prepared (CH2Cl2–MeOH 100/3); [α]D + 64.0 (c 0.1, CHCl3); mp 138 °C;
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1H NMR (400 MHz, CDCl3): δ 7.38–7.20 (m, 4H, PMB), Methyl 2-O-dodecyloxycarbonylmethyl-3,4-di-O-(4-
6.99–6.82 (m, 4H, PMB), 4.79–4.46 (m, 5H, 2 × OCH2, H-1), methoxybenzyl)-6-O-phthalimido-α-D-glucopyranoside (16)
4.40 (d, J = 17.4 Hz, 1H, OCH), 4.32 (d, J = 17.4 Hz, 1H, OCH),
The phthalimido group was introduced at the 6-position of
4.02–3.75 (m, 8H, 2 × OCH3, H-6), 3.71 (t, J = 8.9 Hz, 1H, H-3),
compound 15 (55 mg, 0.083 mmol) using the Mitsunobu reac-
3.61–3.43 (m, 3H, H-2,4,5), 3.30 (s, 3H, OCH3), 0.91 (s, 9H,
tion according to the general procedure. Purification by
column chromatography over silica gel (petroleum ether/
EtOAc: 3/1) afforded the desired compound (66 mg, 98%) as a
tBu), 0.16–0.02 (m, 6H, Si(CH3)2); 13C NMR (100 MHz, CDCl3):
δ 172.1 (CvO), 159.9, 159.7 (Cq); 130.2, 130.0 (CH); 129.5,
128.6 (Cq); 114.2, 114.1 (CH); 96.8 (C-1), 82.0, 78.5, 77.6 (CH);
74.8, 72.4 (CH2); 71.5 (CH), 70.5, 61.9 (CH2); 55.4, 55.1 (OCH3);
26.0 (CH3, tBu), 18.4 (Cq, tBu), −5.0, −5.2 (CH3, Si(CH3)2);
HRMS (ESI) m/z 629.2759, Calcd for C31H46NaO10Si [M + Na]+
629.2758.
colourless paste: Rf = 0.77 (petroleum ether–EtOAc 1/1); [α]D
+
65.7 (c 0.1, CHCl3); 1H NMR (400 MHz, CDCl3): δ 7.88–7.72 (m,
4H, Phth), 7.36–7.26 (m, 4H, PMB), 6.91–6.82 (m, 4H, PMB),
4.98 (d, J = 10.1 Hz, 1H, OCH), 4.82 (d, J = 10.1 Hz, 1H, OCH),
4.75–4.33 (m, 7H, 2 × OCH2, H-1,6), 4.15 (t, J = 6.9 Hz, 2H,
OCH2), 3.91–3.72 (m, 9H, 2 × OCH3, H-3,4,5), 3.58 (dd, J = 9.1,
3.4 Hz, 1H, H-2), 3.35 (s, 3H, OCH3), 1.70–1.57 (m, 2H, CH2),
1.43–1.19 (m, 18H, 9 × CH2), 0.88 (t, J = 6.8 Hz, 3H, CH3);
13C NMR (100 MHz, CDCl3): δ 170.3, 163.3 (CvO); 159.5, 159.3
(Cq); 134.6 (CH), 130.6, 130.2 (Cq); 130.1, 129.9 (CH); 129.0
(Cq), 123.6 (CH), 113.93, 113.88 (CH); 98.2 (C-1), 83.4, 79.1
(CH); 76.4 (CH2), 76.0 (CH), 74.9, 73.1, 70.9 (CH2); 69.1 (CH),
65.1 (CH2), 55.6, 55.3 (OCH3); 32.0, 29.8, 29.7, 29.6, 29.5, 29.4,
28.7, 26.0, 22.8 (CH2); 14.3 (CH3); HRMS (ESI) m/z 844.3678,
Calcd for C45H59KNO12 [M + K]+ 844.3674.
Methyl 2-O-dodecyloxycarbonylmethyl-3,4-di-O-(4-
methoxybenzyl)-6-O-tert-butyldimethylsilyl-α-D-
glucopyranoside (14)
Esterification of compound 13 (148 mg, 0.24 mmol) with
1-dodecanol according to the general procedure and purifi-
cation by column chromatography over silica gel (petroleum
ether/EtOAc: 5/1) afforded compound 14 (144 mg, 76%) as a
white paste: Rf = 0.63 (petroleum ether–EtOAc 4/1); [α]D + 23.0
1
(c 0.1, CHCl3); H NMR (400 MHz, CDCl3): δ 7.50–7.19 (m, 4H,
PMB), 7.05–6.80 (m, 4H, PMB), 5.00–4.32 (m, 7H, 3 × OCH2,
H-1), 4.10 (t, J = 6.7 Hz, 2H, OCH2), 4.04–3.68 (m, 9H, 2 ×
OCH3, H-3,6), 3.64–3.44 (m, 3H, H-2,4,5), 3.26 (s, 3H, OCH3),
1.70–1.54 (m, 2H, CH2), 1.52–1.17 (m, 18H, 9 × CH2), 1.02–0.82
(m, 12H, tBu, CH3), 0.16–0.02 (m, 6H, Si(CH3)2); 13C NMR
(100 MHz, CDCl3): δ 170.4 (CvO), 159.4, 159.3, 130.7, 130.3
(Cq); 129.8, 113.8 (CH); 97.7 (C-1), 83.6, 79.7, 76.8 (CH); 74.7,
73.0 (CH2); 71.3 (CH), 70.9, 65.0, 62.3 (CH2); 55.3, 54.9 (OCH3);
32.0, 29.7, 29.6, 29.4, 29.3, 28.7 (CH2); 26.0 (CH3, tBu), 25.9,
22.8 (CH2); 18.4 (Cq, tBu), 14.2 (CH3), −5.1, −5.3 (CH3,
Si(CH3)2); HRMS (ESI) m/z 797.4639, Calcd for C43H70NaO10Si
[M + Na]+ 797.4636.
Methyl 6-O-amino-2-O-dodecyloxycarbonylmethyl-3,4-di-O-(4-
methoxybenzyl)-α-D-glucopyranoside (17)
Hydrazinolysis of compound 16 (58 mg, 0.071 mmol) according
to the general procedure and purification by column chromato-
graphy over silica gel (petroleum ether/EtOAc: 1/1) afforded
compound 17 (35 mg, 73%) as a yellowish paste: Rf = 0.39
(petroleum ether–EtOAc 1/1); [α]D + 45.3 (c 0.1, CHCl3); 1H NMR
(400 MHz, CDCl3): δ 7.34–7.24 (m, 4H, PMB), 6.93–6.84 (m, 4H,
PMB), 4.93–4.34 (m, 7H, 3 × OCH2, H-1), 4.13 (t, J = 6.8 Hz, 2H,
OCH2), 3.91–3.74 (m, 9H, 2 × OCH3, H-3,6), 3.72–3.65 (m, 1H,
H-5), 3.56–3.45 (m, 2H, H-2,4), 3.30 (s, 3H, OCH3), 1.69–1.57 (m,
2H, CH2), 1.39–1.17 (m, 18H, 9 × CH2), 0.88 (t, J = 6.8 Hz, 3H,
CH3); 13C NMR (100 MHz, CDCl3): δ 170.4 (CvO), 159.5, 159.4,
130.5, 130.2 (Cq); 130.1, 129.9, 114.0, 113.9 (CH); 98.1 (C-1),
83.5, 79.4, 76.7 (CH); 74.8, 74.3, 73.1, 70.9 (CH2); 69.4 (CH), 65.0
(CH2), 55.4, 55.3 (OCH3); 32.0, 29.8, 29.7, 29.6, 29.5, 29.4, 28.7,
26.0, 22.8 (CH2); 14.3 (CH3); HRMS (ESI) m/z 698.3884, Calcd
for C37H57NaNO10 [M + Na]+ 698.3880.
Methyl 2-O-dodecyloxycarbonylmethyl-3,4-di-O-(4-
methoxybenzyl)-α-D-glucopyranoside (15)
Desilylation of compound 14 (74 mg, 0.096 mmol) according
to the general procedure and purification by column chromato-
graphy over silica gel (petroleum ether/EtOAc: 1/1) afforded
compound 15 (45 mg, 71%) as a colourless paste: Rf = 0.10
(petroleum ether–EtOAc 3/1); [α]D + 56.7 (c 0.1, CHCl3); 1H
NMR (400 MHz, CDCl3): δ 7.40–7.22 (m, 4H, PMB), 7.00–6.81
Methyl 3,4-di-O-(4-methoxybenzyl)-2-O-palmitoyl-6-O-tert-
butyldimethylsilyl-α-D-glucopyranoside (18)
(m, 4H, PMB), 4.91–4.35 (m, 7H, 3 × OCH2, H-1), 4.10 (t, J = 6.8 Esterification of compound 4 (0.62 g, 1.13 mmol) with palmitic
Hz, 2H, OCH2), 3.91–3.73 (m, 7H, 2 × OCH3, H-3′), 3.73 (dd, J = acid according to the general procedure and purification by
11.9, 2.8 Hz, 1H, H-6a), 3.65 (dd, J = 11.9, 3.2 Hz, 1H, H-6b), column chromatography over silica gel (petroleum ether/
3.57–3.43 (m, 3H, H-2,4,5), 3.26 (s, 3H, OCH3), 1.79 (s, 1H, EtOAc: 8/1) afforded compound 18 (0.88 g, 99%) as a colour-
OH), 1.65–1.55 (m, 2H, CH2), 1.40–1.18 (m, 18H, 9 × CH2), 0.85 less paste: Rf = 0.78 (petroleum ether–EtOAc 3/1); [α]D + 26.0
1
(t, J = 6.8 Hz, 3H, CH3); 13C NMR (100 MHz, CDCl3): δ 170.4 (c 0.1, CHCl3); H NMR (400 MHz, CDCl3): δ 7.25–7.14 (m, 4H,
(CvO), 159.5, 159.4, 130.4, 130.1 (Cq); 130.0, 129.8, 113.9 PMB), 6.94–6.81 (m, 4H, PMB), 5.53 (t, J = 9.6 Hz, 1H, H-3),
(CH); 98.0 (C-1), 83.3, 79.6, 76.4 (CH); 74.7, 73.0, 70.8 (CH2); 4.61–4.47 (m, 5H, 2 × OCH2, H-1), 3.90–3.74 (m, 8H, 2 × OCH3,
70.5 (CH), 65.0, 61.9 (CH2); 55.3, 55.2 (OCH3); 32.0, 29.7, 29.6, H-6), 3.68–3.62 (m, 1H, H-5), 3.52 (t, J = 9.6 Hz, 1H, H-4),
29.4, 29.3, 28.7, 25.9, 22.8 (CH2); 14.2 (CH3); HRMS (ESI) m/z 3.43–3.36 (m, 1H, H-2), 3.33 (s, 3H, OCH3), 2.26–2.18 (m, 2H,
683.3775, Calcd for C37H56NaO10 [M + Na]+ 683.3771.
CH2), 1.68–1.55 (m, 2H, CH2), 1.50–1.16 (m, 24H, 12 × CH2),
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0.98–0.82 (m, 12H, tBu, CH3), 0.11–0.05 (m, 6H, Si(CH3)2); 13C compound 21 (0.28 g, 82%) as a white paste: Rf = 0.25
NMR (100 MHz, CDCl3): δ 172.7 (CvO), 159.4, 159.3, 130.4, (petroleum ether–EtOAc 1/1); [α]D + 31.7 (c 0.1, CHCl3); 1H NMR
130.3 (Cq); 129.5, 129.4, 113.9 (CH); 97.8 (C-1), 77.7, 76.0 (CH); (400 MHz, CDCl3): δ 7.26–7.17 (m, 4H, PMB), 6.94–6.82 (m,
73.8 (CH2), 73.5 (CH), 72.6 (CH2), 71.2 (CH), 62.2 (CH2), 55.4, 4H, PMB), 5.52 (t, J = 9.6 Hz, 1H, H-3), 4.62–4.45 (m, 5H, 2 ×
55.0 (OCH3); 34.7, 32.1, 29.8, 29.6, 29.5, 29.4 (CH2); 26.1 (CH3, OCH2, H-1), 3.94–3.76 (m, 9H, 2 × OCH3, H-5,6), 3.56–3.47 (m,
tBu), 25.1, 22.8 (CH2); 18.5 (Cq, tBu), 14.3 (CH3), −5.0, −5.2 1H, H-4), 3.42 (dd, J = 10.0, 3.4 Hz, 1H, H-2), 3.34 (s, 3H,
(CH3, Si(CH3)2); HRMS (ESI) m/z 809.5005, Calcd for OCH3), 2.30–2.21 (m, 2H, CH2), 1.69–1.56 (m, 2H, CH2),
C45H74NaO9Si [M + Na]+ 809.5000.
1.42–1.17 (m, 24H, 12 × CH2), 0.88 (t, J = 6.8 Hz, 3H, CH3);
13C NMR (100 MHz, CDCl3): δ 172.6 (CvO), 159.5, 159.4, 130.1
(Cq); 129.7, 129.6, 113.9 (CH); 98.0 (C-1), 77.4, 76.0 (CH); 74.3,
73.9 (CH2); 73.3 (CH), 72.7 (CH2), 69.3 (CH), 55.4 (OCH3), 34.7,
Methyl 3,4-di-O-(4-methoxybenzyl)-2-O-palmitoyl-α-D-
glucopyranoside (19)
Desilylation of compound 18 (0.82 g, 1.04 mmol) according to 32.0, 29.8, 29.6, 29.5, 29.4, 25.1, 22.8 (CH2); 14.3 (CH3); HRMS
the general procedure and purification by column chromato- (ESI) m/z 726.3936, Calcd for C39H61KNO9 [M + K]+ 726.3983.
graphy over silica gel (petroleum ether/EtOAc: 1/1) afforded
Methyl 3,4-di-O-(4-methoxybenzyl)-2-O-palmitoyl-6-O-
palmitoylamino-α-D-glucopyranoside (22)
compound 19 (0.48 g, 67%) as a white paste: Rf = 0.13
(petroleum ether–EtOAc 3/1); [α]D + 23.7 (c 0.1, CHCl3); 1H NMR
(400 MHz, CDCl3): δ 7.26–7.17 (m, 4H, PMB), 6.91–6.82 (m, Coupling of compound 21 (0.34 g, 0.50 mmol) with palmitic
4H, PMB), 5.54 (t, J = 9.6 Hz, 1H, H-3), 4.62–4.45 (m, 5H, 2 × acid according to the general procedure followed by purifi-
OCH2, H-1), 3.81, 3.79 (2 × s, 6H, 2 × OCH3), 3.77–3.65 (m, 3H, cation by column chromatography over silica gel (petroleum
H-5,6), 3.56 (t, J = 9.5 Hz, 1H, H-4), 3.40 (dd, J = 10.0, 3.5 Hz, ether/EtOAc: 2/1) afforded compound 22 (0.35 g, 76%) as a
1H, H-2), 3.33 (s, 3H, OCH3), 2.29–2.21 (m, 2H, CH2), white solid: Rf = 0.56 (petroleum ether–EtOAc 1/1); [α]D + 32.7
1
1.67–1.56 (m, 2H, CH2), 1.39–1.18 (m, 24H, 12 × CH2), 0.88 (t, (c 0.1, CHCl3); mp 90 °C; H NMR (400 MHz, CDCl3): δ 8.03 (s,
J = 6.8 Hz, 3H, CH3); 13C NMR (100 MHz, CDCl3): δ 172.7 1H, NH), 7.35–7.12 (m, 4H, PMB), 6.95–6.82 (m, 4H, PMB),
(CvO), 159.5, 130.2, 130.1 (Cq); 129.7, 129.6, 113.9 (CH); 98.1 5.52 (t, J = 9.6 Hz, 1H, H-3), 4.68–4.45 (m, 5H, 2 × OCH2, H-1),
(C-1), 77.4, 75.7 (CH); 74.0 (CH2), 73.4 (CH), 72.7 (CH2), 70.4 4.20–3.96 (m, 2H, H-6), 3.90–3.75 (m, 7H, 2 × OCH3, H-5),
(CH), 61.8 (CH2), 55.4 (OCH3), 34.7, 32.1, 29.8, 29.7, 29.5, 29.4, 3.70–3.58 (m, 1H, H-4), 3.45–3.40 (m, 1H, H-2), 3.34 (s, 3H,
25.1, 22.8 (CH2); 14.3 (CH3); HRMS (ESI) m/z 695.4133, Calcd OCH3), 2.30–1.94 (m, 4H, 2 × CH2), 1.70–1.54 (m, 4H, 2 × CH2),
for C39H60NaO9 [M + Na]+ 695.4135.
1.50–1.15 (m, 48H, 24 × CH2), 0.95–0.84 (m, 6H, 2 × CH3); 13C
NMR (100 MHz, CDCl3): δ 172.7 (CvO), 159.6, 130.1, 130.0
(Cq); 129.6, 114.0 (CH); 98.1 (C-1), 77.4, 75.8 (CH); 74.8, 74.0
(CH2); 73.4 (CH), 72.8 (CH2), 69.4 (CH), 55.6, 55.4 (OCH3);
Methyl 3,4-di-O-(4-methoxybenzyl)-2-O-palmitoyl-6-O-
phthalimido-α-D-glucopyranoside (20)
The phthalimido group was introduced at the 6-position of 34.7, 33.5, 32.1, 29.8, 29.7, 29.5, 29.4, 25.1, 22.8 (CH2); 14.3
compound 19 (0.43 g, 0.64 mmol) using the Mitsunobu reaction (CH3); HRMS (ESI) m/z 948.6542, Calcd for C55H91NaNO10 [M +
according to the general procedure. Purification by column Na]+ 948.6541.
chromatography over silica gel (petroleum ether/EtOAc: 2/1)
Methyl 2-O-palmitoyl-6-O-palmitoylamino-α-D-glucopyranoside
afforded compound 20 (0.51 g, 98%) as a colourless paste: Rf =
1
(23)
0.62 (petroleum ether–EtOAc 1/1); [α]D + 48.3 (c 0.1, CHCl3); H
NMR (400 MHz, CDCl3): δ 7.93–7.73 (m, 4H, Phth), 7.35–7.21 To a solution of compound 22 (150 mg, 0.16 mmol) in CH2Cl2
(m, 4H, PMB), 6.94–6.81 (m, 4H, PMB), 5.57 (t, J = 9.6 Hz, 1H, (4 mL) was added TFA (2 mL, 5% in CH2Cl2). The mixture was
H-3), 4.83–4.38 (m, 7H, 2 × OCH2, H-1,6), 3.99 (t, J = 9.4 Hz, stirred at room temperature for 1 h under argon and then
H-4), 3.93–3.84 (m, 1H, H-5), 3.80, 3.77 (2 × s, 6H, 2 × OCH3), extracted with CH2Cl2 (3 × 20 mL). The combined organic
3.52 (dd, J = 10.1, 3.4 Hz, 1H, H-2), 3.34 (s, 3H, OCH3), 2.27 (t, layers were washed with brine, dried over MgSO4, filtered,
J = 7.7 Hz, 2H, CH2), 1.72–1.56 (m, 2H, CH2), 1.49–1.17 (m, 24H, evaporated and purified by column chromatography over silica
12 × CH2), 0.88 (t, J = 6.8 Hz, 3H, CH3); 13C NMR (100 MHz, gel (CH2Cl2/MeOH: 100/3) to afford compound 23 (85 mg,
CDCl3): δ 172.7, 163.3 (CvO); 159.5, 159.4 (Cq); 134.6 (CH), 77%) as a white powder: Rf = 0.28 (CH2Cl2–MeOH 100/3); [α]D
130.3 (Cq); 129.8, 129.6 (CH); 129.0 (Cq), 123.7 (CH), 113.9 (CH), + 84.7 (c 0.1, CHCl3); mp 96 °C; 1H NMR (400 MHz, CDCl3):
98.3 (C-1), 77.0 (CH), 76.0 (CH2), 75.2 (CH), 74.2 (CH2), 73.5 δ 8.55 (s, 1H, NH), 5.14 (t, J = 9.7 Hz, 1H, H-3), 4.77 (d, 1H, J =
(CH), 72.8 (CH2), 69.4 (CH), 55.7, 55.4 (OCH3); 34.7, 32.1, 29.8, 3.6 Hz, 1H, H-1), 4.25–4.13 (m, 2H, H-6), 3.96 (t, J = 9.6 Hz, 1H,
29.7, 29.5, 29.4, 25.1, 22.8 (CH2); 14.3 (CH3); HRMS (ESI) m/z H-4), 3.83–3.73 (m, 1H, H-5), 3.67–3.56 (m, 1H, H-2), 3.43 (s,
840.4296, Calcd for C47H63NaNO11 [M + Na]+ 840.4299.
3H, OCH3), 2.41 (t, J = 7.6 Hz, 2H, CH2), 2.09 (t, J = 7.3 Hz, 2H,
CH2), 1.73–1.57 (m, 4H, 2 × CH2), 1.45–1.19 (m, 48H, 24 ×
CH2), 0.94–0.84 (m, 6H, 2 × CH3); 13C NMR (100 MHz, CDCl3):
δ 175.0, 171.9 (CvO); 100.0 (C-1), 75.5 (CH2), 75.0, 71.4, 70.7,
Methyl 6-O-amino-3,4-di-O-(4-methoxybenzyl)-2-O-palmitoyl-
α-D-glucopyranoside (21)
Hydrazinolysis of compound 20 (0.41 g, 0.50 mmol) according 68.1 (CH); 55.7 (OCH3), 34.6, 33.2, 32.1, 29.8, 29.6, 29.5, 29.4,
to the general procedure and purification by column chrom- 29.2, 25.3, 25.1, 22.8 (CH2); 14.3 (CH3); HRMS (ESI) m/z
atography over silica gel (petroleum ether/EtOAc: 1/1) afforded 708.5392, Calcd for C39H75NaNO8 [M + Na]+ 708.5390.
Org. Biomol. Chem.
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Paper
19 L. A. Marcaurelle, Y. Shin, S. Goon and C. R. Bertozzi, Org.
Lett., 2001, 3, 3691–3694.
Acknowledgements
N.C. gratefully acknowledges the China Scholarship Council 20 S. Andre, O. Renaudet, I. Bossu, P. Dumy and H. J. Gabius,
(CSC) for a doctoral scholarship.
J. Pept. Sci., 2011, 17, 427–437.
21 J. E. Hudak, H. H. Yu and C. R. Bertozzi, J. Am. Chem. Soc.,
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22 E. L. Smith, J. P. Giddens, A. T. Iavarone, K. Godula,
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