Synthesis of thioglycoside analogues of maradolipid

Article abstract of DOI:10.1021/jo400274s

We describe here the first synthesis of thioglycoside analogues of maradolipid, based on a new procedure for the synthesis of 1-thiotrehalose developed recently in our laboratories. The challenging α,α- (1→1′) thioglycosidic linkage was constructed by Sch

Full text of DOI:10.1021/jo400274s

Note
pubs.acs.org/joc
Synthesis of Thioglycoside Analogues of Maradolipid
Xiaojun Zeng,† Raymond Smith,‡ and Xiangming Zhu*,†,‡
†
College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China
‡ Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield,
Dublin 4, Ireland
S
* Supporting Information
ABSTRACT: We describe here the first synthesis of
thioglycoside analogues of maradolipid, based on a new
procedure for the synthesis of 1-thiotrehalose developed
recently in our laboratories. The challenging α,α-(1→1′)
thioglycosidic linkage was constructed by Schmidt’s inverse
procedure in very high yield and excellent stereoselectivity.
Subsequent protecting group manipulation and coupling with
different fatty acids led smoothly to a group of symmetrical
and unsymmetrical thiomaradolipids which would be of high
value for biological studies.
here has been considerable interest in trehalose-
containing glycolipids1 since trehalose dimycolates were
environmental conditions, as the similar trehalose dimycolates
and trehalose itself are known to confer on bacteria the ability
to survive harsh conditions and reanimate subsequently by
imparting stability to the lipid layer of the cell wall.4 They may
also possess other important immunological activities.3
T
found to be associated with the virulence of pathogenic
mycobacteria. A large number of structurally different trehalose
glycolipids were isolated from bacteria in the past few decades
and have been shown to have various biological activities
including antitumor activity, in vivo macrophage activation, and
other immunostimulatory activity. An excellent review has been
published describing the synthesis and biological activities of
various trehalose glycolipids.2 Very recently, a novel class of
diacyltrehaloses named maradolipids, which are similar to
trehalose dimycolate in structure, were also isolated from the
dauer larvae of Caenorhabditis elegans and represent the first
group of diacyltrehaloses found in animals.3 These glycolipids
are composed of a mixture of at least 60 derivatives of trehalose,
which differ only in the two fatty acid chains at the 6- and 6′-
positions. The fatty acid chains can be identical; i.e., some are
symmetrical maradolipids. But there are also many unsym-
metrical ones in which the two fatty acids are different.3 The
major component was characterized as 6-O-(13-methylmyr-
istoyl)-6′-O-oleoyltrehalose 1 (Figure 1), which amounts to 7−
8% of the total maradolipids. Maradolipids are very likely
involved in protecting dauer larvae against unfavorable
In order to contribute to the unravelling of the biological
function of maradolipids, several maradolipids containing sulfur
in the glycosidic linkage were synthesized in this report as
stable analogues. S-Glycosides are very attractive substitutes for
O-glycosides, as it is well-known that they are much less
susceptible to enzymatic cleavage as well as chemical
degradation.5 Also, they often exhibit similar solution
conformation and similar or even more potent bioactivities
compared to the corresponding O-glycosides. For example, an
S-linked glycopeptide mimic of tyrocidine displayed a greater
inhibitory activity against B. subtilis than the natural antibiotic.6
Therefore, synthesis of thioglycosides has been actively pursued
in many laboratories.7 Recently we achieved the first total
synthesis of the thioglycoside analogue of α-galactosylceramide
KRN7000 by using a nonconventional approach,8 and the
subsequent bioassay demonstrated that this thioglycoside
possessed similar potency to KRN7000 in human NKT cell
activation.9 In view of the biological importance of trehalose
glycolipids,2 investigations toward the synthesis of thioglycosi-
dic trehalose glycolipids that may prove useful in biological
studies and as potential therapeutic agents were also initiated.
We wish to report here the first synthesis of thioglycoside
analogues of maradolipid.10
Conceivably, thiomaradolipids could be assembled in two
ways. One is to synthesize 1-thiotrehalose first and then
introduce the fatty acid chains onto the 6- and 6′-positions, the
other is a more convergent strategy in which 6-O-fatty acylated
Received: February 5, 2013
Published: March 13, 2013
Figure 1. Structures of maradolipid 1 and S-maradolipid 2.
© 2013 American Chemical Society
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Note
Scheme 1. Synthesis of 1-Thiotrehalose 7
sugar building blocks are preprepared and then used to build up
the challenging α,α-(1→1′) thioglycosidic linkage. Apparently,
the former strategy offers some advantage, as it could allow a
rapid means of forming thiomaradolipid libraries through the
simple attachment of different fatty acid chains. As such, this
strategy was applied to our synthesis to provide more valuable
thioglycosides for biological studies. Hence, 1-thiotrehalose was
first synthesized based on our previous work;11 i.e., α-thiosugar
411 was glycosylated with trichloroacetimidate 312 in the
presence of TMSOTf to form the fully protected α,α-
thiotrehalose 5 (Scheme 1). We noted previously that 1.0
equiv of TMSOTf was required for this glycosidation reaction
due to the low reactivity of the α-anomeric thiol.11 The
relatively large amounts of TMSOTf very likely react with the
thiol to generate in situ the glucosyl silyl sulfide which
possessed higher reactivity than the thiol, thereby facilitating
the reaction. Based on this speculation, we thought that
Schmidt’s inverse procedure13 could possibly further increase
the reaction yield because by the inverse procedure the thiol
would first be mixed with TMSOTf prior to the coupling.
Indeed, following the inverse procedure 5 was produced in a
much higher yield (90%), as shown in Scheme 1. Here it should
be mentioned that unlike the normal sugar hemiacetals, which
could mutarotate easily under most conditions, glycosyl thiols
are quite stable in terms of configuration, and their
mutarotation does not occur readily.14 The α-configuration of
thiosugar 4 could thus be well maintained during the
glycosidation reaction, which, together with the high α-
stereoselectivity of the reaction, ensured the α,α-glycosidic
linkage. The anomeric configurations of 5 were confirmed by
the X-ray diffraction analysis of compound 7 (vide infra).
Subsequently, 5 was converted into the fully acetylated 1-
thiotrehalose 6 as described previously in 86% overall yield.11
To access the target glycolipids, the 6- and 6′-positions of
compound 6 must be selectively exposed for the introduction
of the fatty acid chains. Considering that the TMS group had
already been used successfully for this purpose in the synthesis
of maradolipid 1,10a acetyl groups were thus replaced with TMS
groups, as shown in Scheme 1, under the normal deacetylation
and silylation conditions, to provide the TMS-protected 1-
thiotrehalose 7 in 80% overall yield. Suitable crystals of 7 were
obtained for X-ray analysis by slow crystallization from
methanol at −15 °C. The crystallographic data clearly show
the constructed α,α-(1→1′) glycosidic linkage (Figure 2).
Figure 2. X-ray crystal structure of 7; thermal ellipsoids are drawn on
the 15% probability level, and TMS groups are represented by the Si
atoms only.
Next, 7 was treated with K2CO3 in methanol and
dichloromethane following Kulkarni’s procedure10a in order
to selectively remove the more labile primary TMS groups, but
unfortunately the reaction did not work well leading to the
formation of a mixture of several products. Some attempts to
optimize the yield of the desired product, including changes in
solvent ratio, the amount of K2CO3, and reaction temperature,
were unsuccessful. Apparently, the anomeric sulfur impairs the
chemoselective alkaline hydrolysis. We then turned to acidic
hydrolysis, which was also known in the literature for selective
removal of the TMS group on carbohydrate substrates.15
Hence, compound 7 was subjected to acidic conditions using
50 equiv of HOAc in acetone and methanol solvent mixture, as
expected, the desired product 8 was produced in a very high
yield (Scheme 2). Coupling between the alcohol and fatty acids
was subsequently conducted in the presence of DCC and
DMAP in dichloromethane. As a test, commercially available
palmitic acid was first chosen as the fatty acid and coupled with
8 under the action of DCC to furnish the maradolipid analogue
9 in 87% yield. Similarly, coupling of 8 with eicosanoic acid and
docosanoic acid under the same conditions also proceeded
smoothly to give the corresponding glycolipids 10 and 11 in
84% and 45% yields, respectively. Biologically more relevant
fatty acids, oleic acid and 13-methylmyristic acid,16 were also
introduced onto the 6,6′-positions of thiotrehalose 8 by the
same procedure to give rise to the desired maradolipid
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Note
Scheme 2. Synthesis of S-Maradolipids 9−13
analogues 12 and 13 in 90% and 89% yields, respectively. In all
these coupling reactions, an excess of fatty acids (3 equiv) was
used to ensure the acylation of both 6,6′-positions to form the
symmetrical thiomaradolipids.
Scheme 3. Synthesis of S-Maradolipid 15
Here it is worth noting that these smooth couplings, together
with the above-mentioned highly stereoselective procedure for
the synthesis of 1-thiotrehalose, provided a convenient access
to various symmetrical thiomaradolipids, which can be used for
biological evaluation upon deprotection.
Our attention then turned toward applying the DCC
coupling to the synthesis of unsymmetrical thiomaradolipids.
Following Kulkarni’s procedure,10a 8 was first treated with 1.0
equiv of 13-methylmyristic acid16 in the presence of DCC and
DMAP to afford the desired monoacylated intermediate 14 in a
satisfactory yield of 50%, which was then further acylated with
oleic acid under the same conditions to give the unsymmetrical
thiomaradolipid 15 in very high yield (Scheme 3).
Finally, compounds 9−13 and 15 were all treated with acidic
ion-exchange resin Amberlite IR120 in methanol to furnish the
corresponding desired target molecules 16−20 and 2 in very
high yields (80−93%), as shown in Scheme 4. The synthetic
samples were purified by flash chromatography on silica gel
(eluant: CH2Cl2/MeOH 10:1) and characterized by NMR and
HR-ESIMS.
strategy presented here could also be applied to the preparation
of other thioglycoside analogues of trehalose glycolipids. Work
is in progress to test the immunological bioactivities of the
synthesized glycolipids.
In summary, as an extension of our previous project,8,17 in
this report, a series of 1-thiotrehalose-derived glycolipids
including unsymmetrical thiomaradolipid 2 were synthesized
as catabolically stable analogues of maradolipid. In view of the
important bioactivities of maradolipids, these compounds are of
particular interest for studying their biological properties. In
addition, a great advantage of the synthesis is that the key α,α-
(1→1′) thioglycosidic linkage was constructed in a high-
yielding and highly stereoselective manner. The synthetic
EXPERIMENTAL SECTION
■
General Remarks. Reactions were performed in oven-dried
glassware. Solvents were evaporated under reduced pressure while
maintaining the water bath temperature below 40 °C. All reactions
were monitored by thin-layer chromatography (TLC) using silica gel
60 F254 and the compounds visualized by UV or by treatment with 8%
H2SO4 in methanol followed by heating. Flash chromatography was
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Note
20.6, 20.5; ESI-MS m/z 717.2 [M + Na]+; ESI-HRMS calcd for
C28H38NaO18S [M + Na]+ 717.1677, found 717.1671.
Scheme 4. Synthesis of S-Maradolipids 16−20 and 2
2,3,4,6,2′,3′,4′,6′-Octa-O-trimethylsilyl-1-thio-α,α-D-treha-
lose (7). A solution of NaOMe (1.0 M) in MeOH was added to a
solution of compound 6 (1.5 g, 2.16 mmol) in CH2Cl2 (12 mL) and
MeOH (20 mL) until a pH of approximately 10 was reached. The
reaction mixture was stirred at room temperature for 4 h, after which
Amberlite-120 acidic resin was added to neutralize the solution. The
mixture was then filtered and concentrated in vacuo to give a residue,
which was azeotroped three times with toluene and directly used in the
next step without purification. The crude deacetylated product was
dissolved in CH2Cl2 (10 mL) and cooled at 0 °C. Et3N (10 mL, 86
mmol) and TMSCl (3.2 mL, 25.9 mmol) were added to the solution,
and the resulting mixture was stirred at room temperature overnight.
Another portion of TMSCl (1 mL, 8.6 mmol) was added to the
mixture at 0 °C, and the reaction was stirred until completion
indicated by TLC and then concentrated in vacuo. The crude product
was extracted with CH2Cl2 (25 mL × 3), and the combined organic
layer was dried over Na2SO4, filtered, and concentrated to give a
residue, which was purified by flash column chromatography
(petroleum ether/EtOAc, 30:1) to give the title compound 7 (1.61
g, 80%) as a white amorphous solid: [α]D +155.2 (c 0.48, CHCl3); 1H
NMR (400 MHz, CDCl3) δ 5.27 (d, J = 4.5 Hz, 2H), 3.91 (d, J = 8.6
Hz, 2H), 3.79 (dd, J = 11.6, 3.2, Hz, 2H), 3.68 (m, 2H), 3.63 (m, 4H),
3.56 (dd, J = 8.1, 17.1 Hz, 2H), 0.19 (s, 18H), 0.17 (s, 18H), 0.16 (s,
18H), 0.10 (s, 18H); 13C NMR (100 MHz, CDCl3) δ 83.9, 75.6, 73.1,
72.8, 71.5, 61.6, 1.3, 0.9, 0.5, −0.2; ESI-MS m/z 957.1 [M + Na]+; ESI-
HRMS calcd for C36H86NaO10SSi8 [M + Na]+ 957.3994, found
957.4022.
performed with the appropriate solvent system using 160−200 mesh
1
silica. Optical rotations were measured at 20 °C. H NMR spectra
were obtained on a 400 or 600 MHz and reported in parts per million
(δ) relative to the response of the solvent or to tetramethylsilane (0.00
ppm). Coupling constants (J) are reported in hertz (Hz). 13C NMR
spectra were recorded at 100 or 150 MHz and reported in δ relative to
the response of the solvent. The HRMS data were recorded on an LC-
time-of-flight mass spectrometer. Yields refer to chromatographically
pure compounds and are calculated based on reagents consumed.
6-O-Acetyl-2,3,4,2′,3′,4′,6′-hepta-O-benzyl-1-thio-α,α-D-tre-
halose (5). To a stirred suspension of thiol 4 (1.62 g, 3.2 mmol) and
4 Å molecular sieves (800 mg) in dry ether (15 mL) and CH2Cl2 (3
mL) was added TMSOTf (580 μL, 3.2 mmol) at −78 °C under N2.
After stirring for 30 min at the low temperature, trichloroacetimidate 3
(2.40 g, 3.5 mmol) was added to the mixture. The reaction was stirred
at the low temperature for 1 h and then quenched with Et3N and
filtered. The filtrates were concentrated in vacuo to give a residue,
which was purified by flash column chromatography (petroleum
ether/EtOAc, 5:1) to give the product 5 (2.96 g, 90%) as a colorless
2,3,4,2′,3′,4′-Hexa-O-trimethylsilyl-1-thio-α,α-D-trehalose
(8). HOAc (1.8 mL) was added to a solution of compound 7 (1.5 g,
1.6 mmol) in acetone (6 mL) and MeOH (8 mL) at 0 °C. When the
selective desilylation was deemed complete (TLC monitoring), the
reaction was quenched with aqueous NaHCO3 and extracted with
CH2Cl2 (25 mL × 3). The combined organic layer was washed with
brine (20 mL), dried over Na2SO4, filtered, and concentrated to give a
residue, which was purified by flash column chromatography
(petroleum ether/EtOAc, 4:1) to afford the title compound 8 (1.0
1
syrup: [α]D +124.0 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ
7.35−7.17 (m, 35H), 5.66 (d, J = 5.3 Hz, 1H), 5.63 (d, J = 4.1 Hz,
1H), 4.96 (d, J = 10.8 Hz, 1H), 4.94 (d, J = 10.8 Hz, 1H), 4.88 (d, J =
11.2 Hz, 1H), 4.85 (d, J = 11.2 Hz, 1H), 4.77 (d, J = 10.8 Hz, 1H),
4.76 (d, J = 11.2 Hz, 1H), 4.72−4.61 (m, 2H), 4.58 (d, J = 3.4 Hz,
1H), 4.54 (d, J = 5.08 Hz, 1H), 4.51−4.45 (m, 4H), 4.38−4.26 (m,
3H), 4.18 (dd, J = 1.8, 11.8 Hz, 1H), 3.93−3.88 (m, 3H), 3.81 (dd, J =
5.3, 9.6 Hz, 1H),3.64 (dd, J = 4.3, 10.6 Hz, 1H) 3.62−3.57 (m, 2H),
3.48 (t, J = 9.6, 9.0 Hz, 1H), 1.97 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 170.6, 138.7, 138.5, 138.4, 138.0, 137.7, 137.6, 128.5, 128.4,
128.0, 127.8, 110.0, 82.8, 82.7, 80.6, 80.4, 79.1, 78.8, 77.6, 77.3, 77.2,
75.8, 75.0, 73.6, 72.3, 72.0, 71.7, 69.9, 63.4, 29.8, 20.9; ESI-MS m/z
1053.4 [M + Na]+; ESI-HRMS calcd for C63H66NaO11S [M + Na]+
1053.4224, found 1053.4218.
2,3,4,6,2′,3′,4′,6′-Octa-O-acetyl-1-thio-α,α-D-trehalose (6).
To liquid NH3 (15 mL) at −78 °C was added Na° until the solution
became blue. A solution of thiotrehalose 5 (342 mg, 0.33 mmol) in
THF (4 mL) was then added to the above blue solution, and the
resulting mixture was stirred for 45 min at −78 °C. The reaction was
quenched by the addition of ammonium chloride until the blue color
disappeared. The NH3 was allowed to evaporate slowly, and the crude
residue was then poured into H2O (30 mL) and extracted with CHCl3
(20 mL). The aqueous layer was concentrated in vacuo to give the
crude 1-thiotrehalose, which was directly used in the next reaction.
Ac2O (4.5 mL) was added to a solution of the crude 1-thiotrehalose in
dry pyridine (10 mL), and the reaction was stirred at room
temperature overnight. The mixture was then concentrated in vacuo
to give a residue which was purified by flash column chromatography
(petroleum ether/EtOAc, 2:1) to afford 1-thiotrehalose octaacetate 6
as a white amorphous solid (197 mg, 86% over two steps): [α]D
+173.8 (c 0.4, CHCl3); 1H NMR (400 MHz, CDCl3) δ 5.83 (d, J = 5.8
Hz, 2H), 5.35 (t, J = 9.8 Hz, 2H), 5.06 (t, J = 5.9, 4.8 Hz, 2H), 5.02 (t,
J = 5.1, 9.3 Hz, 2H), 4.25 (s, 2H), 4.23 (s, 2H), 4.08 (t, J = 4.6, 9.7 Hz,
2H), 2.10 (s, 12H), 2.04 (s, 6H), 2.03 (s, 6H); 13C NMR (100 MHz,
CDCl3) δ 170.7, 169.9, 169.6, 169.5, 78.5, 70.4, 70.2, 68.5, 68.4, 61.8,
1
g, 79%) as a colorless syrup: [α]D +203.4 (c 0.39, CHCl3); H NMR
(600 MHz, CDCl3) δ 5.31 (d, J = 4.7 Hz, 2H), 3.98 (dt, J = 9.3, 2.9
Hz, 2H), 3.76 (s, 4H), 3.74−3.64 (m, 4H), 3.73−3.65 (t, J = 8.4, 2H),
1.92 (br s, 2H), 0.21 (s, 18H), 0.19 (s, 18H), 0.17 (s, 18H); 13C NMR
(150 MHz, CDCl3) δ 83.1, 75.3, 73.0, 72.7, 71.4, 61.4, 1.3, 0.9, 0.4;
ESI-MS m/z 813.9 [M + Na]+; ESI-HRMS calcd for C30H70NaO10SSi6
[M + Na]+ 813.3203, found 813.3218.
6,6′-Di-O-palmitoyl-2,3,4,2′,3′,4′-hexa-O-trimethylsilyl-1-
thio-α,α-D-trehalose (9). To a solution of diol 8 (79 mg, 0.1 mmol)
and palmitic acid (77 mg, 0.3 mmol) in CH2Cl2 (2 mL) were added
DCC (103 mg, 0.5 mmol) and DMAP (15.2 mg, 0.13 mmol) at 0 °C.
The cooling bath was then removed, the mixture was stirred at room
temperature overnight and concentranted in vacuo, and the residue
was purified by flash column chromatography (petroleum ether/
EtOAc, 25:1) to give the desired product 9 (110 mg, 87%) as a
1
colorless syrup: [α]D +115.9 (c 0.96, CHCl3); H NMR (400 MHz,
CDCl3) δ 5.30 (d, J = 4.9 Hz, 2H), 4.32 (dd, J = 11.9, 1.9 Hz, 2H),
4.15−4.10 (m, 2H), 4.07 (dd, J = 11.9, 3.3 Hz, 2H), 3.69 (dd, J = 9.1,
5.0 Hz, 2H), 3.63 (t, J = 8.6 Hz, 2H), 3.56−3.51 (t, J = 9.9, 2H), 2.34
(m, 4H), 1.67−1.58 (m, 4H), 1.27 (m, 48H), 0.88 (t, J = 6.8 Hz, 6H),
0.18 (s, 18H), 0.17 (s, 18H), 0.16 (s, 18H); 13C NMR (100 MHz,
CDCl3) δ 173.6, 83.5, 75.4, 72.6, 72.0, 70.7, 63.0, 34.2, 31.9, 29.72,
29.71, 29.67, 29.65, 29.5, 29.4, 29.3, 29.2, 24.8, 22.7, 14.1, 1.3, 0.9, 0.5;
ESI-MS m/z 1291.3 [M
+
Na]+; ESI-HRMS calcd for
C62H130NaO12SSi6 [M + Na]+ 1289.7796, found 1289.7832.
6,6′-Di-O-eicosanoyl-2,3,4,2′,3′,4′-hexa-O-trimethylsilyl-1-
thio-α,α-D-trehalose (10). The reaction procedure was identical to
that described for 9 except that eicosanoic acid (94 mg, 0.3 mmol) was
used instead of palmitic acid. Compound 10 (116 mg, 84%) was
1
isolated as a colorless syrup: [α]D +141.6 (c 0.83, CHCl3); H NMR
(400 MHz, CDCl3) δ 5.30 (d, J = 4.8 Hz, 2H), 4.32 (d, J = 11.0 Hz,
2H), 4.12 (d, J = 9.5 Hz, 2H), 4.07 (d, J = 12.0 Hz, 2H), 3.72−3.67
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Note
(m, 2H), 3.63 (t, J = 8.6 Hz, 2H), 3.55 (t, J = 8.6 Hz, 2H), 2.35 (m,
4H), 1.62 (m, 4H), 1.26 (m, 64H), 0.89 (t, J = 6.6 Hz, 6H), 0.18 (s,
18H), 0.17 (s, 18H), 0.16 (s, 18H); 13C NMR (100 MHz, CDCl3) δ
173.6, 83.5, 75.4, 72.6, 72.0, 70.7, 63.0, 34.2, 32.0, 29.73, 29.69, 29.68,
29.67, 29.5, 29.39, 29.35, 29.2, 24.8, 22.7, 14.2, 1.3, 0.9, 0.5; ESI-MS
m/z 1403.6 [M + Na]+; ESI-HRMS calcd for C70H146NaO12SSi6 [M +
Na]+ 1401.9048, found 1401.9088.
6-O-(13-Methylmyristyl)-6′-O-oleoyl-2,3,4,2′,3′,4′-hexa-O-
trimethylsilyl-1-thio-α,α-D-trehalose (15). To a solution of the
monoacylated maradolipid 14 (80 mg, 79 μmol) and oleic acid (51 μL,
0.16 mmol) in CH2Cl2 (3 mL) were added DCC (65 mg, 0.32 mmol)
and DMAP (10 mg, 79 μmol) at 0 °C. The cooling bath was then
removed, the mixture was stirred at room temperature overnight and
concentranted in vacuo, and the residue was purified by flash column
chromatography (petroleum ether/EtOAc, 25:1) to give the title
compound 15 (90 mg, 89%) as a colorless syrup: [α]D +116.9 (c 1.9,
CHCl3); 1H NMR (600 MHz, CDCl3) δ 5.37−5.36 (m, 2H), 5.32 (d,
J = 5.5 Hz, 2H), 4.33 (d, J = 11.8 Hz, 2H), 4.14−4.12 (m, 2H), 4.09
(dd, J = 12.1, 3.3 Hz, 2H), 3.71 (dd, J = 9.2, 5.1 Hz, 2H), 3.65 (t, J =
8.8 Hz, 2H), 3.61−3.47 (t, J = 8.9 Hz, 2H), 2.38−2.32 (m, 4H), 2.10−
2.00 (m, 4H), 1.64−1.63 (m, 4H), 1.55−1.50 (m, 1H), 1.30 (m, 36H),
1.17−1.15 (m, 2H), 0.91−0.87 (m, 9H), 0.19 (s, 18H), 0.181 (s,
18H), 0.176 (s, 18H); 13C NMR (150 MHz, CDCl3) δ 173.6, 173.5,
130.0, 129.7, 83.5, 75.4, 72.5, 72.0, 70.7, 63.0, 39.1, 34.2, 34.1, 31.9,
30.0, 29.8, 29.74, 29.73, 29.67, 29.65, 29.54, 29.50, 29.34, 29.25, 29.18,
29.16, 29.15, 28.0, 27.4, 27.22, 27.19, 24.79, 24.77, 22.70, 22.68, 14.1,
1.3, 0.9, 0.5; ESI-MS m/z 1303.4 [M+Na]+ ; ESI-HRMS calcd for
C63H130NaO12SSi6 [M + Na]+ 1301.7796, found 1301.7836.
6,6′-Di-O-palmitoyl-1-thio-α,α-D-trehalose (16). A solution of
compound 9 (66 mg, 52 μmol) in CH2Cl2/MeOH (4:1, 10 mL) was
treated with Amberlite IR120 (H+) resin (360 mg) at room
temperature for 1 h. The resin was removed and washed with
MeOH, and the solution was evaporated under vacuum to give a
residue, which was then purified by flash column chromatography
(CH2Cl2/MeOH, 10:1) to give the maradolipid 16 (39 mg, 89%) as a
white amorphous solid: [α]D +186.0 (c 0.3, Py); 1H NMR (600 MHz,
C5D5N) δ 6.27 (d, J = 4.7 Hz, 2H), 5.06 (t, J = 7.2 Hz, 2H), 4.90 (d, J
= 11.0 Hz, 2H), 4.81 (dd, J = 11.7, 5.7 Hz, 2H), 4.60−4.55 (m, 4H),
4.17 (m, t, J = 8.9 Hz, 2H), 2.33−2.23 (m, 4H), 1.59−1.57 (m, 4H),
1.16−1.24 (m, 48H), 0.84 (t, J = 6.8 Hz, 6H); 13C NMR (150 MHz,
C5D5N) δ 174.9, 84.6 77.7, 74.3, 73.3, 73.0, 65.7, 35.6 33.4, 31.29,
31.26, 31.22, 31.21, 31.06, 30.91, 30.88, 30.7, 26.5, 24.2, 15.6; ESI-MS
m/z 858.3 [M + Na]+; ESI-HRMS calcd for C44H82NaO12S [M + Na]+
857.5425, found 857.5425.
6,6′-Di-O-docosanoyl-2,3,4,2′,3′,4′-hexa-O-trimethylsilyl-1-
thio-α,α-D-trehalose (11). The reaction procedure was identical to
that described for 9 except that docosanoic acid (102 mg, 0.3 mmol)
was used instead of palmitic acid. Compound 11 (65 mg, 45%) was
1
isolated as a colorless syrup: [α]D +90.0 (c 1.9, CHCl3); H NMR
(600 MHz, CDCl3) δ 5.29 (d, J = 5.1 Hz, 2H), 4.30 (dd, J = 12.0, 2.1
Hz, 2H), 4.13−4.08 (m, 2H), 4.05 (dd, J = 12.1, 3.4 Hz, 2H), 3.67
(dd, J = 9.2, 5.1 Hz, 2H), 3.62 (t, J = 8.8 Hz, 2H), 3.53 (t, J = 8.9 Hz,
2H), 2.40−2.26 (m, 4H), 1.65−1.52 (m, 4H), 1.35−1.19 (m, 72H),
0.87 (t, J = 7.0 Hz, 6H), 0.16 (s, 18H), 0.15 (s, 18H), 0.14 (s, 18H);
13C NMR (150 MHz, CDCl3) δ 173.6, 83.5, 75.4, 72.6, 72.0, 70.6,
63.0, 34.9, 32.0, 29.73, 29.70, 29.69, 29.67, 29.5, 29.40, 29.35, 29.2,
25.5, 22.7, 14.2, 1.3, 0.9, 0.5; ESI-MS m/z 1459.6 [M + Na]+; ESI-
HRMS calcd for C74H154NaO12SSi6 [M + Na]+ 1457.9674, found
1457.9724.
6,6′-Di-O-oleoyl-2,3,4,2′,3′,4′-hexa-O-trimethylsilyl-1-thio-
α,α-D-trehalose (12). The reaction procedure was identical to that
described for 9 except that oleic acid (97 μL, 0.3 mmol) was used
instead of palmitic acid. Compound 12 (121 mg, 90%) was isolated as
1
a colorless syrup: [α]D +125.0 (c 0.4, CHCl3); H NMR (400 MHz,
CDCl3) δ 5.33 (m, 4H), 5.30 (d, J = 4.8 Hz, 2H), 4.32 (d, J = 11.6 Hz,
2H), 4.11 (d, J = 9.6 Hz, 2H), 4.06 (dd, J = 12.0, 3.1 Hz, 2H), 3.68
(dd, J = 9.1, 5.1 Hz, 2H), 3.63 (t, J = 8.6 Hz, 2H), 3.54 (t, J = 8.7 Hz,
2H), 2.34 (m, 4H), 2.01 (m, 8H), 1.62 (m, 4H), 1.29 (m, 40H), 0.88
(m, 6H), 0.17 (s, 18H), 0.16 (s, 18H), 0.15 (s, 18H); 13C NMR (100
MHz, CDCl3) δ 173.6, 130.0, 129.7, 83.6, 75.4, 72.6, 72.0, 70.7, 63.0,
34.2, 31.9, 29.8, 29.7, 29.5, 29.3, 29.24, 29.15, 29.1, 27.22, 27.18, 24.8,
22.7, 14.1, 1.3, 0.9, 0.5; ESI-MS m/z 1343.5 [M + Na]+; ESI-HRMS
calcd for C66H134NaO12SSi6 [M + Na]+ 1341.8109, found 1341.8177.
6,6′-Di-O-(13-methylmyristyl)-2,3,4,2′,3′,4′-hexa-O-trime-
thylsilyl-1-thio-α,α-D-trehalose (13). The reaction procedure was
identical to that described for 9 except that 13-methylmyristic acid (73
mg, 0.3 mmol) was used instead of palmitic acid. Compound 13 (110
mg, 89%) was isolated as a colorless syrup: [α]D +101.4 (c 1.2,
CHCl3); 1H NMR (600 MHz, CDCl3) δ 5.32 (d, J = 5.1 Hz, 2H), 4.33
(dd, J = 12.0, 2.0 Hz, 2H), 4.13 (m, 2H), 4.09 (dd, J = 12.1, 3.3 Hz,
2H), 3.71 (dd, J = 9.2, 5.1 Hz, 2H), 3.65 (t, J = 5.6 Hz, 2H), 3.56 (t, J
= 5.8 Hz, 2H), 2.41−2.31 (m, 4H), 1.65−1.63 (m, 4H), 1.56−1.50 (m,
2H), 1.31−1.27 (m, 32H), 1.17−1.15 (m, 4H), 0.89 (d, J = 6.6 Hz,
12H), 0.19 (s, 18H), 0.18 (s, 18H), 0.17 (s, 18H); 13C NMR (150
MHz, CDCl3) δ 173.6, 83.5, 75.4, 72.6, 72.0, 70.7, 63.0, 39.1, 34.2
30.0, 29.74, 29.68, 29.66, 29.5, 29.3, 29.2, 28.0, 27.4, 24.8, 22.7, 1.3,
0.9, 0.5; ESI-MS m/z 1263.2 [M + Na]+; ESI-HRMS calcd for
C60H126NaO12SSi6 [M + Na]+ 1261.7483, found 1261.7480.
6-O-(13-Methylmyristyl)-2,3,4,2′,3′,4′-hexa-O-trimethylsilyl-
1-thio-α,α-D-trehalose (14). To a solution of diol 8 (158 mg, 0.2
mmol) and 13-methylmyristic acid (48 mg, 0.2 mmol) in CH2Cl2 (3
mL) were added DCC (82 mg, 0.4 mmol) and DMAP (12.6 mg, 0.1
mmol) at 0 °C. The resulting mixture was allowed to warm up to
room temperature, stirred for 5 h, and then concentranted in vacuo,
and the residue was purified by flash column chromatography
(petroleum ether/EtOAc, 8:1) to give the product 14 (101 mg,
50%) as a colorless syrup: [α]D +131.3 (c 1.3, CHCl3); 1H NMR (400
MHz, CDCl3) δ 5.34 (d, J = 3.4 Hz, 1H), 5.31 (d, J = 3.8 Hz, 1H),
4.36 (d, J = 11.5 Hz, 1H), 4.12 (m, 2H), 3.95 (m, 1H), 3.72−3.74 (m,
2H), 3.70−3.68 (m, 4H), 3.56−3.51 (m, 2H), 2.32−2.36 (m, 2H),
1.70 (t, J = 6.5 Hz, 1H), 1.67−1.62 (m, 2H), 1.57−1.50 (m, 1H), 1.28
(m, 16H), 1.18 (m, 2H), 0.88 (d, J = 6.6 Hz, 6H), 0.19 (s, 18H), 0.18
(s, 18H), 0.17 (s, 18H); 13C NMR (100 MHz, CDCl3) δ 173.4, 83.3,
83.2, 75.5, 75.4, 73.1, 73.0, 72.8, 72.4, 71.7, 71.0, 63.2, 61.6, 39.0, 34.2,
29.9, 29.61, 29.57, 29.55, 29.4, 29.2, 29.1, 27.9, 27.3, 24.8, 22.5, 1.21,
1.18, 0.9, 0.8, 0.4, 0.3; ESI-MS m/z 1038.9 [M + Na]+; ESI-HRMS
calcd for C45H98NaO11SSi6 [M + Na]+ 1037.5343, found 1037.5371.
6,6′-Di-O-eicosanoyl-1-thio-α,α-D-trehalose (17). The reaction
procedure was identical to that described for 16. Compound 10 (60
mg, 43 μmol) yielded the title compound 17 (34 mg, 82%) as a white
amorphous solid: [α]D +210.0 (c 0.3, Py); 1H NMR (600 MHz,
C5D5N) δ 6.29 (d, J = 4.7 Hz, 2H), 5.08−5.09 (m, 2H), 4.91 (dd, J =
11.54 1.58 Hz, 2H), 4.82 (dd, J = 11.7, 5.8 Hz, 2H), 4.63−4.56 (m,
4H), 4.19 (dd, J = 9.7, 8.3 Hz, 2H), 2.33−2.23 (m, 4H), 1.62−1.55
(m, 4H), 1.27−1.15 (m, 64H), 0.84 (t, J = 7.0 Hz, 6H); 13C NMR
(150 MHz, C5D5N) δ 173.4, 83.1, 76.2, 72.8, 71.8, 71.5, 64.2, 34.1,
31.9, 29.83, 29.82, 29.81, 29.79, 29.78, 29.74, 29.72, 29.6, 29.41, 29.40,
29.2, 25.0, 22.7, 14.1; ESI-MS m/z 970.4 [M + Na]+; ESI-HRMS calcd
for C52H97O12S [M − H]+ 945.6701, found 945.6734.
6,6′-Di-O-docosanoyl-1-thio-α,α-D-trehalose (18). The reac-
tion procedure was identical to that described for 16. Compound 11
(50 mg, 35 μmol) yielded the title compound 18 (28 mg, 80%) as a
white amorphous solid: [α]D +105.0 (c 0.13, Py); 1H NMR (600
MHz, C5D5N) δ 6.28 (d, J = 4.7 Hz, 2H), 5.09−5.06 (m, 2H), 4.91
(dd, J = 11.6, 1.45 Hz, 2H), 4.81 (dd, J = 11.7, 5.8 Hz, 2H), 4.61−4.56
(m, 4H), 4.18 (dd, J = 9.7, 8.3 Hz, 2H), 2.31−2.22 (m, 4H), 1.55−
1.59 (m, 4H), 1.23−1.28 (m, 72H), 0.84 (t, J = 7.0 Hz, 6H); 13C
NMR (150 MHz, C5D5N) δ 174.9, 84.6, 77.7, 74.3, 73.3, 73.1, 65.7,
35.6, 33.4, 31.33, 31.32, 31.31, 31.30, 31.29, 31.25, 31.23, 31.1, 30.9,
30.7, 27.2, 24.2, 15.6; ESI-MS m/z 1026.3 [M + Na]+; ESI-HRMS
calcd for C56H105O12S [M − H]+ 1001.7327, found 1001.7296.
6,6′-Di-O-oleoyl-1-thio-α,α-D-trehalose (19). The reaction
procedure was identical to that described for 16. Compound 12 (62
mg, 47 μmol) yielded the title compound 19 (38 mg, 92%) as a white
1
amorphous solid: [α]D +114.9 (c 1.2, MeOH); H NMR (600 MHz,
CD3OD) δ 5.46 (d, J = 5.5 Hz, 2H), 5.39−5.34 (m, 4H), 4.38 (dd, J =
11.6, 1.6 Hz, 2H), 4.28 (dd, J = 11.6, 5.7 Hz, 2H), 4.24 (m, 2H), 3.76
(dd, J = 9.6, 5.5 Hz, 2H), 3.59 (t, J = 9.2 Hz, 2H), 3.36 (t, J = 9.3 Hz,
2H), 2.40−2.35 (m, 4H), 2.10−2.05 (m, 8H), 1.65−1.62 (m, 4H),
1.35−1.32 (m, 44H), 0.95−0.90 (m, 6H); 13C NMR (150 MHz,
4169
dx.doi.org/10.1021/jo400274s | J. Org. Chem. 2013, 78, 4165−4170

The Journal of Organic Chemistry
Note
CD3OD) δ 174.0, 129.5, 129.4, 81.9, 74.5, 71.4, 70.6, 70.4, 63.2, 33.7,
31.7, 29.53, 29.50, 29.3, 29.1, 29.04, 29.01, 28.9, 26.8, 24.7, 22.4, 13.2;
ESI-MS m/z 910.2 [M + Na]+; ESI-HRMS calcd for C48H86NaO12S
[M + Na]+ 909.5738, found 909.5765.
Senaratne, R. H.; Mougous, J. D.; Riley, L. W.; Williams, S. J.; Bertozzi,
C. R. J. Biol. Chem. 2004, 279, 28835−28843.
(5) Driguez, H. ChemBioChem 2001, 2, 311−318.
(6) Thayer, D. A.; Yu, H. N.; Galan, M. C.; Wong, C. H. Angew.
Chem., Int. Ed. 2005, 44, 4596−4599.
6,6′-Di-O-(13-methylmyristyl)-1-thio-α,α-D-trehalose (20).
The reaction procedure was identical to that described for 16.
Compound 13 (60 mg, 48 μmol) yielded the title compound 20 (36
mg, 93%) as a white amorphous solid: [α]D +291.0 (c 0.7, MeOH); 1H
NMR (600 MHz, CD3OD) δ 5.45 (d, J = 5.5 Hz, 2H), 4.38 (dd, J =
11.6, 1.7 Hz, 2H), 4.28 (dd, J = 11.6, 5.8 Hz, 2H), 4.25−4.22 (m, 2H),
3.76 (dd, J = 9.6, 5.5 Hz, 2H), 3.60 (t, J = 9.2 Hz, 2H), 3.36 (t, J = 9.3
Hz, 2H), 2.37 (t, J = 7.5 Hz, 4H), 1.65−1.62 (m, 4H), 1.58−1.51 (m,
2H), 1.33 (m, 32H), 1.22−1.18 (m, 4H), 0.91 (d, J = 6.6 Hz, 12H);
13C NMR (150 MHz, CD3OD) δ 174.0, 81.8, 74.5, 71.4, 70.5, 70.4,
(7) Pachamuthu, K.; Schmidt, R. R. Chem. Rev. 2006, 106, 160−187.
(8) Dere, R. T.; Zhu, X. Org. Lett. 2008, 10, 4641−4644.
(9) Hogan, A. E.; O’Reilly, V.; Dunne, M. R.; Dere, R. T.; Zeng, S.
G.; O’Brien, C.; Amu, S.; Fallon, P. G.; Exley, M. A.; O’Farrelly, C.;
Zhu, X.; Doherty, D. Clin. Immunol. 2011, 140, 196−207.
(10) For the synthesis of maradolipids, see: (a) Sarpe, V. A.;
Kulkarni, S. S. J. Org. Chem. 2011, 76, 6866−6870. (b) Passler, U.;
̈
Gruner, M.; Penkov, S.; Kurzchalia, T. V.; Knolker, H.-J. Synlett 2011,
̈
2482−2486. (c) Paul, N. K.; Twibanire, J. K.; Grindley, T. B. J. Org.
63.2, 38.9, 33.7, 29.7, 29.51, 29.47, 29.4, 29.3, 29.1, 28.9, 27.8, 27.2,
24.7, 21.7; ESI-MS m/z 830.2 [M + Na]+; ESI-HRMS calcd for
C42H78NaO12S [M + Na]+ 829.5112, found 829.5145.
Chem. 2013, 78, 363−369.
(11) Xin, G.; Zhu, X. Tetrahedron Lett. 2012, 53, 4309−4312.
(12) Schmidt, R. R.; Michel, J. Angew. Chem., Int. Ed. 1980, 19, 731−
732.
6-O-(13-Methylmyristyl)-6′-O-oleoyl-1-thio-α,α-D-trehalose
(2). The reaction procedure was identical to that described for 16.
Compound 15 (58 mg, 45 μmol) yielded the maradolipid 2 (34 mg,
(13) Schmidt, R. R.; Toepfer, A. Tetrahedron Lett. 1991, 32, 3353−
3356.
1
90%) as a white amorphous solid: [α]D +128.0 (c 2.0, MeOH); H
(14) Zhu, X.; Dere, R. T.; Jiang, J.; Zhang, L.; Wang, X. J. Org. Chem.
2011, 76, 10187−10197.
NMR (600 MHz, CD3OD) δ 5.46 (d, J = 5.5 Hz, 2H), 5.40−5.35 (m,
2H), 4.38 (dd, J = 11.6, 1.6 Hz, 2H), 4.28 (dd, J = 11.7, 5.7 Hz, 2H),
4.25−4.22 (m, 2H), 3.77 (dd, J = 9.6, 5.5 Hz, 2H), 3.60 (t, J = 9.3 Hz,
2H), 3.36 (t, J = 9.4 Hz, 2H), 2.37 (t, J = 7.5 Hz, 4H), 2.10−2.04 (m,
4H), 1.66−1.63 (m, 4H), 1.58−1.21 (m, 1H), 1.36 (m, 36H), 1.21−
1.18 (m, 2H), 1.00−0.84 (m, 9H); 13C NMR (150 MHz, CD3OD) δ
174.0, 173.9, 129.5, 129.4, 81.9, 74.5, 71.4, 70.5, 70.4, 63.2, 38.9, 33.71,
33.69, 31.8, 29.8, 29.53, 29.50, 29.46, 29.4, 29.3, 29.2, 29.1, 29.0, 28.93,
28.90, 27.8, 27.3, 26.8, 24.69, 24.68, 22.4, 21.8, 13.2; ESI-MS m/z
870.2 [M + Na]+; ESI-HRMS calcd for C45H81O12S [M − H]+
845.5449, found 845.5414.
(15) Fernan
A.; Fernan
(16) Foglia, T. A.; Vail, P. D. Org. Prep. Proced. Int. 1993, 25, 209−
213.
́
dez, C.; Nieto, O.; Rivas, E.; Montenegro, G.; Fontenla, J.
dez-Mayoralas, A. Carbohydr. Res. 2000, 327, 353−365.
́
(17) Zhu, X.; Dere, R. T.; Jiang, J. Tetrahedron Lett. 2011, 52, 4971−
4974.
ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray crystallographic data for 7, H and 13C NMR spectra for
1
all new compounds. This material is available free of charge via
the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: Xiangming.Zhu@ucd.ie.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was supported by the Natural Science Foundation of
Zhejiang Province (R4110195) and Research Frontier Program
■
of Science Foundation Ireland. We thank Dr. Helge Muller-
̈
Bunz for the X-ray structure determination.
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