Multicomponent synthesis of Ugi-type ceramide analogues and neoglycolipids from lipidic isocyanides

Article abstract of DOI:10.1021/jo300462m

Unique types of ceramide and glycolipid architectures were obtained by means of Ugi reactions incorporating lipidic isocyanides as surrogates of sphingolipids. The multicomponent nature of this approach allowed for a highly efficient assembly process, whe

Full text of DOI:10.1021/jo300462m

Article
pubs.acs.org/joc
Multicomponent Synthesis of Ugi-Type Ceramide Analogues and
Neoglycolipids from Lipidic Isocyanides
Karell Perez-Labrada,†,‡,§ Ignacio Brouard,*,‡ Inmaculada Mendez,‡ and Daniel G. Rivera*,§
́
́
†Institute of Pharmacy and Food, University of Havana, San Laz
́
aro y L, 10400, La Habana, Cuba
‡Instituto de Productos Naturales y Agrobiología-C.S.I.C., Avda. Astrofísico Francisco San
́
chez 3, 38206 La Laguna, Tenerife, Spain
§Center for Natural Products Study, Faculty of Chemistry, University of Havana, Zapata y G, 10400, La Habana, Cuba
S
* Supporting Information
ABSTRACT: Unique types of ceramide and glycolipid
architectures were obtained by means of Ugi reactions
incorporating lipidic isocyanides as surrogates of sphingolipids.
The multicomponent nature of this approach allowed for a
highly efficient assembly process, wherein two of the
components provided the lipidic tails while a third one
incorporated either the functionality suitable for the
conjugation to sugar or the sugar moiety itself. Two dissimilar
strategies were implemented: (i) the initial assembly of
ceramide analogues followed by glycosylation to produce a
glycolipid skeleton and (ii) the one-pot construction of glycolipid frameworks by condensation of lipidic isocyanides either with
lipidic amines and oligosaccharidic acids or with fatty acids and oligosaccharidic amines. Whereas both approaches are amenable
for accessing analogues of anticancer glycolipids, the latter one proved to have greater potential owing to its more straightforward
and efficient character. Overall, the methodology developed shows great promise toward the massive (eventually combinatorial)
production of neoglycolipids suitable for biological screening.
INTRODUCTION
■
Glycosphingolipids are important components of eukaryotic
cell membranes, wherein their lipophilic portions are inserted
into the bilayer leaving the hydrophilic moiety exposed toward
the cell surface.1 These molecules play crucial roles in various
stages of the cell cycle, including proliferation, differentiation,
adhesion, and apoptosis, etc.1,2 They are also involved in
signaling functions3 and interaction in the cell surface with
external agents such as toxins, viruses, and bacteria.4 The
interest on glycosphingolipids and their analogues has increased
dramatically in the last years,5 as some members of this family
have proven success as anticancer agents6 and in the prevention
of microbial infections,7 among other applications.8
The amphipathic structure of glycosphingolipids incorpo-
rates either mono- or oligosaccharide residues linked to a
lipophilic ceramide unit by a glycosyl bond. The most common
naturally occurring ceramide derives from sphingosine (i.e.,
C4−C5 trans double bond and D-erythro configuration), which
is the hydrophobic portion of several cerebrosides and of
tumor-associated antigens such as the ganglioside GM3 (1,
Figure 1. Glycolipids including natural and synthetic ceramides.
variation of the lipidic chain lengths,12a−c introduction of
Figure 1). Other biologically relevant ceramides derive from
phytosphingosine, which bears an additional hydroxyl group at
aromatic moieties,12d,e and isosteric replacement of the amide
C4 and is the aglycone of the immunostimulant α-galactosyl-
bond by a triazole unit12f are among the structural variations
ceramide 2 (Figure 1).9 The great potential of galactosyl-
performed in this glycolipid platform.
ceramides as anticancer chemotherapeutics has prompted the
design of various synthetic strategies6b,10 as well as the
performance of structure−activity relationship stud-
Received: March 3, 2012
Published: April 25, 2012
ies.5c,6b,c,11,12 Hence, modifications at the galactosyl moiety,5c,11
© 2012 American Chemical Society
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The design of glycolipids including non-natural ceramide
scaffolds has also shown success in the pursuit of novel
cytotoxic agents. For example, the trisaccharide β-chacotriose,
commonly found in steroid saponins,13 has been conjugated to
double-lipidic scaffolds to produce a new type of cytotoxic
glycolipids (e.g., compound 3, Figure 1).14
Scheme 1. Synthesis of Lipidic Isocyanides from Long-Chain
Aliphatic Amines
Ceramides are not only structural components of glyco-
sphingolipids, but they also regulate by themselves crucial
biological processes such as cell cycle arrest, proliferation,
differentiation, and apoptosis.15 Because of the medicinal
significance of ceramides and their sugar conjugates, extensive
synthetic efforts toward these metabolites have been carried out
in the past years.16 Nevertheless, the utilization of multi-
component reactions (MCRs) either for the construction of
ceramide-like skeletons or for their conjugation to carbohy-
drates has remained elusive so far, despite the huge number of
applications that have been described for this type of
procedure.17 As glycosphingolipids incorporate three different
components, i.e., a long-chain amino alcohol (e.g., sphingosine
or phytosphingosine), a fatty acid, and a sugar moiety, we
envisioned that this type of hybrid scaffold could be assembled
in one pot by means of a multicomponent approach.
Herein we report on the one-pot synthesis of ceramide
analogues and neoglycolipids by the Ugi four-component
reaction (Ugi-4CR).18 The multicomponent nature of this
process enables the utilization of a unique assembly process, i.e.,
two of the components providing the lipidic tails while one or
the two others incorporating either the functionality suitable for
the conjugation to the carbohydrate or the sugar moiety itself.
To prove the scope of this idea, two dissimilar strategies were
implemented: (i) the construction of a double-lipidic chain
framework analogous to ceramide followed by glycosylation
with a glucosyl donor and (ii) the one-pot multicomponent
assembly of varied hybrid carbohydrate/ceramide-like scaffolds
from properly functionalized saccharidic and lipidic substrates.
Additionally, we describe the synthesis of novel lipidic
isocyanides, a unique class of compound that may be
considered as surrogate either of fatty acids or of sphingolipids
on the design of novel membrane active compounds.
phosphorylchloride-mediated dehydration20 of the correspond-
ing formamides to produce isocyanides 7, 8, and 9, respectively,
in excellent yields after flash column chromatography
purification. These compounds are stable, pale yellow oils,
whose smells are not as intense as for volatile aliphatic
isocyanides such as the t-butyl, n-butyl, and cyclohexyl ones. In
all procedures the isocyanide formation was confirmed by 13C
NMR analysis, wherein the typical triplets indicative of the
isocyano functionality showed up. Interestingly, the highly
lipophilic nature of these compounds provoked the lack of
ionization in ESI-MS. The three lipidic isocyanides proved to
be as reactive as other aliphatic isocyanides in comparative Ugi-
4CRs (e.g., using propionic acid, butyraldehyde, and isopropyl-
amine), albeit the solvent mixture MeOH/CH2Cl2 (3:1, v/v)
was required because of their low solubility in pure MeOH.
Table 1 illustrates the implementation of the initial step of
the first multicomponent strategy toward glycolipids, which
encompasses the synthesis of ceramide analogues by means of
the Ugi-4CR. Although lipidic aldehydes are known and readily
available through a variety of methods, such prochiral aldehydes
would lead to the formation of stereoisomers of difficult
separation. Accordingly, paraformaldehyde was always em-
ployed as the oxo component, thus leaving the other Ugi-
components for the incorporation of the two lipid chains and
the functionality suitable for the conjugation to the
carbohydrate moiety. As reports of Ugi-4CRs with such long-
chain substrates are quite seldom, the initial efforts were
directed to set up the experimental conditions as well as
assessing the efficiency of such condensations between fatty
acids and lipidic isocyanides of variable chain length.
As depicted in Table 1, ethanolamine was chosen as the
amino component, thus providing the primary hydroxyl group
required for the subsequent glycosylation of the resulting
ceramide analogues. Thus, lauric acid (dodecanoic acid) was
combined with isocyanide 7 to furnish the ceramide analogue
10, which is endowed with two lipid chains of 12 carbon atoms
each. Alternatively, the combination of stearic acid (octadeca-
noic acid) with isocyanides 8 and 9 afforded the ceramide
analogues 11 and 12, respectively, which differ only in the
length of lipid chain attached to the secondary amide. The
reaction yields did not drop significantly while increasing the
chain length of the lipidic components, which is an important
feature while looking for future applications in the production
and biological screening of combinatorial libraries of ceramide
analogues. It must be noticed that the substrate scope can be
significantly expanded with the utilization of building blocks
having further hydroxyl and olefin functionalities, which do not
interfere in the normal course of the Ugi-4CR. Thus, not only a
RESULTS AND DISCUSSION
■
The Ugi-4CR is the one-pot condensation of a primary amine,
an oxo compound (i.e., ketone or aldehyde), a carboxylic acid,
and an isocyanide to produce an N-substituted dipeptide
backbone.18 Despite the great availability of fatty acids and
long-chain aliphatic amines, we are not aware of the utilization
of this MCR for the construction of double-lipidic-chain-based
scaffolds resembling the ceramide skeleton. Moreover, lipidic
aldehydes and isocyanides offer new prospects for the
combinatorial synthesis of ceramide analogues, as they allow
for the fast variation of each of the four different components
upon the one-pot assembly of double-lipidic chain scaffolds by
the Ugi-4CR. Whereas isocyanides featuring long aliphatic
chains have been isolated from a variety of organisms,18a,19
there is not much information regarding their properties and
chemical behavior. Accordingly, we initially focused on the
preparation as well as study of the reactivity and stability of
lipidic isocyanides, which upon incorporation into a ceramide-
like skeleton might be considered as mimics of fatty acids
ubiquitous in cell membranes.
As shown in Scheme 1, n-dodecylamine (4), n-hexadecyl-
amine (5), and n-octadecylamine (6) were subjected to
formylation by refluxing in ethylformate, followed by
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a
Table 1. Synthesis of Ceramide Analogues by the Ugi-4CR
a
All reactions were conducted in MeOH/CH2Cl2 (3:1, v/v) at room temperature using paraformaldehyde as the oxo component.
closer resemblance to the original ceramide skeleton can be
achieved, but also a quite detailed structure−activity relation-
ship study can be carried out through the tunable variation of
the features influencing the interaction of these molecules with
cell membranes. Indeed, the advantages of this one-pot
approach are its efficiency and reproducibility, as well as the
fact that several structural variations can be accomplished at
once as a result of its multicomponent nature.
As proof of concept of the first proposal toward glycolipid,
we turned to evaluate the scope of a traditional glycosylation
protocol for a ceramide analogue prepared by means of the
Ugi-4CR. As depicted in Scheme 2, compound 10 was
in combinatorial synthesis, the chemical efficiency of this two-
step process is not as high as required for this application.
Actually, the greatest limitation of this strategy is the fact that
most glycosylation approaches proceed only in moderate
yields5a when applied to ceramide and its analogues, likely
because of the bulky character of these substrates. To overcome
this limitation, we turned to the development of an alternative
strategy comprising the construction of the whole glycolipid
scaffold in one pot.
Previously, it was proven that the Ugi-4CR is a reliable and
efficient method for the production of ceramide analogues from
lipidic isocyanides and fatty acids. Accordingly, we envisioned
that this process would allow for the incorporation not only of
the two lipidic tails, but also the sugar moiety forming the
glycolipid platform. To this end, the first step would be the
functionalization of saccharidic building blocks with Ugi-
reactive functional groups. Considering the success reported
for the production of biologically active glycolipids derived
from the β-chacotriosyl moiety14 (i.e., 2,4-di-O-(α-L-rhamno-
pyranosyl)-β-D-glucopyranosyl; see compound 3, Figure 1), we
focused on the preparation of β-chacotriosyl building blocks
suitably functionalized with Ugi-reactive groups for the
construction of new glycolipid architectures. With this, we
also aim to demonstrate that such bulky 2,4-branched
oligosaccharides can be readily incorporated into complex
hybrid architectures in one pot.22
Scheme 2. Synthesis of a Neoglycolipid by Glycosylation of a
Ceramide Analogue
Scheme 3 depicts the synthesis of β-chacotriosides function-
alized with amino and carboxyl groups. To this end, the 2′-
azidoethyl β-D-glucopyranoside 16, prepared according to a
reported procedure,23 was subjected to deprotection under
typical Zemplen conditions (NaOMe/MeOH) followed by
selective pivaloylation24 to furnish the 3,6-dipivaloylated β-D-
glucosides 17 in 62% yield over two steps. Glucoside 17 was
then subjected to double glycosylation with 2,3,4-tri-O-acetyl-α-
L-rhamnopyranosyl trichloroacetimidate (18)25 according to
the Schmidt’s inverse procedure,26 and subsequent palladium-
catalyzed hydrogenation of the azido group to produce the 2′-
aminoethyl β-chacotrioside 19 in 71% yield over two steps.
Alternatively, the allyl β-chacotrioside 20,14 also prepared
subjected to glycosylation with 2,3,4,6-tetra-O-benzoyl-α-D-
glucopyranosyl trichloroacetimidate 1321 to furnish conjugate
14 in 56% yield. Further global deprotection produced the
neoglycolipid 15, which can be considered as a new class of
cerebroside mimetic. Whereas the sequential Ugi-4CR/
glycosylation protocol toward glycolipids might ensure the
levels of molecular diversity desired for a future implementation
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Scheme 3. Synthesis of β-Chacotriosides Functionalized with Amino and Carboxyl Groups
Table 2. One-Pot Multicomponent Synthesis of Neoglycolipids from Fatty Acids, Lipidic Isocyanides, and an Amino-Containing
a
Oligosaccharide
a
All reactions were conducted in MeOH/CH2Cl2 (3:1, v/v) at room temperature using paraformaldehyde as the oxo component.
through 3,6-dipivaloylation of an allyl β-D-glucoside followed by
glycosylation with the α-L-rhamnosyl donor 18, was subjected
to ozonolysis and subsequent oxidation with Oxone27 to
furnish the carboxymethyl β-chacotrioside 21 in 84% yield over
two steps. With these functionalized sugars in hands, we turned
to demonstrate the synthetic potential of the second Ugi-4CR-
based strategy, which aims the incorporation of two lipidic
chains and a large oligosaccharide moiety into a complex,
glycolipid architecture, all over in a single step.
Table 2 shows the first three examples of this one-pot
multicomponent approach that combines the 2′-aminoethyl β-
chacotrioside 19 with lipidic isocyanides 7 and 9 as well as
lauric and stearic acids, always utilizing paraformaldehyde as the
oxo-component. Thus, conjugates 22, 24, and 26 were obtained
in about 70% yield, which are remarkable results considering
the great molecular complexity that is achieved in a single
reaction step. Global deprotection of the β-chacotrioside/
ceramide-like hybrids 22, 24, and 26 afforded the final
neoglycolipids 23, 25, and 27, respectively, in excellent overall
yields. It must be noticed that compounds produced by this
approach exhibit the same type of ceramide skeleton that those
obtained by the former two-step protocol (e.g., compounds 15
and 23). Indeed, the earlier preparation of functionalized
glycosides to be subsequently reacted with the other two
components by such multicomponent means shows more
promise with regard to applications in combinatorial synthesis.
This is not only due to the higher chemical efficiency of this
second strategy, but also due to the greater structural diversity
that can be accessed in one step with a process incorporating
directly the three components into the final glycolipids.
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Table 3. One-Pot Multicomponent Synthesis of Neoglycolipids from Lipidic Isocyanides, Lipidic Amines, and a Carboxy-
a
Containing Oligosaccharide
a
All reactions were conducted in MeOH/CH2Cl2 (3:1, v/v) at room temperature using paraformaldehyde as the oxo component.
Table 3 illustrates three examples of alternative approach that
combines carboxymethyl β-chacotrioside 21 with lipidic
isocyanides and lipidic amines to produce the β-chacotrio-
side/ceramide-like hybrids 28, 30, and 32. As before, the yields
of these multicomponent procedures were as high as 70% yield,
thus corroborating that large substrates such as 2,4-branched
oligosaccharides can be incorporated into very complex
glycolipid platforms in an efficient, reproducible manner.
Global deprotection of glycosides 28, 30, and 32 led to the
final neoglycolipids 29, 31, and 33, respectively, in excellent
overall yields. Analysis of Tables 2 and 3 shows that
neoglycolipids 23, 25, and 27 are isomeric with 29, 31, and
33, respectively, just differing in the positioning of the tertiary
amide bond. This characteristic confirms the skeletal
diversification that can be achieved only with minor changes
in the component structures, as well as paves the way for the
development of further one-pot approaches focused on the
generation of higher levels of molecular diversity.
temperature between the two rotamers. These experiments
showed that, e.g., at 30 °C there are two doublets
corresponding to the anomeric proton of the inner β-D-
glucoside, while at 70 °C both signals collapse into a single
doublet (see the Supporting Information). The same effect
takes place with other sets of duplicated signals such as the two
protons of position 6 of the D-glucose and the methylenes
nearby to the tertiary amide.
The occurrence of various conformations with similar energy
for these glycolipids may comprise the generation, and
therefore possibility of screening, of a larger conformational
space compared to those accessible by methods producing only
secondary-amide-based ceramide analogues. Finally, it must be
mentioned that this method is not restricted to Ugi-type
ceramide analogues derived from formaldehyde, as prochiral
oxo-compounds can also be employed with similar success.
CONCLUSIONS
■
NMR analysis of the neoglycolipids demonstrates the
occurrence of two conformers at room temperature, owing to
the presence of a tertiary amide in the ceramide-like scaffolds.
We have developed a multicomponent approach for the
construction of double-lipidic scaffolds resembling bioactive
ceramides and glycolipids. This is the first time that the Ugi-
4CR is utilized for the synthesis of such lipid-based molecules,
thus proving once more the tremendous potential of this
reaction for the rapid creation of compounds resembling
biologically relevant molecules. Lipidic isocyanides were
initially produced from long-chain aliphatic amines and were
next incorporated into ceramide-like skeletons, thus acting as
mimics of sphingolipids. Two different multicomponent
strategies were implemented: (i) the condensation of such
isocyanides with fatty acids and a hydroxyl-containing amine to
yield ceramide-like scaffolds, followed by their glycosylation to
produce the glycolipid framework, and (ii) the one-pot
construction of varied glycolipid skeletons by condensation of
1
Thus, two different sets of signals appear in the H NMR
spectra for those protons of the methylenes nearby to the
tertiary amides and those of the inner D-glucose units (see the
Supporting Information). Also, duplicated signals of the amide
bonds are observed in the 13C NMR spectra, thereby
confirming the presence of both the cis and the trans rotamers
for the tertiary amide of each glycolipid. This is a typical feature
of peptoid-type skeletons, wherein the N-alkylation of the
amide bonds leads to similarly populated conformers derived
from the s-cis and the s-trans configurations. Temperature-
dependent NMR experiments were performed with glycolipid
26 to evaluate the possibility of fast interconversion at higher
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3.37 (tt, 2H, J = 1.9/6.8 Hz, CH2NC); 13C NMR (125 MHz, CDCl3)
δ = 14.1 (CH3); 22.7, 26.3, 28.7, 29.1, 29.3, 29.5, 29.6, 29.7, 31.9
(CH2); 41.5 (t, J = 6.4 Hz, CH2NC); 155.6 (t, J = 5.3 Hz, NC). Anal.
Calcd. for C19H37N: C, 81.7; H, 13.3; N, 5.0. Found: C, 81.8; H, 13.1;
N, 5.1.
General Procedure for the Ugi-4CR. A solution of the amine
(1.0 mmol) and paraformaldehyde (1.0 mmol) in MeOH/CH2Cl2 (20
mL, 3:1, v/v) was stirred for 1 h at room temperature. The acid (1.0
mmol) and the isocyanide (1.0 mmol) were then added, and the
reaction mixture was stirred overnight at room temperature and then
concentrated under reduced pressure to dryness. The crude product
was purified by flash column chromatography to afford the
corresponding ceramide analogue or glycolipid.
lipidic isocyanide either with lipidic amines and oligosaccharidic
acids or with fatty acids and oligosaccharidic amines. The
second approach proved greater success and higher efficiency
owing to its more straightforward character and the possibility
of accessing higher levels of molecular diversity in a single step.
Nevertheless, both protocols show great promise toward the
combinatorial production and biological screening of libraries
of ceramide analogues and glycolipids. For example, consider-
ing that a tunable variation of the oligosaccharidic portion is
quite compatible with the multicomponent nature of this
approach, applications in the development of anticancer
glycolipids analogous to galactosyl-ceramides and gangliosides
are foreseeable.
Ceramide Analogue 10. 2-Amino-1-ethanol (40 μL, 0.66 mmol),
paraformaldehyde (20 mg, 0.66 mmol), lauric acid (132 mg, 0.66
mmol), and n-dodecylisocyanide (129 mg, 0.66 mmol) were reacted in
MeOH/CH2Cl2 (12 mL) according to the general procedure for the
Ugi-4CR. Flash column chromatography purification (n-hexane/
EtOAc 3:1) afforded the ceramide analogue 10 (250.6 mg, 81%) as
a white solid: Rf = 0.30 (n-hexane/EtOAc 3:1); mp 75−77 °C; IR
(KBr, cm−1) νmax 3353, 2925, 2851, 1641, 1558, 1155; 1H NMR (400
MHz, CDCl3) δ = 0.81 (t, 6H, J = 6.7 Hz, 2 × CH3); 1.20−1.34 (m,
35H); 1.49 (m, 2H, CH2); 1.61 (m, 2H, CH2); 2.23, 2.40 (2 × t, 2H, J
= 7.6 Hz, CH2); 3.21−3.28 (m, 2H, CH2); 3.51, 3.62 (2 × t, 2H, J =
5.0 Hz, CH2); 3.74, 3.80 (2 × m, 2H, CH2); 3.87, 4.00 (2 × s, 2H,
CH2); 5.04, 6.35 (2 × m, 1H, NH); 13C NMR (100 MHz, CDCl3) δ =
14.1 (CH3); 22.6, 22.7, 25.0, 25.1, 26.9, 27.0, 29.3, 29.4, 29.5, 29.6,
29.7, 31.9, 33.2, 33.4, 39.8, 39.9, 51.2, 51.6, 52.9, 53.8, 60.2, 60.3
(CH2); 170.8, 174.7 (CO); HRMS (ESI-FT-ICR) m/z 491.4190
[M + Na]+; calcd. for C28H56N2O3Na 491.4189.
Ceramide Analogue 11. 2-Amino-1-ethanol (40 μL, 0.66 mmol),
paraformaldehyde (20 mg, 0.66 mmol), stearic acid (188 mg, 0.66
mmol), and n-hexadecylisocyanide (83 mg, 0.66 mmol) were reacted
in MeOH/CH2Cl2 (6 mL) according to the general procedure for the
Ugi-4CR. Flash column chromatography purification (n-hexane/
EtOAc 3:1) afforded the ceramide analogue 11 (314 mg, 78%) as a
white solid: Rf = 0.32 (n-hexane/EtOAc 3:1); mp 84−86 °C; IR (KBr,
cm−1) νmax 3355, 2916, 2857, 1646, 1556, 1163; 1H NMR (400 MHz,
CDCl3) δ = 0.87 (t, 6H, J = 6.6 Hz, 2 × CH3); 1.25−1.30 (m, 55H);
1.49 (m, 2H, CH2); 1.61 (m, 2H, CH2); 2.23, 2.32, 2.40 (3 × m, 2H,
CH2); 3.21−3.28 (m, 2H, CH2); 3.51, 3.62 (2 × m, 2H, CH2); 3.74,
3.80 (2 × m, 2H, CH2); 3.87, 4.00 (2 × s, 2H, CH2); 6.43, 6.81, 7.12
(3 × m, 1H, NH); 13C NMR (100 MHz, CDCl3) δ = 14.1 (CH3);
22.7, 24.8, 24.9, 25.0, 26.8, 26.9, 27.0, 27.1, 29.1, 29.2, 29.3, 29.4, 29.5,
29.6, 29.7, 31.9, 33.2, 33.4, 34.2, 39.4, 39.8, 39.9, 51.2, 51.7, 53.0, 53.9,
54.4, 59.2, 60.4, 60.5, 61.8 (CH2); 170.1, 170.8, 174.7 (CO); HRMS
(ESI-FT-ICR) m/z 609.5931 [M + H]+; calcd. for C38H77N2O3
609.5929.
Ceramide Analogue 12. 2-Amino-1-ethanol (25 μL, 0.41 mmol),
paraformaldehyde (12 mg, 0.41 mmol), stearic acid (117 mg, 0.41
mmol), and n-octadecylisocyanide (115 mg, 0.41 mmol) were reacted
in MeOH/CH2Cl2 (8 mL) according to the general procedure for the
Ugi-4CR. Flash column chromatography purification (n-hexane/
EtOAc 3:1) afforded the ceramide analogue 12 (191 mg, 73%) as a
white solid: Rf = 0.32 (n-hexane/EtOAc 3:1); mp 91−93 °C; IR (KBr,
cm−1) νmax 3357, 2916, 2849, 1648, 1148; 1H NMR (400 MHz,
CDCl3) δ = 0.88 (t, 6H, J = 7.1 Hz, 2 × CH3); 1.22−1.31 (m, 59H);
1.50 (m, 2H, CH2); 1.62 (m, 2H, CH2); 2.24, 2.33, 2.40 (3 × m, 2H,
CH2); 3.22−3.29 (m, 2H, CH2); 3.52, 3.62 (2 × m, 2H, CH2); 3.75,
3.81 (2 × m, 2H, CH2); 3.87, 4.00 (2 × s, 2H, CH2); 6.25, 6.75, 6.99
(3 × m, 1H, NH); 13C NMR (100 MHz, CDCl3) δ = 14.1 (CH3);
22.7, 25.1, 26.9, 29.3, 29.4, 29.5, 29.6, 29.7, 31.9, 33.2, 39.9, 51.7, 53.0,
60.5 (CH2); 170.8, 174.7 (CO); HRMS (ESI-FT-ICR) m/z
637.6242 [M + H]+; calcd. for C40H81N2O3 637.6242.
EXPERIMENTAL SECTION
■
1
General Methods. Melting points are uncorrected. H NMR and
13C NMR spectra were recorded at 400 and 500 MHz for 1H and 100
and 125 MHz for 13C, respectively. Chemical shifts (δ) are reported in
parts per million relative to the residual solvent signals, and coupling
constants (J) are reported in hertz. NMR peak assignments were
1
accomplished by analysis of the H−1H COSY and HSQC data. High
resolution ESI mass spectra were obtained from a Fourier transform
ion cyclotron resonance (FT-ICR) mass spectrometer, an RF-only
hexapole ion guide, and an external electrospray ion source. Flash
column chromatography was carried out using silica gel 60 (230−400
mesh), and analytical thin layer chromatography (TLC) was
performed using silica gel aluminum sheets. Compounds 13, 16, 18,
and 20 were prepared according to refs 21, 23, 25, and 14, respectively.
All commercially available chemicals were used without further
purification. For compounds arising from the Ugi-4CR, the assigned
signals belong to a mixture of conformers.
General Procedure for the Synthesis of the Lipidic
Isocyanides. The lipidic amine (1 mmol) was dissolved in
ethylformate (10 mL), and the resulting solution was stirred at reflux
for 20 h. The volatiles were removed under reduced pressure to
furnish the corresponding formamide. This crude product was
dissolved in dry CH2Cl2 (5 mL), and the solution was cooled to
−60 °C and treated with Et3N (2 mL). A solution of POCl3 (1 mmol)
in dry CH2Cl2 (0.5 mL) was added dropwise under nitrogen
atmosphere, and the resulting reaction mixture was stirred at −60
°C for 2 h, then allowed to reach room temperature, and stirred for
additional 4 h. The resulting suspension was poured into 20 mL of
cold water, and the mixture was extracted with CH2Cl2 (2 × 25 mL).
The organic phases were combined, washed with brine, and
evaporated under reduced pressure to dryness. The resulting crude
product was purified by flash column chromatography (n-hexane/
EtOAc 10:1) to yield the pure isocyanide.
n-Dodecylisocyanide (7). 94% yield. Pale yellow oil: Rf = 0.53 (n-
hexane/EtOAc 10:1); IR (KBr, cm−1) νmax 2927, 2857, 2148, 1460; 1H
NMR (500 MHz, CDCl3) δ = 0.88 (t, 3H, J = 6.9 Hz, CH3); 1.26−
1.29 (m, 16H, 8 × CH2); 1.42 (m, 2H, CH2); 1.67 (m, 2H, CH2); 3.37
(tt, 2H, J = 1.9/6.7 Hz, CH2NC); 13C NMR (125 MHz, CDCl3) δ =
14.0 (CH3); 22.6, 26.3, 28.6, 29.1, 29.2, 29.3, 29.4, 29.5, 31.8 (CH2);
41.5 (t, J = 6.4 Hz, CH2NC); 155.6 (t, J = 6.0 Hz, NC). Anal. Calcd.
for C13H25N: C, 79.9; H, 12.9; N, 7.2. Found: C, 79.8; H, 13.0; N, 7.3.
n-Hexadecylisocyanide (8). 91% yield. Pale yellow oil: Rf = 0.46
(n-hexane/EtOAc 8:1); IR (KBr, cm−1) νmax 2925, 2856, 2147, 1461;
1H NMR (500 MHz, CDCl3) δ = 0.87 (t, 3H, J = 6.8 Hz, CH3); 1.25−
1.29 (m, 24H, 12 × CH2); 1.42 (m, 2H, CH2); 1.67 (m, 2H, CH2);
3.36 (tt, 2H, J = 1.9/6.6 Hz, CH2NC); 13C NMR (125 MHz, CDCl3)
δ = 14.0 (CH3); 22.6, 26.3, 28.7, 29.1, 29.3, 29.4, 29.5, 29.6, 29.7, 31.9
(CH2); 41.5 (t, J = 6.4 Hz, CH2NC); 155.6 (t, J = 5.5 Hz, NC). Anal.
Calcd. for C17H33N: C, 81.2; H, 13.2; N, 5.6. Found: C, 81.1; H, 13.3;
N, 5.5.
Glycolipid 14. The ceramide-like compound 10 (0.100 g, 0.21
mmol) and the glucosyl donor 13 (0.079 g, 0.106 mmol) were
suspended in dry CH2Cl2 (2 mL) in the presence of 4 Å molecular
sieves. The reaction mixture was stirred at room temperature under
nitrogen atmosphere for 2 h, and then BF3·OEt2 (27.3 μL, 0.22 mmol)
was added. After stirring for 3 h, the reaction was quenched with aq 0.5
n-Octadecylisocyanide (9). 87% yield. Pale yellow oil: Rf = 0.53
(n-hexane/EtOAc 8:1); IR (KBr, cm−1) νmax 2920, 2852, 2149, 1466;
1H NMR (500 MHz, CDCl3) δ = 0.88 (t, 3H, J = 6.9 Hz, CH3); 1.25−
1.31 (m, 28H, 14 × CH2); 1.42 (m, 2H, CH2); 1.67 (m, 2H, CH2);
4665
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M NaHCO3 (2 mL). The organic phase was dried over anhydrous
Na2SO4 and evaporated under reduced pressure to dryness. The crude
product was purified by flash column chromatography (n-hexane/
EtOAc 1:1) to afford the glycolipid 14 (64 mg, 56%) as an amorphous
solid: Rf = 0.35 (n-hexane/EtOAc 1:1); [α]2D0 +17.3 (c 5.2, CHCl3); IR
(KBr, cm−1) νmax 2922, 2848, 2361, 1733, 1651, 1455, 1269, 1107,
1097, 1070; 1H NMR (500 MHz, CDCl3) δ = 0.79 (t, 6H, J = 7.0 Hz,
2 × CH3); 1.17 (m, 34H, 17 × CH2); 1.31 (m, 2H, CH2); 1.41 (m,
2H, CH2); 1.85, 2.01 (2 × m, 2H, CH2); 2.23 (t, 1H, J = 7.6 Hz); 3.02,
3.16 (2 × m, 2H, CH2); 3.28, 3.44, 3.55, 3.65 (4 × m, 2H, CH2);
3.72−3.78 (m, 2H, CH2); 3.97 (m, 1H); 4.09 (m, 1H, H-5 Glc); 4.41
(m, 1H, H-6a Glc); 4.58 (m, 1H, H-6b Glc); 4.76, 4.78 (2 × d, 1H, J =
7.9 Hz, H-1 Glc); 5.43 (m, 1H, H-2 Glc); 5.60 (m, 1H, H-4 Glc); 5.84
(m, 1H, H-3 Glc); 6.04, 6.28 (2 × m, 1H, NH); 7.19 (m, 2H, Ar-H);
7.24−7.35 (m, 7H, Ar-H); 7.44 (m, 3H, Ar-H); 7.73 (m, 2H, Ar-H);
7.82−7.89 (m, 4H, Ar-H); 7.95 (m, 2H, Ar-H); 13C NMR (125 MHz,
CDCl3) δ = 14.5 (CH3); 23.0, 25.2, 25.6, 27.2, 27.3, 29.7, 29.8, 29.9,
30.0, 30.1, 32.3, 33.3, 33.4, 39.8, 40.0, 47.6, 49.3, 51.4, 53.4 (CH2);
56.5 (CH); 63.3, 67.4 (CH2); 69.6, 70.0, 72.2, 72.6, 72.9, 73.1, 73.2,
99.7, 101.5, 101.6, 128.6, 128.7, 128.8 (CH); 128.9, 129.2, 129.4, 129.9
(C); 130.1, 130.2, 130.3, 133.5, 133.6, 133.7, 133.8, 133.9 (CH); 165.4,
165.6, 165.8, 166.0, 166.1, 166.5, 168.7, 169.8, 174.6, 174.9 (CO);
HRMS (ESI-FT-ICR) m/z 1069.5780 [M + Na]+; calcd. for
C62H82N2O12Na 1069.5765.
Glycolipid 15. NaOMe was added to a solution of compound 14
(64 mg, 0.061 mmol) in THF/MeOH (4 mL, 1:1) until pH was set to
9−10. The reaction mixture was stirred overnight at room temper-
ature, then neutralized with acid resin Dowex-50 (H+), and filtered.
The filtrate was concentrated under reduced pressure, and the crude
product was purified by flash column chromatography (CH2Cl2/
MeOH 9:1) to afford glycolipid 15 (33 mg, 85%) as a white solid: Rf =
0.30 (CH2Cl2/MeOH 9:1); mp 129−131 °C; [α]2D0−1.0 (c 5.0,
CHCl3); IR (KBr, cm−1) νmax 3428, 2918, 2855, 2361, 1638, 1544,
1468, 1078, 1047; 1H NMR (500 MHz, CDCl3) δ = 0.88 (m, 6H, 2 ×
CH3); 1.20−1.35 (m, 34H, 17 × CH2); 1.62 (m, 2H, CH2); 1.80 (m,
2H, CH2); 2.56 (m, 2H, CH2); 3.49 (m, 2H, CH2); 3.86−4.65 (m,
12H); 4.86, 4.88 (2 × d, 1H, J = 7.6 Hz, H-1 Glc); 8.33, 8.63 (2 × m,
1H, NH); 13C NMR (125 MHz, CDCl3) δ = 14.7 (CH3); 23.3, 26.0,
26.1, 27.7, 27.8, 30.0, 30.1, 30.2, 30.3, 30.4, 30.5, 30.6, 32.5, 33.7, 33.9,
40.2, 40.3, 48.3, 49.9, 51.0, 53.3, 63.0, 63.1, 68.5 (CH2); 68.9, 71.9,
75.5, 75.6, 78.9, 79.0, 105.2, 105.3 (CH); 170.1, 170.3, 174.5, 174.6
(CO); HRMS (ESI-FT-ICR) m/z 653.4722 [M + Na]+; calcd. for
C34H66N2O8Na 653.4717.
2′-Azido-ethyl 3,6-Di-O-pivaloyl-β-D-glucopyranoside (17).
NaOMe was added to a solution of compound 16 (2.94 g, 7.04
mmol) in CH2Cl2/MeOH (40 mL, 1:1, v/v) until pH was set to 9−10.
The reaction mixture was stirred for 1 h at room temperature, then
neutralized with acid resin Dowex-50 (H+), and filtered. The filtrate
was concentrated under reduced pressure, and the residue was dried in
vacuo to furnish the deprotected β-D-glucoside. This product was
dissolved in anhydrous pyridine (40 mL), and the solution was cooled
to −15 °C and stirred under nitrogen atmosphere. Pivaloyl chloride
(4.3 mL, 35.2 mmol) was added dropwise, and the reaction course was
monitored by TLC. The stirring was continued at room temperature
until the disappearance of the starting material. The mixture was then
diluted with EtOAc (50 mL) and washed with dilute aq HCl, saturated
aq NaHCO3, and brine. The organic phase was dried over anhydrous
Na2SO4 and evaporated to dryness. The crude product was purified by
flash column chromatography (n-hexane/EtOAc 3:1) to afford 17
(1.73 g, 59%) as an amorphous solid: Rf = 0.31 (n-hexane/EtOAc
3:1); [α]2D0 +87.2 (c 1.0, CHCl3); IR (KBr, cm−1) νmax 3445, 2959,
2862, 2373, 2344, 2118, 1726, 1287, 1160, 1050; 1H NMR (400 MHz,
CDCl3) δ = 1.21, 1.24 (2 × s, 2 × 9H, 2 × (CH3)3C); 3.35 (m, 1H, H-
2′a); 3.45−3.59 (m, 4H, H-2, H-4, H-5, H-2′b); 3.76 (m, 1H, H-1′a);
4.03 (m, 1H, H-1′b); 4.29 (dd, 1H, J = 5.8/12.0 Hz, H-6a); 4.40 (d,
1H, J = 7.7 Hz, H-1); 4.44 (dd, 1H, J = 2.4/12.0 Hz, H-6b); 4.89 (t,
1H, J = 9.2 Hz, H-3); 13C NMR (100 MHz, CDCl3) δ = 27.0, 27.1
(CH3); 38.9, 39.0 (C); 50.7, 63.1, 68.8 (CH2); 69.7, 72.2, 74.5, 77.6,
103.0 (CH); 178.7, 180.2 (CO); HRMS (ESI-FT-ICR) m/z
440.2021 [M + Na]+ (calculated for C18H31N3O8Na 440.2009).
2′-Amino-ethyl 2,4-Di-O-(2,3,4-tri-O-acetyl-α-L-rhamnopyra-
nosyl)-3,6-di-O-pivaloyl-β-D-glucopyranoside (19). BF3·Et2O
(2.2 mL, 17.0 mmol) was added under nitrogen atmosphere to a
stirring suspension of acceptor 17 (1.61 g, 3.86 mmol) and 4 Å
molecular sieves in dry CH2Cl2 (20 mL) at −80 °C. After it was stirred
for 1 h at this temperature, a solution of rhamnopyranosyl
trichloroacetimidate 18 (5.22 g, 12.0 mmol) in CH2Cl2 (20 mL)
was added, and the stirring was continued for 5 h at room temperature.
The reaction mixture was diluted with CH2Cl2 (60 mL) and filtered
through a pad of Celite. The filtrate was washed with saturated aq
NaHCO3 (30 mL) and brine (15 mL). The organic phase was dried
over anhydrous Na2SO4 and evaporated to dryness. The crude product
was partially purified by flash column chromatography (n-hexane/
EtOAc 3:2), yielding the crude trisaccharide as a white foam (4.02 g).
This crude product was dissolved in MeOH (100 mL), and 5% Pd/C
(81.8 mg, 0.039 mmol) was added. The reaction mixture was subjected
successively to hydrogen atmosphere and vacuum and finally stirred
under hydrogen atmosphere for 48 h, when TLC analysis revealed that
all of the azide was consumed. The catalyst was removed by filtration
over a pad of Celite, and the resulting solution was evaporated under
reduced pressure. The crude product was purified by flash column
chromatography (CHCl3/MeOH 15:1) to afford the pure trisacchar-
ide 19 (2.56 g, 71%) as a white solid: Rf = 0.30 (CHCl3/MeOH 15:1);
mp 96−97 °C; [α]D20 +10.2 (c 1.6, CHCl3); IR (KBr, cm−1) νmax 3425,
2980, 2941, 2881, 1752, 1371, 1247, 1228, 1146, 1080, 1046; 1H NMR
(400 MHz, CDCl3) δ = 1.14 (d, 3H, J = 6.3 Hz, CH3 Rha); 1.16 (s,
9H, (CH3)3C); 1.17 (d, 3H, J = 6.3 Hz, CH3 Rha′); 1.20 (s, 9H,
(CH3)3C); 1.92, 1.95, 2.01, 2.02, 2.08, 2.09 (6 × s, 6 × 3H, 6 ×
CH3CO); 2.23 (s, 2H, NH2); 2.89 (s, 2H, H-2′); 3.57 (t, 1H, J = 7.6
Hz, H-2 Glc); 3.63 (m, 1H, H-1′a); 3.73 (m, 2H, H-4 Glc, H-5 Glc);
3.83−3.92 (m, 2H, H-1′b, H-5 Rha); 4.11 (m, 1H, H-5 Rha′); 4.21
(dd, 1H, J = 2.8/12.0 Hz, H-6a Glc); 4.48 (d, 1H, J = 7.0 Hz, H-1
Glc); 4.53 (d, 1H, J = 12.0 Hz, H-6b Glc); 4.84 (s, 1H, H-1 Rha); 4.86
(s, 1H, H-1 Rha′); 4.96−5.04 (m, 3H, H-2 Rha, H-4 Rha, H-4 Rha′);
5.13−5.19 (m, 3H, H-2 Rha′, H-3 Rha, H-3 Rha′); 5.24 (m, 1H, H-3
Glc); 13C NMR (100 MHz, CDCl3) δ = 16.8, 16.9, 20.2, 20.3, 20.4,
20.5, 26.5, 26.8 (CH3); 38.4, 38.5 (C); 41.4, 62.0 (CH2); 66.5, 67.7,
68.4, 68.5, 69.3, 69.6, 70.2, 70.7 (CH); 71.6 (CH2); 72.1, 74.5, 76.3,
77.4, 97.2, 97.3, 100.8 (CH); 169.1, 169.2, 169.3, 169.4, 169.5, 176.1,
177.5 (CO); HRMS (ESI-FT-ICR) m/z 936.4066 [M + H]+
(calculated for C42H66NO22 936.4076).
Carboxymethyl 2,4-Di-O-(2,3,4-tri-O-acetyl-α-L-rhamnopyra-
nosyl)-3,6-di-O-pivaloyl-β-D-glucopyranoside (21). Ozone was
bubbled into a solution of the allyl trisaccharide 20 (2.33 g, 2.50
mmol) in CH2Cl2 (100 mL) for 5 min at −78 °C. The light-blue
solution was then treated with PPh3 (984 mg, 3.75 mmol), and the
reaction mixture was allowed to warm to room temperature and stirred
for 30 min. The solvent was removed under reduced pressure, and the
crude aldehyde was dissolved in DMF (25 mL) and teated with Oxone
(1.54 g, 2.50 mmol). The reaction mixture was stirred for 8 h at room
temperature, then diluted with EtOAc (50 mL), and washed with
dilute aq HCl and brine. The organic phase was dried over anhydrous
Na2SO4 and evaporated to dryness. The crude product was purified by
flash column chromatography (EtOAc/MeOH 10:1) to afford acid 21
(2.01 g, 84%) as a white solid: Rf = 0.50 (EtOAc); mp 122−123 °C;
[α]D20 −65.0 (c 1.2, CHCl3); IR (KBr, cm−1) νmax 3357, 2967, 2937,
2373, 1736, 1223, 1145, 1044; 1H NMR (400 MHz, CDCl3) δ = 1.15
(d, 3H, J = 6.1 Hz, CH3 Rha); 1.16 (d, 3H, J = 6.2 Hz, CH3 Rha′);
1.18, 1.21 (2 × s, 2 × 9H, 2 × (CH3)3C); 1.95, 1.96, 2.02, 2.03 (4 × s,
4 × 3H, 4 × CH3CO); 2.10 (s, 6H, 2 × CH3CO); 3.65 (t, 1H, J = 7.3
Hz, H-2 Glc); 3.80 (m, 2H, H-4 Glc, H-5 Glc); 3.90 (m, 1H, H-5
Rha); 4.17−4.29 (m, 4H, H-5 Rha′, OCH2, H-6a Glc); 4.49 (d, 1H, J =
11.9 Hz, H-6b Glc); 4.68 (d, 1H, J = 7.0 Hz, H-1 Glc); 4.85 (d, 1H, J =
1.7 Hz, H-1 Rha); 4.92 (s, 1H, H-1 Rha′); 4.97−5.07 (m, 3H, H-2
Rha, H-4 Rha, H-4 Rha′); 5.15−5.18 (m, 2H, H-2 Rha′, H-3 Rha);
5.23 (t, 1H, J = 7.7 Hz, H-3 Glc); 5.27 (dd, 1H, J = 4.0/9.7 Hz, H-3
Rha′); 13C NMR (100 MHz, CDCl3) δ = 17.0, 17.2, 20.6, 20.7, 20.8,
26.9, 27.1 (CH3); 38.8, 38.9 (C); 62.3, 66.4 (CH2); 67.2, 68.0, 68.8,
69.1, 69.7, 70.0, 70.6, 70.9, 72.9, 74.6, 76.1, 77.6, 97.5, 97.6, 100.4
(CH); 169.7, 169.8, 169.9, 170.0, 170.1, 170.2, 176.6, 178.1 (CO);
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HRMS (ESI-FT-ICR) m/z 973.3542 [M + Na]+ (calculated for
C42H62O24Na 973.3529).
1H, H-6b Glc); 4.83, 4.85 (2 × d, 2H, J = 1.3 Hz, J = 1.9 Hz, H-1 Rha,
H-1 Rha′); 4.97−5.05 (m, 2H, H-4 Rha, H-4 Rha′); 5.08 (m, 1H, H-2
Rha); 5.14 (m, 1H, H-2 Rha′); 5.18 (m, 2H, H-3 Rha, H-3 Rha′); 5.24
(m, 1H, H-3 Glc); 6.29, 6.43 (2 × m, 1H, NH); 13C NMR (125 MHz,
CDCl3) δ = 14.1, 17.2, 17.3, 17.4, 20.6, 20.7, 20.8, 20.9 (CH3); 22.7,
24.9, 25.3 (CH2); 26.8 (CH3); 26.9, 27.0 (CH2); 27.1 (CH3); 29.3,
29.4, 29.5, 29.6, 29.7, 31.9, 32.9 (CH2); 38.8, 38.9 (C); 39.4, 39.6, 48.3,
48.4, 50.4, 53.2, 62.1, 66.8 (CH2); 66.9, 68.0, 68.1, 68.7, 68.8, 69.7,
69.8, 69.9, 70.5, 70.6, 70.8, 70.9, 72.6, 72.7, 74.5, 74.7, 76.4, 76.5, 78.3,
78.4, 97.4, 97.7, 97.8, 101.3, 101.9 (CH); 169.2, 169.6, 169.7, 169.8,
169.9, 170.0, 174.2, 176.3, 176.4, 177.8, 177.9 (CO); HRMS (ESI-
FT-ICR) m/z 1449.8586 [M + Na]+ (calculated for C74H126N2O24Na
1449.8598).
Glycolipid 22. Chacotriose-based amine 19 (100 mg, 0.107
mmol), paraformaldehyde (3.2 mg, 0.107 mmol), lauric acid (21.4 mg,
0.107 mmol), and n-dodecylisocyanide (20.9 mg, 0.107 mmol) were
reacted in MeOH/CH2Cl2 (12 mL, 3:1, v/v) according to the general
procedure for the Ugi-4CR. Flash column chromatography purification
(n-hexane/EtOAc 1:1 → 2:3) afforded the glycolipid 22 (102 mg,
71%) as an amorphous solid: Rf = 0.21 (n-hexane/EtOAc 1:1); [α]D20
−67.1 (c 0.8, CHCl3); IR (KBr, cm−1) νmax 3346, 2928, 2862, 2383,
1743, 1245, 1223, 1146, 1051; 1H NMR (500 MHz, CDCl3) δ = 0.87
(t, 6H, J = 6.8 Hz, 2 × CH3); 1.15 (m, 6H, CH3 Rha, CH3 Rha′); 1.18,
1.19 (2 × s, 9H, (CH3)3C); 1.21 (s, 9H, (CH3)3C); 1.23−1.31 (m,
34H, 17 × CH2); 1.46 (m, 2H, CH2); 1.60 (m, 2H, CH2); 1.95 (m,
6H, 2 × CH3CO); 2.03 (m, 6H, 2 × CH3CO); 2.10 (m, 6H, 2 ×
CH3CO); 2.22, 2.36 (2 × t, 2H, J = 7.5 Hz, CH2); 3.21 (m, 2H, CH2);
3.50 (m, 2H, CH2); 3.62 (m, 1H); 3.69−3.78 (m, 3H); 3.85−3.93 (m,
3H); 3.99 (m, 2H); 4.22 (dd, 1H, J = 4.0/12.1 Hz, H-6a); 4.45 (t, 1H,
J = 8.1 Hz, H-1 Glc); 4.56 (m, 1H, H-6b Glc); 4.82 (m, 2H, H-1 Rha,
H-1 Rha′); 4.96−5.06 (m, 3H, H-4 Rha, H-4 Rha′, H-2 Rha); 5.11−
5.29 (m, 4H, H-2 Rha′, H-3 Rha, H-3 Rha′, H-3 Glc); 6.35, 6.47 (2 ×
m, 1H, NH); 13C NMR (125 MHz, CDCl3) δ = 14.0, 17.2, 17.3, 17.4,
20.5, 20.6, 20.7, 20.8, 20.9 (CH3); 22.6, 24.9, 25.3 (CH2); 26.8, 27.1
(CH3); 29.3, 29.4, 29.5, 29.6, 31.9, 32.9, 33.3 (CH2); 38.8, 38.9 (C);
39.4, 39.6, 48.4, 48.5, 50.4, 53.2, 62.1, 66.8 (CH2); 66.9, 68.0, 68.1,
68.8, 68.9, 69.7, 69.8, 69.9, 70.5, 70.6, 70.8, 70.9, 72.6, 72.7, 74.6, 74.8,
76.3, 76.5, 78.3, 78.4, 97.4, 97.7, 97.8, 101.3, 101.9 (CH); 168.4, 169.1,
169.5, 169.6, 169.7, 169.8, 169.9, 170.0, 174.2, 174.3, 176.4, 176.5,
177.7, 177.9 (CO); HRMS (ESI-FT-ICR) m/z 1365.7642 [M +
Na]+ (calculated for C68H114N2O24Na 1365.7659).
Glycolipid 23. An aqueous solution of NaOH (1.0 M, 0.5 mL) was
added to a solution of glycolipid 22 (105 mg, 0.078 mmol) in THF/
MeOH (3 mL, 1:1, v/v), and the reaction mixture was stirred at 50 °C
overnight. The solution was then neutralized with acid resin Dowex-50
(H+) and filtered to remove the resin. The filtrate was concentrated
under reduced pressure, and the resulting crude product was purified
by flash column chromatography (EtOAc/MeOH 4:1) to furnish the
glycolipid 23 (64 mg, 89%) as a white solid: Rf = 0.44 (CHCl3/MeOH
3:1); mp 184−185 °C; [α]D20 +88.2 (c 1.2, MeOH); IR (KBr, cm−1)
νmax 3358, 2924, 2855, 2372, 1635, 1055; 1H NMR (400 MHz,
pyridine-d5) δ = 0.85 (m, 6H, 2 × CH3); 1.17−1.32 (m, 36H, 18 ×
CH2); 1.50−1.84 (m, 10H, CH3 Rha, CH3 Rha′, 2 × CH2); 2.54 (m,
2H, CH2); 3.37−3.56 (m, 3H, H-5 Rha, CH2); 3.86−4.20 (m, 7H);
4.31 (m, 3H); 4.44−4.77 (m, 7H); 4.83 (m, 1H, H-1 Glc); 5.76 (m,
1H, H-1 Rha); 6.29, 6.35 (2 × s, 1H, H-1 Rha′); 8.43, 8.62 (2 × m,
1H, NH); 13C NMR (100 MHz, pyridine-d5) δ = 14.5, 18.7, 18.9
(CH3); 23.2, 25.8, 25.9, 27.5, 27.6, 28.8, 28.9, 29.9, 30.0, 30.1, 30.3,
30.4, 30.5, 32.4, 33.4, 33.7, 40.0, 40.1, 48.4, 49.5, 50.5, 53.2, 56.4, 61.3,
61.4, 68.4, 68.8 (CH2); 69.8, 69.9, 70.6, 72.6, 72.7, 72.8, 72.9, 74.0,
74.3, 74.4, 77.2, 77.7, 77.9, 78.4, 78.6, 78.8, 101.9, 102.3, 103.1, 103.2,
103.3 (CH); 169.7, 169.9, 174.4, 174.5 (CO); HRMS (ESI-FT-
ICR) m/z 945.5897 [M + Na]+ (calculated for C46H86N2O16Na
945.5875).
Glycolipid 25. Compound 24 (93 mg, 0.065 mmol) was treated
with NaOH (1.0 M, 0.5 mL) in THF/MeOH (3 mL, 1:1, v/v)
according to the deprotection procedure described for the synthesis of
23. Flash column chromatography purification (CHCl3/MeOH 4:1)
afforded the glycolipid 25 (62.2 mg, 95%) as a white solid: Rf = 0.47
(CHCl3/MeOH 3:1); mp 188−189 °C; [α]2D0 +28.4 (c 1.20, MeOH);
1
IR (KBr, cm−1) νmax 3345, 2923, 2851, 1624, 1060, 1041; H NMR
(400 MHz, pyridine-d5) δ = 0.89 (m, 6H, 2 × CH3); 1.23−1.35 (m,
48H, 24 × CH2); 1.53−1.87 (m, 10H, CH3 Rha, CH3 Rha′, 2 × CH2);
2.55 (m, 2H, CH2); 3.40−3.59 (m, 3H, H-5 Rha, CH2); 3.89−4.24
(m, 7H); 4.34 (m, 3H); 4.46−4.83 (m, 7H); 4.87 (m, 1H, H-1 Glc);
5.80 (m, 1H, H-1 Rha); 6.34, 6.40 (2 × s, 1H, H-1 Rha′); 8.43, 8.62 (2
× m, 1H, NH); 13C NMR (100 MHz, pyridine-d5) δ = 14.8, 18.9, 19.1
(CH3); 23.4, 26.0, 26.1, 27.8, 27.9, 30.0, 30.1, 30.2, 30.3, 30.4, 30.5,
30.6, 30.7, 32.6, 33.7, 33.9, 40.2, 40.3, 48.7, 50.8, 53.4, 61.5, 61.6, 69.0
(CH2); 70.1, 70.2, 70.9, 72.8, 72.9, 73.1, 74.3, 74.5, 74.6, 77.4, 77.9,
78.2, 78.6, 78.8, 78.9, 102.1, 103.3, 103.5 (CH); 169.9, 170.1, 174.6,
174.7 (CO); HRMS (ESI-FT-ICR) m/z 1029.6829 [M + Na]+
(calculated for C52H98N2O16Na 1029.6814).
Glycolipid 26. Chacotriose-based amine 19 (100 mg, 0.107
mmol), paraformaldehyde (3.2 mg, 0.107 mmol), stearic acid (30.2
mg, 0.107 mmol), and n-octadecylisocyanide (29.6 mg, 0.107 mmol)
were reacted in MeOH/CH2Cl2 (12 mL) according to the general
procedure for the Ugi-4CR. Flash column chromatography purification
(n-hexane/EtOAc 1:1) afforded the glycolipid 26 (117 mg, 73%) as an
amorphous solid: Rf = 0.29 (n-hexane/EtOAc 1:1); [α]2D0 −38.2 (c
0.90, CHCl3); IR (KBr, cm−1) νmax 3372, 2925, 2855, 1752, 1245,
1
1223, 1145, 1046; H NMR (500 MHz, CDCl3) δ = 0.87 (t, 6H, J =
7.1 Hz, 2 × CH3); 1.15 (m, 6H, CH3 Rha, CH3 Rha′); 1.18, 1.19 (2 ×
s, 9H, (CH3)3C); 1.21 (s, 9H, (CH3)3C); 1.22−1.30 (m, 58H, 29 ×
CH2); 1.47 (m, 2H, CH2); 1.60 (m, 2H, CH2); 1.95 (m, 6H, 2 ×
CH3CO); 2.03 (m, 6H, 2 × CH3CO); 2.11 (m, 6H, 2 × CH3CO);
2.22 (t, 1H, J = 7.6 Hz); 2.36 (t, 1H, J = 7.5 Hz); 3.17, 3.25 (2 × m,
2H, CH2); 3.47−3.54 (m, 2H); 3.62 (m, 1H); 3.67−3.78 (m, 3H);
3.84−3.94 (m, 3H); 3.97−4.03 (m, 2H); 4.22 (dd, 1H, J = 4.2/12.0
Hz, H-6a Glc); 4.44, 4.46 (2 × d, 1H, J = 7.3 Hz, H-1 Glc); 4.56 (m,
1H, H-6b Glc); 4.83 (m, 2H, H-1 Rha, H-1 Rha′); 4.97−5.04 (m, 2H,
H-4 Rha, H-4 Rha′); 5.06 (m, 1H, H-2 Rha); 5.12 (m, 1H, H-2 Rha′);
5.17 (m, 2H, H-3 Rha, H-3 Rha′); 5.24 (m, 1H, H-3 Glc); 6.33, 6.46
(m, 1H, NH); 13C NMR (125 MHz, CDCl3) δ = 14.1, 17.1, 17.2, 17.3,
17.4, 20.5, 20.6, 20.7, 20.8 (CH3); 22.6, 24.9, 25.3, 25.6 (CH2); 26.8,
26.9, 27.0, 27.1 (CH3); 29.2, 29.3, 29.4, 29.5, 29.6, 29.7, 31.9, 32.9,
33.2 (CH2); 38.8, 38.9 (C); 39.4, 39.6, 48.3, 48.4, 50.4, 62.0, 66.8
(CH2); 66.9 (CH); 67.9 (CH2); 68.0, 68.8, 68.9, 69.7, 69.9, 70.4, 70.5,
70.8, 70.9, 72.6, 72.7, 74.5, 74.8, 76.3, 76.5, 78.3, 78.4, 97.4, 97.7, 97.8,
101.3, 101.9 (CH); 169.5, 169.6, 169.7, 169.8, 169.9, 170.0, 174.2,
174.4, 177.7, 177.9 (CO); HRMS (ESI-FT-ICR) m/z 1533.9546
[M + Na]+ (calculated for C80H138N2O24Na 1533.9537).
Glycolipid 27. Compound 26 (103.6 mg, 0.069 mmol) was treated
with NaOH (1.0 M, 0.5 mL) in THF/MeOH (3 mL, 1:1, v/v)
according to the procedure described for the synthesis of 23. Flash
column chromatography purification (CHCl3/MeOH 4:1) afforded
the glycolipid 27 (70 mg, 93%) as a white solid: Rf = 0.45 (CHCl3/
MeOH 3:1); mp 179−181 °C; [α]2D0 +49.1 (c 0.9, MeOH); IR (KBr,
cm−1) νmax 3368, 2919, 2852, 2116, 1634, 1420, 1216, 1044; 1H NMR
(400 MHz, pyridine-d5) δ = 0.89 (m, 6H, 2 × CH3); 1.22−1.40 (m,
59H); 1.53−1.88 (m, 10H, CH3 Rha, CH3 Rha′, 2 × CH2); 2.56 (m,
Glycolipid 24. Chacotriose-based amine 19 (100 mg, 0.107
mmol), paraformaldehyde (3.2 mg, 0.107 mmol), lauric acid (21.4 mg,
0.107 mmol), and n-octadecylisocyanide (29.9 mg, 0.107 mmol) were
reacted in MeOH/CH2Cl2 (12 mL) according to the general
procedure for the Ugi-4CR. Flash column chromatography purification
(n-hexane/EtOAc 1:1 → 2:3) afforded the glycolipid 24 (105.3 mg,
69%) as an amorphous solid: Rf = 0.24 (n-hexane/EtOAc 1:1); [α]D20
−18.4 (c 0.85, CHCl3); IR (KBr, cm−1) νmax 3419, 2927, 2862, 2108,
1653, 1222, 1145, 1045; 1H NMR (500 MHz, CDCl3) δ = 0.88 (t, 6H,
J = 7.1 Hz, 2 × CH3); 1.16 (m, 6H, CH3 Rha, CH3 Rha′); 1.19, 1.20 (2
× s, 9H, (CH3)3C); 1.22 (s, 9H, (CH3)3C); 1.23−1.31 (m, 46H, 23 ×
CH2); 1.48 (m, 2H, CH2); 1.60 (m, 2H, CH2); 1.95 (m, 6H, 2 ×
CH3CO); 2.03 (m, 6H, 2 × CH3CO); 2.11 (m, 6H, 2 × CH3CO);
2.23 (t, 1H, J = 7.5 Hz); 2.37 (t, 1H, J = 7.4 Hz); 3.18, 3.26 (2 × m,
2H, CH2); 3.48−3.56 (m, 2H); 3.62 (m, 1H); 3.67−3.79 (m, 3H);
3.86−3.94 (m, 3H); 3.98−4.04 (m, 2H); 4.23 (dd, 1H, J = 4.2/12.0
Hz, H-6a Glc); 4.45, 4.47 (2 × d, 1H, J = 7.3 Hz, H-1 Glc); 4.56 (m,
4667
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Article
2H, CH2); 3.40−3.59 (m, 3H, H-5 Rha, CH2); 3.89−4.25 (m, 7H);
4.34 (m, 3H); 4.46−4.80 (m, 8H); 4.87 (m, 1H, H-1 Glc); 5.80 (m,
1H, H-1 Rha); 6.34, 6.40 (2 × s, 1H, H-1 Rha′); 8.42, 8.61 (2 × m,
1H, NH); 13C NMR (100 MHz, pyridine-d5) δ = 14.7, 18.9, 19.1
(CH3); 23.4, 26.0, 26.1, 27.8, 27.9, 30.0, 30.1, 30.2, 30.3, 30.4, 30.5,
30.6, 30.7, 32.6, 33.7, 33.9, 40.2, 40.3, 48.7, 49.7, 50.8, 53.5, 61.5, 61.6,
68.7, 69.1 (CH2); 70.0, 70.2, 70.9, 72.8, 73.0, 73.1, 73.2, 74.3, 74.5,
74.6, 77.4, 77.9, 78.1, 78.2, 78.6, 78.9, 79.0, 102.1, 102.5, 103.3, 103.5
(CH); 169.8, 170.0, 174.6, 174.7 (CO); HRMS (ESI-FT-ICR) m/z
1113.7749 [M + Na]+ (calculated for C58H110N2O16Na 1113.7753).
Glycolipid 28. n-Dodecylamine (40 mg, 0.216 mmol), parafor-
maldehyde (6.5 mg, 0.216 mmol), chacotriose-based acid 21 (205.4
mg, 0.216 mmol), and n-dodecylisocyanide (42.1 mg, 0.216 mmol)
were reacted in MeOH/CH2Cl2 (18 mL) according to the general
procedure for the Ugi-4CR. Flash column chromatography purification
(n-hexane/EtOAc 1:1) afforded the glycolipid 28 (197 mg, 68%) as an
amorphous solid: Rf = 0.22 (n-hexane/EtOAc 1:1); [α]2D0 −54.8 (c
0.90, CHCl3); IR (KBr, cm−1) νmax 3357, 2927, 2856, 1752, 1368,
4.99−5.06 (m, 3H, H-2 Rha, H-4 Rha′, H-4 Rha); 5.15−5.29 (m, 4H,
H-2 Rha′, H-3 Rha, H-3 Rha′, H-3 Glc); 6.44, 6.50 (2 × m, 1H, NH);
13C NMR (125 MHz, CDCl3) δ = 14.1, 17.2, 20.6, 20.7, 20.8, 20.9
(CH3); 22.7 (CH2); 26.8 (CH3); 26.9 (CH2); 27.2 (CH3); 28.6, 29.2,
29.3, 29.4, 29.5, 29.6, 29.8, 31.9 (CH2); 38.8, 38.9 (C); 39.5, 39.7, 49.2,
51.2, 62.2, 66.6 (CH2); 66.9, 67.1, 67.9, 68.1, 68.7, 68.9, 69.7, 69.8,
69.9, 70.4, 70.5, 70.8, 70.9, 72.3, 72.7, 74.8, 74.9, 76.2, 76.4, 77.8, 78.2,
97.7, 97.8, 97.9, 98.1, 100.2, 100.5 (CH); 168.8, 169.0, 169.6, 169.7,
169.8, 169.9, 170.0, 176.5, 177.6 (CO); HRMS (ESI-FT-ICR) m/z
1449.8656 [M + Na]+ (calculated for C74H126N2O24Na 1449.8598).
Glycolipid 31. Compound 30 (46 mg, 0.032 mmol) was treated
with NaOH (1.0 M, 0.5 mL) in THF/MeOH (2 mL, 1:1, v/v)
according to the procedure described for the synthesis of 23. Flash
column chromatography purification (CHCl3/MeOH 3:1) afforded
the glycolipid 31 (31 mg, 96%) as a white solid: Rf = 0.39 (CHCl3/
MeOH 4:1); mp 196−198 °C; [α]2D0 +38.1 (c 0.65, MeOH); IR (KBr,
cm−1) νmax 3355, 2924, 2855, 1640, 1052; 1H NMR (400 MHz,
pyridine-d5) δ = 0.87 (t, 6H, J = 6.8 Hz, 2 × CH3); 1.26 (m, 45H);
1.54−1.78 (m, 10H, CH3 Rha, CH3 Rha′, 2 × CH2); 3.41−3.66 (m,
5H, H-5 Glc, 2 × CH2); 3.76 (m, 1H); 4.02 (m, 1H, H-6a Glc); 4.12−
4.54 (m, 10H); 4.62−4.87 (m, 8H); 4.88, 4.94 (2 × d, 1H, J = 7.6 Hz,
H-1 Glc); 5.78 (s, 1H, H-1 Rha); 6.34, 6.41 (2 × s, 1H, H-1 Rha′);
8.45, 8.55 (2 × m, 1H, NH); 13C NMR (100 MHz, pyridine-d5) δ =
14.3, 18.5, 18.7, 18.8 (CH3); 23.0, 27.2, 27.4, 27.8, 29.1, 29.6, 29.7,
29.8, 29.9, 30.0, 30.1, 30.2, 30.3, 30.4, 32.1, 32.2, 39.8, 40.0, 49.4, 50.2,
51.3, 61.0, 61.2, 68.1, 69.4 (CH2); 69.6, 69.7, 70.4, 72.3, 72.4, 72.5,
72.6, 72.7, 72.8, 73.9, 74.4, 77.1, 77.2, 77.4, 77.6, 77.7, 77.8, 78.3, 78.5,
101.8, 102.0, 102.7, 102.8 (CH); 169.6, 169.7, 169.8, 169.9 (CO);
HRMS (ESI-FT-ICR) m/z 1029.6836 [M + Na]+ (calculated for
C52H98N2O16Na 1029.6814).
1
1245, 1224, 1147, 1046; H NMR (500 MHz, CDCl3) δ = 0.85−0.89
(m, 6H, 2 × CH3); 1.13−1.18 (m, 15H, (CH3)3C, CH3 Rha, CH3
Rha′); 1.20−1.29 (m, 45H); 1.48, 1.59 (2 × m, 4H, 2 × CH2); 1.96
(m, 6H, 2 × CH3CO); 2.03 (m, 6H, 2 × CH3CO); 2.10 (m, 6H, 2 ×
CH3CO); 3.17, 3.29 (2 × m, 4H, 2 × CH2); 3.52−4.50 (m, 11H, H-2
Glc, H-4 Glc, H-5 Glc, H-6a Glc, H-6b Glc, H-5 Rha, H-5 Rha′, 2 ×
CH2); 4.56, 4.68 (2 × m, 1H, H-1 Glc); 4.81, 4.85, 4.89 (3 × m, 2H,
H-1 Rha, H-1 Rha′); 4.98−5.08 (m, 3H, H-2 Rha, H-4 Rha′, H-4 Rha);
5.15−5.29 (m, 4H, H-2 Rha′, H-3 Rha, H-3 Rha′, H-3 Glc); 6.44, 6.50
(2 × m, 1H, NH); 13C NMR (125 MHz, CDCl3) δ = 14.1, 17.2, 20.5,
20.6, 20.7, 20.8, 20.9 (CH3); 22.6 (CH2); 26.8 (CH3); 26.9 (CH2);
27.2 (CH3); 28.6, 29.2, 29.3, 29.4, 29.6, 31.9 (CH2); 38.8, 38.9 (C);
39.5, 49.2, 51.2, 62.2, 66.6 (CH2); 66.9, 67.1, 67.9, 68.1, 68.9, 69.7,
70.0, 70.4, 70.6, 70.8, 70.9, 72.3, 72.7, 75.0, 76.2, 77.8, 97.7, 97.8, 97.9,
98.1, 100.2 (CH); 168.8, 169.0, 169.5, 169.6, 169.8, 169.9, 175.8,
176.1, 176.5, 177.6 (CO); HRMS (ESI-FT-ICR) m/z 1365.7672
[M + Na]+ (calculated for C68H114N2O24Na 1365.7659).
Glycolipid 32. n-Octadecylamine (62 mg, 0.230 mmol),
paraformaldehyde (6.9 mg, 0.230 mmol), chacotriose-based acid 21
(218.7 mg, 0.230 mmol), and n-octadecylisocyanide (64.2 mg, 0.230
mmol) were reacted in MeOH/CH2Cl2 (24 mL) according to the
general procedure for the Ugi-4CR. Flash column chromatography
purification (n-hexane/EtOAc 1:1) afforded the glycolipid 32 (247 mg,
71%) as an amorphous solid: Rf = 0.27 (n-hexane/EtOAc 1:1); [α]D20
−31.5 (c 0.60, CHCl3); IR (KBr, cm−1) νmax 3687, 2926, 2859, 2372,
Glycolipid 29. Compound 28 (70 mg, 0.052 mmol) was treated
with NaOH (1.0 M, 0.5 mL) in THF/MeOH (3 mL, 1:1, v/v)
according to the procedure described for the synthesis of 23. Flash
column chromatography purification (CHCl3/MeOH 4:1) afforded
the glycolipid 29 (70 mg, 93%) as a white solid: Rf = 0.42 (CHCl3/
MeOH 3:1); mp 178−180 °C; [α]2D0 +64.8 (c 0.8, MeOH); IR (KBr,
cm−1) νmax 3425, 2927, 2851, 2106, 1640, 1053; 1H NMR (400 MHz,
pyridine-d5) δ = 0.87 (t, 6H, J = 6.9 Hz, 2 × CH3); 1.24 (m, 36H, 18 ×
CH2); 1.54−1.74 (m, 10H, CH3 Rha, CH3 Rha′, 2 × CH2); 3.43−3.68
(m, 3H, H-5 Glc, CH2); 3.74 (m, 1H); 4.02 (m, 1H, H-6a Glc); 4.12−
4.53 (m, 9H); 4.61−4.86 (m, 8H); 4.87, 4.94 (2 × d, 1H, J = 7.6 Hz,
H-1 Glc); 5.78, 5.84 (2 × s, 1H, H-1 Rha); 6.33, 6.40 (2 × s, 1H, H-1
Rha′); 8.44, 8.53 (2 × m, 1H, NH); 13C NMR (100 MHz, pyridine-d5)
δ = 14.3, 18.4, 18.5, 18.6, 18.7 (CH3); 22.9, 27.1, 27.4, 27.7, 29.0, 29.6,
29.7, 29.8, 29.9, 30.0, 30.1, 30.2, 32.1, 39.8, 39.9, 47.8, 49.4, 50.1, 51.2,
60.9, 61.2, 68.1, 69.3 (CH2); 69.6, 69.7, 70.4, 72.3, 72.4, 72.5, 72.6,
72.7, 73.8, 74.3, 74.4, 77.0, 77.1, 77.4, 77.6, 77.7, 77.8, 78.3, 78.5,
101.8, 102.0, 102.2, 102.6, 102.8 (CH); 169.6, 169.7, 169.8, 169.9
(CO); HRMS (ESI-FT-ICR) m/z 945.5891 [M + Na]+ (calculated
for C46H86N2O16Na 945.5875).
1
1716, 1555, 1221; H NMR (500 MHz, CDCl3) δ = 0.88 (t, 6H, J =
6.9 Hz, 2 × CH3); 1.14−1.23 (m, 24H, 2 × (CH3)3C, CH3 Rha, CH3
Rha′); 1.23−1.30 (m, 62H, 31 × CH2); 1.47 (m, 2H, CH2); 1.95, 1.97
(2 × s, 2 × 3H, 2 × CH3CO); 2.03 (m, 6H, 2 × CH3CO); 2.10, 2.11
(2 × s, 2 × 3H, 2 × CH3CO); 3.17 (m, 2H, CH2); 3.30 (m, 2H, CH2);
3.52−4.55 (m, 11H, H-2 Glc, H-4 Glc, H-5 Glc, H-6a Glc, H-6b Glc,
H-5 Rha, H-5 Rha′, 2 × CH2); 4.59, 4.68 (2 × d, 1H, J = 7.2 Hz, H-1
Glc); 4.85 (d, 1H, J = 1.6 Hz, H-1 Rha); 4.90 (d, 1H, J = 1.3 Hz, H-1
Rha′); 4.99−5.08 (m, 3H, H-2 Rha, H-4 Rha′, H-4 Rha); 5.16−5.25
(m, 4H, H-2 Rha′, H-3 Rha, H-3 Rha′, H-3 Glc); 6.43, 6.50 (2 × m,
1H, NH); 13C NMR (125 MHz, CDCl3) δ = 14.1, 17.2, 20.6, 20.7,
20.8 (CH3); 22.7 (CH2); 26.8 (CH3); 26.9 (CH2); 27.2 (CH3); 28.6,
29.2, 29.3, 29.4, 29.5, 29.6, 29.7, 31.9 (CH2); 38.8, 38.9 (C); 39.3, 39.5,
51.2, 59.2, 62.2, 66.6 (CH2); 66.9, 68.0, 68.7, 68.9, 69.7, 70.6, 71.0,
72.3, 75.0, 76.3, 77.8, 97.7, 97.9, 98.1, 100.1, 100.2, 100.5 (CH); 168.8,
169.0, 169.5, 169.6, 169.9, 170.0, 170.3, 176.4, 176.5, 177.6 (CO);
HRMS (ESI-FT-ICR) m/z 1533.9532 [M + Na]+ (calculated for
C80H138N2O24Na 1533.9537).
Glycolipid 33. Compound 32 (106 mg, 0.070 mmol) was treated
with NaOH (1.0 M, 0.5 mL) in THF/MeOH (3 mL, 1:1, v/v)
according to the procedure described for the synthesis of 23. Flash
column chromatography purification (CHCl3/MeOH 4:1) afforded
the glycolipid 33 (70 mg, 92%) as a white solid: Rf = 0.53 (CHCl3/
MeOH 3:1); mp 181−183 °C; [α]2D0 +59.1 (c 0.95, MeOH); IR (KBr,
cm−1) νmax 3369, 2914, 2855, 1640, 1054; 1H NMR (400 MHz,
pyridine-d5) δ = 0.89 (t, 6H, J = 6.9 Hz, 2 × CH3); 1.28 (m, 60H, 30 ×
CH2); 1.56−1.80 (m, 10H, CH3 Rha, CH3 Rha′, 2 × CH2); 3.42−3.68
(m, 5H, H-5 Glc, 2 × CH2); 3.74 (m, 1H); 4.04 (m, 1H, H-6a Glc);
4.14−4.87 (m, 15H); 4.89, 4.96 (2 × d, 1H, J = 7.7 Hz, H-1 Glc); 5.79
(s, 1H, H-1 Rha); 6.35, 6.42 (2 × s, 1H, H-1 Rha′); 8.42, 8.51 (2 × m,
1H, NH); 13C NMR (100 MHz, pyridine-d5) δ = 14.6, 18.8, 19.1
(CH3); 23.3, 27.5, 27.8, 28.1, 29.4, 30.0, 30.1, 30.2, 30.3, 30.4, 30.5,
Glycolipid 30. n-Dodecylamine (40 mg, 0.216 mmol), parafor-
maldehyde (6.5 mg, 0.216 mmol), chacotriose-based acid 21 (205.4
mg, 0.216 mmol) and n-octadecylisocyanide (60.3 mg, 0.216 mmol)
were reacted in MeOH/CH2Cl2 (18 mL) according to the general
procedure for the Ugi-4CR. Flash column chromatography purification
(n-hexane/EtOAc 1:1) afforded the glycolipid 30 (222 mg, 72%) as an
amorphous solid: Rf = 0.24 (n-hexane/EtOAc 1:1); [α]2D0 −22.3 (c
1
0.80, CHCl3); IR (KBr, cm−1) νmax 3436, 2104, 1657, 1646, 1640; H
NMR (500 MHz, CDCl3) δ = 0.87 (t, 6H, J = 6.8 Hz, 2 × CH3);
1.13−1.18 (m, 15H, (CH3)3C, CH3 Rha, CH3 Rha′); 1.20−1.29 (m,
57H); 1.47, 1.59 (2 × m, 4H, 2 × CH2); 1.95 (m, 6H, 2 × CH3CO);
2.03 (m, 6H, 2 × CH3CO); 2.11 (m, 6H, 2 × CH3CO); 3.17 (m, 2H,
CH2); 3.30 (m, 2H, CH2); 3.52−4.49 (m, 11H, H-2 Glc, H-4 Glc, H-5
Glc, H-6a Glc, H-6b Glc, H-5 Rha, H-5 Rha′, 2 × CH2); 4.59, 4.68 (2
× m, 1H, H-1 Glc); 4.81, 4.85, 4.90 (3 × m, 2H, H-1 Rha, H-1 Rha′);
4668
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30.6, 32.5, 40.2, 40.3, 48.2, 49.8, 50.6, 51.6, 61.4, 61.7, 68.5, 69.8
(CH2); 69.9, 70.0, 70.8, 72.6, 72.7, 72.8, 72.9, 73.0, 73.1, 74.2, 74.8,
77.4, 77.5, 77.8, 77.9, 78.1, 78.2, 78.9, 79.0, 102.2, 102.4, 102.6, 103.0,
103.3 (CH); 169.6, 169.7, 169.8, 169.9 (CO); HRMS (ESI-FT-
ICR) m/z 1113.7775 [M + Na]+ (calculated for C58H110N2O16Na
1113.7753).
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ASSOCIATED CONTENT
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R. R. Carbohydr. Res. 2000, 328, 95−102.
S
* Supporting Information
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1H and 13C NMR spectra of building blocks and final products.
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: dgr@fq.uh.cu (D.G.R.); ibrouard@ipna.csic.es (I.B.).
Bendelac, A.; Savage, P. B. Org. Lett. 2002, 4, 1267−1270. (f) Laco
V.; Hunault, J.; Pipelier, M.; Blot, V.; Lecourt, T.; Rocher, J.; Turcot-
Dubois, A.-L.; Marionneau, S.; Douillard, J.-Y.; Clement, M.; Le
Pendu, J.; Bonneville, M.; Micouin, L.; Dubreuil, D. J. Med. Chem.
2009, 52, 4960−4963.
̂
ne,
Notes
The authors declare no competing financial interest.
́
ACKNOWLEDGMENTS
■
This work was supported by CSIC (Proyecto Intramural de
Incorporacio
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n-2007022). K.P.-L. gratefully acknowledges
MAEC-AECID for a doctoral scholarship.
DEDICATION
■
Dedicated to Professor Ludger Wessjohann on the occasion of
his 50th birthday.
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