Synthesis of β-C-galactosyl ceramide and its new aza variant via the horner-wadsworth-emmons reaction

Article abstract of DOI:10.1021/jo500769f

A simple strategy for the synthesis of β-C-galactosyl ceramide and its new aza-variant analogue is described using the Horner-Wadsworth-Emmons reaction as the key step in combining the sugar and aglycone portions.

Full text of DOI:10.1021/jo500769f

Article
pubs.acs.org/joc
Synthesis of β‑C‑Galactosyl Ceramide and Its New Aza Variant via the
Horner−Wadsworth−Emmons Reaction
Jaggaiah N. Gorantla†,‡ and Ravi S. Lankalapalli*,†,‡
†Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
‡Agroprocessing and Natural Products Division, CSIR-National Institute for Interdisciplinary Science and Technology,
Thiruvananthapuram 695019, Kerala, India
S
* Supporting Information
ABSTRACT: A simple strategy for the synthesis of β-C-
galactosyl ceramide and its new aza-variant analogue is
described using the Horner−Wadsworth−Emmons reaction
as the key step in combining the sugar and aglycone portions.
reported the first synthesis of a β-C-GalCer analogue, via the
ring-closing metathesis approach, which exhibited antisolid
tumor activity.10
A careful scrutiny of the reported β-GalCer analogues (vide
supra) led us to design a piperidine aza-sugar coupled to
phytosphingosine-derived ceramide. As aza-sugar C-glycosides
offer promising biological and therapeutic properties,11 we set
our goal toward development of a methodology for the
synthesis of aza-β-C-GalCer (2; Figure 1). In this pursuit, we
INTRODUCTION
■
Mammalian glycosphingolipids (GSLs) are essential compo-
nents of cellular membranes which play a critical role in a
variety of biochemical functions.1 A simple GSL comprises a β-
glycosidic linkage of a carbohydrate attached to the primary
hydroxyl group of ceramide. The carbohydrate portion is
present in the outer leaflet of the plasma membrane, serving as
a receptor for various pathogens.2 An important initial event
behind HIV infection is interaction of cell surface expressed
GSL galactosylceramide (GalCer) with the V3 loop region of
HIV gp120.3 This and other findings enabled the exploration of
GalCer analogues, with β-anomeric configuration, as potential
inhibitors for HIV infection.4 In a different design for β-GalCer
mimetics, a derivative with a simplified aliphatic chain in place
of ceramide and replacement of galactose with 1-deoxynojir-
imycin has displayed a potent and specific affinity (28.5 mN/
m) in an assay based on the change in surface pressure of the
glycolipid monolayers on exposure to a solution of gp120.5 The
C-glycoside analogues of β-GalCer were also synthesized, using
olefin cross metathesis and Wittig reaction as key steps, as these
methylene isosteres render chemical and enzymatic stability to
the analogues.6
Figure 1. Retrosynthetic analysis for β-C-glycosides.
In a related family of GSLs, KRN 7000, a synthetic glycolipid
that was designed following structure−activity studies on the
naturally occurring agelasphin which was discovered from the
marine sponge Agelas mauritianus, has been well studied due to
its potent immunomodulatory properties.7 KRN 7000, also
referred to as α-GalCer, contains the phytosphingosine base
which upon complexation with an antigen presenting
glycoprotein CD1d and subsequent complexation with an
iNKT cell receptor results in the release of cytokines offering
protection against several pathologies.8 The C-glycoside
analogue of α-GalCer was 100 times more effective in
comparison to the O-glycoside at a 10 ng dosage level in a
melanoma challenge assay on C57BL/6 mice.9 Chaulagain et al.
report a simple strategy for synthesis of β-C-glycosides in a
convergent manner using the Horner−Wadsworth−Emmons
(HWE) reaction of β-keto phosphonate 10 (Scheme 1) derived
from D-galactose and the aglycone aldehyde 15 (Figure 1).
Reports on the synthesis of β-C-GalCer for the most part relied
on the stereoselective synthesis of the sphingosine backbone
starting from a functionalized carbohydrate at the anomeric
position.10,12 Attempts concerning the application of the HWE
Received: April 4, 2014
© XXXX American Chemical Society
A
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
methodology for C-glycoside synthesis have involved the
presence of β-keto phosphonate in the aglycone portion.13 In
the present work, the HWE strategy was applied toward the
total synthesis of β-C-GalCer 1 and its new variant aza-β-C-
GalCer 2 from the common intermediate 17 (Scheme 3),
derived from the HWE reaction using phytosphingosine-1-al 15
as the aglycone component. The present work offers a new
entry to the repertoire of GSLs with a piperidine aza-sugar
which could serve as a potential inhibitor for HIV infection and
which may also have potential immunogenic properties.
elimination of the C-3 benzyl group; however, changing the
solvent to dry toluene produced the desired alkene 7 in 81%
yield. Protection of the 2° alcohol as an MPM afforded alkene 8
in 94% yield. Osmylation in the presence of stoichiometric
oxidant NMO, followed by oxidative cleavage of the diol
product using aqueous NaIO4 in THF, produced aldehyde 9 in
88% yield over two steps. Nucleophilic addition of the anion
generated from dimethyl methylphosphonate and n-BuLi to
aldehyde 9 afforded the 2° alcohol, which was subsequently
oxidized using Dess−Martin periodinane, giving rise to the
galactosyl β-keto phosphonate 10 in 49% yield over two steps.
In an attempt to develop a simple HWE methodology for β-
C-glycosides, β-keto phosphonate 10 was subjected to HWE
conditions with octanal by variation of base and solvent. In all
of the trials (Table 1) compound 10 was pretreated with base
RESULTS AND DISCUSSION
■
In our initial attempt, we sought a direct synthesis of aza-O-
GalCer by extending the O-glycosidation of phytosphingosine
by a galactose donor to the N-Boc azagalactose analogue 5
(Figure 2). The sugar portion with the N-Boc-protected
Table 1. Horner−Wadsworth−Emmons Reaction
Optimization Conditions
amt of
octanal,
equiv
base (amt,
equiv)
a
entry
solvent
time, h
yield, %
1
2
3
4
5
NaH (2)
2
3
3
3
2
THF
overnight
15
DIPEA (2)
CH3CN
EtOH
IPA
overnight
trace
28
K2CO3 (1.8)
Cs2CO3 (2.1)
3
Figure 2. Attempt to synthesize aza-O-GalCer.
6
41
Ba(OH)2·
8H2O (1.25)
THF
overnight
65
piperidin-2-ol 3 was synthesized from D-galactose in nine
steps,14 and phytosphingosin-1-ol 4 was prepared from
phytosphingosine in four steps.15 The glycosylation reaction
was performed using TMSOTf as the promoter in THF at −10
°C, which afforded the desired glycosylated product 5.
Unfortunately, under deprotective conditions the glycosylated
product cleaved to individual starting materials, as evidenced by
TLC as well as mass spectral data of the crude reaction mixture
(see the Supporting Information). This result demonstrated the
labile nature of aza-O-GalCer 5; therefore, we focused our
attempts on C-glycoside using the HWE strategy.
6
t-BuOK (4)
4
THF
overnight
47
a
Isolated yields.
for 30 min before addition of octanal. The initial attempt with
NaH in THF afforded the HWE product 11 in 15% yield (entry
1). Use of an organic base, DIPEA, gave rise to a trace amount
of product (entry 2). However, with K2CO3 in EtOH the
reaction was complete within 3 h, affording the product in 28%
yield (entry 3). There was a slight improvement in the yield
with Cs2CO3 to 41% (entry 4). Interestingly, using Ba(OH)2·
8H2O (1.25 equiv) the reaction was complete overnight with
an improved yield of 65%. Finally, with t-BuOK (4 equiv) the
HWE product was formed in 47% yield.
α,β-unsaturated ketone 11 was subjected to deprotective
conditions, DDQ in DCM, to produce the hemiketal 12
(Scheme 2). The 3° hydroxy group was removed by reduction
using Et3SiH and TMSOTf, followed by alkene reduction and
debenzylation using 10% Pd/C under H2, and finally the
resulting product was subjected to global acetylation, affording
Synthesis of HWE precursor β-keto phosphonate 10
(Scheme 1) commenced from lactol 6, which was prepared
in three steps from D-galactose.16 The Wittig reaction of lactol 6
in dry THF led to formation of the diene product with
Scheme 1. Synthesis of β-Keto Phosphonate 10 from D-
Galactose
Scheme 2. Synthesis of β-C-Glycoside 13
B
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
peracetylated galactosyl-β-C-glycoside 13 in 48% yield over
three steps. The presence of COSY correlation between H-1 at
δH 3.36 (m, 1H) and H-2 at δH 5.08 (app t, J = 9.5 Hz, 1H) and
trans coupling constant helped to determine the β config-
uration of C-glycoside 13 (see the Supporting Information).
Successful synthesis of the β-C-glycoside 13 from keto-
phosphonate 10 and octanal via the HWE reaction encouraged
us to apply this methodology toward the synthesis of
biologically relevant structures β-C-GalCer 1 and its new
variant aza-β-C-GalCer 2 from a common intermediate. In a
convergent approach, first, the HWE aldehyde precursor of
ceramide was synthesized from commercially available
phytosphingosine following a known procedure to afford the
protected phytosphingosin-1-ol 14 (Scheme 3).17 Alcohol 14
Scheme 4. Confirmation of Stereochemistry
the phytosphingosine aldehyde 15 under HWE reaction
conditions, compound 21 was converted into the oxazolidinone
22. Comparison of the H-4 and H-5 coupling constant value
(J4,5 = 8 Hz) with that in the literature confirms that under
HWE conditions the C-2 stereocenter did not undergo
epimerization.6a,12 Dondoni et al. reported epimerization of
Garner aldehyde under Wittig reaction conditions using n-
BuLi,19 whereas Compostella et al. reported no such
epimerization under HWE reaction conditions using a milder
base such as K2CO3 even with stirring for 18 h.12 Nevertheless,
the present HWE reaction using K2CO3 facilitated con-
sumption of phytosphingosin-1-al 15 within 1 h. Deprotection
of Boc and isopropylidene groups of compound 21 in EtOH/2
M HCl (4/1) at 70 °C produced the free amine, which was
subjected to amidation using p-nitrophenyl decanoate to afford
ceramide 23 (Scheme 5) in 74% yield over two steps.
Scheme 3. Synthesis of β-C-GalCer 1
Scheme 5. Synthesis of aza-β-C-GalCer 2
was oxidized using Dess−Martin periodinane in the presence of
excess NaHCO3, which resulted in phytosphingosin-1-al 15.
The initial HWE reaction between aldehyde 15 and β-keto
phosphonate 10 using Ba(OH)2·8H2O afforded the HWE
adduct 16 in a poor yield. However, a change of base to K2CO3
afforded the desired product 16 in 39% yield over two steps.
MPM deprotection using DDQ in DCM/H2O (10/1) formed
the hemiketal product 17 in 69% yield. Removal of the 3°
hydroxyl group under reductive conditions and deprotection of
Boc and isopropylidene groups under acidic conditions resulted
in free amine, which was subjected to amidation using p-
nitrophenyl decanoate to afford the advanced intermediate 18
in 53% yield over three steps. Finally, debenzylation using 10%
Pd/C under H2 afforded β-C-GalCer 1 in a quantitative yield,
which was subjected to global acetylation, affording the
peracetylated β-C-GalCer 19. In this context, the present
work offers an alternative route to β-C-GalCer 1 prepared by
Chaulagain et al.10
Synthesis of aza-β-C-GalCer 2 was envisaged by utilizing the
standard double reductive amination conditions usually
employed for piperidine aza-D-sugar synthesis.18 Initially, the
hemiketal product 17 was oxidized with Dess−Martin period-
inane, which afforded diketone 20 (Scheme 4) in 91% yield. A
double reductive amination reaction facilitated facile cyclization
to form the piperidine aza-D-sugar 21 in 66% yield. To address
the concern of stereochemical integrity of C-2 stereocenter of
Surprisingly, during the latter amidation conditions only the
sphingosine amine was affected, leaving the piperidine aza-sugar
unaltered, perhaps due to steric hindrance. The indifference of
the 2° amine of the piperidine aza-sugar toward amide bond
formation was further substantiated by a previous report for N-
benzoylation utilizing Grignard reagent for deprotonation.20
Finally, global debenzylation with 10% Pd/C under H2 afforded
aza-β-C-GalCer 2 in quantitative yield, which was treated with
Ac2O/pyridine to produce the peracetylated aza-β-C-GalCer
24. The presence of a COSY correlation in compound 23
between H-1 at δH 3.14 (dd, J = 9, 7 Hz) with H-1′ at δH 5.72
(dd, J = 16, 7 Hz) and H-2 at δH 3.63 (app t, J = 9 Hz) helped
to confirm the β configuration by trans-coupling constant (see
Supporting Information). Furthermore, the presence of H-5 δH
2.85, which is upfield from H-1, indicates that H-1 and H-5 are
neighbors to NH of the sugar. The presence of three COSY
correlations for H-5 with δH 3.33, 3.48, and 3.95 further
confirms the identity of H-5 in the sugar. This COSY analysis
C
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
4.68−4.63 (m, 2H), 4.48 (d, J = 12 Hz, 1H), 4.49−4.33 (m, 4H),
4.12−4.06 (m, 2H), 3.82−3.78 (m, 1H), 3.53−3.46 (m, 2H), 3.03(d, J
= 5.5 Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ 138.3, 138.2, 138.1,
138.0, 135.7, 128.3, 128.1, 128.0, 127.74, 127.70, 127.6, 119.2, 80.7,
76.5, 75.2, 73.1, 71.2, 70.3, 69.6; HR-ESI-MS [M + Na]+ C35H38O5Na
calcd for m/z 561.2616, found 561.2625.
confirms amidation of the sphingosine backbone, leaving the
aza portion of the sugar unaffected.
CONCLUSION
■
In summary, we have successfully demonstrated the Horner−
Wadsworth−Emmons reaction in β-C-glycoside synthesis using
a β-keto phosphonate generated from a sugar and an aglycone
aldehyde. This methodology was successfully employed in the
total synthesis of biologically relevant glycosphingolipids: β-C-
galactosylceramide (GalCer) and its new variant aza-β-C-
GalCer. In light of the importance of β-GalCer derivatives as
potential inhibitors for HIV infection as well as possession of
immunogenic properties by activation of iNKT cells leading to
release of Th1/Th2 immune response which are involved in
protection against several diseases, aza-β-C-GalCer marks a new
entry in glycolipid-related therapeutic approaches. To the best
of our knowledge, this is the first report of a glycosphingolipid
with a piperidine aza-sugar. Aza substitution of a sugar also
opens a new diversity element which can be further
functionalized to prepare a library of therapeutically relevant
molecules.
3,4,5,7-Tetra-O-benzyl-6-O-p-methoxybenzyloxy-D-galacto-
hept-1-ene (8). To a solution of compound 7 (9.5 g, 17.6 mmol, 1
equiv) in DMF (70 mL) at 0 °C was added NaH 60% suspension in
mineral oil (1.4 g, 35.3 mmol, 2 equiv), and the resulting mixture was
stirred for 30 min. At the same temperature 4-methoxybenzyl chloride
(3.6 mL, 26.4 mmol, 1.5 equiv) was added dropwise and the reaction
mixture was warmed to room temperature slowly. After 3 h, the
reaction mixture was quenched with ice−water (250 mL) at 0 °C and
extracted with ethyl acetate (2 × 300 mL) and the extracts were dried
over anhydrous Na2SO4 and concentrated. Purification by flash
chromatography using hexane/EtOAc 95/5 to 90/10 afforded
compound 8 (10.9 g, 94%) as a colorless viscous solid: Rf 0.38
1
(hexane/EtOAc 4/1); H NMR (CDCl3, 500 MHz) δ 7.34−7.18 (m,
22H), 6.79 (d, J = 8.5 Hz, 2H), 5.98−5.90 (m, 1H), 5.34−5.25 (m.,
2H), 4.68−4.61 (m, 3H), 4.56−4.50 (m, 4H), 4.42−4.30 (m, 3H),
4.16 (dd, J = 7.5, 4.5 Hz, 1H), 3.98−3.94 (m, 2H), 3.80−3.78 (m,
1H), 3.7 (s, 3H), 3.64 (dd, J = 10, 5.5 Hz, 1H), 3.59 (dd, J = 9.5, 4.5
Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ 159.0, 138.8, 138.7, 138.6,
138.2, 136.5, 131.1, 129.4, 128.3, 128.2, 127.8, 127.6, 127.5, 127.3,
118.5, 81.8, 78.5, 73.1, 72.2, 70.7, 70.5, 70.3, 55.2; HR-ESI-MS [M +
Na]+ C43H46O6Na calcd for m/z 681.3192, found 681.3195.
EXPERIMENTAL SECTION
■
The solvents were dried as follows: THF was heated at reflux over
sodium, CH3CN and CH2Cl2 were distilled over calcium hydride,
toluene was dried over molecular sieves, and EtOH was dried over
magnesium turnings. All reactions were carried out under an argon
atmosphere using oven-dried glassware. Silica gel 60 F254 aluminum
TLC plates were used to monitor the reactions with short-wavelength
ultraviolet light to visualize the spots, charring the TLC plate after
spraying with 15% sulfuric acid. Flash column chromatography was
performed on silica gel 120−200 and 230−400 mesh. 1H NMR
spectra were recorded at 500 MHz, chemical shifts are given in parts
per million and coupling constant in hertz. 13C NMR spectra were
recorded at 125 MHz. HRMS analysis was performed using
electrospray ionization technique with ions given in m/z.
2,3,4,6-Tetra-O-benzyl-5-O-p-methoxybenzyloxy-D-galacto-
1-hexanal (9). To a solution of compound 8 (10.9 g, 16.5 mmol, 1
equiv) in acetone/water (4/1, 150 mL) were added NMO (2.9 g, 24.8
mmol, 1.5 equiv) and OsO4 (189.5 mg, 0.74 mmol, 0.045 equiv), and
then the reaction mixture was stirred for 8 h at room temperature
under an argon atmosphere. The reaction mixture was quenched with
saturated aqueous NaHSO3, washed with water (2 × 400 mL), and
extracted with ethyl acetate (2 × 300 mL), and the extracts were dried
over anhydrous Na2SO4 and concentrated. Purification by flash
chromatography using hexane/EtOAc 90/10 to 70/30 afforded the
diol as a colorless viscous solid: Rf 0.3 (hexane/EtOAc 6/4); 1H NMR
(CDCl3, 500 MHz) δ 7.31−7.14 (m, 22H), 6.81 (d, J = 8.5 Hz, 2H),
4.76−4.71 (m, 2H), 4.67−4.60 (m, 2H), 4.58−4.54 (m, 3H), 4.49−
4.47 (m, 2H), 4.43−4.38 (m, 2H), 4.09 (app t, J = 5.5 Hz, 1H), 4.00−
3.97 (m, 1H), 3.87−3.85 (m, 2H), 3.76 (s, 3H), 3.75 (s, 1H), 3,70−
3.66 (m, 1H), 3.60−3.56 (m, 2H), 3.4 (d, J = 4 Hz, 1H), 1.77 (s, 1H);
13C NMR (CDCl3, 125 MHz) δ 159.2, 138.2, 138.1, 137.9, 130.6,
2,3,4,6-Tetra-O-benzyl-5-[N-(tert-butoxycarbonyl)amino]-5-
deoxy-α-D-galactopyranosyl-(2S,3S,4R)-2-azido-3,4-di-O-ben-
zyloctadecane-1,3,4-triol (5). To a solution of N-Boc-protected
piperidin-2-ol 3 (60 mg, 0.093 mmol, 1 equiv) and phytosphingosin-1-
ol 4 (97 mg, 0.102 mmol, 2 equiv) in dry THF (4 mL) was added
TMSOTf (9 μL, 0.046 mmol, 0.5 equiv) at −10 °C, and the resulting
mixture was stirred for 2 h at 0 °C under an argon atmosphere. The
reaction mixture was quenched with saturated aqueous NaHCO3,
washed with water (2 × 50 mL), and extracted with EtOAc (2 × 50
mL), and the extracts were dried over anhydrous MgSO4 and
concentrated. Purification by flash chromatography using hexane/
EtOAc 90/10 to 80/20 afforded glycosylated product 5 (50 mg, 47%)
as a colorless viscous solid: Rf 0.5 (hexane/EtOAc 9/1); HR-ESI-MS
[M + Na]+ C71H92N4O9Na calcd for m/z 1167.6762, found
1167.6771.
129.9, 129.6, 128.4, 128.3, 128.2, 127.9, 127.8, 127.6, 113.7, 79.6, 79.1,
78.2, 73.3, 73.0, 72.9, 71.8, 70.0, 63.8, 55.2; HR-ESI-MS [M + Na]+
C43H48O8Na calcd for m/z 715.3246, found 715.3250.
To a solution of the diol (4.5 g, 6.5 mmol, 1 equiv) in THF (70
mL) was added a solution of aqueous NaIO4 (2.79 g, 13.1 mmol, 2
equiv) at 0 °C, and the mixture was stirred overnight at room
temperature under an argon atmosphere. The reaction mixture was
quenched with brine (50 mL) and extracted with ethyl acetate (2 ×
200 mL), and the extracts were washed with water (2 × 300 mL),
dried over anhydrous MgSO4, and concentrated. Purification by flash
chromatography using hexane/EtOAc 90/5 to 90:10 afforded
aldehyde 9 (3.98 g) as a colorless viscous solid (88% over 2 steps):
3,4,5,7-Tetra-O-benzyl-D-galactohept-1-enitol (7). A solution
of methyltriphenylphosphonium bromide (37.7 g, 105.5 mmol, 3
equiv) in dry toluene (200 mL) was stirred for 10 min at room
temperature, and then a 1.6 M solution of n-BuLi in hexane (65.9 mL,
105.5 mmol, 3 equiv) was slowly added at 0 °C under an argon
atmosphere. The resulting yellow solution was stirred for 2 h at 0 °C
to room temperature, and then a solution of 2,3,4,6-tetra-O-benzyl-D-
galactose 6 (19 g, 35.2 mmol, 1 equiv) in dry toluene (80 mL) was
added at room temperature. After it was stirred overnight, the reaction
mixture was brought to 0 °C, quenched with acetone (150 mL), and
extracted with Et2O (2 × 400 mL). The organic layer was washed with
excess water, dried over anhydrous MgSO4, concentrated, and purified
by flash chromatography using hexane/EtOAc 95/5 to 90/10, which
afforded compound 7 (15.3 g, 81%) as a pale brown viscous solid: Rf
1
Rf 0.4 (hexane/EtOAc 7/3); H NMR (CDCl3, 500 MHz) δ 9.68 (s,
1H), 7.32−7.17 (m, 22H), 6.79 (d, J = 8.5 Hz, 2H), 4.66 (d, J = 11.5
Hz, 1H), 4.63−4.56 (m, 3H), 4.51−4.47 (m, 2H), 4.45−4.40 (m, 4H),
4.11−4.09 (m, 2H), 4.01 (app t, J = 5 Hz, 1H), 3.95−3.94 (m, 1H),
3.77 (s, 3H), 3.61−3.59 (m, 2H); 13C NMR (CDCl3, 125 MHz) δ
201.6, 159.1, 138.3, 138.1, 137.8, 130.7, 130.4, 129.5, 128.5, 128.3,
128.0, 127.9, 127.8, 127.6, 127.5, 113.6, 83.6, 79.2, 79.0, 76.8, 74.4,
73.3, 73.08, 73.0, 72.5, 69.9, 55.2; HR-ESI-MS [M + Na]+
C42H44O7Na calcd for m/z 683.2984, found 683.2982 and [M +
MeOH + Na]+ 715.3239.
Dimethyl [(3,4,5,7-Tetra-O-benzyl-6-O-p-methoxybenzy-
loxy-D-galacto)-1-oxomethyl]phosphonate (10). To a solution
of dimethyl methylphosphonate (1.28 mL, 11.9 mmol, 2.1 equiv) in
THF (15 mL) at −78 °C was slowly added n-BuLi (7.13 mL, 11.4
1
0.4 (hexane/EtOAc 3/1); H NMR (CDCl3, 500 MHz) δ 7.36−7.16
(m, 20H), 5.90−5.83 (m, 1H), 5.35−5.29 (m, 2H), 4.74 (s, 2H),
D
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
mmol, 2 equiv), and then the resulting yellow solution was stirred for
20 min at the same temperature under an argon atmosphere. A
solution of compound 9 (3.7 g, 5.7 mmol, 1 equiv) in THF (30 mL)
was added, and the resulting mixture was stirred for 1 h at −78 °C
under an argon atmosphere. The reaction mixture was quenched with
saturated aqueous NH4Cl (50 mL) and extracted with ethyl acetate (2
× 200 mL), and the extracts were washed with water (3 × 300 mL),
dried over anhydrous MgSO4, and concentrated. Purification by flash
chromatography hexane/EtOAc 90/10 to 40/60 afforded the β-
hydroxy phosphonate: Rf 0.2 (hexane/EtOAc 7/3); HR-ESI-MS [M +
Na]+ C45H53O10PNa calcd for m/z 807.3274, found 807.3281.
(t, J = 6.5 Hz, 3H); 13C NMR (CDCl3, 125 MHz) δ 200.8, 149.2,
138.8, 137.9, 137.6, 137.2, 128.4, 128.3, 128.26, 128.21, 128.0, 127.9,
127.8, 127.74, 127.72, 127.6, 127.5, 126.0, 97.0, 84.1, 79.9, 74.7, 73.7,
73.4, 73.2, 72.5, 71.3, 69.0, 32.6, 31.8, 29.3, 29.1, 29.0, 28.8, 27.9, 22.6,
14.1; HR-ESI-MS [M + Na]+ C43H52O6Na calcd for m/z 687.3661,
found 687.3668.
2,3,4,6-Tetra-O-acetyl-1-C-nonyl-β-D-galactopyranose (13).
To a solution of compound 12 (39 mg, 0.06 mmol, 1 equiv) in
CH3CN (3 mL) were added Et3SiH (94 μL, 0.58 mmol, 10 equiv) and
TMSOTf (32 μL, 0.17 mmol, 3 equiv), at 0 °C, and the mixture was
stirred for 20 min. The reaction mixture was quenched with saturated
aqueous NaHCO3 (10 mL) and extracted with EtOAc (2 × 30 mL),
and the extracts were washed with brine (25 mL), dried over
anhydrous MgSO4, and concentrated. The crude mixture was dissolved
in 3 mL of EtOH/THF (6/1), and then 10% Pd/C (30 mg) and TFA
(18 μL, 0.23 mmol, 4 equiv) were added. The resulting mixture was
purged with H2 gas for 5 min at room temperature, and then the
reaction mixture was stirred overnight under an H2 atmosphere
(balloon). The reaction mixture was then diluted with EtOH (3 mL),
filtered through a Celite pad, and washed with MeOH, and the filtrate
was concentrated under vacuum, resulting in a white solid in a
quantitative yield. The resulting product was dissolved in pyridine (2
mL) and Ac2O (0.5 mL), and the reaction mixture stirred was
overnight at room temperature under an argon atmosphere. The
reaction mixture was diluted with H2O (5 mL) and extracted with
EtOAc (2 × 25 mL), and the organic layer was washed with saturated
aqueous NaHCO3 (2 × 10 mL), dried over anhydrous MgSO4, and
concentrated. Purification by flash chromatography using hexane/
EtOAc 90/10 to 85/15 afforded compound 13 (13 mg, 48% over
To a solution of the β-hydroxy phosphonate (3.15 g, 4.02 mmol, 1
equiv) in CH2Cl2 (30 mL) was added Dess−Martin periodinane (3.4
g, 8.04 mmol, 2 equiv), and the mixture was stirred for 1 h at room
temperature under an argon atmosphere. The reaction mixture was
then quenched with saturated aqueous Na2S2O3 (75 mL) and
saturated aqueous NaHCO3 (100 mL) and extracted with CH2Cl2
(2 × 150 mL), and the extracts were washed with water (2 × 400 mL),
dried over anhydrous MgSO4, and concentrated. Purification by flash
chromatography using hexane/EtOAc 95/5 to 80/20 to 60/40
afforded compound 10 (2.16 g, 49% over two steps) as a pale yellow
1
viscous solid: Rf 0.3 (hexane/EtOAc 6/4); H NMR (CDCl3, 500
MHz) δ 7.31−7.12 (m, 22H), 6.79 (d, J = 8.5 Hz, 2H), 4.68 (app t, J =
12 Hz, 2H), 4.61−4.58 (m, 1H), 4.55−4.51 (m, 3H), 4.49−4.44 (m,
2H), 4.39−4.36 (m, 2H), 4.29 (d, J = 11.5 Hz, 1H), 4.04−4.01 (m,
1H), 3.99−3.94 (m, 2H), 3.77 (s, 3H), 3.64 (s, 3H), 3.62 (s, 3H),
3.60−3.59 (m, 1H), 3.55−3.53 (m, 1H), 3.33 (dd, JHbHa = 14.5 Hz,
JHbP = 22.0 Hz, CHaHbP, 1H), 2.91 (dd, JHaHb = 14.5 Hz, JHaP = 21.0
Hz, CHaHbP, 1H); 13C NMR (CDCl3, 125 MHz) δ 200.9, 159.0,
138.4, 138.1, 137.8, 137.6, 130.8, 129.6, 129.4, 128.3, 127.9, 127.4,
113.6, 83.8, 79.6, 79.4, 74.9, 73.2, 72.7, 72.5, 69.8, 55.7, 52.7, 38.7,
37.6; HR-ESI-MS [M + Na]+ C45H51O10PNa calcd for m/z 805.3117,
found 805.3126.
2,3,4,6-Tetra-O-benzyl-5-(p-methoxybenzyloxy)-1-anhydro-
D-galacto-1-C-nonene (11). To a solution of compound 10 (295
mg, 0.37 mmol, 1 equiv) in THF (6 mL) was added Ba(OH)2·8H2O
(148.7 mg, 0.47 mmol, 1.25 equiv), and then the mixture was stirred
for 30 min at room temperature under an argon atmosphere. Octanal
(176.7 μL, 1.13 mmol, 3 equiv) was added directly to the reaction
mixture, and this mixture was stirred at room temperature under an
argon atmosphere. After the mixture was stirred overnight, the reaction
was stopped and solvents were evaporated; the crude mixture was
directly subjected to purification by flash chromatography using
hexane/EtOAc 95/5, affording compound 11 (190 mg, 65%) as a
colorless viscous solid: Rf 0.40 (hexane/EtOAc 4/1); 1H NMR
(CDCl3, 500 MHz) δ 7.32−7.10 (m, 22H), 7.01−6.95 (m, 1H), 6.78
(d, J = 8.5 Hz, 2H), 6.58 (d, J = 15.5 Hz, 1H), 4.64−4.60 (m, 2H),
4.54−4.46 (m, 2H), 4.44−4.40 (m, 4H), 4.32−4.30 (m, 2H), 4.18 (dd,
J = 8.5, 3 Hz, 1H), 3.99−3.97 (m, 1H), 3.75 (s, 3H), 3.68−3.66 (m,
1H), 3.63−3.61 (m, 1H), 2.11−2.07 (m, 2H), 1.33−1.26 (m, 10H),
0.86 (t, J = 7 Hz, 3H); 13C NMR (CDCl3, 125 MHz) δ 200.9, 159.0,
138.5, 138.2, 138.1, 137.5, 130.8, 129.2, 128.3, 128.2, 127.7, 127.5,
126.2, 113.6, 84.1, 79.9, 78.0, 73.8, 73.6, 73.1, 72.6, 72.0, 55.2, 32.6,
31.7, 29.2, 29.0, 27.9, 22.6, 14.0; HR-ESI-MS [M + Na]+ C51H60O7Na
calcd for m/z 807.4236, found 807.4228.
1
three steps) as a white solid: Rf 0.46 (hexane/EtOAc 6/4); H NMR
(CDCl3, 500 MHz) δ 5.41 (d, J = 3 Hz, 1H), 5.08 (app t, J = 9.5 Hz,
1H), 5.02 (dd, J = 10.5, 3.5 Hz, 1H), 4.14 (dd, J = 9.5, 5 Hz, 1H), 4.06
(dd, J = 11, 6.5 Hz, 1H), 3.84 (app t, J = 6.5 Hz, 1H), 3.38−3.34 (m,
1H), 2.15 (s, 3H), 2.05 (s, 6H), 1.98 (s, 3H), 1.51−1.50 (m, 2H),
1.30−1.26 (m, 14H), 0.88 (t, J = 7 Hz, 3H); 13C NMR (CDCl3, 125
MHz) 170.5, 170.4, 170.3, 169.9, 78.3, 74.0, 72.3, 69.5, 67.7, 31.9, 31.8,
31.4, 29.7, 29.5, 29.3, 25.1, 22.6, 20.8, 20.7, 20.6, 14.1; HR-ESI-MS [M
+ Na]+ C23H38O9Na calcd for m/z 481.2413, found 481.2395.
(2S,3S,4R)-2-[N-(tert-Butoxycarbonyl)amino]-3,4-O-isopro-
pylideneoctadecan-1-al (15). To a solution of protected
phytosphingosin-1-ol 14 (100 mg, 0.22 mmol, 1 equiv) in CH2Cl2
(5 mL) were added NaHCO3 (45.9 mg, 0.54 mmol, 2.5 equiv) and
Dess−Martin periodinane (185.5 mg, 0.43 mmol, 2 equiv), and the
reaction mixture was stirred for 1 h at room temperature under an
argon atmosphere. The reaction mixture was quenched with saturated
aqueous Na2S2O3 (20 mL) and saturated aqueous NaHCO3 (50 mL)
and extracted with CH2Cl2 (2 × 50 mL), and the extracts were dried
over anhydrous Na2SO4, concentrated, and passed through a short
silica pad by washing with ethyl acetate; the resulting filtrate was dried
over anhydrous Na2SO4 and concentrated to afford phytosphingosin-
1-al as a white solid, which was directly used for the next step without
1
further purification: Rf 0.48 (hexane/EtOAc 7/3); H NMR (CDCl3,
500 MHz) δ 9.74 (s, 1H), 5.37 (d, J = 7 Hz), 4.45 (d, J = 5 Hz), 4.32−
4.28 (m, 2H), 1.77−1.73 (m, 2H), 1.46 (s, 9H), 1.39 (s, 6H), 1.26 (m,
24H), 0.88 (t, J = 6.5 Hz); 13C NMR (CDCl3, 125 MHz) δ 198.7,
155.3, 108.7, 80.2, 78.9, 60.5, 31.9, 29.7, 29.65, 29.62, 29.55, 29.51,
29.4, 29.3, 28.2, 28.1, 26.9, 24.9, 22.6, 14.1; HR-ESI-MS [M + MeOH
+ Na]+ C27H53NO6Na calcd for m/z 510.3770, found 510.3779.
(2E,3S,4S,5R)-3-[N-(tert-Butoxycarbonyl)amino]-4,5-O-iso-
propylidene-1-anhydro(2,3,4,6-tetra-O-benzyl-5-O-p-methox-
ybenzyloxy-D-galacto)-2-nonadecene (16). To a solution of
compound 10 (341 mg, 0.44 mmol, 2 equiv) in EtOH (4 mL) were
added a solution of phytosphingosin-1-al 15 (0.22 mmol) in EtOH
(2.5 mL) and K2CO3 (90.6 mg, 0.65 mmol, 3 equiv), and the mixture
was stirred at room temperature for 1 h under an argon atmosphere.
The reaction mixture was quenched with aqueous citric acid (1 g in 5
mL of H2O), washed with H2O (30 mL), and extracted with EtOAc (2
× 50 mL), and the extracts were dried over anhydrous Na2SO4 and
concentrated. Purification by flash chromatography using hexane/
EtOAc 95/5 to 90/10 afforded compound 16 (95 mg, 39% over two
2,3,4,6-Tetra-O-benzyl-1-C-nonenyl-β-D-galactopyranose
(12). To a solution of compound 11 (170 mg, 0.21 mmol, 1 equiv) in
CH2Cl2 (5 mL) was added DDQ (54.1 mg, 0.23 mmol, 1.1 equiv) at 0
°C, and the resulting brownish reaction mixture was stirred for 2.5 h at
room temperature under an argon atmosphere. The reaction mixture
was then quenched with saturated aqueous NaHCO3 (20 mL) and
extracted with CH2Cl2 (2 × 70 mL), and the extracts were washed
with water (2 × 250 mL), dried over anhydrous MgSO4, and
concentrated. Purification by flash chromatography using hexane/
EtOAc 95/5 to 90/10 afforded compound 12 (97 mg, 68%) as a pale
1
yellow viscous solid: Rf 0.37 (hexane/EtOAc 4/1); H NMR (CDCl3,
500 MHz) δ 7.34−7.23 (m, 20H), 7.14−7.00 (m, 1H), 6.61 (d, J =
15.5 Hz, 1H), 4.71−4.57 (m, 3H), 4.53−4.43 (m, 3H), 4.38−4.30 (m,
3H), 4.22 (d, J = 3 Hz, 1H), 4.16−4.06 (m, 2H), 3.88−3.85 (m, 2H),
3.59−3.49 (m, 2H), 1.37−01.33 (m, 2H), 1.25−1.21 (m, 10H), 0.87
E
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
1
steps) as a colorless viscous solid: Rf 0.45 (hexane/EtOAc 7/3); H
NMR (CDCl3, 500 MHz) δ 7.34−7.19 (m, 22H), 7.10 (dd, J = 16, 8
Hz, 1H), 6.81 (d, J = 8 Hz, 2H), 6.75 (d, J = 15.5 Hz, 1H), 4.64−4.63
(m, 2H), 4.61−4.57 (m, 2H), 4.50−4.47 (m, 2H), 4.44−4.40 (m, 3H),
4.37−4.33 (m, 3H), 4.23 (d, J = 7.5 Hz, 1H), 4.14−4.11 (m, 1H),
4.01−3.98 (m, 2H), 3.93−3.91 (m, 1H), 3.78 (s, 3H), 3.69−3.60 (m,
2H), 1.44 (s, 9H), 1.34 (s, 6H), 1.31−1.27 (m, 26H), 0.89 (t, J = 6.5
Hz, 3H); 13C NMR (CDCl3, 125 MHz) δ 200.3, 159.0, 154.7, 145.3,
138.5, 138.1, 138.0, 137.5, 130.8, 129.2, 128.4, 128.2, 127.7, 127.5,
127.4, 125.9, 113.6, 108.4, 84.3, 79.9, 79.5, 77.9, 73.5, 73.1, 72.8, 72.2,
70.2, 55.2, 52.0, 31.9, 31.5, 29.6, 29.3, 28.9, 28.3, 27.1, 26.9, 25.3, 22.7,
14.1; HR-ESI-MS [M + Na]+ C69H93NO11Na calcd for m/z
1134.6646, found 1134.6648.
(2E,3S,4S,5R)-3-[N-(tert-Butoxycarbonyl)amino]-4,5-O-
isopropylidene(2,3,4,6-tetra-O-benzyl-D-galactopyranosyl)-2-
nonadecene (17). To a solution of compound 16 (200 mg, 0.18
mmol, 1 equiv) in CH2Cl2/H2O (10/1, 11 mL) was added DDQ (69
mg, 0.3 mmol, 1.7 equiv) at 0 °C, and the reaction mixture was
warmed to room temperature under an argon atmosphere. After 5 h,
the reaction mixture was quenched with saturated aqueous NaHCO3
(2 × 50 mL) and extracted with CH2Cl2 (2 × 75 mL), and the extracts
were washed with water (2 × 100 mL) and brine (30 mL), dried over
anhydrous Na2SO4, and concentrated. Purification by flash chroma-
tography using hexane/EtOAc 90/10 to 80/20 afforded compound 17
(123 mg, 69%) as a colorless viscous solid: Rf 0.23 (hexane/EtOAc 4/
1); 1H NMR (CDCl3, 500 MHz) δ 7.36−7.26 (m, 20H), 7.15 (dd, J =
8, 2 Hz, 1H), 6.19 (dd, J = 16, 4 Hz, 1H), 5.81 (d, J = 16 Hz, 1H), 4.95
(d, J = 12 Hz, 1H), 4.79−4.75 (m, 2H), 4.63−4.61 (m, 3H), 4.52−
4.33 (m, 3H), 4.19−4.11 (m, 2H), 4.0 (d, J = 1.5 Hz, 1H), 3.95−3.91
(m, 1H), 3.85 (d, J = 10 Hz, 1H), 3.59−3.54 (m, 2H), 3.04 (s, 1H),
1.43 (s, 9H), 1.37 (s, 6H), 1.32−1.27 (m, 26H), 0.89 (t, J = 6.5 Hz,
3H); 13C NMR (CDCl3, 125 MHz) δ 154.9, 138.8, 138.5, 138.1,
137.9, 128.5, 128.3, 128.1, 127.9, 127.7, 127.5, 108.2, 96.9, 80.5, 79.3,
75.7, 74.4, 73.4, 72.8, 70.3, 68.8, 31.9, 29.7, 29.6, 29.5, 29.3, 28.3, 22.7,
14.1; HR-ESI-MS [M + Na]+ C61H85NO10Na calcd for m/z
1014.6071, found 1014.6066.
53.5, 36.7, 33.7, 31.9, 31.8, 29.7, 29.6, 29.4, 29.3, 25.7, 22.7, 22.6, 14.1;
HR-ESI-MS [M + Na]+ C63H91NO8Na calcd for m/z 1012.6642,
found 1012.6657.
(3S,4S,5R)-1-(2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl)-3-
N-(decanoylamino)-4,5-di-O-acetylnonadecane (19). To a sol-
ution of compound 18 (45 mg, 0.04 mmol, 1 equiv) in EtOH (4 mL)
were added 35 mg of 10% Pd/C and TFA (14 μL, 0.18 mmol, 4
equiv). H2 gas was purged into the reaction mixture for 2 min, and the
mixture was stirred overnight under a H2 atmosphere (balloon). The
reaction mixture was diluted with MeOH (60 mL), filtered through a
Celite pad, and concentrated to afford compound 1 in a quantitative
yield. To 18 mg (0.03 mmol) of compound 1 in pyridine (2 mL) was
added acetic anhydride (0.3 mL), and then the reaction mixture was
stirred at room temperature overnight under an argon atmosphere.
The reaction mixture was diluted with H2O (10 mL) and extracted
with EtOAc (2 × 25 mL), and the extracts were dried over anhydrous
Na2SO4 and concentrated. Purification by flash chromatography using
hexane/EtOAc 80/20 to 50/50 afforded compound 19 (11 mg) as a
white solid: Rf 0.60 (EtOAc 100%); [α] = +9.09° (0.11, CH2Cl2); 1H
NMR (CDCl3, 500 MHz) δ 5.71 (d, J = 10 Hz, 1H), 5.41 (s, 1H),
5.05−4.99 (m, 2H), 4.96−4.91 (m, 2H), 4.15−4.12 (m, 2H), 4.05 (dd,
J = 11, 7.5 Hz, 1H), 3.86 (t, J = 6.5 Hz, 1H), 3.43−3.41 (m, 1H),
2.19−2.16 (m, 2H), 2.14 (s, 3H), 2.11 (s, 3H), 2.05 (s, 6H), 2.04 (s,
3H), 1.98 (s, 3H), 1.61−1.54 (m, 2H), 1.45−1.38 (m, 2H), 1.30−1.25
(m, 40H), 0.88 (t, J = 6.5 Hz, 6H); 13C NMR (CDCl3, 125 MHz) δ
173.0, 171.0, 170.48, 170.46, 170.2, 170.1, 170.0, 75.6, 74.0, 72.8, 72.1,
67.8, 67.7, 61.5, 47.8, 36.7, 31.9, 31.8, 29.7, 29.6, 29.4, 29.3, 29.2, 28.7,
26.9, 25.7, 25.6, 22.6, 21.0, 20.9, 20.8, 20.7, 14.1; HR-ESI-MS [M +
Na]+ C47H81NO14Na calcd for m/z 906.5554, found 906.5528.
(2E,3S,4S,5R)-3-[N-(tert-Butoxycarbonyl)amino]-4,5-O-iso-
propylidene-(2,3,4,6-tetra-O-benzyl)-1,5-anhydro-D-galacto-2-
nonadecene (20). To a solution of hemiketal 17 (160 mg, 0.16
mmol, 1 equiv) in DCM (15 mL) were added NaHCO3 (67.7 mg, 0.8
mmol, 5 equiv) and Dess−Martin periodinane (205.4 mg, 0.48 mmol,
3 equiv), and then the reaction mixture was stirred for 1 h at room
temperature under an argon atmosphere. The reaction mixture was
quenched with saturated aqueous Na2S2O3 (30 mL) and saturated
aqueous NaHCO3 (50 mL) and extracted with CH2Cl2 (2 × 80 mL),
and the extracts were dried over anhydrous Na2SO4 and concentrated.
Purification by flash chromatography using hexane/EtOAc 90/10 to
85/15 afforded diketone 20 (145 mg, 91%), as a colorless viscous
solid: Rf 0.47 (hexane/EtOAc 7/3), [α] = −5.00° (c = 0.2, CH2Cl2);
1H NMR (CDCl3, 500 MHz) δ 7.32−7.16 (m, 20H), 7.08 (dd, J = 16,
4 Hz, 1H), 6.73 (d, J = 16 Hz, 1H), 4.64−4.61 (m, 2H), 4.56−4.47
(m, 2H), 4.43−4.36 (m, 4H), 4.32 (s, 2H), 4.26−4.23 (m, 2H), 4.20−
4.17 (m, 2H), 4.10−4.06 (m, 1H), 3.98 (app t, J = 5.5 Hz, 1H), 1.44
(s, 9H), 1.38 (s, 6H), 1.30−1.27 (m, 26H), 0.89 (t, J = 6.5 Hz, 3H);
13C NMR (CDCl3, 125 MHz) δ 207.0, 198.9, 154.7, 145.7, 137.3,
137.0, 136.8, 128.5, 128.39, 128.30, 128.1, 128.0, 127.9, 127.8, 127.6,
125.9, 108.4, 83.4, 81.0, 80.0, 74.6, 74.5, 73.3, 73.1, 72.4, 31.9, 29.7,
29.6, 29.5, 28.3, 26.9, 25.3, 22.7, 14.1; HR-ESI-MS [M + Na]+
C61H83NO10Na calcd for m/z 1012.5914, found 1012.5922.
(2E,3S,4S,5R)-3-[N-(tert-Butoxycarbonyl)amino]-4,5-O-iso-
propylidene-(2,3,4,6-tetra-O-benzylaza-β-D-galactopyranosyl)-
2-nonadecene (21). To a solution of diketone 20 (140 mg, 0.14
mmol, 1 equiv) in MeOH (8 mL) were added ammonium formate
(35.5 mg, 0.56 mmol, 4 equiv) and NaCNBH3 (35.6 mg, 0.56 mmol, 4
equiv), and then the reaction mixture was stirred overnight at room
temperature under an argon atmosphere. The reaction mixture was
quenched with saturated aqueous NaHCO3 (30 mL) and extracted
with EtOAc (2 × 80 mL), and the organic layer was washed with H2O
(2 × 70 mL), dried over anhydrous Na2SO4, and concentrated.
Purification by flash chromatography using hexane/EtOAc 90/10 to
70/30 afforded compound 21 (90 mg, 66%) as a pale yellow viscous
solid: Rf 0.40 (hexane/EtOAc 5/3); [α] = −7.89° (c = 0.38, CH2Cl2);
1H NMR (CDCl3, 500 MHz) δ 7.36−7.27 (m, 20H), 5.93 (dd, J = 16,
(2E,3S,4S,5R)-1-(2,3,4,6-Tetra-O-benzyl-β-D-galactopyrano-
syl)-3-N-(decanoylamino)-4,5-dihydroxy-2-nonadecene (18).
To a solution of compound 17 (40 mg, 0.04 mmol, 1 equiv) in
CH3CN (5 mL) were added Et3SiH (64 μL, 0.40 mmol, 10 equiv) and
TMSOTf (22 μL, 0.12 mmol, 3 equiv) at 0 °C, and the mixture was
stirred for 10 min. The reaction mixture was quenched with saturated
aqueous NaHCO3 (30 mL) and extracted with EtOAc (2 × 50 mL),
and the organic layer was washed with H2O (30 mL), dried over
anhydrous Na2SO4, and concentrated. Without further purification the
resulting crude mixture was treated with 4 mL of EtOH/2 M HCl/
THF (4/1/1) at 70 °C overnight. The reaction mixture was cooled to
room temperature and then diluted with 20 mL of H2O and extracted
with CHCl3/MeOH (7/1, 3 × 30 mL), and the extracts were dried
over anhydrous Na2SO4 and concentrated. The resulting crude free 1°
amine was dried under vacuum and then dissolved in 2 mL of DCM/
DMF (5/2). 4-Nitrophenyldecanoate (17.1 mg, 0.06 mmol, 1.5 equiv)
and K2CO3 (17 mg, 0.12 mmol, 3 equiv) were added, and the mixture
was stirred vigorously overnight at room temperature under an argon
atmosphere. The reaction mixture was quenched with saturated
aqueous NaHCO3 (15 mL) and extracted with EtOAc (2 × 30 mL),
and the organic layer was thoroughly washed with water (3 × 30 mL)
and brine (10 mL), dried over anhydrous Na2SO4, and concentrated.
Purification by flash chromatography using hexane/EtOAc 90/10 to
60/40 afforded compound 18 (21 mg, 53% over three steps) as a
white solid: Rf 0.37 (hexane/EtOAc 7/3); [α] = −3.03° (0.33,
1
CH2Cl2); H NMR (CDCl3, 500 MHz) δ 7.38−7.26 (m, 20H), 6.04
(d, J = 8 Hz, 1H), 6.01 (d, J = 6 Hz, 1H), 5.78 (dd, J = 15.5, 6 Hz,
1H), 4.95 (d, J = 11.5 Hz, 1H), 4.81 (d, J = 12 Hz, 1H), 4.75−4.74 (m,
3H), 4.62 (dd, J = 10.5, 2.5 Hz, 2H), 4.48−4.40 (m, 2H), 3.95 (d, J =
2.5 Hz, 1H), 3.78−3.69 (m, 2H), 3.61−3.55 (m, 3H), 3.50−3.48 (m,
3H), 2.18−2.16 (m, 2H), 1.65−1.60 (m, 2H), 1.33−1.26 (m, 38H),
0.87−0.91 (m, 6H); 13C NMR (CDCl3, 125 MHz) δ 173.2, 138.5,
138.3, 138.2, 137.7, 130.2, 129.8, 128.4, 128.3, 128.1, 127.9, 127.7,
127.6, 127.5, 84.1, 79.8, 78.7, 75.1, 74.6, 73.9, 73.5, 73.0, 72.6, 69.0,
3.5 Hz, 1H), 5.79 (dd, J = 15.5, 7 Hz, 1H), 4.95 (d, J = 11.5 Hz, 1H),
4.96−4.74 (m, 3H), 4.66−4.58 (m, 3H), 4.50−4.38 (m, 3H), 4.32 (m,
1H), 4.13−4.12 (m, 1H), 3.94−3.90 (m, 2H), 3.65 (app t, J = 9 Hz,
1H), 3.53−3.46 (m, 2H), 3.27 (app t, J = 7 Hz, 1H), 3.19 (app t, J = 8
F
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Hz, 1H), 2.85 (app t, J = 6.5 Hz, 1H), 1.43 (s, 9H), 1.29−1.31 (m,
32H), 0.89 (t, J = 6.5 Hz, 3H); 13C NMR (CDCl3, 125 MHz) δ 154.8,
138.7, 138.6, 138.5, 137.9, 128.5, 128.4, 127.7, 127.5, 80.0, 80.8, 79.4,
75.3, 74.2, 73.9, 73.4, 72.8, 70.6, 57.5, 31.9, 29.7, 29.6, 29.5, 29.3, 28.8,
28.3, 25.4, 22.7, 14.1; HR-ESI-MS [M + H]+ C61H87N2O8 calcd for m/
z 975.6462, found 975.6483.
pyridine (2 mL) and acetic anhydride (0.5 mL). The resulting mixture
was stirred overnight under an argon atmosphere at room temper-
ature. The reaction mixture was diluted with H2O (10 mL) and
extracted with EtOAc (2 × 25 mL), and the extracts were dried over
anhydrous Na2SO4 and concentrated. Purification by flash chromatog-
raphy using hexane/EtOAc 80/20 to 40/60 afforded compound 24 (8
mg) as a white solid: Rf 0.45 (hexane/EtOAc 1/1); 1H NMR (CDCl3,
500 MHz) δ 5.66 (d, J = 9.5 Hz, 1H), 5.40 (s, 1H), 4.95−4.89 (m,
4H), 4.17−4.16 (m, 1H), 4.05−3.95 (m, 2H), 3.16 (app t, J = 7 Hz,
1H), 2.71−2.68 (m, 1H), 2.18 (t, J = 7.5 Hz, 2H), 2.14 (s, 3H), 2.12
(s, 3H), 2.07 (s, 3H), 2.06 (s, 3H), 2.04 (s, 3H), 1.97 (s, 3H), 1.30−
1.26 (m, 44H), 0.89 (t, J = 6 Hz, 6H); 13C NMR (CDCl3, 125 MHz) δ
172.9, 171.1, 170.6, 170.55, 170.53, 170.2, 170.0, 75.3, 73.2, 72.8, 70.9,
68.4, 62.3, 57.4, 54.9, 48.0, 36.8, 31.9, 31.8, 30.9, 29.7, 29.6, 29.5, 29.4,
29.3, 27.0, 25.9, 25.7, 25.4, 21.0, 20.9, 20.8, 20.7, 14.1; HR-ESI-MS [M
+ H]+ C47H83N2O13 calcd for m/z 883.5895, found 883.5872.
Oxazolidinone 22. A solution of compound 21 (28 mg, 0.03
mmol) in 3 mL of EtOH/2 M HCl (4/1) was heated at reflux for 3 h.
After consumption of the starting material as indicated by TLC, the
reaction mixture was diluted with MeOH (10 mL) and evaporated.
The resulting crude mixture was lyophilized over benzene (3 mL). To
12 mg (0.014 mmol) of free amine in dry THF (1 mL) was added
N,N-carbonyldiimidazole (21 mg, 0.126 mmol, 9 equiv) at 0 °C, and
then the reaction mixture was stirred for 6 h at room temperature
under an argon atmosphere. Evaporation of solvent and purification by
flash chromatography using hexane/EtOAc 80/20 to 40/60 afforded
compound 22 (6 mg, 49% over two steps) as a viscous solid: Rf 0.44
1
(hexane/EtOAc 2/8); H NMR (CDCl3, 500 MHz) δ 7.37−7.27 (m,
ASSOCIATED CONTENT
■
20H), 5.80 (H-3, dd, J = 15.5, 7.5 Hz, 1H), 5.73 (H-2, dd, J = 15.5, 6
Hz, 1H), 4.96−4.92 (m, 2H), 4.79−4.69 (m, 3H), 4.64−4.56 (m, 2H),
4.48−4.36 (m, 2H), 4.30 (H-5, app t, J = 8.0 Hz, 1H), 4.20 (H-4, app
t, J = 7.5 Hz, 1H), 3.98 (s, 1H), 3.63−3.56 (m, 3 H), 3.47 (app t, J = 9
Hz, 1H), 3.35 (app t, J = 8 Hz, 1H), 3.14 (H-1, dd, J = 9.5, 6 Hz, 1H),
2.87 (t, J = 7 Hz, 1H), 1.26 (m, 26H), 0.89 (t, J = 6.5 Hz, 3H); 13C
NMR (CDCl3, 125 MHz) δ 158.2, 138.4, 138.3, 138.1, 137.6, 133.9,
128.5, 128.4, 128.3, 128.2, 128.0, 127.9, 127.8, 127.7, 127.6, 127.3,
85.6, 81.0, 79.6, 74.7, 74.5, 73.9, 73.5, 72.4, 70.1, 60.7, 57.5, 56.3, 33.9,
31.9, 29.7, 29.6, 29.3, 24.6, 22.7, 14.1; HR-ESI-MS [M + H]+
C54H73N2O7 calcd for m/z 861.5417, found 861.5440.
S
* Supporting Information
1
Figures giving HRMS of aza-O-galactosylceramide 5, H and
13C NMR spectra of 7−13, 15−18, 1, and 19−24, and COSY
spectra of 13, 22, and 23 and a table giving a comparison of 1H
and 13C NMR of compound 1 with reported data. This material
is available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail for R.S.L.: ravishankar@niist.res.in.
(2E,3S,4S,5R)-1-(2,3,4,6-Tetra-O-benzylaza-β-D-galactopyra-
nosyl)-3-N-(decanoylamino)-4,5-dihydroxy-2-nonadecene
(23). Compound 21 (80 mg, 0.08 mmol) was dissolved in 8 mL of
EtOH/2 M HCl (4/1), and then the mixture was heated at reflux for 3
h. After consumption of the starting material as indicated by TLC, the
reaction mixture was diluted with H2O (10 mL) and extracted with
CHCl3/MeOH (7/1, 4 × 50 mL), and the combined organic layers
were dried over anhydrous Na2SO4 and concentrated. The resulting
free amine was dried under vacuum and dissolved in 8 mL of DMF/
DCM (2/5), and then 4-nitrophenyldecanoate (36.1 mg, 0.12 mmol,
1.5 equiv) and K2CO3 (34 mg, 0.24 mmol, 3 equiv) were added, and
this mixture was stirred vigorously overnight at room temperature
under an argon atmosphere. After completion of the starting material
as indicated by TLC, the reaction mixture was quenched with
saturated aqueous NaHCO3 (2 × 10 mL) and extracted with EtOAc
(2 × 75 mL), the organic layer was thoroughly washed with water (3 ×
50 mL), dried over anhydrous Na2SO4, and concentrated. Purification
by flash chromatography (hexane/EtOAc 80/20 to 60/40 to 40/60)
afforded compound 23 (60 mg, 74% over two steps) as a white solid:
Rf 0.55 (EtOAc 100%), [α] = 10.7° (0.28, MeOH); 1H NMR (CDCl3,
500 MHz) δ 7.38−7.26 (m, 20H), 5.93 (dd, J = 15.5, 6 Hz, 1H), 5.91
(m, 1H), 5.72 (dd, J = 16, 7 Hz, 1H), 4.96 (d, J = 11.5 Hz, 1H), 4.84
(d, J = 10.5 Hz, 1H), 4.77−4.69 (m, 3H), 4.63−4.58 (m, 2H), 4.47−
4.41 (m, 2H), 3.95 (s, 1H), 3.63 (app t, J = 9 Hz, 1H), 3.54−3.46 (m,
4H), 3.42 (dd, J = 6.5, 3 Hz, 1H), 3.33 (dd, J = 9, 7 Hz, 1H), 3.14 (dd,
J = 9, 7 Hz, 1H), 2.85 (t, J = 7 Hz, 1H), 2.18−2.16 (m, 2H), 1.31−
1.26 (m, 40H), 0.87−0.90 (m, 6H); 13C NMR (CDCl3, 125 MHz) δ
173.7, 138.6, 138.5, 137.7, 128.5, 128.4, 128.3, 128.1, 128.0, 127.9,
127.7, 127.6, 127.5, 85.2, 80.4, 76.8, 75.1, 74.4, 74.1, 73.0, 72.6, 70.1,
61.8, 57.6, 53.3, 36.7, 36.6, 31.9, 31.8, 29.7, 29.6, 29.4, 29.3, 25.7, 22.6,
14.1; HR-ESI-MS [M + H]+ C63H93N2O7 calcd for m/z 989.6982,
found 989.6996.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support from the Department of Science &
Technology (DST) of India, grant SR/FT/CS-45/2010, is
gratefully acknowledged.
REFERENCES
■
(1) D’Angelo, G.; Capasso, S.; Sticco, L.; Russo, D. FEBS J. 2013,
280, 6338−6353.
(2) (a) Varki, A. Glycobiology 1993, 3, 97−130. (b) Fantini, J.;
Maresca, M.; Hammache, D.; Yahi, N.; Delezay, O. Glycoconjugate J.
2001, 17, 173−179.
(3) (a) Harouse, J. M.; Bhat, S.; Spitalnik, S. L.; Laughlin, M.;
Stefano, K.; Silberberg, D. H.; Gonzalez-Scarano, F. Science 1991, 253,
320−323. (b) Yahi, N.; Baghdiguian, S.; Moreau, H.; Fantini, J. J. Virol.
1992, 66, 4848−4854. (c) Fantini, J.; Cook, D. G.; Nathanson, N.;
Spitalnik, S. L.; Gonzalez-Scarano, F. Proc. Natl. Acad. Sci. U.S.A. 1993,
90, 2700−2704.
(4) For selected references, see: (a) Bertozzi, C. R.; Cook, D. G.;
Cobertz, W. R.; Gonzalez-Scarano, F.; Bednarski, M. D. J. Am. Chem.
Soc. 1992, 114, 10639−10641. (b) Fantini, J.; Hammache, D.; Delezay,
O.; Yahi, N.; Andre-Barres, C.; Rico-Lattes, I.; Lattes, A. J. Biol. Chem.
1997, 272, 7245−7252. (c) Faroux-Corlay, B.; Greiner, J.; Terreux, R.;
Cabrol-Bass, D.; Aubertin, A. M.; Vierling, P.; Fantini, J. J. Med. Chem.
2001, 44, 2188−2203. (d) LaBell, R. Y.; Jacobsen, N. E.; Gervay-
Hague, J.; O’Brien, D. F. Bioconjugate Chem. 2002, 13, 143−149.
(e) Blanzat, M.; Turrin, C. O.; Aubertin, A. M.; Couturier-Vidal, C.;
Caminade, A.-M.; Majoral, J.-P.; Rico-Lattes, I.; Lattes, A.
ChemBioChem 2005, 6, 2207−2213.
(5) (a) Weber, K. T.; Hammache, D.; Fantini, J.; Ganem, B. Bioorg.
Med. Chem. Lett. 2000, 10, 1011−1014. (b) Augustine, L. A.; Fantini,
J.; Mootoo, D. R. Bioorg. Med. Chem. 2006, 14, 1182−1188. (c) Garg,
H.; Francella, N.; Tony, K. A.; Augustine, L. A.; Barchi, J. J., Jr.;
Fantini, J.; Puri, A.; Mootoo, D. R.; Blumenthal, R. Antiviral Res. 2008,
80, 54−61.
(3S,4S,5R)-1-(2,3,4,6-Tetra-O-acetylaza-β-D-galactopyrano-
syl)-3-N-(decanoylamino)-4,5-di-O-acetylnonadecane (24). To
a solution of compound 23 (55 mg, 0.05 mmol, 1 equiv) in EtOH (5
mL) was added 40 mg of 10% Pd/C and 2 drops of concentrated HCl.
H2 gas was purged into the reaction mixture for 2 min, and the mixture
was stirred overnight under an H2 atmosphere (balloon). The reaction
mixture was then diluted with MeOH (50 mL), filtered through a
Celite pad, and concentrated to afford the desired compound 2 in
quantitative yield. To 20 mg (0.03 mmol) of compound 2 were added
G
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
(6) (a) Dondoni, A.; Perrone, D.; Turturici, E. J. Org. Chem. 1999,
64, 5557−5564. (b) Thota, V. N.; Brahmaiah, M.; Kulkarni, S. S. J.
Org. Chem. 2013, 78, 12082−12089.
(7) Morita, M.; Motoki, K.; Akimoto, K.; Natori, T.; Sakai, T.; Sawa,
E.; Yamaji, K.; Koezuka, Y.; Kobayashi, E.; Fukushima, H. J. Med.
Chem. 1995, 38, 2176−2187.
(8) For reviews, see: (a) Wu, D.; Fujio, M.; Wong, C.-H. Bioorg. Med.
́
Chem. 2008, 16, 1073−1083. (b) Banchet-Cadeddu, A.; Henon, E.;
Dauchez, M.; Renault, J.-H.; Monneaux, F.; Haudrechy, A. Org. Biomol.
Chem. 2011, 9, 3080−3104.
(9) Yang, G.; Schmieg, J.; Tusji, M.; Franck, R. W. Angew. Chem., Int.
Ed. 2004, 43, 3818−3822.
(10) Chaulagain, M. R.; Postema, M. H. D.; Valeriote, F.;
Pietraszkewicz, H. Tetrahedron Lett. 2004, 45, 7791−7794.
(11) Compain, P.; Chagnault, V.; Martin, O. R. Tetrahedron:
Asymmetry 2009, 20, 672−711.
(12) Modica, E.; Compostella, F.; Colombo, D.; Franchini, L.;
Cavallari, M.; Mori, L.; De Libero, G.; Panza, L.; Ronchetti, F. Org.
Lett. 2006, 8, 3255−3258.
̀ ́
(13) (a) Ranoux, A.; Lemiegre, L.; Benoit, M.; Guegan, J.-P.;
Benvegnu, T. Eur. J. Org. Chem. 2010, 1314−1323. (b) McAllister, G.
D.; Paterson, D. E.; Taylor, R. J. K. Angew. Chem., Int. Ed. 2003, 42,
1387−1391.
(14) Granier, T.; Vasella, A. Helv. Chim. Acta 1998, 81, 865−880.
(15) Zhang, W.; Xi, C.; Nadas, J.; Chen, W.; Gu, L.; Wang, P. G.
Bioorg. Med. Chem. 2011, 19, 2767−2776.
(16) Gorantla, J. N.; Kovval, D.; Lankalapalli, R. S. Tetrahedron Lett.
2013, 54, 3230−3232.
(17) Chen, G.; Chien, M.; Tsuji, M.; Franck, R. W. ChemBioChem
2006, 7, 1017−1022.
(18) (a) Leeuwenburgh, M. A.; Picasso, S.; Overkleeft, H. S.; Van der
Marel, G. A.; Vogel, P.; Van Boom, J. H. Eur. J. Org. Chem. 1999,
1185−1189. (b) Cheng, X.; Kumaran, G.; Mootoo, D. R. Chem.
Commun. 2001, 811−812.
(19) Dondoni, A.; Catozzi, N.; Marra, A. J. Org. Chem. 2004, 69,
5023−5036.
(20) Saavedra, O. M.; Martin, O. R. J. Org. Chem. 1996, 61, 6987−
6993.
H
dx.doi.org/10.1021/jo500769f | J. Org. Chem. XXXX, XXX, XXX−XXX