C-Galactosylceramide diastereomers via Sharpless asymmetric epoxidation chemistry

Article abstract of DOI:10.1016/j.tet.2008.06.007

C-Glycoside analogs of α-galactosylceramide (KRN7000) were synthesized in 19 linear steps with Sharpless asymmetric epoxidation as a key reaction. Opening of a hydroxy epoxide with sodium azide provided an anti vicinal azido diol with inversion of configuration at the azide-bearing carbon while opening with Ti(O-i-Pr)₂(N₃)₂ gave syn vicinal azido diol with retention. The latter, unusual outcome could be rationalized either by invoking Ti-catalyzed intramolecular double S_N2 inversion or by epoxide opening/intramolecular delivery of azide from the Ti complex.

Full text of DOI:10.1016/j.tet.2008.06.007

Tetrahedron 64 (2008) 8618–8629
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
C-Galactosylceramide diastereomers via Sharpless
asymmetric epoxidation chemistryq
*
Jun Pu, Richard W. Franck
Department of Chemistry and Biochemistry, Hunter College of CUNY, 695 Park Avenue, New York, NY 10021, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
C-Glycoside analogs of
a-galactosylceramide (KRN7000) were synthesized in 19 linear steps with
Received 14 March 2008
Received in revised form 29 May 2008
Accepted 3 June 2008
Sharpless asymmetric epoxidation as a key reaction. Opening of a hydroxy epoxide with sodium azide
provided an anti vicinal azido diol with inversion of configuration at the azide-bearing carbon while
opening with Ti(O-i-Pr)2(N3)2 gave syn vicinal azido diol with retention. The latter, unusual outcome
could be rationalized either by invoking Ti-catalyzed intramolecular double SN2 inversion or by epoxide
opening/intramolecular delivery of azide from the Ti complex.
Available online 7 June 2008
Dedicated to the memory of Professor Giu-
seppe Capozzi (1941–2008), Dipartimento
di Chimica Organica, Universita di Firenze,
a friend and a colleague
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
gal-4-OH to the NKT, but the 6-OH seems to be free.4 The effect of
the second protein molecule’s recognition of the initial complex is
In the early 1990’s, researchers at Kirin Pharma reported the
to produce a powerful surge of cytokines interferon-g, (IFNg),
results of their studies on glycolipid extracts of Agelas Mauritianus,
interleukin-4 (IL-4), and interleukin-12 (IL-12), which then signal
for the eventual cytotoxic immune response. Extensive analog
studies in the O-glycoside series revealed the importance of the
galactose configuration and the free hydroxyls. The only allowed
substitution of the galactose OH’s is N-acyl at the 6-position of
galactose. Variation of lipid chain length and degrees of unsatura-
tion in both the phytosphingosine and the N-acyl side chains is
permissible.5 In most cases, small changes in cytokine levels are the
an Okinawan sponge. An optimized synthetic material,
a-gal-
actosylceramide 1 (Fig. 1, also known as KRN7000 and -Galcer),
a
a slightly simplified version of the active materials found in the
sponge extracts, displayed potent anti-tumor activity in a whole
animal murine assay.1
An intensive series of biological experiments in the ensuing
decade unveiled the activity of the
a
-Galcer as stemming from its
immunostimulant activity.2 Thus,
a
-Galcer is not cytotoxic and
high-throughput cell-based assays would not have revealed its
activity. The molecular basis for -Galcer stimulation of the im-
mune system is its initial binding to a protein receptor, named
CD1d, found on the surface of antigen-presenting cells. The com-
O
O
OH
O
OH
O
HO
HO
HO
HO
a
HN
(CH2)24CH3
OH
HN
(CH2)24CH3
OH
HO
HO
O
O
(CH2)4CH3
(CH2)13CH3
plex between the receptor and the a-Galcer has been crystallized
and analyzed by X-ray diffraction and shows that two lipid chains of
the ceramide are buried in two hydrophobic channels of the protein
and that the 2,3 hydroxyls of galactose and the 3 hydroxyl of the
phytosphingosine side chain participate in hydrogen bonds with
the protein.3 This binding motif leaves the 4 and 6 hydroxyls of the
OH
OH
2, OCH, truncated side
chain analog of KRN7000
1, α-galactosylceramide
(KRN7000, α-Galcer)
O
OH
O
O
a-Galcer available to be recognized by receptors on natural killer T
OH
O
HO
HO
HO
HO
cells. In a very recent disclosure, the crystal structure of the triple
complex of CD1d/ a-Galcer/NKT receptor shows the binding of the
HN
(CH2)24CH3
OH
HN
(CH2)24CH3
OH
HO
HO
(CH2)13CH
(CH2)13CH3
OH
OH
3, C-glycoside analog of KRN7000
q
Taken from the doctoral dissertation of J.P. submitted to the City University of
New York, 2006.
4, E alkene analog
5, Z alkene analog
* Corresponding author.
E-mail address: rfranck@hunter.cuny.edu (R.W. Franck).
Figure 1. a-Galactosylceramide 1 (KRN7000) and its analogs.
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.06.007

J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
8619
result; but in one striking example, shortening the lipid of the
phytosphingosine from 14 to 5 carbons (Fig. 1, compound 2, named
as OCH) stimulates almost exclusive production of IL-4 with a great
Since stereochemistry in both the galactose and the linker re-
gion had been found to be a critical element for activity, we deemed
it worthwhile to examine the effects of stereoisomers in the phy-
tosphingosine chain. There had been an early report on a study in
the O-series where the four possible stereoisomers 6 bearing the 4-
deoxyphytosphingosine chain were studied.7 Interestingly, the only
isomer other than the natural 2S,3R to show tumor growth in-
hibitory effects was 7 with the phytosphingosine in the unnatural,
enantiomeric 2R,3S form. Also, there has been a recent evaluation
diminution of IFNg and IL-12. In immunology terms, this change is
said to favor a TH2 immune response whereas the reverse, a de-
crease in IL-4 and an increase in the other cytokines, is called a TH1
response. In the mouse, the TH2 effect offers protection against
autoimmune diseases while the TH1 pathway protects against
‘foreign’ pathogens.
The investigation of
a
-Galcer in our laboratory began with the
of the natural 4-deoxy series with the exact analogs of both a-
concept that the C-glycoside 3 might provide a more deep-seated
change in the structure–activity profile. Aside from the obvious
stability to enzymatic hydrolysis provided by replacement of
anomeric O by CH2, the important changes are (i) the loss of one
hydrogen-bond acceptor and (ii) the destabilization of the galactose
chair through replacement of axial O-anomeric stabilization with
axial CH2 steric repulsion. In the event, the C-glycoside 3 was
prepared and we were rewarded with striking enhancement of in
vivo activity in blocking malaria and melanoma in mice. Assay for
Galcer and OCH. The activities 6 and 8 in the 4-deoxy series were
similar to those of the parent materials (Fig. 2).8
Since our earlier preparations of C-glycoside 3 had been con-
vergent and involved coupling of intact phytosphingosines with
galactose, they would not be suitable for our proposed stereo-
isomerism study. Thus, we embarked on a scheme where the
phytosphingosine was elaborated from a pre-formed C-glycoside,
which we now describe.9
The known aldehyde 10 was obtained in five steps from com-
cytokines revealed that IFN
g
and IL-12 levels were about the same
mercially available
literature procedure (Scheme 1).10 Homologation of 10 via Horner–
Wadsworth–Emmons reaction afforded (E)- -unsaturated ester
b-D-galactose pentaacetate 9 according to a
as for the O-glycoside while the IL-4 titer was dramatically reduced.
We also studied the E and Z alkene analogs 4 and 5 and found that
the E material 4 was active whereas the Z analog 5 was essentially
inert in our assays (Fig. 1).6
a,b
11. DIBAL-H reduction gave the (E)-allylic alcohol 12 in 92% yield.
Sharpless asymmetric epoxidation (SAE)11 using substoichiometric
OH
O
OH
O
HO
HO
OH
HO
HO
O
HO
HO
O
O
O
HN
(CH2)24CH3
(CH2)13CH3
HN
(CH2)24CH3
(CH2)4CH3
HN
(CH2)24CH3
(CH2)13CH3
HO
HO
O
HO
O
O
OH
OH
OH
8
6
7
Figure 2. 4-Deoxy analogs 6–8 of
a-Galcer and OCH.
OBn
O
OAc
O
OBn
BnO
BnO
AcO
AcO
Ref. 9
O
b
O
a
BnO
OAc
BnO
BnO
OMe
OAc
BnO
O
9
10
11
OBn
O
OBn
OBn
O
BnO
BnO
BnO
BnO
BnO
BnO
O
c
d
N3
O
BnO
(R)
OH
BnO
BnO
OH
OH
(R)
OH
12
13
14, 1,2 diol
OBn
O
OBn
O
OBn
O
BnO
BnO
BnO
BnO
BnO
+
BnO
e
OH
N3
NHBoc
OH
OH
+
BnO
BnO
OH
BnO
OH
OH
NHBoc
16
17
15, 1,3 diol
OBn
O
OBn
BnO
BnO
BnO
BnO
O
+
f
OH
NHBoc
OH
BnO
BnO
OTBS
OTBS
NHBoc
18
19
Scheme 1. Regents and conditions: (a) (MeO)2POCHCO2Me, MeCN, rt, overnight, 89%. (b) DIBAL-H, CH2Cl2, ꢀ78 ꢁC, 2 h, 90%. (c) TTIP, D-(ꢀ)-DIPT, TBHP, 4 Å MS, CH2Cl2, ꢀ20 ꢁC, 18 h,
70%. (d) NaN3/NH4Cl, MeOH/H2O (8:1), 80 ꢁC, overnight, 93%. (e) (i) P(Me)3, THF, overnight; (ii) 1 N NaOH, 2 h; (iii) (t-Boc)2O, satd NaHCO3, THF/1,4-dioxane(1:1), rt, overnight, 78%
for three steps. (f) TBSCl, imidazole, CH2Cl2, rt, 88%.

8620
J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
amount of catalysts (50 mol % TTIP, 60 mol %
D
-(ꢀ)-DIPT) ensured
configuration at the three contiguous stereocenters. The structural
assignment was confirmed later by correlation with the corre-
sponding final products (Scheme 2).
conversion of 12 to (2R,3R) epoxy alcohol 13 in high enantiomeric
excess (ee>95%). Opening the (2R,3R) epoxy alcohol 13 using NaN3/
NH4Cl in asimple SN2 conversionprovidedan inseparable mixtureof
the desired 3-azido-1,2 vicinal diol 14 and by-product 1,3 diol 15 in
90% yield.12 The 8:1 ratio of 14/15 was determined at a later stage.
Thus, the mixture of azides was reduced with P(Me)3 to provide
amine intermediate,13 which was then protected with (t-Boc)2O to
afford an inseparable mixture of regioisomers 16 and 17. To our
delight, selective protection of the primary hydroxyl group as its TBS
ether gave a separable mixture of 18 and 19 in a ratio of 8:1 in 90%
yield. To assign their structures, 18 and 19 were deprotected with
TBAF and the products were treated with NaIO4. Only a compound
derived from 1,2 diol could be cleaved by NaIO4 to give the corre-
sponding aldehyde while the 1,3 diol could not be cleaved by NaIO4.
In this way, 18 was confirmed to be the 1,2 vicinal diol.
Acidic hydrolysis of 24 removed MOM and Boc groups in one
step and the resulting amine was converted to amide 25 in 80%
yield. Hydrogenation of amide 25 using Pearlman’s catalyst
(Pd(OH)2/C) in THF/EtOH solution afforded the fully deprotected C-
glycoside analog of KRN7000 3. Its NMR spectra matched with
those of the previously synthesized C-glycoside analog of KRN7000
(see Supplementary data). Similarly, the major isomer 23 was
converted to the corresponding C-glycoside analog 26, which is a
5-OH epimer of the target C-glycoside analog of the KRN7000
(Scheme 3).
As described above, the key step of opening of epoxide 13 by
sodium azide was not a very clean reaction, requiring extended
reaction time in refluxing MeOH. Furthermore, about 10% of the
regioisomeric azide (at C-4), which was obtained required separa-
tion via careful chromatography at a later stage. Therefore, we
adopted the Ti(O-i-Pr)2(N3)2 conditions described by Sharpless.16 In
our case, treatment of the (2R,3R) epoxy alcohol 13 with Ti(O-i-
Pr)2(N3)2 gave a single product, which we assigned as the desired
anti-3-azido-2-OH 14 on the basis of the hypothesis that ring
opening of the oxirane was a single SN2 reactionas in the sodium
azide experiment. Spectral comparison with the authentic 14 was
not definitive because the batch obtained in the sodium azide ex-
periment was a mixture. In actual fact, the Ti(O-i-Pr)2(N3)2 single
product was ultimately revealed to be 3-azido-1,2 vicinal diol 27. As
our synthesis proceeded via duplication of the sequence described
above, detailed comparison of the final products derived from the
Protection of the secondary hydroxyl of compound 18 with
MOM and removal of the TBS group gave primary alcohol 21 in high
yield. Oxidation of alcohol to aldehyde 22 proceeded without epi-
merization at the neighboring
a stereocenter using either Dess–
Martin periodinane or a novel Kirschning solid phase oxidant,14
both procedures taking place in high yield without causing
epimerization at the
a position. Inverse addition of the crude al-
dehyde 22 to freshly prepared tetradecyl magnesium bromide
(C14H29MgBr) provided a separable mixture of 23 and 24 in a ratio
of 5:1 and in 60% combined yield for two steps. Based on the ‘Cram-
chelation control rule’,15 the stereochemistry of 23 and 24 was
tentatively assigned as (3S,4S,5S) and (3S,4S,5R), respectively, with
the minor isomer 24 proposed as the desired or natural (3S,4S,5R)
OBn
OBn
BnO
OBn
O
BnO
BnO
BnO
BnO
O
O
b
BnO
a
NHBoc
(S)
NHBoc
(S)
NHBoc
(S)
BnO
BnO
BnO
OTBS
OMOM
OH
OMOM
(S)
(S)
(S)
OTBS
OH
18
20
21
OBn
O
c
OBn
O
OBn
O
BnO
BnO
BnO
BnO
BnO
BnO
NHBoc
OH
(S)
NHBoc
d
Kirschning reagent:
+
OH
NHBoc
BnO
BnO
(S)
BnO
C14H29
C14H29
(R)
(S)
PhI(OAc)2
(S)
(S)
+
NMe3 Br
O
OMOM
24, minor isomer, 10%
OMOM
23, major isomer, 50%
OMOM
Br(OAc)2
NMe3
22
Scheme 2. Reagents and conditions: (a) MOMCl, DIPEA, CH2Cl2, 0 ꢁC to rt, 12 h, 95%. (b) TBAF, THF, rt, 2 h, 100%. (c) Kischning reagent, TEMPO (cat.), CH2Cl2, rt, 2 h, or Dess–Martin
oxidation, CH2Cl2, rt, 1 h, quantitative. (d) C14H29MgBr, THF, 0 ꢁC to rt, 2 h, 58% for two steps.
OBn
O
BnO
BnO
OBn
O
BnO
BnO
OH
O
HO
HO
NHBoc
OH
(S)
NHCO(CH2)24CH3
NHCO(CH2)24CH3
OH
(S)
b
OH
a
BnO
BnO
(S)
C14H29
C14H29
HO
(R)
(R)
(S)
(S)
C14H29
(R)
(S)
OMOM
OH
OH
24, minor isomer
25
3
BnO
BnO
OH
O
OBn
HO
HO
NHBoc
O
NHCO(CH2)24CH3
OH
(S)
2 steps
OH
BnO
(S)
HO
C14H29
(S)
C14H29
(S)
(S)
(S)
OMOM
23, major isomer
OH
26
Scheme 3. Reagents and conditions: (a) (i) HCl, THF/MeOH/1,4-dioxane (1:1:1), rt, overnight; (ii) CH3(CH2)24COOPhNO2, DMAP, THF, rt, 24 h, 72% for two steps. (b) H2, Pd(OH)2/C,
THF/EtOH (1:1), 24 h, 42%. For compound 26, 35% for three steps.

J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
8621
OBn
BnO
OBn
O
OBn
O
BnO
BnO
BnO
BnO
O
BnO
a
c
b
N3
NHBoc
OH
O
BnO
OH
BnO
(R)
BnO
OH
(S)
(R)
OH
(R)
OH
13
27
28
OBn
O
OBn
O
OBn
O
BnO
BnO
BnO
BnO
BnO
BnO
d
NHBoc
OH
NHBoc
e
f
NHBoc
BnO
BnO
BnO
OTBS
OTBS
OMOM
OH
OMOM
29
30
31
OBn
OBn
O
OBn
O
BnO
BnO
BnO
BnO
BnO
BnO
NHBoc
OH
C14H29
OMOM
NHBoc
OH
C14H29
OMOM
O
g
NHBoc
+
BnO
BnO
BnO
O
OMOM
32
1
1.3
33, major isomer
34, minor isomer
Scheme 4. Reagents and conditions: (a) Ti(i-OPr)2(N3)2, benzene, 70 ꢁC,10 min, 64%. (b) (i) P(Me)3, THF, rt, 18 h; (ii) 1 N NaOH, 2 h; (iii) (t-Boc)2O, THF/1,4-dioxane(1:1), satd
NaHCO3, rt,12 h; 91% for three steps. (c) TBSCl, imidazole, CH2Cl2, rt, 2 h, 99%. (d) MOMCl, DIPEA, CH2Cl2, 0 ꢁC to rt, 24 h, 99%. (e) TBAF, THF, 0 ꢁC to rt, 2 h, 92%. (f) Dess–Martin
oxidation, CH2Cl2, rt, 2 h. (g) C14H29MgBr, THF, 0 ꢁC to rt, 2 h, 50% combined yield for two steps.
Ti(O-i-Pr)2(N3)2 opening of the epoxy alcohol 13 did not match with
those compounds derived from NaN3 opening. The correct struc-
tural assignment in this section (Scheme 4) reveals a series that are
diastereomeric to those obtained from the sodium azide opening.
The (2S,3R) epoxy alcohol 27 was converted to aldehyde 32 in an
identical manipulation sequence as described in the previous sec-
tion. Grignard reaction between the aldehyde 32 and C14H29MgBr
gave a separable mixture, and the ratio of the major isomer 33 and
minor isomer 34 was 1.3:1. The stereochemical assignment was
based on the ‘Cram-chelation control’ model as was shown to be
operative in the epimeric series (Scheme 4).
Both major isomer 33 and minor isomer 34 were converted to
the corresponding C-glycoside analogs 36 and 38, respectively
(Scheme 5). The revelation that neither of the NMR spectra of these
two final products (see Supplementary data) matched with those of
the a-C-Galcers from the sodium azide sequence forced us to assign
their stereochemistries and to account for a divergence from the
expected stereochemical outcome.
In fact, the C-glycoside analog 38, the minor isomer derived
from the Ti-catalyzed sequence, was identical to the C-3 epimer 42,
which had been obtained in earlier work from our group. This
material arose from the linking of a phytosphingosine derivative 40,
epimeric at C-3, to a galactose 39 via cross-metathesis. The epi-
meric configuration of the amino group was unambiguous because
it was derived from natural phytosphingosine in which the primary
alcohol had been oxidized to an aldehyde, which had then been
treated to form an epimeric mixture at the N-bearing carbon
(Scheme 6).17
The NMR spectrum of epimer 38 also closely matched with the
spectrum of the C-glycoside 48, a material of the same configura-
tion prepared by Annoura, differing only in carbon chain length
(Scheme 7).18
Therefore, it must have been the case that the Ti-aided azide
opening of epoxide 13 had occurred with retention of the 3-N
stereocenter. To obtain diagnostic NMR confirmation of stereo-
chemistry, the trans-amino alcohol 18 and cis-amino alcohol 29,
OBn
BnO
BnO
OH
HO
OBn
BnO
NHBoc
OH
O
NHCO(CH2)24CH3
OH
a
NHCO(CH2)24CH3
OH
O
O
b
HO
BnO
BnO
HO
BnO
(CH2)13CH3
OMOM
(CH2)13CH3
OH
(CH2)13CH3
OH
33, major isomer
35
36
OBn
OBn
OH
BnO
BnO
BnO
BnO
HO
HO
NHCO(CH2)24CH3
OH
NHCO(CH2)24CH3
OH
O
O
NHBoc
OH
O
b
a
BnO
BnO
HO
(CH2)13CH3
OMOM
(CH2)13CH3
OH
(CH2)13CH3
OH
38
34, minor isomer
37
Scheme 5. Reagents and conditions: (a) (i) 6 N HCl, THF/MeOH (1:1) overnight; (ii) CH3(CH2)24COOPhNO2, DMAP, THF, 24 h. (b) Pd(OH)2/C, THF/EtOH (1:1), H2, 24 h; 54% for 36,
three steps from 33; 55% for 38, three steps from 34.

8622
J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
OH
O
HO
HO
OAc
AcO
OAc
O
NHCO(CH2)24CH3
OH
AcO
AcO
NHBoc
C14H29
O
3 steps
NHBoc
O
Grubbs II
AcO
+
C14H29
O
HO
ethylene,
refluxing,
72%
AcO
AcO
O
C14H29
OH
O
R1
39, R1=H or CH3
40
41
42
Scheme 6. Alternative synthesis of C-3 epimer 42 (Guangwu Chen, Hunter College).
OBn
O
OBn
O
BnO
BnO
BnO
BnO
OBn
O
BnO
BnO
BnO
BnO
O
C5H11
+
nBuLi, -48 °C
C5H11
O
C5H11
O
+
O
O
BnO
HO
HO
O
46, S
O
43
44
45, R
O
OH
HO
O
OH
O
HO
HO
(CH2)24CH3
OH
O
(CH2)24CH3
OH
HN
HO
HN
HO
HO
C5H11
C5H11
OH
OH
48, C-3 epimer
47
Scheme 7. Annoura et al.’s synthesis of C-glycoside analog of OCH and its C-3 epimer.
derived from opening of epoxide 13 with NaN3 and Ti-aided azide,
respectively, were transformed to the corresponding cis five-
membered oxazolidine benzoyl ester 51 and trans-benzoyl ester 54
(Scheme 8).
stereochemical relationship between the 3-azide and 2-hydroxy of
1,2 diol 27 was proved to be syn, thus, the 3-C stereocenter was
proved unambiguously to be retained during Ti(O-i-Pr)2(N3)2
opening of epoxide 13.
0
In its NOESY spectrum, strong correlation between H2, H2 and
This epoxide opening with retention can be rationalized by in-
voking Ti-catalyzed intramolecular participation by the pyranosidic
O or 2-BnO to form an intermediate oxonium ion (Scheme 9, path A
or B, respectively), inverting the epoxide center, reminiscent of
earlier work of Fraser-Reid and Mootoo.19 This would be followed
by an intermolecular azide opening with a second inversion, i.e., net
retention, to afford azido alcohol 27. It is also possible to rationalize
the stereochemcial result by invoking a Ti-catalyzed epoxide
opening/intramolecular delivery of azide from the Ti complex as
suggested by Tan et al. (path C) (Scheme 9).20 There is no simple
experiment that will distinguish between these two retention
pathways.
0
H5, H5 of the p-bromo benzoyl ester 51 clearly demonstrated
the cis relationship of these groups, therefore, the corollary cis
relationship of H3 and H4, thus establishes the anti relationship of
the corresponding H3 and H4 in the 1,2 diol 14 before the hetero-
cycle is formed (Fig. 3).
For the p-bromo benzoyl ester 54, which was derived from Ti(O-
i-Pr)2(N3)2 opening of epoxide 13, no correlation in the NOESY
between H3 and H4 was detected. Significantly, two sets of corre-
0
lation were observed: between H3 and H5, H5 protons and H4 and
0
H2, H2 protons. This correlation is that which is anticipated for
a trans five-membered cyclic ring system (Fig. 4). In this way, the
OBn
OBn
OBn
O
BnO
BnO
BnO
BnO
BnO
BnO
O
OTBS
O
OH
O
O
O
c
4
b
a
Br
O
BnO
3
18
O
N
N
Boc
Boc
49
50
51
OBn
O
OBn
O
OBn
O
BnO
BnO
BnO
BnO
O
BnO
BnO
OH
OTBS
O
O
4
a
b
c
Br
3
BnO
29
O
BnO
BnO
O
N
N
Boc
Boc
52
53
54
Scheme 8. Reagents and conditions: (a) 2,2-dimethoxy-propane, p-TsOH, CH2Cl2, 0 ꢁC to rt; 75% for 49, 91% for 52. (b) TBAF, THF, 0 ꢁC to rt; 95% for 50, 90% for 53. (c) 4-BrPhCOCl,
pyridine, CH2Cl2, rt; 82% for 51, 90% for 54.

J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
8623
OBn
BnO
OBn
O
O
BnO
BnO
O
BnO
H5'
H5
BnO
H2
H2'
N
O
N3
Br
BnO
O
OH
Boc
OH
14
51
Figure 3. NOESY effect of 51, derived from NaN3 opening of epoxide 13.
H
5 H5'
H3
N
BnO
BnO
OBn
O
OBn
O
O
H4
BnO
BnO
H2
O
BnO
H2'
Br
N3
O
BnO
OH
(S)
(R)
Boc
OH
54
27
Figure 4. NOESY effect of 54, derived from Ti(O-i-Pr)2(N3)2 opening of epoxide 13.
OBn
O
BnO
BnO
O
(R)
BnO
OH
(R)
13
Path C
TMSN3/TiCl(O-i-Pr)3
Path A
O-i-Pr
TMSN3/TiCl(O-i-Pr)3
Path B
OBn
i-Pr-O
OBn
BnO
OBn
O
BnO
BnO
O-i-Pr
OH
i-Pr-O
BnO
BnO
O-i-Pr
O
N3
O
O-i-Pr
Ti
Ti
BnO
O
Ti
O
O
O
O
BnO
BnO
BnO
(R) (R)
56
55
55
OBn
O
BnO
O-i-Pr
O
i-Pr-O
OBn
i-Pr-O
N3
BnO
BnO
i-Pr-O
OBn
O
O-i-Pr
BnO
BnO
BnO
O
H
O
r
O-i-P
Ti
O
Bn
O
OH
O
O
BnO
BnO
-
-
N3
N3
59
57
58
OBn
O
BnO
BnO
N3
BnO
OH
(S)
(R)
OH
27
Scheme 9. Mechanism for the retention of configuration of 3-N stereocenter.
1.1. Immunostimulant activity
unnatural stereoisomers.21 Our observations may be compared
with those recently reported for O-galcer stereoisomers where
a range of bioactivity was detected.22,23
Our collaborating immunology group conducted in vitro as-
says for cytokine production using a system three separate NKT
cell hybridomas paired with a CD1d antigen-presenting HeLa cell.
With NKT line 829, the stereoisomers described (compounds 26,
In summary, the C-glycoside analog 3 of a-galactosylceramide 1
(KRN7000) was synthesized in 19 linear steps in 3.3% overall yield
through the Sharpless asymmetric epoxidation method as the
controller of stereochemistry. Sodium azide opening of epoxide 13
gave anti vicinal azido diol 14 with inverted stereocenter at C-3 but
Ti(O-i-Pr)2(N3)2 opening of epoxide 13 provided syn vicinal azido
diol 27 with retention of the C-3 configuration. This unusual
36, and 38) produced 40-fold less IFN
g than the positive control
of -Galcer. With NKT 912, our stereoisomers were seven fold
a
less productive and with NKT 926, they were 50-fold less pro-
ductive. Further, there was no significant difference among these

8624
J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
phenomenon could be rationalized by related pathways, which find
literature precedent, and therefore this result should serve as
a cautionary note for researchers planning to use Ti catalysis for
epoxide opening.
extracted with ethyl acetate (3ꢂ50 mL). The combined organic
layer was dried over Na2SO4, filtered, and concentrated in vacuo.
Purification by flash chromatography eluting with 30–50% ethyl
acetate/petroleum ether afforded the allylic alcohol 12 (1.03 g, 90%
yield) as pale yellow oil. MS: m/z 626 (MþþNH4þ). HRMS calcd for
2. Experimental
C
39H44O6 608.3138, found 608.3134. 1H NMR (500 MHz, CDCl3):
d
7.35–7.20 (m, 20H, Ph), 5.71–5.65 (m, 2H, –CH]CH–), 4.75–4.52
2.1. Instruments and materials
(m, 8H, CH2Ph), 4.05 (m, 2H, –CH2OH), 3.99–3.90 (m, 3H), 3.85–3.75
(m, 2H), 3.73–3.67 (m,1H), 3.65–3.3.0 (dd, J¼10.3, 4.5 Hz,1H), 2.20(m,
1H), 2.05–1.99 (m, 1H), 1.74–1.70 (m, 1H), and 1.60–1.50 (br, 1H).
NMR spectra were recorded with a QE 300 MHz (1H) and
75 MHz (13C) with a TECMAG data system or Bruker 500 MHz (1H)
and 125 MHz (13C) in deuterated solvents. The assignment of pro-
ton and carbon NMR peaks was supported by routine COSY and
HSQC spectra and for some cases by NOESY spectra. Melting points
were determined on a Fisher–Johns apparatus and were un-
corrected. Electrospray ionization (ESI) mass spectral experiments
were performed at the Hunter College Mass Spectrometry Facility
on an Agilent Technologies 1100 LC/MSD. Typical ESI method: sol-
13C NMR (125 MHz, CDCl3):
d 138.8, 138.7, 138.5, 138.5, 132.7, 129.6,
128.6,128.6,128.6,128.5,128.4,128.2,128.0,127.9,127.9,127.8,127.8,
127.8, 127.7, 127.6, 77.0, 76.9, 74.7, 73.5, 73.4, 73.4, 73.3, 73.1, 72.3,
68.0, 63.8, and 28.7.
2.1.3. (30R,40R)-1-(30,40-Oxiran-50-hydroxy-pentanyl)-
(2,3,4,6-tetra-O-benzyl)-a-C-D-galactopyranoside (13)
A 100 mL round bottom flask containing powdered 4 Å molec-
ular sieves (4 g) was heated with a heating gun in vacuo for 10 min
and was cooled down to room temperature under N2. The flask was
then filled with dry CH2Cl2 (10 mL) and was cooled to ꢀ20 ꢁC.
vent: 1:1 acetonitrile/waterþ0.1% HOAcþ50
mL NH4Ac, flow:
0.5 mL/min, positive ion mode, fragmentor voltage: 30–200 V,
drying gas at 175 ꢁC. All air and moisture sensitive reactions were
performed under a positive pressure of dry N2 gas. All solvents and
reagents were purified prior to use according to standard labora-
tory procedures. Low temperatures were recorded as bath tem-
peratures. Thin layer chromatographic analysis was carried out on
precoated aluminum sheets of silica gel 60 F254. UV light, vanillin,
phosphomolybdic acid spray or DNP spray was used to visualize the
components on the TLC plates. Flash column chromatography was
carried out with silica gel 60 (230–400 mesh) purchased from
ChemAbsorb, using ACS reagent grade petroleum ether, hexane,
ethyl acetate, methylene chloride, chloroform, and methanol as
eluents.
Titanium(IV) isopropoxide (0.4 mL, 1.35 mmol) and diisopropyl D-
(ꢀ)-tartrate (0.28 mL, 1.62 mmol) were then added. The solution
was stirred for 30 min at ꢀ20 ꢁC. tert-Butyl hydroperoxide
(0.54 mL, 2.7 mmol, 5 M in toluene) was added dropwise over
a period of 10 min. The solution was stirred for another 30 min at
ꢀ20 ꢁC. Allylic alcohol 12 (0.82 g, 1.35 mmol, pre-dried with 4 Å MS
for 30 min) in dry CH2Cl2 (5 mL) was added dropwise. The solution
was stirred at ꢀ20 ꢁC for 18 h (stored in freezer overnight) and
was cooled to 0ꢁ C. H2O (10 mL) was added and the mixture was
stirred for 30 min at 0 ꢁC, then 30% NaOH solution saturated
by NaCl (10 mL) was added, and the solution was stirred for 30 min
at 0 ꢁC. The mixture was filtered through a pad of Celite and the
Celite was washed with CH2Cl2 (50 mL). The organic phase was
separated and the aqueous layer was extracted with CH2Cl2
(3ꢂ30 mL). The organic phase was combined and washed with
brine (20 mL), dried over Na2SO4, filtered, and concentrated in
vacuo. The crude mixture was purified by flash chromatography
eluting with 50% ethyl acetate/petroleum ether to provide epoxide
13 (0.50 g, 70% yield) as pale yellow oil. MS: m/z 642 (MþþNH4þ).
HRMS calcd for C39H44O7 624.3087, found 624.3082. 1H NMR
2.1.1. 5-(3,4,5-Tris-benzyloxy-6-benzyloxymethyl-tetrahydro-
pyran-2-yl)-pent-2-enoic acid methyl ester (11)
To a solution of crude 3-(3,4,5-tris-benzyloxy-6-benzyloxymethyl-
tetrahydro-pyran-2-yl)-propionaldehyde (10) (1.3 g, 2.3 mmol) in
anhydrous MeCN (30 mL) was added methyl(triphenylphosphoro-
nylidene)acetate (1.5 g, 4.5 mmol) in one portion at room tempera-
ture under N2. The solution was stirred overnight at room
temperature. The mixture was diluted with CH2Cl2 (50 mL), washed
with H2O (20 mL), extracted with CH2Cl2 (3ꢂ50 mL), dried over
Na2SO4 (anhydrous), filtered, and concentrated in vacuo. Purification
by flash chromatography eluting with 30% ethyl acetate/petroleum
(300 MHz, C6D6):
d 7.0 (m, 20H, Ph), 4.45–4.10 (m, 8H, CH2Ph),
3.95–3.85 (m, 2H), 3.83–3.80 (m, 1H), 3.80–3.75 (m, 1H, –CH2OH),
3.70–3.60 (m, 1H, –CH2OH), 3.50–3.45 (m, 1H), 3.35–3.3.14 (m, 3H),
2.70 (m,1H), 2.55–2.45 (m,1H),1.80–1.46 (m, 3H), and 1.40–1.11 (m,
ether provided a,b unsaturated ester 11 (1.27 g, 89% yield) as yellow
oil.MS:m/z654 (MþþNH4þ). HRMScalcdforC40H44O7636.3087, found
2H). 13C NMR (125 MHz, CDCl3):
d 138.7, 138.5, 138.4, 138.2, 128.5,
636.3085.1H NMR (500 MHz, CDCl3):
d
7.45–7.20 (m, 20H, Ph), 7.0–6.9
128.4,128.4,128.3,128.2,128.1,128.0,127.9,127.8,127.8,127.8,127.7,
76.9, 74.6, 73.7, 73.5, 73.4, 73.3, 73.2, 72.4, 68.0, 61.8, 58.5, 55.6, 28.2,
and 23.4.
(d, t, J¼15.6, 6.9 Hz,1H, CH]), 5.80 (d, J¼15.5 Hz, 1H, ]CH), 4.76–4.78
(m, 8H, CH2Ph), 4.05–3.90 (m, 4H), 3.85–3.75 (m, 5H), 3.70–3.65 (m,
1H), 2.40–2.30 (m,1H), 2.25–2.10 (m,1H),1.90–1.80 (m,1H), and 1.65–
1.55 (m, 1H). 13C NMR (125 MHz, CDCl3):
d
167.2, 149.1, 138.7, 138.6,
2.1.4. 3-Azido-1,2 diol 14 and 2-azido-1,3 diol (15)
138.5,138.4,128.6,128.6, 128.5, 128.6,128.5,128.5,128.4, 128.3, 128.1,
128.0, 128.0, 127.9, 127.9, 127.8, 127.7, 121.4, 77.4, 77.1, 76.8, 74.5, 73.4,
73.3, 73.2, 72.4, 67.8, 51.5, and 28.7.
The (2R,3R) epoxide 13 (23.8 g, 38 mmol) was dissolved in
a mixed solution of MeOH/H2O (400 mL/50 mL, 8:1). NaN3 (12.4 g,
190 mmol) and NH4Cl (4.5 g, 84 mmol) were added in one portion.
The solution was refluxed at 80 ꢁC under N2 for 16 h. The solution
was cooled down to room temperature and the solvent was re-
moved under reduced pressure. The mixture was diluted with ethyl
acetate (200 mL) and washed with H2O (200 mL). The aqueous
layer was separated from organic layer and was extracted with
ethyl acetate (3ꢂ150 mL). The combined organic layers were dried
over Na2SO4 (anhydrous), filtered, and concentrated in vacuo. The
crude mixture was purified by flash chromatography eluting with
30–50% ethyl acetate/petroleum ether to afford a mixture of 1,2 diol
14 and 1,3 diol 15 (23.6 g, 93% yield) as yellow oil. MS: m/z 685
(MþþNHþ4 ). HRMS calcd for C39H45N3O7, 667.3258, found 667.3256.
2.1.2. 5-(3,4,5-Tris-benzyloxy-6-benzyloxymethyl-tetrahydro-
pyran-2-yl)-pent-2-en-1-ol (12)
a,b Unsaturated ester 11 (1.20 g, 1.89 mmol) was dissolved in
anhydrous CH2Cl2 (10 mL) and was cooled to ꢀ78 ꢁC under N2.
DIBAL-H (5.7 mL, 5.7 mmol, 1 M in hexane) was added dropwise
over 10 min. After completion of addition, the reaction mixture was
slowly warmed up to room temperature and was stirred for 2 h at
room temperature. The solution was cooled to 0 ꢁC and MeOH
(10 mL) was added dropwise followed by addition of satd potas-
sium sodium tartrate solution (30 mL). The solution was stirred
vigorously until two clear phases appeared. The mixture was
1H NMR (500 MHz, CDCl3):
d 7.34–7.24 (m, 20H, Ph), 4.74–4.49 (m,

J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
8625
8H, CH2Ph), 4.03–3.86 (m, 4H), 3.82–3.71 (m, 2H), 3.66–3.61 (m,
2.1.7. (30S,40S)-1-{30-N-tert-Butyl carbamate-40-methoxymethoxy-
50-(tert-butyl-dimethyl-silanyloxy)-pentanyl}-(2,3,4,6-tetra-
O-benzyl)- -C- -galactopyranoside (20)
1H), 3.58–3.53 (m, 3H), 3.52–3.48 (m, 1H), 2.71 (br s, 1H, –OH), 1.96
(br s, 1H, –OH), 1.85–1.78 (m, 1H), 1.74–1.68 (m, 2H), and 1.51–1.42
a
D
(m, 1H). 13C NMR (125 MHz, CDCl3):
d
138.5, 138.4, 138.2, 138.1,
The TBS protected ether 18 (5.8 g, 6.8 mmol) was dissolved in
anhydrous CH2Cl2 (200 mL). Freshly distilled diisopropylethyl-
amine (11.8 mL, 67.9 mmol) was added at 0 ꢁC under N2. Methoxy-
methyl chloride (2.1 mL, 27.2 mmol) was then added dropwise
over 10 min. The solution was stirred at room temperature for 18 h.
The reaction was quenched by addition of satd NH4Cl solution
(100 mL) and extracted with CH2Cl2 (3ꢂ100 mL). The combined
organic layers were dried over Na2SO4 (anhydrous), filtered, and
concentrated in vacuo. The crude mixture was purified by flash
chromatography eluting with 10–20% ethyl acetate/petroleum
ether to get the fully protected compound 20 (5.79 g, 95%) as yellow
oil. MS: m/z 917 (MþþNH4þ). HRMS calcd for C52H73NO10Si
128.5, 128.5, 128.4, 128.4, 128.1, 128.1, 128.0, 128.0, 127.9, 127.8,
127.7, 127.7, 127.6, 127.6, 74.4, 73.8, 73.3, 73.3, 73.2, 72.4, 67.7, 64.4,
63.2, and 27.1.
2.1.5. 1,2 Diol 16 and 1,3 diol (17)
The mixture of 1,2 diol 14 and 1,3 diol 15 (24.6 g, 37 mmol) was
dissolved in anhydrous THF (400 mL). A solution of P(Me)3
(220 mL, 221 mmol, 1 M in THF) was added dropwise at 0 ꢁC un-
der N2 over 30 min. The solution was then stirred at room tem-
perature overnight. A solution of NaOH (200 mL, 0.4 mol, 2 M) was
added and the solution was stirred for 2 h. The mixture was
extracted with ethyl acetate (3ꢂ200 mL). The combined organic
layers were dried over Na2SO4 (anhydrous), filtered, and concen-
trated in vacuo. The crude amine was dissolved in a solution of
THF/1,4-dioxane (100 mL/100 mL, 1:1). A satd solution of NaHCO3
(50 mL) was added followed by addition of (t-Boc)2O (11.1 mL,
48.1 mmol). The solution was stirred for 24 h at room tempera-
ture. The mixture was concentrated to a total volume of 50 mL
under reduced pressure. The solution was extracted with ethyl
acetate (3ꢂ200 mL). The combined organic layers were dried over
Na2SO4 (anhydrous), filtered, and concentrated in vacuo. The
crude mixture was purified by flash chromatography eluting with
30–50% ethyl acetate/petroleum ether to afford a mixture of 1,2
diol 16 and 1,3 diol 17 (21.3 g, 78% combined yield) as yellow oil.
MS: m/z 759 (MþþNH4þ). HRMS calcd for C44H55NO9 741.3877,
899.5004, found 899.5007. 1H NMR (500 MHz, CDCl3):
d 7.31–7.26
(m, 20H, Ph), 5.52–5.23 (d, J¼8.5 Hz, 1H, NH), 4.69–4.47 (m, 10H,
CH2Ph and OCH2O), 3.97 (br s, 2H), 3.89 (br s, 1H), 3.77–3.76 (m,
3H), 3.73–3.70 (m, 2H), 3.67–3.64 (m, 2H), 3.57–3.56 (m, 1H), 3.35
(s, 3H, OCH3), 1.68 (br s, 3H), 1.53 (s, 1H), 1.42 (s, 9H, (CH3)3), 0.89 (s,
9H, CH3), 0.05 (s, 3H, CH3), and 0.04 (s, 3H, CH3). 13C NMR (125 MHz,
CDCl3):
d 156.0, 138.7, 138.6, 138.5, 138.4, 128.3, 128.2, 128.1, 128.0,
128.0, 128.0, 127.9, 127.7, 127.6, 127.5, 127.5, 127.2, 96.5, 79.4, 78.8,
77.4, 77.1, 74.8, 73.6, 73.4, 73.3, 73.2, 72.2, 68.0, 64.2, 55.8, 52.2, 28.7,
27.9, 18.4, and ꢀ5.9.
2.1.8. (30S,40S)-1-{30-N-tert-Butyl carbamate-40-methoxymethoxy-
50-hydroxy-pentanyl}-(2,3,4,6-tetra-O-benzyl)-
a-C-D-galactopyranoside (21)
found 741.3874. 1H NMR (500 MHz, CDCl3):
d 7.32–7.25 (m, 20H,
The fully protected compound 20 (4.6 g, 5.2 mmol) was dis-
Ph), 4.921 (d, J¼8.4 Hz, 1H, NH), 4.71–4.44 (m, 8H, CH2Ph), 4.05 (br
s, 1H), 3.97–3.93 (m, 3H), 3.74–3.73 (br s, 1H), 3.69 (br s, 1H), 3.59
(dd, J¼10.4, 3.52 Hz, 1H), 3.54–3.42 (m, 3H), 3.21–3.19 (br s, 1H),
3.12 (br s, 1H), 2.66 (br peak, OH), 2.41 (br peak, OH), 1.87–1.86 (m,
1H), 1.71–1.69 (m, 1H), 1.58–1.55 (m, 1H), 1.43 (s, 9H, (CH3)3), and
solved in anhydrous THF (100 mL) and the solution was cooled to
0 ꢁC under N2. A solution of tetrabutylammonium fluoride (10.3 mL,
10.3 mmol, 1 M THF solution) was added. The mixture was stirred
for 2.5 h at room temperature. The solution was washed with satd
NH4Cl solution (100 mL) and extracted with ethyl acetate
(3ꢂ100 mL). The combined organic layers were dried over Na2SO4
(anhydrous), filtered, and concentrated in vacuo. The crude mixture
was purified by flash chromatography eluting with 20–60% ethyl
acetate/petroleum ether to get the primary alcohol 21 (4.0 g, 100%
yield) as white solid. MS: m/z 803 (MþþNH4þ). HRMS calcd for
1.36–1.28 (m, 1H). 13C NMR (125 MHz, CDCl3):
d 157.5, 138.7, 138.5,
138.4, 138.4, 128.6, 128.6, 128.5, 128.5, 128.3, 128.2, 128.1, 128.1,
128.0, 127.9, 127.8, 127.7, 127.7, 127.7, 80.1, 76.5, 74.6, 74.5, 73.4,
73.3, 73.2, 73.2, 72.4, 67.5, 63.1, 53.9 (NHCO), 53.1 (NHCO), 29.1,
28.5, 27.0, 24.6, and 20.9.
C
46H59NO10 785.4139, found 785.4135. 1H NMR (500 MHz, CDCl3):
2.1.6. (30S,40S)-1-{30-N-tert-Butylcarbamate-40-hydroxy-50-
(tert-butyl-dimethyl-silanyloxy)-pentanyl}-(2,3,4,6-tetra-
O-benzyl)-a-C-D-galactopyranoside (18)
d
7.33–7.26 (m, 20H, Ph), 4.88 (d, J¼8.9 Hz, 1H, NH), 4.71–4.47 (m,
10H, CH2Ph and OCH2O), 4.02 (br s, 1H), 3.96 (br s, 1H), 3.95–3.3.85
(m, 2H), 3.72 (br s, 2H), 3.69–3.62 (m, 1H), 3.61–3.54 (m, 2H), 3.54–
3.48 (m,1H), 3.36 (s, 3H, OCH3), 3.35 (br peak, 1H), 3.28 (m,1H),1.78
(br s, 1H), 1.71–1.69 (br s, 1H), 1.61–1.55 (br s, 1H), 1.43 (s, 9H,
(CH3)3), and 1.29–1.26 (br s, 1H). 13C NMR (125 MHz, CDCl3):
The mixture of compounds 16 and 17 (11.8 g, 15.9 mmol) was
dissolved in anhydrous CH2Cl2 (200 mL) at room temperature
under N2. Imidazole (3.3 g, 48.0 mmol) and tert-butyl-dimethylsilyl
chloride (3.2 g, 20.7 mmol) were added in one portion. The solution
was stirred for 1 h at room temperature. The mixture was washed
with satd NH4Cl solution (200 mL) and extracted with CH2Cl2
(3ꢂ150 mL). The combined organic layers were dried over Na2SO4
(anhydrous), filtered, and concentrated in vacuo. The crude mixture
was purified by flash chromatography eluting with 10–20% ethyl
acetate/petroleum ether to get the first fraction 19 (1.3 g, 10% yield)
and the second fraction 18 (10.6 g, 78% yield), which is the desired
product as yellow oil. MS: m/z 873 (MþþNH4þ). HRMS calcd for
d
156.6, 138.8, 138.7, 138.5, 128.6, 128.5, 128.5, 128.4, 128.4, 128.3,
128.2, 128.1, 127.9, 127.8, 127.8, 127.8, 127.7, 96.9, 82.7, 79.7, 77.4,
77.1, 76.7, 74.7, 73.3, 73.3, 72.2, 67.8, 62.3, 55.9, 51.6, 28.6, and 26.9.
2.1.9. (30S,40S,50S)-1-{30-N-tert-Butylcarbamate-40-methoxy-
methoxy-50-hydroxy-nonadecanyl}-(2,3,4,6-tetra-
O-benzyl)-a-C-D-galactopyranoside (23)
The primary alcohol 21 (0.6 g, 0.77 mmol) was dissolved in an-
hydrous CH2Cl2 (10 mL) under N2. Dess–Martin periodinane (0.42 g,
1 mmol)wasaddedinoneportionatroomtemperature. Thesolution
was stirred for 45 min at room temperature and was diluted with
CH2Cl2 (20 mL)followed byadditionof satd NaHCO3 solution (10 mL)
and satd Na2S2O3 solution (10 mL). The mixture was stirred until two
clear phases appeared. The solution was extracted with CH2Cl2
(3ꢂ60 mL). The combined organic layers were dried over Na2SO4
(anhydrous), filtered, and concentrated in vacuo. The crude product
was coevaporated with anhydrous toluene (3ꢂ10 mL) and was then
put under high vacuum to afford the crude aldehyde 22 (0.55 g),
which was used in the next step without further purification.
C
50H69NO9Si 855.4742, found 855.4738. 1H NMR (500 MHz, CDCl3):
d
7.33–7.20 (m, 20H, Ph), 4.99–4.97 (d, J¼8.9 Hz, 1H, NH), 4.67–4.44
(m, 8H, CH2), 4.02–3.95 (br s, 1H), 3.92–3.91 (m, 1H), 3.87–3.86 (m,
1H), 3.81–3.77 (m, 1H), 3.72 (br s, 1H), 3.68–3.66 (m, 1H), 3.61–3.53
(m, 4H), 3.49–3.39 (m, 1H), 1.74–1.64 (m, 4H), 1.38 (s, 9H, (CH3)3),
0.89–0.70 (s, 9H, CH3), and 0.02 (s, 6H, CH3). 13C NMR (125 MHz,
CDCl3):
d 156.4, 138.8, 138.7, 138.6, 138.5, 128.6, 128.5, 128.5, 128.5,
128.4, 128.2, 128.1, 128.1, 128.0, 127.9, 127.8, 127.8, 127.7, 127.6, 79.3,
77.1, 74.7, 73.4, 73.4, 73.3, 72.3, 67.9, 64.7, 53.9, 28.6, 27.9, 26.1, 18.4,
ꢀ5.2, and ꢀ5.3.

8626
J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
2.1.9.1. Kirschning oxidation14. A mixture of the primary alcohol 21
(0.8 g, 0.8 mmol) and a polymer bound resin prepared according to
the literature procedure14 (1.4 g, 4.9 mmol) in dry CH2Cl2 (10 mL)
with catalytic amount of 2,2,6,6-tetramethyl-1-piperidinyloxyl
(TEMPO) under nitrogen was stirred at room temperature for 2 h.
After disappearance of starting material, the resin was washed with
CH2Cl2 (3ꢂ30 mL) and the combined organic washings and filtrate
were concentrated under reduced pressure to afford the crude al-
dehyde 22 (0.97 g), which was used in the next step without further
purification.
The aldehyde 22 was dissolved in anhydrous THF (5 mL) and the
solution was added dropwise to a solution of freshly prepared
tetradecyl magnesium bromide (C14H29MgBr, 2.3 mmol) in anhy-
drous THF (5 mL) at 0 ꢁC under N2 over 10 min. The mixture was
stirred at 0 ꢁC for 30 min and was then stirred for 2 h at room
temperature. The reaction was quenched by addition of satd NH4Cl
solution (20 mL) and the mixture was stirred for 10 min. The
mixture was extracted with ethyl ether (3ꢂ50 mL). The combined
organic layers were dried over Na2SO4 (anhydrous), filtered, and
concentrated in vacuo. The crude mixture was purified by flash
chromatography eluting with ethyl acetate/petroleum ether (po-
larity increased from 5% to 20%) to get the major isomer 23 (0.36 g,
48% yield) as the first fraction and the minor isomer 24 (72 mg, 10%
yield) as the second fraction.
The amine was dissolved in anhydrous THF (2 mL). The activated
ester C25H51COOPhNO2 (55 mg, 0.091 mmol) and DMAP (3 mg)
were added at room temperature under N2. The mixture was stirred
at room temperature overnight. Celite 545 (0.5 g) was added and
the solvent was removed in vacuo to get powder. Flash chromato-
graphic purification eluting with 10% ethyl acetate/petroleum ether
to remove the excess amount of ester and using 20–30% ethyl
acetate/petroleum ether to give the amide 25 (0.04 g, 72% yield).
The amide 25 (0.04 g, 0.033 mmol) was dissolved in a solvent of
THF/EtOH (3 mL/3 mL, 1:1). Pd(OH)2/C (0.10 g, 20% by weight)
was added in one portion. The solution was degassed three times
and was stirred under H2 balloon (1 atm) for 24 h. At the end of
the reaction, a white precipitate formed. The solution was filtered
through a pad of Celite, which was washed with 50% CHCl3/MeOH
solution (30 mL) followed by pyridine (20 mL). The solvent was
removed in vacuo and the solid was dissolved in pyridine (2 mL).
Celite 545 (0.5 g) was added and the solvent was removed in
vacuo. The powder was put to the top of the column. Flash chro-
matographic separation eluting with CHCl3 and 5%, 10%, and 20%
MeOH/CHCl3 afforded the target C-glycoside 3 (0.016 g, 42% and
30% yield for three steps) as a white solid. Mp 176–179 ꢁC. HRMS
calcd for
(500 MHz, C5D5N):
C
51H101N1O8 855.7527, found 855.7514. 1H NMR
d
8.49 (d, J¼8.9 Hz, 1H, NH), 4.73 (dd, J¼8.8,
5.5 Hz, 1H), 4.52 (m, 3H), 4.37 (dd, J¼11.2, 4.5 Hz, 1H), 4.25 (m, 4H),
3.97 (s, 1H, impurity), 2.72 (m, 1H), 2.55 (m, 1H), 2.48 (m, 3H), 2.33
(m, 2H), 2.20 (m, 1H), 2.05 (m, 5H, impurity), 1.96 (m, 2H), 1.86 (m,
3H), 1.69 (m, 1H), 1.57 (m, 5H), 1.31 (m, 56H), 1.03 (m, 3H), and 0.89
2.1.9.2. The major isomer 23. MS: m/z 999 (MþþNH4þ). HRMS calcd
for C60H87NO10 981.6330, found 981.6322. 1H NMR (500 MHz,
CDCl3):
d
7.35–7.29 (m, 20H, Ph), 5.26 (d, J¼9.1 Hz,1H, NH), 4.76–4.48
(t, J¼6.9 Hz, 6H, CH3). 13C NMR (125 MHz, C5D5N):
d 173.9, 78.9,
(m, 10H, CH2Ph and OCH2O), 3.99 (br s, 2H), 3.96 (m, 1H), 3.86–3.74
(m, 4H), 3.65–3.63 (m, 2H), 3.41 (s, 3H, OCH3), 3.31 (m, 1H), 2.76 (d,
J¼5.2 Hz, 1H), 1.71–1.66 (m, 4H), 1.57–1.54 (m, 2H), 1.45 (s, 9H,
77.5, 74.3, 73.2, 72.7, 71.1, 70.9, 63.2, 53.2, 37.3, 34.8, 32.4, 30.7, 30.5,
30.3, 30.3, 30.2, 30.2, 30.2, 30.1, 29.9, 29.9, 26.8, 26.7, 23.2, 23.0,
and 14.6.
(CH3)3),1.33–1.19 (br s, 24H, CH2), and 0.91 (t, J¼6.9 Hz, 3H, CH3). 13
C
NMR (125 MHz, CDCl3):
d
156.4, 138.8, 138.7, 138.6, 128.5, 128.5,
2.1.12. (30S,40S,50S)-30-N-Hexacosanoyl-40,50-dihydroxy-
128.4, 128.3, 128.1, 128.1, 128.0, 127.9, 127.9, 127.8, 127.8, 127.7, 97.9,
83.9, 79.3, 77.4, 77.3, 76.8, 76.8, 74.8, 73.5, 73.5, 73.3, 72.2, 67.9, 56.3,
52.1, 34.0, 32.1, 30.0, 29.9, 29.8, 29.6, 28.6, 27.4, 25.8, 22.9, and 14.3.
nonadecacyl-a-C-D-galactopyranoside (26)
This material was obtained from major isomer 23 (35% overall
yield for three steps) following the same procedures as described
for processing isomer 24. Mp 170–175 ꢁC. HRMS calcd for
2.1.10. (30S,40S,50R)-1-{30-N-tert-Butylcarbamate-40-methoxy-
methoxy-50-hydroxy-nonadecanyl}-(2,3,4,6-tetra-O-benzyl)-
C
d
51H101N1O8 855.7527, found 855.7515. 1H NMR (500 MHz, C5D5N):
6.80 (br peak, OH), 6.51 (br peak, OH), 6.33 (br peak, OH), 6.09 (br
a
-C-
D
-galactopyranoside (24)
peak, OH), 5.72 (br peak, OH), 4.77–4.73 (m, 2H), 4.66 (s, 1H), 4.53
(s, 2H), 4.48 (s, 1H), 4.31–4.29 (m, 2H), 4.20 (s, 1H), 3.79 (s, 1H), 2.89
(br s, 1H), 2.63 (br s, 1H), 2.48 (t, J¼7.2 Hz, 2H), 2.31–2.24 (m, 3H),
2.22–2.14 (m, 1H), 2.09–1.97 (m, 1H), 1.91–1.73 (m, 7H), 1.71–1.59
(m, 2H), 1.39–1.26 (m, 58H), and 0.92–0.87 (m, 6H). 13C NMR
(125 MHz, C5D5N): d 175.5, 77.3, 74.3, 72.6, 71.4, 70.7, 62.7, 53.4, 37.1,
34.6, 32.4, 37.1, 34.6, 32.4, 30.6, 30.5, 30.3, 30.2, 30.1, 30.1, 29.9, 29.9,
29.1, 27.2, 26.8, 23.3, 23.1, and 14.6.
MS: m/z 999 (MþþNH4þ). HRMS calcd for C60H87NO10 981.633,
found 981.6320. 1H NMR (500 MHz, CDCl3):
d 7.37–7.29 (m, 20H,
Ph), 4.89 (d, J¼9.4 Hz, 1H, NH), 4.75–4.48 (m, 10H, CH2Ph and
OCH2O), 3.99–3.96 (m, 3H), 3.84–3.77 (m, 3H), 3.75 (d, J¼5.2 Hz,
1H), 3.61–3.59 (m, 1H), 3.56 (dd, J¼10.6, 3.8 Hz, 1H), 3.39 (s, 3H,
OCH3), 3.34 (t, J¼5.0 Hz,1H), 2.73 (d, J¼6.1 Hz,1H), 1.91 (m,1H), 1.71
(m, 2H), 1.62–1.59 (m, 2H), 1.53 (m, 1H), 1.45 (s, 9H, (CH3)3), 1.38–
1.27 (m, 24H, CH2), and 0.91 (t, J¼6.6 Hz, 3H, CH3). 13C NMR
(125 MHz, CDCl3):
d
155.9, 138.9, 138.7, 138.6, 138.5, 128.6, 128.6,
2.1.13. (30R,40S)-1-{30-Azido-40,50-dihydroxy-pentanyl}-
128.4, 128.3, 128.2, 128.1, 128.1, 128.0, 127.9, 127.8, 127.7, 98.6, 87.5,
79.3, 77.1, 76.9, 76.5, 74.9, 73.6, 73.4, 73.3, 71.8, 68.4, 56.2, 51.8, 33.0,
32.1, 29.9, 29.8, 29.6, 28.7, 27.1, 26.4, 22.9, and 14.3.
(2,3,4,6-tetra-O-benzyl)-a-C-D-galactopyranoside (27)
Titanium(IV) isopropoxide (0.22 mL, 0.73 mmol) and azido tri-
methylsilane (0.2 mL, 1.5 mmol) were added to anhydrous benzene
(10 mL), and the solution was refluxed at 80 ꢁC under N2 for at least
5 h. Epoxide 13 (0.30 g, 0.48 mmol) was dissolved in anhydrous
benzene (10 mL) and was added to the solution in one portion. The
mixture was stirred for 15–30 min at 80 ꢁC and was cooled to room
temperature. The solvent was removed under reduced pressure.
Diethyl ether (20 mL) was added followed by addition of 5% H2SO4
(10 mL, v/v). The solution was stirred at room temperature until
two clear phases appeared. The mixture was extracted with CH2Cl2
(3ꢂ30 mL). The organic phase was dried over Na2SO4, filtered, and
concentrated in vacuo. Flash chromatographic purification eluting
with 50% ethyl acetate/petroleum ether afforded 3-azido-1,2 diol
27 (0.21 g, 64% yield) as yellow oil. MS: m/z 685.3 (MþþNH4þ).
HRMS calcd for C39H45N3O7 667.3258, found 667.3254. IR (KBr):
3435.98, 2873.99, 2100.89, 763.72 cmꢀ1. 1H NMR (300 MHz, CDCl3):
2.1.11. (30S,40S,50R)-30-N-Hexacosanoyl-40,50-dihydroxy-
nonadecacyl-a-C-D-galactopyranoside (3)
To a solution of the minor isomer 24 (45 mg, 0.046 mmol) in
MeOH/1,4-dioxane (1 mL/1 mL) was added HCl solution (2 mL,
12 mmol, 6 M in MeOH) and the solution was stirred at room tem-
perature overnight. The solution was concentrated to dryness under
reduced pressure. The mixture was dissolved in THF (5 mL) and was
neutralized with satd ammonium hydroxide solution (5 mL). The
mixture was extracted with CHCl3 (3ꢂ20 mL). The combined organic
layers were dried over Na2SO4 (anhydrous), filtered, and concen-
trated in vacuo. The crude compound was coevaporated with an-
hydrous toluene (3ꢂ10 mL) and was then put under high vacuum
pump for 1 h to afford crude amine (40 mg) as yellow oil.

J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
8627
d
7.30 (m, 20H), 4.8–4.4 (m, 8H), 4.01–3.83 (m, 4H), 3.77–3.69 (m,
2.1.18. (30R,40S,50R)-1-{30-N-tert-Butyl carbamate-40-methoxy-
methoxy-50-hydroxy-nonadecanyl}-(2,3,4,6-tetra-O-benzyl)-
2H), 3.60–3.45 (m, 4H), 3.42–3.34 (m, 1H), 2.5–2.4 (br, OH), 2.25–
2.15 (br, OH), 1.90–1.75 (m, 1H), and 1.74–1.50 (m, 3H). 13C NMR
a-C-D-galactopyranoside (33)
(75 MHz, CDCl3):
128.1, 128.0, 127.9, 127.8, 127.7, 127.6, 77.4, 76.9, 74.7, 74.0, 73.8, 73.5,
73.5, 73.4, 72.5, 70.5, 68.1, 64.0, 63.5, 26.9, and 23.9.
d
138.7, 138.6, 138.5, 138.3, 128.5, 128.4, 128.3,
Major isomer: yield: 28% for two steps from 31. MS: m/z 999
(MþþNHþ4 ). HRMS calcd for C60H87NO10 981.6330, found 981.6322.
1H NMR (500 MHz, CDCl3):
d 7.35–7.21 (m, 20H, Ph), 4.74–4.49 (m,
10H, CH2Ph and OCH2O), 4.05–3.96 (m, 3H), 3.85–3.74 (m, 3H),
3.74–3.69 (m, 1H), 3.65–3.60 (dd, J¼3.9, 10.3 Hz, 1H), 3.55–3.52 (br
s, 1H), 3.34 (s, 3H, OCH3), 3.21 (d, J¼6.9 Hz, 1H), 3.05 (d, J¼2.3 Hz,
–OH), 1.76–1.51 (m, 4H), 1.42 (s, 9H, Boc), 1.35–1.22 (m, 26H), and
2.1.14. (30R,40S)-1-{30-N-tert-Butyl carbamate-40,50-dihydroxy-
pentanyl}-(2,3,4,6-tetra-O-benzyl)-a-C-D-galactopyranoside (28)
The following materials were obtained from azido diol 27 via the
procedures used for azido diol 13. Yield: 91% yield for two steps
from 27. MS: m/z 742.3 (MþþHþ). HRMS calcd for C44H55NO9
0.90 (t, J¼6.7 Hz, 3H, CH3). 13C NMR (125 MHz, CDCl3):
d 155.8,
138.9, 138.8, 138.7, 138.6, 128.6, 128.5, 128.2, 128.1, 128.0, 127.9,
127.9, 127.8, 127.8, 127.7, 99.2, 87.4, 79.3, 77.1, 76.6, 76.4, 76.4, 74.7,
73.5, 73.3, 73.3, 73.1, 71.6, 68.1, 56.3, 50.8, 32.9, 32.2, 30.0, 29.9, 29.9,
29.8, 29.6, 28.6, 25.8, 22.9, and 14.3.
741.3877, found 741.3869. 1H NMR (500 MHz, CDCl3):
d 7.35–7.22
(m, 20H, Ph), 4.75–4.50 (m, 8H, CH2Ph), 4.05–3.98 (br, 1H), 3.98–
3.95 (br, 2H), 3.93–3.88 (m, 1H), 3.76–3.72 (m, 2H), 3.69–3.63 (m,
1H), 3.62–3.56 (m, 2H), 3.55–3.48 (m, 1H), 3.44–3.39 (m, 1H), 3.10–
3.00 (br, 1H, –OH), 2.18–2.10 (br, 1H, –OH), 1.80–1.72 (m, 1H), 1.69–
1.62 (m, 1H), 1.62–1.52 (m, 1H), 1.52–1.47 (m, 1H), and 1.46–1.42 (s,
2.1.19. (30R,40S,50S)-1-{30-N-tert-Butyl carbamate-40-methoxy-
methoxy-50-hydroxy-nonadecanyl}-(2,3,4,6-tetra-O-benzyl)-
a-C-D-galactopyranoside (34)
9H, (CH3)3). 13C NMR (125 MHz, CDCl3):
d
157.5, 138.8, 138.6, 138.5,
138.4, 128.6, 128.6, 128.5, 128.3, 128.1, 128.1, 128.0, 127.9, 127.8,
127.7, 80.1, 77.2, 76.8, 74.7, 74.6, 73.5, 73.4, 73.4, 73.3, 72.5, 68.1, 63.6,
51.6, 28.6, and 24.1.
Minor isomer, yield: 22% for two steps from 31. MS: m/z 999
(MþþNHþ4 ). HRMS calcd for C60H87NO10 981.6330, found 981.6325.
1H NMR (500 MHz, CDCl3):
d 7.51–7.24 (m, 20H, Ph), 4.76–4.48 (m,
10H, 4CH2 and OCH2O–), 4.05–3.90 (m, 4H), 3.90–3.85 (m, 1H),
3.85–3.74 (m, 2H), 3.74–3.70 (m, 1H), 3.65–3.60 (m, 1H), 3.31 (s, 3H,
OCH3), 3.19 (m, 1H), 1.78–1.51 (m, 4H), 1.50–1.45 (m and s, 11H),
1.45–1.21 (m, 24H), and 0.90 (t, 3H, CH3). 13C NMR (125 MHz,
2.1.15. (30R,40S)-1-{30-N-tert-Butyl carbamate-40-hydroxy-
50-(tert-butyl-dimethyl-silanyloxy)-pentanyl}-(2,3,4,6-tetra-
O-benzyl)-a-C-D-galactopyranoside (29)
Yield: 99%. MS: m/z 873.3 (MþþNH4þ). HRMS calcd for
50H69NO9Si 855.4742, found 855.4736. 1H NMR (500 MHz, CDCl3):
7.35–7.22 (m, 20H, Ph), 4.75–4.50 (m, 8H, CH2Ph), 4.05–3.95 (m,
CDCl3): d 157.5, 138.9, 138.7, 138.6, 138.5, 128.7, 128.6, 128.5, 128.4,
C
d
128.4, 128.3, 128.2, 128.1, 128.0, 127.9, 127.9, 127.8, 127.8, 127.7, 98.7,
85.2, 80.0, 76.9, 76.6, 74.8, 73.6, 73.5, 73.4, 73.3, 73.2, 70.8, 68.1, 56.5,
50.8, 32.8, 32.1, 30.1, 29.9, 29.6, 29.1, 28.5, 26.1, 22.9, and 14.3.
3H), 3.85–3.80 (m, 1H), 3.78–3.73 (m, 1H), 3.73–3.70 (m, 1H), 3.65–
3.60 (m, 3H), 3.55–3.50 (m, 1H), 3.48–3.45 (m, 1H), 2.65–2.60 (br,
1H, –OH), 1.76–1.65 (m, 2H), 1.60–1.50 (m, 2H), 1.45–1.40 (s, 9H,
(CH3)3), 0.92 (s, 9H, CH3), and 0.06 (s, 6H, CH3). 13C NMR (125 MHz,
2.1.20. (30R,40S,50S)-30-N-Hexacosanoyl-40,50-dihydroxy-
nonadecacyl-a-C-D-galactopyranoside (36)
CDCl3):
d
156.2, 138.8, 138.7, 138.6, 138.5, 128.5, 128.5, 128.4, 128.3,
Yield: 54% for three steps from 33. Mp 183–185 ꢁC. HRMS calcd
128.2, 128.1, 128.0, 127.9, 127.9, 127.8, 127.7, 127.7, 127.7, 127.6, 127.6,
79.1, 76.9, 76.8, 74.6, 73.3, 73.2, 73.1, 73.0, 72.4, 67.8, 65.0, 50.9, 29.0,
28.5, 26.0, 18.4, ꢀ5.2, and ꢀ5.3.
for C51H101N1O8 855.7527, found 855.7522. 1H NMR (500 MHz,
C5D5N):
d
8.05 (d, J¼9.2 Hz, 1H, NH), 6.65 (br, OH), 6.40 (br, OH),
6.20 (br, OH), 5.80 (br, OH), 4.76–4.72 (m, 1H), 4.72–4.66 (m, 2H),
4.54–4.48 (m, 1H), 4.45–4.34 (m, 2H), 4.32–4.27 (m, 1H), 4.12–4.06
(m, 1H), 4.01–3.94 (m, 1H), 2.49–2.35 (m, 5H), 2.27–2.23 (m, 1H),
2.16–2.10 (m, 1H), 1.91–1.77 (m, 5H), 1.52–1.21 (m, 66H), and 0.87 (t,
2.1.16. (30R,40S)-1-{30-N-tert-Butyl carbamate-40-methoxy-
methoxy-50-(tert-butyl-dimethyl-silanyloxy)-pentanyl}-
(2,3,4,6-tetra-O-benzyl)-
a
-C-
D
-galactopyranoside (30)
6H, CH3). 13C NMR (125 MHz, C5D5N):
d 173.7, 77.5, 75.8, 74.7, 73.0,
Yield: 99%. MS: m/z 917 (MþþNH4þ). HRMS calcd for C52H73NO10Si
72.7, 71.0, 70.7, 62.8, 50.9, 37.3, 32.6, 32.5, 30.8, 30.7, 30.6, 30.5, 30.4,
30.4, 30.3, 30.3, 30.2, 30.0, 30.0, 27.0, 27.0, 23.4, and 14.7.
899.5004, found 855.4993. 1H NMR (500 MHz, CDCl3):
d 7.35–7.22
(m, 20H, Ph), 4.83 (d, J¼9.7 Hz,1H, NH), 4.75–4.50 (m,10H, 4CH2 and
OCH2O–), 4.05–3.96 (m, 3H), 3.80–3.70 (m, 3H), 3.70–3.65 (m, 1H),
3.65–3.55 (m, 4H), 3.29(s, 3H, OCH3),1.76–1.74 (m,1H),1.70–1.55 (m,
2H),1.56–1.48 (m,1H),1.42 (s, 9H, (CH3)3, Boc), 0.85 (s, 9H, CH3), and
2.1.21. (30R,40S,50R)-30-N-Hexacosanoyl-40,50-dihydroxy-
nonadecacyl-a-C-D-galactopyranoside (38)
Yield: 55% for three steps from 34. Mp 178–182 ꢁC. HRMS calcd
0.05 (s, 6H, CH3). 13C NMR (125 MHz, CDCl3):
d
155.9, 138.9, 138.8,
for C51H101N1O8 855.7527, found 855.7523. 1H NMR (500 MHz,
138.7,138.6,128.5,128.5,128.4,128.1,128.0,127.9,127.8,127.7,127.6,
97.9, 79.5, 78.9, 77.2, 74.7, 73.4, 73.2, 72.4, 67.9, 63.9, 55.9, 50.9, 29.1,
28.6, 26.1, 18.4, and ꢀ5.4.
C5D5N):
d
8.65 (d, J¼9.0 Hz, 1H, NH), 6.65 (br, OH), 6.40 (br, OH),
6.20 (br, OH), 5.80 (br, OH), 5.02–5.01 (m, 1H), 4.76–4.72 (m, 1H),
4.72–4.66 (br s, 1H), 4.59–4.56 (m, 1H), 4.42 (m, 1H), 4.38 (m, 1H),
4.33 (m, 1H), 4.19 (br, 1H), 3.94 (m, 1H), 3.89 (m, 1H), 3.63 (d,
J¼4.7 Hz, less than 1H), 2.49–2.35 (m, 5H), 2.27–2.23 (m, 1H), 2.16–
2.10 (m, 1H), 1.91–1.769 (m, 5H), 1.52–1.21 (m, 66H), and 0.87 (m,
2.1.17. (30R,40S)-1-{30-N-tert-Butyl carbamate-40-methoxymethoxy-
50-hydroxy-pentanyl}-(2,3,4,6-tetra-O-benzyl)-
a
-C-
D
-galactopyranoside (31)
6H, CH3). 13C NMR (125 MHz, C5D5N):
d 175.2, 77.8, 76.3, 74.5, 72.8,
72.7, 71.0, 70.9, 63.1, 51.5, 37.1, 34.9, 32.7, 32.7, 30.9, 30.8, 30.8, 30.7,
30.6, 30.6, 30.5, 30.5, 30.4, 30.3, 30.2, 30.1, 29.6, 27.3, 27.2, 23.5,
23.3, and 14.8.
Yield: 92%. MS: m/z 803 (MþþNH4þ). HRMS calcd for
C
52H73NO10Si 785.4139, found 785.4133. 1H NMR (500 MHz,
CDCl3):
d 7.34–7.24 (m, 20H, Ph), 4.73–4.45 (m, 10H, –CH2Ph and
OCH2O), 3.97–3.93 (m, 3H), 3.85–3.79 (m, 2H), 3.74–3.3.71 (m, 2H),
3.65–3.57 (m, 3H), 3.51–3.48 (m, 1H), 3.42–3.40 (m, 1H), 3.33–3.31
(s, 3H, OCH3), 1.76–1.71 (m, 1H), 1.68–1.66 (m, 1H), 1.56–1.53 (m,
2.1.22. (30S,40S)-1-{50-(tert-Butyl-dimethyl-silanyloxy)-20,20-
dimethyl-40-propyl-oxazolidine-30-N-tert-butylcarbamate-
pentanyl}-(2,3,4,6-tetra-O-benzyl)-a-C-D-galactopyranoside (49)
2H), and 1.42 (s, 9H, –C(CH3)3). 13C NMR (125 MHz, CDCl3):
d
156.9,
138.5, 138.4, 138.3, 138.1, 128.4, 128.3, 128.2, 128.2, 128.1, 128.0,
127.9, 127.8, 127.7, 127.6, 127.5, 127.5, 127.4, 97.0, 81.0, 79.5, 77.3,
76.9, 74.4, 73.2, 73.1, 72.9, 72.8, 72.3, 70.5, 67.8, 61.8, 55.6, 50.3, 28.3,
and 28.2.
The TBS ether compound 18 (0.51 g, 0.6 mmol) was dissolved in
anhydrous CH2Cl2 (10 mL). 2,2-Dimethoxy-propane (1 mL) was
added followed by addition of p-TsOH (7 mg) at 0 ꢁC under N2. The
solution was then stirred at room temperature for 1 h. The solution

8628
J. Pu, R.W. Franck / Tetrahedron 64 (2008) 8618–8629
was washed with satd NaHCO3 solution (10 mL) and extracted with
CH2Cl2 (3ꢂ50 mL). The combined organic layer was dried over
Na2SO4 (anhydrous), filtered, and concentrated under reduced
pressure. The crude mixture was purified by flash chromatography
eluting with 10–30% ethyl acetate/petroleum ether to afford the
cyclic compound 49 (0.41 g, 75% yield) as yellow oil. MS: m/z 913
(MþþNHþ4 ) (calcd for C53H73NO9Si, 895). 1H NMR (500 MHz,
2.1.25. (30R,40S)-1-{50-(tert-Butyl-dimethyl-silanyloxy)-20,20-
dimethyl-40-propyl-oxazolidine-30-N-tert-butylcarbamate-
pentanyl}-(2,3,4,6-tetra-O-benzyl)-a-C-D-galactopyranoside (52)
Yield: 91% from TBS ether compound 29. MS: m/z 913
(MþþNH4þ) (calcd for C53H73NO9Si 895). 1H NMR (500 MHz, CDCl3):
d
7.33–7.24 (m, 20H, Ph), 4.735–4.43 (m, 8H, CH2Ph), 3.98 (s, 1H),
3.93–3.91 (m, 2H), 3.85–3.71 (m, 4H), 3.69 (dd, J¼7.9, 2.5 Hz, 1H),
3.65 (dd, J¼10.0, 5.3 Hz, 1H), 3.59 (s, 2H), 1.91–1.89 (m, 1H), 1.57–
1.52 (s, 6H, CH3 and CH2), 1.49 (s, 3H, CH3), 1.42 (s, 9H, (CH3)3), 0.88
(s, 9H, CH3), 0.07 (s, 3H, CH3), and 0.04 (s, 3H, CH3). 13C NMR
CDCl3):
d 7.32–7.25 (m, 20H, Ph), 4.79–4.37 (m, 8H, CH2Ph),
4.09–4.05 (m, 2H), 3.97–3.94 (br s, 2H), 3.91–3.86 (m, 3H), 3.79–
3.75 (m, 1H), 3.73 (d, J¼7.5 Hz, 1H), 3.67–3.55 (m, 2H), 1.82–1.79 (m,
2H), 1.66–1.63 (m, 1H), 1.59–1.55 (br s, 4H), 1.51 (s, 3H, CH3), 1.44 (s,
3H, CH3), 1.39 (s, 6H, CH3), 0.87 (s, 9H, CH3), 0.05 (s, 3H, CH3),
(125 MHz, CDCl3):
d 152.1, 138.9, 138.8, 138.7, 128.5, 128.4, 128.1,
128.1, 128.0, 127.9, 127.8, 127.7, 127.7, 127.3, 94.7, 94.4, 80.9, 79.8,
79.1, 76.9, 76.6, 76.3, 74.7, 73.5, 73.2, 72.1, 68.0, 64.8, 59.6, 28.7, 27.7,
26.2, 23.7, 18.5, ꢀ5.1, and ꢀ5.2.
and 0.03 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3):
d 152.7,
152.2, 138.9, 138.9, 138.8, 138.7, 138.6, 138.4, 128.8, 128.8, 128.7,
128.5, 128.4, 128.3, 128.2, 128.1, 127.9, 127.8, 127.7, 127.7, 127.6, 93.4,
92.9, 79.9, 79.7, 77.3, 77.1, 76.6, 74.9, 73.8, 73.6, 73.5, 73.4, 73.1, 71.6,
68.5, 68.2, 61.3, 58.8, 28.7, 28.6, 28.3, 27.5, 27.4, 27.0, 26.1, 25.3, 23.9,
23.7, 18.5, ꢀ5.0, and ꢀ5.1. (Note. Because the existence of two
conformers of amide, the carbon peaks become to two series of
peaks.)
2.1.26. (30R,40S)-1-{20,20-Dimethyl-40-propyl-oxazolidine-30-N-tert-
butylcarbamate-50-hydroxy-pentanyl}-(2,3,4,6-tetra-O-benzyl)-
a
-C-D-galactopyranoside (53)
Yield: 90%. MS: m/z 799 (MþþNH4þ) (calcd for C47H59NO9 781).
1H NMR (500 MHz, CDCl3):
d 7.33–7.24 (m, 20H, Ph), 4.74–4.45 (m,
8H, CH2Ph), 4.05–3.81 (m, 6H), 3.73–3.69 (s, 2H), 3.66–3.55 (m, 2H),
3.47–3.42 (br s, 2H),1.94–1.85 (m,1H),1.67–1.59 (m, 3H),1.54 (s, 3H,
CH3), 1.48 (s, 3H, CH3), and 1.42 (s, 9H, (CH3)3). 13C NMR (125 MHz,
2.1.23. (30S,40S)-1-{20,20-Dimethyl-40-propyl-oxazolidine-
30-N-tert-butylcarbamate-50-hydroxy-pentanyl}-(2,3,4,6-
tetra-O-benzyl)-
a-C-D-galactopyranoside (50)
CDCl3): d 152.1, 138.8, 138.6, 138.5, 128.6, 128.5, 128.4, 128.4, 128.4,
To a solution of cyclic compound 49 (0.40 g, 0.45 mmol) in an-
hydrous THF (5 mL) was added tetrabutylammonium fluoride
(1.4 mL, 1.4 mmol, 1 M in THF) dropwise at 0 ꢁC under N2. The so-
lution was stirred at room temperature for 1 h. The solvent was
removed under reduced pressure. The crude mixture was purified
by flash chromatography eluting with 10–30% ethyl acetate/pe-
troleum ether to afford the primary alcohol 50 (0.34 g, 95% yield) as
yellow oil. MS: m/z 799 (MþþNH4þ) (calcd for C47H59NO9 781). 1H
128.3, 128.2, 128.2, 128.1, 128.0, 127.9, 127.8, 127.7, 127.7, 79.9, 77.4,
77.1, 74.5, 73.7, 73.6, 73.3, 63.9, 58.4, and 28.7. (Note. C(CH3)3 peak at
94 ppm was too small.)
2.1.27. (30R,40S)-1-{20,20-Dimethyl-40-propyl-oxazolidine-30-N-tert-
butylcarbamate-50-(4-bromo-benzoyloxymethyl)-pentanyl}-
(2,3,4,6-tetra-O-benzyl)-a-C-D-galactopyranoside (54)
Yield: 90%. MS: m/z 981 (MþþNH4þ). HRMS calcd for
NMR (500 MHz, CDCl3):
d
7.33–7.23 (m, 20H, Ph), 4.74–4.49 (m, 8H,
C
54H62BrNO10 963.3557, found 963.3550. 1H NMR (500 MHz,
CH2Ph), 4.13–4.11 (br s, 1H), 3.93–3.83 (m, 5H), 3.82–3.62 (m, 4H),
3.62–3.53 (br s, 1H), 1.79 (br s, 2H), 1.67 (br s, 2H), 1.55 (br s, 6H,
CDCl3):
d
7.92–7.90 (d, J¼8.42 Hz, 2H), 7.57–7.55 (d, J¼8.4 Hz, 2H),
7.37–7.29 (m, 20H, Ph), 4.76–4.47 (m, 8H, CH2), 4.35–4.34 (m, 2H),
4.22–4.19 (m, 1H), 4.01 (m, 4H), 3.82 (br s, 2H), 3.74–3.72 (m, 1H),
3.69–3.66 (dd, J¼10.2, 4.6 Hz, 1H), 2.00–1.98 (m, 1H), 1.62 (br s, 5H),
CH3), and 1.41 (s, 9H, C(CH3)3). 13C NMR (125 MHz, CDCl3):
d 152.1,
138.9, 138.8, 138.7, 138.4, 128.6, 128.5, 128.4, 128.2, 128.1, 128.0,
127.8, 127.8, 127.7, 93.6, 93.0, 79.8, 77.9, 76.8, 76.5, 76.3, 74.9, 73.8,
73.6, 73.3, 72.3, 71.9, 69.1, 68.5, 61.1, 58.8, 28.7, 28.3, 27.6, 25.3, 24.3,
and 23.9.
1.56 (br s, 4H), and 1.47 (s, 9H). 13C NMR (125 MHz, CDCl3):
d 165.7,
152.1, 138.7, 138.6, 138.4, 131.9, 131.4, 128.9, 128.6, 128.5, 128.5,
128.4, 128.2, 128.1, 127.9, 127.8, 127.8, 127.7, 95.3, 94.5, 80.2, 77.4,
76.7, 76.4, 74.6, 73.5, 73.3, 59.7, and 28.7.
2.1.24. (30S,40S)-1-{20,20-Dimethyl-40-propyl-oxazolidine-30-N-tert-
butylcarbamate-50-(4-bromo-benzoyloxymethyl)-pentanyl}-
Acknowledgements
(2,3,4,6-tetra-O-benzyl)-a-C-D-galactopyranoside (51)
To a solution of alcohol 50 (0.33 g, 0.42 mmol) was dissolved in
anhydrous CH2Cl2 (10 mL) were added anhydrous pyridine (0.5 mL)
and para-bromobenzoyl chloride (0.18 g, 0.84 mmol) at 0 ꢁC under
N2. The solution was stirred at room temperature for 2 h. The so-
lution was washed with satd NH4Cl solution (20 mL) and extracted
with CH2Cl2 (3ꢂ50 mL). The combined organic layer was dried over
Na2SO4 (anhydrous), filtered, and concentrated under reduced
pressure. The crude mixture was purified by flash chromatography
eluting with 10–20% ethyl acetate/petroleum ether to afford ben-
zoyl ester 51 (0.34 g, 82% yield) as yellow oil. MS: m/z 981
(MþþNHþ4 ) (calcd for C54H62BrNO10 963). 1H NMR (500 MHz,
The research was supported by funding from NIH: to R.W.F. for
synthesis (GM 60271); by a subcontract from the NIH-supported
NIAID Tetramer Facility at Emory University; by the Division of
Research Resources to Hunter College for infrastructure support
(RCMI-RR 03037). We thank Dr. Clifford E. Soll at Hunter College/
CUNY for MS support and Dr. Michael Blumenstein for his excellent
assistance in the NMR experiments. Special thanks to Dr. H.
Annoura from Daiichi Suntory Pharma Co., Ltd. Japan for supplying
a copy of the spectrum of compound 48, the C-3 epimer of the
C-glycoside analog of OCH.
CDCl3):
d
7.88–7.86 (d, J¼8.4 Hz, 2H), 7.52–7.51 (d, J¼8.4 Hz, 2H),
Supplementary data
7.33–7.23 (m, 20H, Ph), 4.72–4.43 (m, 8H, –CH2Ph), 4.31–4.30 (dd,
J¼11.2, 5.8 Hz, 2H, CH2OCO), 4.17–4.16 (s, 1H, CHO), 4.02–3.90 (m,
4H), 3.73 (br s, 1H), 3.69–3.68 (br s, 1H), 3.65–3.62 (dd, J¼9.9,
4.8 Hz, 1H), 1.96–1.91 (m, 1H), 1.73–1.54 (br s, 5H), 1.53–1.49 (br s,
4H), and 1.49–1.42 (m, 9H, C(CH3)3). 13C NMR (125 MHz, CDCl3):
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2008.06.007.
References and notes
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165.6, 152.6, 152.0 (amide CO), 138.8, 138.6, 138.2, 131.9, 131.5,
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