Synthesis of n-octyl 2,6-dideoxy-α-l-lyxo-hexopyranosyl-(1→2)-3-amino-3-deoxy-β-d-galactopyranoside, an analog of the H-disaccharide antigen

Article abstract of DOI:10.1016/j.carres.2006.03.018

The synthesis of an analog of the H-disaccharide antigen (2), in which the galactopyranosyl moiety bears an amino group at C-3 and the fucopyranosyl residue is deoxygenated at C-2, is reported. The key reaction in the preparation of 2 was the glycosylatio

Full text of DOI:10.1016/j.carres.2006.03.018

Carbohydrate Research 341 (2006) 1702–1707
Note
Synthesis of n-octyl 2,6-dideoxy-a-L-lyxo-hexopyranosyl-
(1!2)-3-amino-3-deoxy-b-D-galactopyranoside,
an analog of the H-disaccharide antigen
Yu Bai,a Shuang-Jun Lin,a Guizhong Qi,a Monica M. Palcicb and Todd L. Lowarya,*
aDepartment of Chemistry and Alberta Ingenuity Centre for Carbohydrate Science, Gunning-Lemieux Chemistry Centre,
University of Alberta, Edmonton, Canada AB T6G 2G2
bThe Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
Received 18 February 2006; received in revised form 9 March 2006; accepted 14 March 2006
Available online 17 April 2006
Abstract—The synthesis of an analog of the H-disaccharide antigen (2), in which the galactopyranosyl moiety bears an amino group
at C-3 and the fucopyranosyl residue is deoxygenated at C-2, is reported. The key reaction in the preparation of 2 was the glyco-
sylation of an appropriately protected n-octyl 3-azido-3-deoxy-galactopyranoside derivative with a 2,6-dideoxy thioglycoside
promoted by 1-(phenylsulfinyl)piperidine and triflic anhydride. Disaccharide 2 is of interest in studies directed towards
understanding the molecular basis of substrate recognition by the blood group A and B glycosyltransferases.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: H-disaccharide antigen; Blood group; Synthesis; Inhibitor; Molecular recognition
The human A and B blood group antigens are among
the most well-known oligosaccharide antigens, and these
structural motifs, which are found in both glycolipids
and glycoproteins, play critical roles in organ trans-
plants and blood transfusions.1–3 These trisaccharide
antigens are biosynthesized4 from the H disaccharide
antigen by the action of either an N-acetylgalactosamin-
yltransferase (A antigen) or a galactosyltransferase (B
antigen), termed GTA and GTB, respectively (Fig. 1).
GTA and GTB are highly homologous, differing in only
four of the 354 amino acids,5 and over the past several
years a series of X-ray crystallographic and kinetics
studies on native and mutant proteins have revealed
the molecular basis for substrate discrimination by these
enzymes.6–12
ride 1, first synthesized in 1994,13 is a potent inhibitor
of both enzymes and has been shown to reduce the
expression of the A-antigen on cell surfaces.14 For
GTB, 1 is a competitive inhibitor with a Ki of 7.8 lM,
while for GTA the mode of inhibition is complex, and
the Ki is estimated to be approximately 200 nM.
HO
H2N
H3C
HO
OH
HO
H2N
H3C
HO
OH
O
O
O(CH2)7CH3
O(CH2)7CH3
O
O
O
O
OH
OH
OH
1
2
In the initial report describing this disaccharide,13 it
was proposed that the strong inhibition resulted from
an ionic interaction between the amino group, which is
protonated a physiological pH, and an anionic group
in the enzyme active site. In the crystal structure of 1
in complex with GTA,11 the disaccharide adopts a con-
formation different from the natural substrate, driven by
As part of these studies, the structures of both GTA
and GTB in complex with a disaccharide inhibitor (1)
in which the reactive hydroxyl group had been replaced
with an amino group moiety were solved.11 Disaccha-
*
Corresponding author. Tel.: +1 780 492 1861; fax: +1 780 492
7705; e-mail: tlowary@ualberta.ca
0008-6215/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2006.03.018

Y. Bai et al. / Carbohydrate Research 341 (2006) 1702–1707
1703
HO
HO
OH
O
HO
O
OH
O
AcNH
H3C
UDP-GalpNAc
GTA
OR
A
O
HO
HO
H3C
HO
OH
O
OH
O
OH
OR
HO
O
O
HO
HO
OH
OH
O
OH
HO
O
OH
UDP-Galp
GTB
O
H
HO
OR
B
O
H3C
HO
Figure 1. Biosynthesis of the A and B blood group antigens from the H antigen; R = glycoprotein or glycolipid.
O
OH
OH
the formation of an intramolecular hydrogen bond be-
tween the protonated amino group and the hydroxyl
group at C-2 of the fucopyranosyl ring. This conforma-
tional change substantially reorients the inhibitor in the
combining site, forcing the fucopyranose ring into a
region normally occupied by the donor, UDP-GalNAc.
The competition of 1 and the donor substrate for the
same region of the active site is consistent with the com-
plex mode of inhibition observed with this disaccharide.
We are interested in further probing the importance of
this intramolecular hydrogen bond on the manner by
which 1 inhibits GTA. Therefore, we report here the
synthesis of an H-disaccharide analog (2) in which the
hydroxyl group at C-3 of the galactopyranosyl ring is
replaced with an amino group, while C-2 of the fuco-
pyranosyl moiety is deoxygenated. This compound,
while maintaining the key amino group required for
inhibition, lacks the hydrogen bond acceptor that drives
the conformational change seen in the complex with
GTA.
derivative 3. Thus, reaction of 3 with boron trifluoride
etherate and p-thiocresol afforded thioglycoside 4 in
90% yield as a 1:3 a:b mixture of anomers. Conversion
of 3 into octyl glycoside 5 was achieved in 78% yield
upon treatment with n-octanol in the presence of N-iodo-
succinimide and silver triflate.16 The b-stereochemistry
of the newly formed glycosidic bond could be unambig-
uously determined from the 1H NMR spectrum of 5; the
multiplicity of the resonance for H-1 appeared as a dou-
blet with J1,2 7.9 Hz. We initially investigated the direct
conversion of 3 into 5 upon reaction with n-octanol and
a Lewis acid. However, when boron trifluoride etherate
was used, only small amounts of the product were ob-
served, even at extended reaction times. The use of a
stronger Lewis acid, tin tetrachloride, provided more
of the product; unfortunately, at the extended reaction
times required, anomerization of 5 to the corresponding
a-glycoside occurred to a significant degree. For this
reason, the indirect approach via thioglycoside 4 is pref-
erable. Treatment of 5 with a methanolic solution of
hydrogen chloride17 enabled the selective cleavage of
the acetate ester affording alcohol 6 in 92% yield.
The synthesis of 2 is shown in Scheme 1 and began
with the known15 3-azido-3-deoxy-galactopyranose
BzO
N3
BzO
N3
OBz
OBz
O
b
O
O(CH2)7CH3
AcO
R
OR
RO
N3
OR
O
5, R = Ac
6, R = H
3, R = OAc
4, R = STol
c
a
O(CH2)7CH3
O
e
STol
H3C
R'O
O
H3C
AcO
H3C
AcO
O
O
d
OR'
OAc
OAc
9, R = Bz, R' = Ac
10, R = R' = H
g
f
2
8
7
Scheme 1. Reagents and conditions: (a) p-TolSH, BF3ÆOEt2, CH2Cl2, 0 ꢁC, 90%; (b) n-octanol, NIS, AgOTf, CH2Cl2, 0 ꢁC!rt, 78%; (c) AcCl,
CH3OH, rt, 92%; (d) p-TolSH, (NH4)2Ce(NO3)6, CH3CN, ꢀ78 ꢁC!rt, 81%; (e) 1-(phenylsulfinyl)piperidine, Tf2O, 2,4,6-tri-tert-butylpyrimidine,
ꢀ60 ꢁC!rt, 48%; (f) NaOCH3, CH3OH, rt, 83%; (g) H2, Pd(OH)2/C, CH3OH, rt, 80%.

1704
Y. Bai et al. / Carbohydrate Research 341 (2006) 1702–1707
To synthesize the disaccharide, we chose to couple 6
Silica Gel 60 (40–60 mM). Iatrobead refers to a beaded
silica gel 6RS–8060, which is manufactured by Iatron
Laboratories (Tokyo). The ratio between silica gel and
crude product ranged from 100 to 50:1 (w/w). Optical
rotations were measured at 22 2 ꢁC and are in units
with thioglycoside 8, which was readily prepared in
one step and in 81% yield from 3,4-di-O-acetyl fucal
(7),18 by reaction with p-thiocresol and ceric ammonium
nitrite, a method reported recently by Paul and Jaya-
raman.19 With both 6 and 8 in hand, the standard N-iodo-
succinimide and silver triflate activation method was
investigated for the glycosylation reaction. However,
under these conditions only low yields of the desired
product were produced. We thus chose to use the 1-
(phenylsulfinyl)piperidine/triflic anhydride promoter
system developed recently by Crich and Smith,20 which
provided disaccharide 9 in a modest 48% yield. The
other reaction products were unreacted starting acceptor
and hydrolyzed donor. Regardless of the yield, sufficient
quantities of 9 were obtained, and treatment under Zem-
1
of degrees mL/g dm. H NMR spectra were recorded
at 500 or 600 MHz and chemical shifts are referenced
to either TMS (0.0, CDCl3) or HOD (4.78, D2O and
CD3OD). 13C NMR spectra were recorded at
125 MHz, and 13C chemical shifts are referenced to
internal CHCl3 (77.23, CDCl3), external acetone (31.07
D2O) or internal CHD2OD (48.9, CD3OD). Electro-
spray-ionization mass spectra (ESIMS) were recorded
on samples suspended in mixtures of THF with CH3OH
and added NaCl.
´
plen transesterification conditions (sodium methoxide in
1.2. n-Octyl 2,6-dideoxy-a-L-lyxo-hexopyranosyl-(1!2)-
3-amino-3-deoxy-b-D-galactopyranoside (2)
methanol) yielded the expected deacylated azidodisac-
charide 10 in 83% yield. This compound was then con-
verted to target 2 in 80% yield upon reaction with
To a solution of 10 (19 mg, 0.31 mmol) in CH3OH
(2.0 mL), 20% palladium hydroxide-on-carbon was
added, and the reaction was stirred under positive pres-
sure of hydrogen for 6 h. The resulting mixture was fil-
tered through Celite and concentrated to give a crude
residue that was purified by chromatography on Iatro-
beads using CH3OH as the eluant to yield 2 (14 mg,
80%) as a white foam after freeze drying: Rf 0.51
(CH3OH); [a]D ꢀ70.1 (c 0.2, H2O); 1H NMR
(600 MHz, D2O, dH) 5.23 (d, 1H, J 3.3 Hz, H-10), 4.39
(d, 1H, J 7.9 Hz, H-1), 4.23 (q, 1H, J 6.6 Hz, H-50),
4.04–3.98 (m, 1H, H-30), 3.92–3.87 (m, 2H, H-4, octyl
OCH2), 3.77–3.70 (m, 2H, H-6), 3.68–3.65 (m, 2H,
H-5, H-40), 3.65–3.58 (m, 1H, octyl OCH2), 3.46 (dd, 1H,
J 9.4, 7.9 Hz, H-2), 2.87 (dd, 1H, J 9.4, 2.7 Hz, H-3),
2.00 (dd, 1H, J 13.1, 5.0 Hz, H-20), 1.90 (ddd, 1H, J
13.1, 13.1, 3.3 Hz, H-20), 1.68–1.58 (m, 2H, octyl
CH2), 1.38–1.35 (m, 10H, octyl CH2), 1.20 (d, 3H, J
6.5 Hz, H-60), 0.88 (t, 3H, J 6.7 Hz, octyl CH3); 13C
NMR (125 MHz, CD3OD, dC) 103.08 (C-1), 100.07
(C-10), 78.47 (C-2), 77.14 (C-5), 71.40 (C-40), 71.06 (octyl
OCH2), 69.82 (C-4), 67.89 (C-50), 66.02 (C-30), 61.58
(C-6), 57.07 (C-3), 32.29 (C-20), 32.09 (octyl CH2),
30.01 (octyl CH2), 29.81 (octyl CH2), 29.68 (octyl
CH2), 26.48 (octyl CH2), 23.14 (octyl CH2), 17.16
(C-60), 14.49 (octyl CH3); ESIMS: m/z calcd for
[C20H40NO8]H+: 422.2748. Found 422.2745.
1
hydrogen and palladium hydroxide-on-carbon. The H
and 13C NMR spectra for 2 were consistent with the
proposed structure. Thus, the anomeric hydrogen of
the fucopyranosyl residue appeared as a doublet (J1,2ax
3.3 Hz; J1,2eq 0 Hz) at 5.23 ppm, while the anomeric car-
bon resonated at 100.07 ppm. Both these data support
the a-stereochemistry of this residue. In addition, the
amino group at C-3 in the galactopyranose residue
could be confirmed by the appearance of the resonance
for H-3 as a doublet of doublets (J3,4 2.7 Hz; J2,3 9.4 Hz)
at 2.87 ppm in the 1H NMR spectrum. In the 13C NMR
spectrum, C-3 of the galactopyranose residue appeared
at 57.07 ppm, consistent with its attachment to an
amino group.
In summary, we describe here the synthesis of an ana-
log of the H-disaccharide in which the galactopyranose
moiety is modified by the substitution of the hydroxyl
group at C-3 with an amino group and in which the
C-2 position of the fucopyranosyl moiety is deoxygen-
ated. X-ray crystallographic and kinetics studies of this
compound with GTA and GTB are in progress and will
be reported in the future.
1. Experimental
1.1. General methods
1.3. p-Tolyl 2-O-acetyl-3-azido-4,6-di-O-benzoyl-3-
deoxy-1-thio-b-D-galactopyranoside (4)
Reactions were carried out in oven-dried glassware.
Solvents were distilled from appropriate drying agents
before use. Unless stated otherwise, all reactions were
carried out under a positive pressure of argon and were
monitored by TLC on Silica Gel 60 F254 (0.25 mm, E.
Merck). Spots were detected under UV light or by char-
ring with 10% H2SO4, in EtOH. Unless otherwise indi-
cated, all column chromatography was performed on
To a solution of p-thiocresol (98 mg, 0.77 mmol) and
1,2-di-O-acetyl-3-azido-4,6-di-O-benzoyl-3-deoxy-b-D-
galactopyranoside (3)15 (349 mg, 0.70 mmol) in dry
CH2Cl2 (15 mL), BF3ÆEt2O (0.88 mL, 7.0 mmol) was
added at 0 ꢁC. The reaction mixture was stirred at
0 ꢁC for 6 h and then diluted with CH2Cl2 (20 mL),

Y. Bai et al. / Carbohydrate Research 341 (2006) 1702–1707
1705
washed with satd aq NaHCO3 (3 · 20 mL), dried
(Na2SO4), and concentrated. Chromatography (4:1 hex-
anes–EtOAc) yielded 4 (354 mg, 90%) in a 1:3 a:b ratio
as a colorless syrup. Data for b anomer: Rf 0.67 (2:1 hex-
anes–EtOAc); [a]D ꢀ2.9 (c 2.0, CH2Cl2); 1H NMR
(500 MHz, CDCl3, dH): 8.04–8.01 (m, 2H, Ar), 7.98–
7.95 (m, 2H, Ar), 7.63–7.57 (m, 2H, Ar), 7.48–7.42 (m,
6H, Ar), 7.03 (d, 2H, J 8.3 Hz, Ar), 5.79 (d, 1H, J
3.2 Hz, H-4), 5.30 (dd, 1H, J 9.9, 9.9 Hz, H-2), 4.71
(d, 1H, J 9.9 Hz, H-1), 4.51 (dd, 1H, J 11.5, 7.1 Hz,
H-6), 4.38 (dd, 1H, J 11.5, 5.5 Hz, H-6), 4.14 (dd, 1H,
J 7.1, 5.5 Hz, H-5), 3.82 (dd, 1H, J 9.9, 3.2 Hz, H-3),
2.36 (s, 3H, tolyl CH3), 2.21 (s, 3H, acetyl CH3); 13C
NMR (125 MHz, CDCl3, dC): 169.31 (CO), 166.02
(CO), 165.34 (CO), 138.52 (Ar), 133.91 (Ar · 2),
133.69 (Ar), 133.28 (Ar), 130.17 (Ar · 2), 129.82
(Ar · 2), 129.62 (Ar · 2), 129.47 (Ar), 128.63 (Ar),
128.53 (Ar · 2), 128.42 (Ar · 2), 127.77 (Ar), 86.47 (C-
1), 75.64 (C-5), 68.54 (C-4), 68.52 (C-2), 63.33 (C-3),
62.51 (C-6), 21.26 (tolyl CH3), 20.94 (acetyl CH3); IR:
2109 cmꢀ1 (N3); ESIMS: m/z calcd for [C29H27N3O7S]-
Na+: 584.1462. Found: 584.1463.
3), 62.01 (C-6), 31.80 (octyl CH2), 29.43 (octyl CH2),
29.27 (octyl CH2), 25.84 (octyl CH2), 22.64 (octyl
CH2), 20.77 (acetyl CH3), 14.08 (octyl CH3); IR:
2107 cmꢀ1 (N3); ESIMS: m/z calcd for [C30H37N3O]-
Na+: 590.2473. Found 590.2472.
1.5. n-Octyl 3-azido-4,6-di-O-benzoyl-3-deoxy-b-D-
galactopyranoside (6)
Compound 5 (152 mg, 0.27 mmol) was dissolved in 50:1
CH3OH–AcCl (5.1 mL), and the solution was stirred for
24 h. The reaction mixture was quenched by the addi-
tion of satd aq NaHCO3 and then diluted with CH2Cl2
(20 mL). After being washed with water (20 mL) and a
satd NaCl solution (20 mL), the organic layer was dried
with Na2SO4 and concentrated. Chromatography (4:1
hexanes–EtOAc) gave 6 (130 mg, 92%) as a colorless
oil: Rf 0.73 (2:1 hexanes–EtOAc); [a]D +0.4 (c 1.5,
1
CH2Cl2); H NMR (500 MHz, CDCl3, dH): 8.12–8.09
(m, 2H, Ar), 8.05–8.01 (m, 2H, Ar), 7.62–7.55 (m, 2H,
Ar), 7.49–7.42 (m, 4H, Ar), 5.73 (dd, 1H, J 3.5,
1.0 Hz, H-4), 4.55 (dd, 1H, J 11.3, 6.6 Hz, H-6), 4.42
(d, 1H, J 7.7 Hz, H-1), 4.32 (dd, 1H, J 11.3, 6.5 Hz,
H-6), 4.09 (ddd, 1H, J 6.6, 6.5, 1.0 Hz, H-5), 3.99–3.93
(m, 2H, H-2, octyl OCH2), 3.71 (dd, 1H, J 10.3,
3.5 Hz, H-3), 3.59 (ddd, 1H, J 9.6, 7.0, 7.0 Hz, octyl
OCH2), 1.72–1.62 (m, 2H, octyl CH2), 1.40–1.23 (m,
10H, octyl CH2), 0.89 (t, 3H, J 7.0 Hz, octyl CH3);
13C NMR (125 MHz, CDCl3, dC): 166.05 (CO), 165.44
(CO), 133.57 (Ar), 133.27 (Ar), 130.11 (Ar · 2), 129.76
(Ar · 2), 129.50 (Ar), 128.99 (Ar), 128.51 (Ar · 2),
128.44 (Ar · 2), 103.38 (C-1), 72.07 (C-5), 70.96 (C-2),
70.67 (octyl OCH2), 68.30 (C-4), 63.30 (C-3), 62.12 (C-
6), 31.79 (octyl CH2), 29.56 (octyl CH2), 29.33 (octyl
CH2), 29.22 (octyl CH2), 25.93 (octyl CH2), 22.64 (octyl
CH2), 14.08 (octyl CH3); IR: 2110 cmꢀ1 (N3); ESIMS:
m/z calcd for [C28H35N3O7]Na+: 548.2367. Found:
548.2365.
1.4. n-Octyl 2-O-acetyl-3-azido-4,6-di-O-benzoyl-3-
deoxy-b-D-galactopyranoside (5)
To a mixture of 4 (262 mg, 0.47 mmol), n-octanol
˚
(88 lL, 0.56 mmol) and 4 A molecular sieves (100 mg)
in CH2Cl2 (15 mL), N-iodosuccinimide (332 mg,
1.40 mmol), and silver triflate (120 mg, 0.47 mmol) were
added in succession at 0 ꢁC. After stirring for 15 min at
0 ꢁC, the reaction mixture was warmed to room temper-
ature and stirred for 1 h. The reaction mixture turned
dark red, and Et3N was added, diluted with CH2Cl2
(25 mL), and filtered through Celite. The filtrate was
washed with satd aq Na2S2O3 (3 · 30 mL), dried
(Na2SO4) and concentrated to give a crude residue that
was purified by chromatography (4:1 hexanes–EtOAc)
to give 5 (208 mg, 78%) as a colorless oil: Rf 0.58 (3:1
1
hexanes–EtOAc); [a]D +14.2 (c 0.9, CH2Cl2); H NMR
1.6. p-Tolyl 3,4-di-O-acetyl-2,6-dideoxy-1-thio-a-L-lyxo-
hexopyranoside (8)
(500 MHz, CDCl3, dH): 8.14–8.12 (m, 2H, Ar), 8.04–
8.02 (m, 2H, Ar), 7.63–7.56 (m, 2H, Ar), 7.50–7.43 (m,
4H, Ar), 5.80 (dd, 1H, J 3.4, 1.0 Hz, H-4), 5.31 (dd,
1H, J 10.5, 7.9 Hz, H-2), 4.56 (dd, 1H, J 11.3, 6.6 Hz,
H-6), 4.54 (d, 1H, J 7.9 Hz, H-1), 4.33 (dd, 1H, J 11.3,
5.6 Hz, H-6), 4.11 (ddd, 1H, J 6.6, 5.6, 1.0 Hz, H-5),
3.92 (ddd, 1H, J 9.7, 6.2, 6.2 Hz, octyl OCH2), 3.78
(dd, 1H, J 10.5, 3.4 Hz, H-3), 3.52 (ddd, 1H, J 9.7,
6.8, 6.8 Hz, octyl OCH2), 2.14 (s, 3H, acetyl CH3),
1.65–1.54 (m, 2H, octyl CH2), 1.37–1.23 (m, 10H, octyl
CH2), 0.89 (t, 3H, J 7.0 Hz, octyl CH3); 13C NMR
(125 MHz, CDCl3, dC): 169.21 (CO), 166.06 (CO),
165.50 (CO), 133.68 (Ar), 133.29 (Ar), 130.20 (Ar · 2),
129.77 (Ar · 2), 129.46 (Ar), 128.75 (Ar), 128.58
(Ar · 2), 128.45 (Ar · 2), 101.58 (C-1), 71.97 (C-5),
70.28 (octyl OCH2), 70.20 (C-2), 68.35 (C-4), 62.12 (C-
To a solution of 3,4-di-O-acetyl-L-fucal (7)18 (0.32 g,
1.49 mmol) in CH3CN (10 mL), (NH4)2Ce(NO3)6
(0.41 g, 0.75 mmol) and p-thiocresol (0.92 g, 7.4 mmol)
were added at ꢀ78 ꢁC. The mixture was allowed to
warm to room temperature slowly over 4 h. The reaction
mixture was diluted with CH2Cl2 (30 mL) and then
washed with satd aq Na2S2O3 and satd aq NaHCO3 be-
fore being dried over MgSO4. The residue obtained after
concentration of the organic layer was purified by chro-
matography (9:1 hexanes–EtOAc) to give 8 (0.41 g,
81%) as a white solid: Rf 0.24 (6:1 hexanes–EtOAc);
[a]D ꢀ304.9 (c 1.4, CH3OH); 1H NMR (500 MHz,
CDCl3, dH): 7.34 (d, 2H, J 8.2 Hz, Ar), 7.12 (d, 2H, J
8.2 Hz, Ar), 5.66 (d, 1H, J 5.7 Hz, H-1), 5.31–5.26 (m,

1706
Y. Bai et al. / Carbohydrate Research 341 (2006) 1702–1707
1H, H-3), 5.23 (br s, 1H, H-4), 4.56 (q, 1H, J 6.5 Hz, H-
5), 2.44 (td, 1H, J 12.9, 5.7 Hz, H-2), 2.33 (s, 3H, tolyl
CH3), 2.16 (s, 3H, acetyl CH3), 2.05 (dd, 1H, J 12.9,
5.0 Hz, H-2), 2.01 (s, 3H, acetyl CH3), 1.15 (d, 3H, J
6.5 Hz, H-6); 13C NMR (125 MHz, CDCl3, dC): 170.57
(CO), 169.93 (CO · 2), 137.38 (Ar), 131.69 (Ar · 2),
130.80 (Ar) 129.74 (Ar · 2), 84.04 (C-1), 69.76 (C-4),
67.27 (C-3), 65.67 (C-5), 30.51 (C-2), 21.08 (acetyl
CH3), 20.88 (acetyl CH3), 16.44 (C-6); ESIMS: m/z calcd
for [C17H22O5S]Na+: 361.1080. Found: 361.1081.
14.08 (octyl CH3); IR: 2108 cmꢀ1 (N3); ESIMS: m/z
calcd for [C38H49N3O12]Na+: 762.3208. Found:
762.3206.
1.8. n-Octyl 2,6-dideoxy-a-L-lyxo-hexopyranosyl-(1!2)-
3-azido-3-deoxy-b-D-galactopyranoside (10)
To a solution of 9 (62 mg, 0.08 mmol) in CH3OH (3 mL)
and CH2Cl2 (3 mL), solid NaOCH3 was added until the
pH was ꢁ10. The solution was allowed to stir at room
temperature for 5 h, followed by neutralization with
HOAc. The resulting mixture was concentrated, and
the residue was purified by chromatography (10:1
CH2Cl2–CH3OH), to yield 8 (31 mg, 83%) as a colorless
semisolid: Rf 0.31 (10:1 CH2Cl2–CH3OH); [a]D ꢀ40.2 (c
1.7. n-Octyl 3,4-di-O-acetyl-2,6-dideoxy-a-L-lyxo-hexo-
pyranosyl-(1!2)-3-azido-4,6-di-O-benzoyl-3-deoxy-b-D-
galactopyranoside (9)
1
Donor 7 (135 mg, 0.40 mmol), 1-(phenylsulfinyl)piperi-
dine (83 mg, 0.4 mmol), 2,4,6-tri-tert-butylpyrimidine
0.4, CH2Cl2); H NMR (500 MHz, CD3OD, dH): 5.23
(d, 1H, J 3.3 Hz, H-10), 4.34 (d, 1H, J 7.7 Hz, H-1),
4.29 (q, 1H, J 6.6 Hz, H-50), 3.98 (d, 1H, J 3.1 Hz, H-
4), 3.94–3.86 (m, 2H, H-30, octyl OCH2), 3.74 (dd, 1H,
J 10.3, 7.7 Hz, H-2), 3.70 (dd, 2H, J 6.6 Hz, H-6),
3.54–3.48 (m, 3H, H-40, H-5, octyl OCH2), 3.48 (dd,
1H, J 10.3, 3.1 Hz, H-3), 1.91 (ddd, 1H, J 12.7, 12.7,
3.3 Hz, H-20), 1.82 (dd, 1H, J 12.7, 5.2 Hz, H-20),
1.62–1.55 (m, 2H, octyl CH2), 1.39–1.25 (m, 10H, octyl
CH2), 1.17 (d, 3H, J 6.6 Hz, H-60), 0.90 (dd, 3H, J 7.1,
6.8 Hz, octyl CH3); 13C NMR (125 MHz, CD3OD,
dC): 103.79 (C-1), 99.25 (C-10), 77.11 (C-5), 74.24 (C-
2), 72.45 (C-40), 70.75 (octyl OCH2), 69.37 (C-4), 68.40
(C-3), 67.90 (C-50), 66.83 (C-30), 62.23 (C-6), 33.34 (C-
20), 33.03 (octyl CH2), 30.97 (octyl CH2), 30.62 (octyl
CH2), 30.45 (octyl CH2), 27.37 (octyl CH2), 23.72 (octyl
CH2), 17.30 (C-60), 14.43 (octyl CH3); IR: 2104 cmꢀ1
(N3); ESIMS: m/z calcd for [C20H37N3O8]Na+:
470.2473. Found: 470.2471.
˚
(200 mg, 0.8 mmol) and 4 A molecular sieves (150 mg)
were dried for 4 h under vacuum in the presence of
P2O5. To this mixture in CH2Cl2 (15 mL), triflic anhy-
dride (72 lL, 0.44 mmol) was added at ꢀ60 ꢁC. After
stirring for 10 min, a solution of vacuum-dried 6 in
CH2Cl2 (3 mL) was added via a syringe. After 40 min,
the reaction mixture was warmed to room temperature
and stirred continuously for 24 h. Satd aq NaHCO3
was added, and the resulting solution was diluted with
CH2Cl2 (25 mL) and filtered through Celite. The filtrate
was washed with satd aq NaHCO3 (30 mL), dried
(Na2SO4), and concentrated to give a crude residue that
was purified by chromatography (5:1 hexanes–EtOAc)
to give 9 (71 mg, 48%) as colorless oil: Rf 0.43 (4:1 hex-
anes–EtOAc); [a]D ꢀ35.2 (c 0.8, CH2Cl2); 1H NMR
(500 MHz, CDCl3, dH): 8.12–8.09 (m, 2H, Ar), 8.05–
8.02 (m, 2H, Ar), 7.63–7.55 (m, 2H, Ar), 7.49–7.42 (m,
4H, Ar), 5.77 (d, 1H, J 3.3 Hz, H-4), 5.33–5.27 (m,
2H, H-10, H-30), 5.19 (br s, 1H, H-40), 4.55 (dd, 1H, J
11.3, 6.8 Hz, H-6), 4.48 (q, 1H, J 6.6 Hz, H-50), 4.46
(d, 1H, J 7.6 Hz, H-1), 4.32 (dd, 1H, J 11.3, 6.5 Hz,
H-6), 4.08 (dd, 1H, J 6.8, 6.5 Hz, H-5), 3.89 (ddd, 1H,
J 9.2, 7.9, 7.9 Hz, octyl OCH2), 3.84 (dd, 1H, J 10.1,
7.6 Hz, H-2), 3.75 (dd, 1H, J 10.1, 3.3 Hz, H-3), 3.55
(ddd, 1H, J 9.2, 7.8, 7.8 Hz, octyl OCH2), 2.16 (s, 3H,
acetyl CH3), 2.09 (ddd, 1H, J 12.8, 12.8, 3.8 Hz, H-20),
2.00 (s, 3H, acetyl CH3), 1.97 (m, 1H, H-20), 1.69–1.61
(m, 2H, octyl CH2), 1.37–1.23 (m, 10H, octyl CH2),
1.15 (d, 3H, J 6.6 Hz, H-60), 0.89 (t, 3H, J 6.9 Hz, octyl
CH3); 13C NMR (125 MHz, CDCl3, dC): 170.76 (CO),
170.15 (CO), 166.03 (CO), 165.57 (CO), 133.60 (Ar),
133.27 (Ar), 130.14 (Ar · 2), 129.75 (Ar · 2), 129.51
(Ar), 128.91 (Ar), 128.53 (Ar · 2), 128.44 (Ar · 2),
102.30 (C-1), 98.50 (C-10), 74.48 (C-2), 71.76 (C-5),
70.44 (octyl OCH2), 69.91 (C-40), 68.51 (C-4), 66.54
(C-30), 65.52 (C-3), 65.27 (C-50), 62.09 (C-6), 31.77 (octyl
CH2), 29.94 (octyl CH2), 29.61 (octyl CH2), 29.34 (octyl
CH2), 29.22 (C-20), 25.93 (octyl CH2), 22.62 (octyl CH2),
20.94 (acetyl CH3), 20.75 (acetyl CH3), 16.48 (C-60),
Acknowledgements
This work was supported by the Alberta Ingenuity Cen-
tre for Carbohydrate Science, The University of Alberta
and The Natural Sciences and Engineering Research
Council of Canada.
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