Synthesis of the trisaccharide repeating unit related to Klebsiella 012 serotype

Article abstract of DOI:10.1016/j.carres.2008.08.006

Synthesis of the trisaccharide, allyl α-l-rhamnopyranosyl-(1→3)-2-acetamido-2-deoxy-β-d-glucopyranosyl-(1→4)-α-l-rhamnopyranoside related to O-chain glycans isolated from the deaminated LPSs of Klebsiella pneumoniae serotype 012, was achieved through condensation of suitably synthesized disaccharide, allyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-β-d-glucopyranosyl-(1→4)-2,3-di-O-benzoyl-α-l-rhamnopyranoside and donor, ethyl 2,3,4-tri-O-acetyl-1-thio α-l-rhamnopyranoside starting from l-rhamnose and d-glucosamine hydrochloride. The trisaccharide can be utilized for the synthesis of neoglycoconjugates for use as a synthetic vaccine by coupling it with a suitable protein after deprotection. Various regio- and stereoselective protecting group strategies have been carefully considered, as protecting groups can influence the reactivity of the electrophile and nucleophile in glycosylation reactions on the basis of steric and electronic requirements.

Full text of DOI:10.1016/j.carres.2008.08.006

Carbohydrate Research 343 (2008) 2822–2825
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Note
Synthesis of the trisaccharide repeating unit related to Klebsiella 012 serotype
*
Jayant Srivastava, Anakshi Khare, Naveen K. Khare
Department of Chemistry, Lucknow University, Lucknow 226 007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of the trisaccharide, allyl a-L-rhamnopyranosyl-(1?3)-2-acetamido-2-deoxy-b-D-glucopyrano-
Received 31 July 2008
Accepted 5 August 2008
Available online 12 August 2008
syl-(1?4)-
siella pneumoniae serotype 012, was achieved through condensation of suitably synthesized disaccharide,
allyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-b- -glucopyranosyl-(1?4)-2,3-di-O-benzoyl- -rhamno-
pyranoside and donor, ethyl 2,3,4-tri-O-acetyl-1-thio -rhamnopyranoside starting from -rhamnose
and -glucosamine hydrochloride. The trisaccharide can be utilized for the synthesis of neoglycoconju-
a-L-rhamnopyranoside related to O-chain glycans isolated from the deaminated LPSs of Kleb-
D
a-L
a-
L
L
Keywords:
Synthesis
Klebsiella 012 serotype
Trisaccharide
Repeating unit
Glycosylation
D
gates for use as a synthetic vaccine by coupling it with a suitable protein after deprotection. Various
regio- and stereoselective protecting group strategies have been carefully considered, as protecting
groups can influence the reactivity of the electrophile and nucleophile in glycosylation reactions on
the basis of steric and electronic requirements.
Ó 2008 Elsevier Ltd. All rights reserved.
The study in the field of complex oligosaccharides related to
bacterial O-LPS has proven to be a principal component of many
biological and medicinal studies in recent years.1–8 The synthesis
of terminal units of the bacterial O-antigens, in combination with
the strategies for the covalent attachment of the hapten to the so-
lid support, permits the use of these compounds as substitutes for
polysaccharides of bacterial origin in several serological tests and
eventually as vaccines.9–14 Vaccines containing bacterial toxins,
for example, lipids, when incorporated as part of the lipopolysac-
charide, cause undesired side effects, thus restraining vaccine
development. With an objective to gain detailed insight into the
structural requirements for studying the pharmacological param-
eters of the biological repeating units of bacterial O-LPS, attention
has been focused on the synthesis of hapten moieties, since it has
been reported that the small carbohydrate epitopes can provoke
vides a two-carbon chain linker arm that is superior to other
widely known linker arms.21 The structure of the repeating unit
has the following structural framework:22
For the synthesis of this trisaccharide, allyl 2,3,4-tri-O-acetyl-
a-L-
rhamnopyranoside23 (1) was prepared from
L
-rhamnose through
an unreported method by acetylating it to the tetra-O-acetyl deriv-
ative, followed by treatment with allyl alcohol and boron trifluoride
diethyl etherate,24 affording 1 as syrup in 70% yield. Compound 1
was deacetylated using the Zemplén method, followed by isopro-
pylidenation with 2,2-dimethoxypropane to yield allyl 2,3-O-iso-
propylidene-
suitably chloroacetylated26 at C-4 using chloroacetyl chloride in
pyridine to afford allyl 4-O-chloroacetyl-2,3-O-isopropylidene-
a
-L
-rhamnopyranoside (2).25 Compound
2
was
the formation of antibodies.15–17 Klebsiella pneumoniae is
a
a-L-
Gram-negative, non-motile, encapsulated, lactose-fermenting, fac-
ultative anaerobic found in the normal flora of the mouth, skin,
and intestines.18 Members of the Klebsiella genus typically express
two types of antigens on their cell surface. The first, O antigen, is
a lipopolysaccharide of which nine varieties exist. The second is K
antigen, a capsular polysaccharide with more than 80 varieties.19
Both contribute to pathogenicity and form the basis for
subtyping.
rhamnopyranoside (3). Removal of the isopropylidene ring of
3 was accomplished by aqueous acetic acid to give allyl 4-O-chloro-
acetyl-
to give allyl 2,3-di-O-benzoyl-4-O-chloroacetyl-
side (5), which was then dechloroacetylated using thiourea26 to
give allyl 2,3-di-O-benzoyl- -rhamnopyranoside (6). Compound
a-L-rhamnopyranoside (4). Compound 4 was then benzoylated
a-L
-rhamnopyrano-
a-L
6 served as an acceptor for the synthesis of the disaccharide frag-
ment present at the reducing end of Klebsiella serotype 012 strain
(Scheme 1).
This paper illustrates the synthesis of the repeating unit of the
oligosaccharide from K. pneumoniae O12 serotype in the form of al-
lyl glycosides that may be conjugated20 to BSA. The allyl group pro-
In a separate experiment ethyl 4,6-O-benzylidene-3-O-chloro-
acetyl-2-deoxy-2-phthalimido-1-thio-b-
synthesized27 from
-glucosamineꢀHCl that served as donor for
the synthesis of the disaccharide fragment present at the reducing
end of the trisaccharide. Compound was condensed with
D-glucopyranoside (7) was
D
* Corresponding author. Tel.: +91 522 2740421.
E-mail address: nkhare58@gmail.com (N. K. Khare).
7
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.08.006

J. Srivastava et al. / Carbohydrate Research 343 (2008) 2822–2825
2823
OAll
OAll
OH
O
b,c
a
O
O
HO
RO
AcO
HO
O
AcO
OH
O
OAc
L-Rhamnose
C
1
2. R = H
3. R = COCH2Cl
d
Ph
O
OAll
O
O
SEt
ClH2CC(O)O
O
e
7
NPhth
RO
h
R'O
OR'
4. R = COCH2Cl, R' = H
f
g
5. R = COCH2Cl, R' = Bz
6
. R = H, R' = Bz
SEt
O
AcO
OAll
Ph
O
AcO
O
10
OAc
O
O
RO
O
j
BzO
NPhth
OBz
8. R = COCH2Cl
9. R = H
OAll
i
O
O
Ph
O
O
O
O
BzO
NPhth
OBz
O
11
AcO
AcO
OAc
OAll
HO
HO
O
O
O
O
HO
NHAc
k
OH
O
12
HO
HO
OH
Scheme 1. Reagents and conditions: (a) Ac2O/Pyr/EtSH/BF3ꢀOEt2/0 °C, rt/4 h; (b) NaOMe/MeOH (1 M)/4 h; (c) 2,2 DMP/acetone/p-TSA, rt/6 h; (d) ClCH2COCl/Pyr/CH2Cl2/0 °C,
rt/16 h; (e) 80% aqueous HOAc/80 °C/7 h; (f) BzCl/Pyr/0 °C, rt/2 h; (g) thiourea/3:2 MeOH–H2Cl2, rt/3 h; (h)NIS/TMSOTf /CH2Cl2/MS-4 Å/0 °CC/20 min; (i) thiourea/3:2
MeOHCH2Cl2/rt/3 h; (j) NIS/TMSOTf/CH2Cl2/MS-4 Å/0 °C/20 min; (k) ethylinediamine, n-butanol, 90 °C/20 h, Ac2O-Pyr, rt/14 h, 80% aqueous HOAc, 80 °C/4 h, MeONa/MeOH,
rt/6 h.
acceptor 6 in the presence of N-iodosuccinimide and trimethylsilyl
triflate as promoter28 to afford the disaccharide, allyl 4,6-O-benzyl-
idene-3-O-chloroacetyl-2-deoxy-2-phthalimido-b-D-glucopyrano-
zoyl-a-L
-rhamnopyranoside (11) in 40% yield. The 1H NMR
spectrum of 11 showed a doublet of 9.0 Hz for one proton at d
5.35 for the H-10 of b-GlcNPhth along with a doublet of 1.2 Hz at
syl-(1?4)-2,3-di-O-benzoyl-
a
-
L
-rhamnopyranoside (8), as a foam
4.85 for H-1 of a a-Rha2.
-Rha1 and a singlet at 4.75 for H-100 of
in 69% yield. The 1H NMR spectrum showed a doublet of 9.3 Hz
The C NMR spectrum showed peaks at 98.6 (C-10), 97.1 (C-100)
and 96.3 (C-1) for the three anomeric carbons. The structure of
the trisaccharide (11) is also supported by its 2D HSQC spectrum
and ESIMS, which showed m/z 1086 (M+Na)+. Removal of the
phthalimido group using ethylenediamine and n-butanol,30 fol-
lowed by debenzylidenation and deacylation, afforded the target
trisaccharide (12) in 58% yield (Scheme 1). The structure of 12
was confirmed by NMR spectroscopy and ESIMS. The 1H NMR spec-
trum of 12 showed a doublet of 7.8 Hz for one proton at d 4.99 for
the H-10 of b-GlcNAc along with two singlets at d 4.75 and 4.59 of
13
at d 5.55 for H-10 of b-GlcNPhth and a doublet of 1.2 Hz at d 4.86
for H-1 of
the disaccharide 8 using thiourea26 yields the acceptor, allyl 4,6-
O-benzylidene-2-deoxy-2-phthalimido-b- -glucopyranosyl-(1?4)-
2,3-di-O-benzoyl- -rhamnopyranoside (9), which was
-rhamnopyr-
a-Rha1. Selective removal of the chloroacetyl group of
D
a-L
condensed with ethyl 2,3,4-tri-O-acetyl-1-thio-a-L
anoside29 (10) in the presence of N-iodosuccinimide and
trimethylsilyl triflate as promoter28 to yield the trisaccharide, allyl
2,3,4-tri-O-acetyl-a-L-rhamnopyranosyl-(1?3)-4,6-O-benzylidene-
2-deoxy-2-phthalimido-b-
D
-glucopyranosyl-(1?4)-2,3-di-O-ben-
one proton each for the H-1 and H-100 of
a-Rha1 and a-Rha2,

2824
J. Srivastava et al. / Carbohydrate Research 343 (2008) 2822–2825
respectively. The structure of the trisaccharide (12) is also sup-
ported by its by ESIMS at m/z 554 (M + H)+.
2H, –COCH2Cl), 4.03–3.91 (m, 3H, –CHHCHCH2, H-2, H-3), 3.86–
3.78 (m, 1H, H-5), 1.21 (d, 3H, J 6.3 Hz, 6–CH3). Anal. Calcd for
C11H17ClO6: C, 47.07; H, 6.10. Found C, 47.02; H, 6.13.
1. Experimental
1.5. Allyl 2,3-di-O-benzoyl-4-O-chloroacetyl-a-L-
rhamnopyranoside (5)
1.1. General experimental methods
All reactions were monitored by TLC on Silica Gel G (E. Merck).
Column chromatography was performed using silica gel (SRL, 60–
120 mesh). Solvents were dried and distilled before use, and evap-
orations were conducted at 40 °C unless otherwise stated. Optical
rotations were measured at 25 °C on AA-5 series polarimeter. 1H
NMR spectra were recorded on a Bruker DPX 300 spectrometer
using CDCl3 as solvent (TMS as internal standard) unless otherwise
stated. Melting points were determined on Büchi 540 melting
point apparatus. The mass spectra were recorded on a Jeol SX
102 mass spectrometer for FABMS and Micromass Quattro II
ESIMS. The disaccharides 8 and 9 and the trisaccharide 11 were
confirmed by a 2D HSQC experiment as well.
A mixture of BzCl (2.2 mL, 18.8 mmol) and pyridine (1.5 mL,
18.4 mmol) was added dropwise at 0 °C into a solution of 4
(1.0 g, 3.6 mmol) in CH3CN (15 mL). The mixture was stirred for
2 h at rt, poured into water and extracted with CH2Cl2. The com-
bined extract was washed successively with dil HCl and aq NaH-
CO3, and brine, dried, and concentrated. Chromatography (9:1
n-hexane–EtOAc) of the residue afforded 5 (1.5 g, 85%), as crystals:
mp 80.5–82.3 °C, ½a D25
ꢁ
+55.2 (c 0.4, CHCl3). 1H NMR: d 8.13–7.31 (m,
10H, aromatic protons) 6.01–5.89 (m, 1H, –CH2CHCH2), 5.70 (dd,
1H, J2,3 3.3 Hz, J3,4 9.9 Hz, H-3), 5.63 (d, 1H, J1,2 1.5 Hz, H-2), 5.49
(t, 1H, J3,4,5 10.2 Hz, H-4), 5.42–5.24 (m, 2H, –CH2CHCH2), 5.01 (s,
1H, H-1), 4.29–4.23 (m, 1H, –CHHCHCH2), 4.16–4.01 (m, 2H,
–CHHCHCH2, H-5), 3.97, 3.95 (2s, 2H, –COCH2Cl), 1.34 (d, 3H, J
6.3 Hz, 6-CH3). Anal. Calcd for C25H25ClO8: C, 61.42; H, 5.15. Found:
C, 61.39; H, 5.17.
1.2. Allyl 2,3,4 tri-O-acetyl-a-L-rhamnopyranoside (1)
Rhamnose (5.0 g, 30.48 mmol) was conventionally acetylated
using Ac2O (25 mL) and pyridine (25 mL) to give the acetylated
product. The crude product (8.14 g, 24.68 mmol) was dissolved in
dry CH2Cl2 (95 mL) and allyl alcohol (3.90 mL, 49.4 mmol), and
BF3ꢀOEt2 (7.8 mL, 61.7 mmol) was added dropwise at 0 °C. The
solution was then allowed to stir for 4 h at 0 °C and washed succes-
sively with satd aq NaHCO3, brine, dried, and concentrated. Chro-
matography (8:2 n-hexane–EtOAc,) of the residue afforded 123
1.6. Allyl 2,3-di-O-benzoyl-a-L-rhamnopyranoside (6)
A solution of compound 6 (1.2 g, 2.5 mmol) and thiourea
(0.93 g, 12.3 mmol) in a mixture of MeOH (30 mL) and CH2Cl2
(20 mL) was stirred at rt for 3 h and concentrated. The residue
was dissolved in CH2Cl2, washed with water, dried, and concen-
trated. Chromatography (9:1 n-hexane–EtOAc) of the residue affor-
(5.7 g, 70%) as syrup: ½a D25
ꢁ
ꢂ53.7 (c 1.3, CHCl3). 1H NMR: d 5.94–
ded 6 as syrup (0.8 g, 80%), ½a D25
ꢁ
+35 (c 1.3, CHCl3). 1H NMR: d 8.13–
5.83 (m, 1H, –CH2CHCH2), 5.35–5.20 (m, 4H, H-2, H-3,
–CH2CHCH2), 5.07 (t, 1H, J3,4,5 9.9 Hz, H-4), 4.78 (d, 1H, J1,2 1.5 Hz,
H-1), 4.22–4.15 (m, 1H, CHHCHCH2), 4.04–3.97 (m, 1H,
–CHHCHCH2), 3.95–3.87 (m, 1H, H-5), 2.14, 2.04, 1.98 (s, 3H each,
7.32 (m, 10H, aromatic protons) 5.97–5.88 (m, 1H, –CH2CHCH2),
5.60 (d 1H, J2,3 1.5 Hz, H-2), 5.54 (dd, 1H, J2,3 3.3 Hz, J3,4 9.6 Hz,
H-3), 5.38–5.22 (m, 2H, –CH2CHCH2), 4.99 (s, 1H, H-1), 4.29–4.23
(m, 1H, –CHHCHCH2), 4.17–4.04 (m, 1H, –CHHCHCH2,), 3.98–3.94
(m, 2H, H-4, H-5), 1.34 (d, 3H, J 6.0 Hz, 6-CH3). Anal. Calcd for
C23H24O7: C, 66.98; H, 5.87. Found: C, 66.91; H, 5.93.
3ꢃ–OCOCH3), 1.26 (d, 3H,
J 6.3 Hz, 6-CH3). Anal. Calcd for
C15H22O8: C, 54.54; H, 6.71. Found: C, 54.41; H, 6.80.
1.3. Allyl 4-O-chloroacetyl-2,3-O-isopropylidene-a-L-
1.7. Allyl 4,6-O-benzylidene-3-O-chloroacetyl-2-deoxy-2-
rhamnopyranoside (3)
phthalimido-b-D-gluco-pyranosyl (1?4)-2,3-di-O-benzoyl-a-L-
rhamnopyranoside (8)
Chloroacetyl chloride (0.7 mL, 9.0 mmol) was added dropwise
at 0 °C to the solution of compound 225 (1.7 g, 7.0 mmol) and pyr-
idine (0.7 mL, 9.0 mmol) in CH2Cl2 (35 mL). The mixture was stir-
red for 16 h at rt and poured into water. The organic layer was
separated, washed successively with aq HCl and aq NaHCO3, and
brine, dried, and concentrated. Chromatography (9:1 n-hexane–
A mixture of 6 (400 mg, 0.97 mmol), 729 (553 mg, 1.1 mmol)
and 4 Å molecular sieves (1.0 g) in CH2Cl2 (13 mL) was cooled un-
der nitrogen to 0 °C and stirred for 10 min. NIS (313 mg, 1.4 mmol)
and TMSOTf (97 lL, 0.53 mmol) were successively added, the mix-
ture was stirred for 20 min, neutralized by the addition of Et3N and
filtered through a layer of Celite. The filtrate was washed succes-
sively with aq Na2S2O3, followed by water, dried and concentrated.
Chromatography (17:3 n-hexane–EtOAc) of the residue afforded 8
EtOAC) of the residue afforded 3 as syrup (1.8 g, 80%): ½a D25
ꢂ25.8
ꢁ
(c 1.7, CHCl3). 1H NMR: d 5.98–5.84 (m, 1H, –CH2CHCH2), 5.34–
5.21 (m, 2H, –CH2CHCH2), 5.06 (s, 1H, H-1), 4.91 (dd, 1H, J
10.2 Hz, H-4), 4.28–4.15 (m, 3H, –CHHCHCH2, H-2, H-3), 4.09 (s,
2H, –COCH2Cl), 4.04–3.98 (m, 1H, –CHHCHCH2), 3.89–3.75 (m,
1H, H-5), 1.56 (s, 3H, –CCH3CH3), 1.34 (s, 3H, –C CH3CH3), 1.18
(d, 3H, J 6.3 Hz, 6–CH3). Anal. Calcd for C14H21ClO6: C, 52.42; H,
6.60. Found: C, 52.35; H, 6.67.
as a foam (613 mg, 69%): ½a D25
ꢁ
+31 (c 1.0, CHCl3). 1H NMR: d 7.94–
7.33 (m, 19H, aromatic protons), 5.89 (dd, 1H, J 10.8 Hz, H-3), 5.85–
5.81 (m, 1H, –CH2CHCH2), 5.55 (d, 1H, J1,2 9.3 Hz, H-10), 5.52 (s, 1H,
–CHC6H5), 5.41 (d, 1H, J1,2 1.2 Hz, H-2), 5.36 (dd, 1H, J2,3 3.6 Hz, J3,4
9.3 Hz, H-3), 5.31–5.18 (m, 2H, –CH2CHCH2), 4.86 (d, 1H, J1,2 1.2 Hz,
H-1), 4.59–4.48 (m, 1H, –CHHCHCHH), 4.31–4.15 (m, 2H, H-20
–CHHCHCHH), 4.03–3.89 (m, 5H, H-4, H-5, H-40, H-50, H-6a0), 3.81
(s, 2H, –COCH2Cl), 3.80–3.76 (m, 1H, H-6b0), 1.39 (d, 3H, J 6.0 Hz,
6-CH3). 13C NMR: d 167.3 (–N[CO]2Ph), 167.2 (–N[CO]2Ph), 166.7
(–COCH2Cl), 165.3 (–COPh), 164.9 (–COPh), 136.7 (–OCH2CHCH2),
133.9–123.4 (aromatic carbons), 118.0 (–OCH2CHCH2), 101.7
(–CHPh), 98.3 (C-10), 96.3 (C-1), 78.9, 71.9, 71.1, 70.3 (2C),
68.5,68.3 (2C), 66.9, 65.5, 55.1 (C-20), 40.2 (–COCH2Cl), 18.0 (C-6,
Rha1). FABMS [M]+ m/z 867. Anal. Calcd for C46H42ClNO14: C,
63.63; H, 4.88. Found: C, 63.56; H, 4.93.
1.4. Allyl 4-O-chloroacetyl-a-L-rhamnopyranoside (4)
Aq HOAc (80%, 20 mL) was added to a solution of 3 (1.5 g,
4.7 mmol) in CH2Cl2 (5 mL). The mixture was stirred for 7 h at
80 °C, cooled to rt and concentrated. Chromatography (4:1 n-hex-
ane–EtOAc,) of the residue afforded 4 as syrup (1.1 g, 85%): ½a D25
ꢁ
ꢂ62.6 (c 1.1, CHCl3). 1H NMR: d 5.96–5.83 (m, 1H, –CH2CHCH2),
5.39–5.19 (m, 2H, –CH2CHCH2), 4.92 (t, 1H, J3,4,5 9.6 Hz, H-4),
4.85 (s, 1H, H-1), 4.19–4.15 (m, 1H, –CHHCHCH2), 4.14, 4.13 (2s,

J. Srivastava et al. / Carbohydrate Research 343 (2008) 2822–2825
2825
1.8. Allyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-b-
glucopyranosyl-(1?4)-2,3-di-O-benzoyl-a-L-rhamnopyranoside
(9)
D
-
red for 20 h at 90 °C, then evaporated to dryness. Toluene (2ꢃ) and
EtOH were added to and evaporated from the residue to give a syr-
up. To this Ac2O (0.6 mL) and pyridine (0.7 mL) were added. After
stirring for 14 h at rt, the solution was concentrated to dryness.
The residue was purified by column chromatography (5:1
C6H5CH3–Et2O). The product was then heated at 80 °C with 80%
aq AcOH (1.5 mL) for 4 h, followed by treatment with a catalytic
amount of MeONa in MeOH (2 mL) with stirring for 6 h at rt. The
reaction mixture was neutralized with Amberlite IR 120 (H+) resin
and filtered through a Celite bed, concentrated, dissolved in water
(1.0 mL) passed through a 0.45 Millipore membrane and dried to
A solution of 8 (400 mg, 0.46 mmol) and thiourea (175 mg,
2.3 mmol) in a mixture of MeOH (9.0 mL) and CH2Cl2 (6.0 mL)
was stirred at rt for 3 h and concentrated. The residue was dis-
solved in CH2Cl2, washed successively with water, dried and con-
centrated. Chromatography (8:2 n-hexane–EtOAc) of the residue
afforded 9 (274 mg, 75%) as a foam: ½a D25
ꢁ
+15.9 (c 1.1, CHCl3). 1H
NMR: d 7.94–7.33 (m, 19H, aromatic protons), 5.99–5.81 (m, 1H,
–CH2CHCH2), 5.54 (s, 1H, –CHC6H5), 5.37 (d, 1H, J1,2 9.0 Hz, H-10),
5.40–5.35 (m, 2H, H-2, H-3), 5.31–5.18 (m, 2H, –CH2CHCH2), 4.86
(d, 1H, J1,2 1.2 Hz, H-1), 4.60 (t, 1H, J2,3,4 9.0 Hz, H-30), 4.45–4.41
(m, 1H, CHHCHCH2), 4.18–4.10 (m, 2H, H-20, –CHHCHCH2), 4.01–
3.80 (m, 4H, H-4, H-5, H-40, H-50), 3.73–3.56 (m, 2-H, H-6a0, 6b0),
1.39 (d, 3H, J 6.0 Hz, 6-CH3). 13C NMR: d 167.7 (2 ꢃ –N[CO]2Ph),
165.3 (–COPh), 164.9 (–COPh), 136.9 (–OCH2CHCH2), 134.3–123.6
(aromatic carbons), 118.0 (–OCH2CHCH2), 101.9 (–CHPh), 98.6 (C-
10), 96.3 (C-1), 82.0, 72.0, 70.4, 68.6, 68.3, 68.1, 67.9, 67.0, 65.6,
60.3, 56.6 (C 20), 18.0 (C-6, Rha1). ESIMS (M + H)+ at m/z 792 and
(M+Na)+ at m/z 814. Anal. Calcd for C44H41NO13: C, 66.74; H,
5.22. Found: C, 66.68; H, 5.26.
afford 12 (9.0 mg, 58%) as colorless syrup: ½a D25
ꢂ67.5 (c 0.4,
ꢁ
H2O). 1H NMR (D2O): d 5.87–5.83 (m, 1H, –CH2CHCH2), 5.13–5.09
(m, 2H, –CH2CHCH2) 4.99 (d, 1H, J1,2 7.8 Hz, H-10), 4.75 (s, 1H, H-
1, Rha1), 4.59 (s, 1H, H-100, Rha2), 4.49–3.69 (m, 16H, –CHHCHCH2,
ring protons), 1.95 (s, 3H, 1 ꢃ –NHCOCH3), 1.36 (d, 3H, J 6.0 Hz, 6-
CH3), 0.90 (d, 3H, J 6.3 Hz, 6-CH300). ESIMS (M+H)+ at m/z 554. Anal.
Calcd for C23H39NO14: C, 49.90; H, 7.10. Found: C, 49.82; H, 7.15.
Acknowledgement
One of us (J.S.) thanks C.S.I.R. (New Delhi, India) for financial
assistance in the form of Junior and Senior Research Fellowship.
1.9. Allyl 2,3,4-tri-O-acetyl-
benzylidene-2-deoxy-2-phthalimido-b-
(1?4)-2,3-di-O-benzoyl- -rhamno-pyranoside (11)
a
-
L
-rhamnopyranosyl-(1?3)-4,6-O-
References
D
-glucopyranosyl-
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4518–4529.
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New York., 2004.
a
-L
A mixture of 9 (47 mg, 0.14 mmol), 1029 (100 mg, 0.13 mmol)
and 4 Å molecular sieves (150 mg) in CH2Cl2 (4 mL) was cooled un-
der nitrogen to 0 °C and stirred for 10 min. NIS (41 mg, 0.18 mmol)
and TMSOTf (13 lL, 0.07 mmol) were successively added. The mix-
ture was stirred for 20 min, neutralized by the addition of Et3N and
filtered through a layer of Celite. The filtrate was washed succes-
sively with aq Na2S2O3, and brine, dried and concentrated. Chro-
matography (3:1 n-hexane–EtOAc) of the residue afforded 11
(55 mg, 40%) as a syrup: ½a D25
ꢁ
+2.6 (c 1.1 CHCl3). 1H NMR: d 7.94–
7.31 (m, 19H, aromatic protons), 5.94–5.83 (m, 1H, –CH2CHCH2),
5.59 (s, 1H, –CHC6H5), 5.39 (d, 1H, J1,2 1.2 Hz, H-2), 5.35 (d, 1H,
J1,2 9.0 Hz, H-10GlcNPhth), 5.31–5.29 (m, 2H, H-200, H-3), 5.25–
5.14 (m, 3H, –CH2CHCH2, H-300), 4.85 (d, 1H, J1,2 1.2 Hz, H-1,
Rha1), 4.75 (s, 1H, 1-H00 Rha2), 4.62 (m, 2H, H-30, H-400), 4.45–4.41
(m, 1H, –CHHCHCH2), 4.22–4.16 (m, 2H, H-20, -CHHCHCH2), 3.99–
3.82 (m, 6H, H-4, H-40, H-5, H-50, H-500, H-6a0), 3.70–3.67 (m, 1H,
H-6b0), 1.95, 1.91, 1.87 (s, 3H each, 3 ꢃ –COCH3), 1.38 (d, 3H, J
6.0 Hz, 6-CH3), 0.50 (d, 3H, J 6.3 Hz, 6-CH300). 13C NMR: d 169.8
(2 ꢃ –COCH3), 169.7 (1 ꢃ –COCH3), 169.2 (–N[CO]2Ph), 169.1
(–N[CO]2Ph), 165.3 (–COPh), 164.9 (–COPh), 136.9 (–OCH2CHCH2),
134.2–123.7 (aromatic carbons), 118.1 (–OCH2CHCH2), 102.1
(–CHPh), 98.6(C-10), 97.1 (C-100), 96.3 (C-1), 80.2, 76.0, 73.9, 72.0,
71.1 (2C), 70.3, 70.1, 68.7, 68.3 (2C), 66.9, 66.5, 66.3, 65.9, 56.4
(C-20), 20.6 (–COCH3), 20.3 (–COCH3), 20.2 (–COCH3), (18.0 C-6
Rha1), 16.3 (C-6 Rha2). ESIMS (M+Na)+, m/z 1086. Anal. Calcd for
C56H57NO20: C, 63.21; H, 5.40. Found: C, 63.17; H, 5.47.
19. Podschun, R.; Ullman, U. Clin. Microbiol. Rev. 1998, 11, 589–603.
20. Lemieux, R. U.; Bundle, D. R.; Baker, D. A. J. Am. Chem. Soc. 1975, 97, 4076–4083.
21. Himmelspach, K.; Westphal, O.; Teichmann, B. Eur. J. Immunol. 1971, 1, 106–
112.
22. Vinogradov, E.; Frirdich, E.; MacLean, L. L.; Perry, M. B.; Petersen, B. O.; Duus, J.
O.; Whitfield, C. J. Biol. Chem. 2002, 277, 25070–25081.
23. Westerduin, P.; De Haan, P. E.; Dees, M. J.; Van Boom, J. H. Carbohydr. Res. 1988,
180, 195–205.
24. Takano, T.; Nakatsubo, F.; Murakami, K. Carbohydr. Res. 1990, 203, 341–342.
25. Zhang, J.; Kong, F. Carbohydr. Res. 2003, 338, 19–27.
26. Lemanski, G.; Ziegler, T. Eur. J. Org. Chem. 2000, 181–186.
27. Sarkar, K.; Mukherjee, I.; Roy, N. J. Carbohydr. Chem. 2003, 22, 95–107.
28. Demchenko, A.; Stauch, T.; Boons, G. J. Synlett 1997, 818–820.
29. Das, K. S.; Roy, N. Carbohydr. Res. 1996, 296, 275–277.
30. Kanie, O.; Crawley, S. C.; Palcic, M. M.; Hindsgaul, O. Carbohydr. Res. 1993, 243,
139–164.
1.10. Allyl
b-D-glucopyranosyl-(1?4)-a-L
a
-
L
-rhamnopyranosyl-(1?3)-2-acetamido-2-deoxy-
-rhamnopyranoside (12)
Compound 11 (30 mg, 0.028 mmol) in n-BuOH (5.0 mL) was
added to ethylenediamine (1.0 mL) under N2. The solution was stir-