First synthesis of an α-D-Fucp3NAc containing oligosaccharide: A study on D-Fucp3NAc glycosylation

Article abstract of DOI:10.1016/j.tet.2005.04.013

3-Acetamido-3,6-dideoxy-D-galactopyranose (D-Fucp3NAc) is an aminosugar almost exclusively found in phytopathogenic O-antigens. The glycosylation reaction involving D-Fucp3NAc donors was studied with several rhamnosyl acceptors, revealing that the best yi

Full text of DOI:10.1016/j.tet.2005.04.013

Tetrahedron 61 (2005) 5439–5448
First synthesis of an a-D-Fucp3NAc containing oligosaccharide:
a study on D-Fucp3NAc glycosylation
*
Emiliano Bedini, Antonella Carabellese, Marialuisa Schiattarella and Michelangelo Parrilli
`
Dipartimento di Chimica Organica e Biochimica, Universita di Napoli ‘Federico II’, Complesso Universitario Monte Santangelo,
Via Cintia, 4, 80126 Napoli, Italy
Received 14 January 2005; revised 21 March 2005; accepted 7 April 2005
Abstract—3-Acetamido-3,6-dideoxy-D-galactopyranose (D-Fucp3NAc) is an aminosugar almost exclusively found in phytopathogenic
O-antigens. The glycosylation reaction involving D-Fucp3NAc donors was studied with several rhamnosyl acceptors, revealing that the best
yields and highest a-stereoselectivity were obtainable by coupling a N-phenyl trifluoroacetimidate glycosyl donor in a ternary mixture
(dioxane/DME/toluene 4:1:1) as solvent. For the first time a synthetic access to a-D-Fucp3NAc containing oligorhamnans, that are interesting
molecules for studying the effects of O-antigen model oligosaccharides on the modulation of plant response to bacteria, was reported.
An example is the pentasaccharide repeating unit of the major O-antigen component from Pseudomonas syringae pv. holci IMV 8300, which
was synthesized as its methyl glycoside.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
known, the O-chain should be highly involved in the
interaction mechanism,5 because of its extension out from
the bacterial cell.
Lipopolysaccharides (LPSs) are amphiphilic macro-
molecules that are located on the external membrane of
Gram-negative bacteria.1 They consist of three different
domains:2 a lipid part, named Lipid-A, an oligosaccharide
region, named Core and a polysaccharide portion
(O-specific chain, or simply O-chain), consisting of a 1–8
sugar residues repeating unit, and extends out from the
bacterial membrane surface. The role of LPSs in bacterial
interactions both with animals and plants is surely crucial, as
they cover almost 80% of the cell surface; therefore, they
have been the object of many studies, especially in relation
to Gram-negative bacteria that are pathogenic to humans
and mammals.3 These studies elucidated that most of the
biological activities of LPS are played by Lipid-A, never-
theless O-chain is also involved in interactions between
bacterial cells and their eukaryotic hosts with its antigenic
properties.
The O-chain from phytopathogenic bacteria is typically
made of a repeating unit with a linear L- and/or D-rhamnosyl
skeleton. This backbone usually bears, as a branch, a single
monosaccharide, that can be a common monose (L- or
D-Xylp, L- or D-Rhap, D-GlcpNAc, D-Fucf) or a peculiar
aminosugar, 3-acetamido-3,6-dideoxy-D-galactopyranose
(D-Fucp3NAc), that is almost exclusively found in LPS
from phytopathogenic bacteria.6 Interestingly, the linkage
between D-Fucp3NAc and the rhamnosyl backbone occurs
in natural oligosaccharides exclusively as the a-glycoside.
In a recent study, synthetic linear oligorhamnans, mimick-
ing the common structure of the O-chain backbones from
phytopathogenic bacteria, have been proved to be effective
in preventing HR,7 demonstrating in this way that
oligosaccharides are also plant-recognizable pathogen-
associated molecular patterns (PAMPs).8 In order to
investigate deeper the effects of oligosaccharides on the
modulation of plant response to bacteria, the synthesis of
model oligosaccharides, related to the repeating units
of O-chain, has recently become a topic of interest in
carbohydrate synthesis.9
However, the effects of LPSs on plant cells have still been
poorly elucidated. The only extensive study is on the ability
of LPS to prevent the hypersensitive response (HR) caused
in plants by avirulent bacteria.4,5 Even if the molecular basis
of the LPS-plant interaction is still very far from completely
Keywords: O-chain; Repeating unit; D-Fucp3NAc; Glycosylation; N-
Phenyl trifluoroacetimidate; Pseudomonas holci.
In particular, in this paper we have studied the coupling
reaction between D-Fucp3NAc trihaloacetimidate donors
and some L- and D-rhamnosyl acceptors, in order to open a
*
Corresponding author. Tel.: C39 81 674146; fax: C39 81 674393;
e-mail: ebedini@unina.it
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.04.013

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E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
synthetic access to a-D-Fucp3NAc containing oligorham-
nans, which are model oligosaccharides of the repeating
units of O-chain from phytopathogenic bacteria. To
demonstrate the effectiveness of this route, we have
synthesized the methyl glycoside of the pentasaccharide
repeating unit of the major O-antigen component from
Pseudomonas syringae pv. holci IMV 830010 (Fig. 1).
To the best of our knowledge, this is the first synthesis of an
a-D-Fucp3NAc containing oligosaccharide.
The anomeric allyl protecting group of 3 was removed with
PdCl2 (84%); the conversion of the resulting hemi-acetal 4
into the a-trichloroacetimidate 5 by treatment with Cl3CCN
and DBU proceeded with only moderate yield (53%). The
coupling of 5 with the rhamnosyl acceptors 617 and 718 in
CH2Cl2 using catalytic TMSOTf (0.01 equiv) as activator
led to the consumption of the donor in few min, even
working at K50 8C, affording only traces of the desired
disaccharides (Fig. 2 and Table 1, entries 1 and 2). A milder
activator (BF3$OEt2), was unfortunately not able to activate
5, even when used in a more than stoichiometric amount in
CH2Cl2 at reflux (entry 3).
The rapid decomposition of a 4-O-acyl-2-benzylated
fucosyl trichloroacetimidate with catalytic TMSOTf in
CH2Cl2 has been recently reported;19 moreover, a tri-
methylated fucosyl trichloroacetimidate revealed a high
instability towards many activation conditions,20 demon-
strating in this way the difficulty, in some cases, in
glycosylating armed fucosyl-trichloroacetimidates. The
difficulty in coupling a D-Fucp3N TCAI-donor as 5 and
the not very satisfying yield in obtaining it from 4,
suggested the use of a different glycosyl donor.
Figure 1. The repeating unit of the major O-antigen component from
P. syringae pv. holci IMV 8300.
2. Results and discussion
2.1. Study on D-Fucp3NAc glycosidation reaction
Recently, a different trihaloacetimidate, the N-phenyl
trifluoroacetimidate leaving group, has been installed on
the anomeric position of carbohydrates to act as novel
glycosyl donor.21 Since fucosyl N-phenyl trifluoroacetimi-
dates have been already successfully glycosylated,22 the use
of this donor also in the D-Fucp3N case has been attempted.
Thus, 4 was treated with CF3C(NPh)CCl and NaH23 giving
8 in a better yield (74%; a/b 3:1) than 5.
The preparative synthesis of the D-Fucp3N building-block 1
from D-fucose has recently been reported.11 This molecule
could be further elaborated to afford D-Fucp3N donors,
firstly by protecting position O-2. Since D-Fucp3NAc
exclusively occurs in the natural polysaccharides as the
a-glycoside, a non-participating protecting group, such as
the benzyl group, was chosen. Thus, 1 was benzylated to
give 2 (68%) that was then subjected to cleavage of the
oxazoline ring by acid hydrolysis, and subsequent acetyl-
ation of the obtained amino-alcohol (63% over two steps)
(Scheme 1). Also the use of an acyl group in position O-4
was in accordance with the required a-stereoselectivity in
D-Fucp3N glycosidations. Actually, a long range partici-
pation effect was firstly postulated12 and then evidenced13
to be active in glycosylations involving 4-O-acyl-galactose
donors; nevertheless it has not been observed in two recent
worksregardingthe couplingof4-O-acyl-thioglycosides.14,15
We therefore decided to activate D-Fucp3N as trichloro-
acetimidate, since the use of this kind of glycosyl donor for
performing fucosylations with high a-selectivities has been
already reported.16
Gratifyingly, the coupling of 8 respectively with 6 and 7 in
CH2Cl2 proceeded smoothly, giving disaccharides 9 and 10
in good yields but with moderate a-selectivity (Table 1,
entries 4 and 5). Interestingly, 0.1 equiv of TMSOTf were
necessary to perform the couplings, but the use of so much
activator did not cause significant glycosyl donor decompo-
sition. In order to enhance the a-selectivity of the couplings,
we turned to different solvent systems. In particular,
a-selectivity is generally favored in electron-donating
solvents such as ethers, even if their use can sometimes
decrease the total yield of the glycosylation;24 nevertheless,
the use of an ‘ether-based’ ternary mixture (dioxane/DME/
toluene 4:1:1) as solvent for glycosylations involving armed
N-phenyl trifluoroacetimidate donors, led to higher stereo-
selectivities of 1,2-cis-adducts without affecting the yield
of the reactions.22,25 Actually, performing the coupling
between 8 and 7 in this solvent system, the a-stereoselec-
tivity was highly enhanced without a noticeable decrease of
the yield (entry 6).
2.2. Synthesis of the pentasaccharide repeating unit of
the major O-antigen component from P. syringae pv.
holci IMV 8300
The optimization of the conditions for the a-stereoselective
coupling between a D-Fucp3N donor as 8 and rhamno-
syl acceptors led us to perform the first synthesis of an
a-Fucp-3NAc containing repeating unit of O-chain from
phytopathogenic bacteria, in order to demonstrate the
effectiveness of this synthetic approach to this kind of
Scheme 1. Reagents and conditions: (a) BnBr, NaH, DMF, rt, 68%; (b) (i)
1 M HCl, THF, rt, (ii) Ac2O, py, rt, 63% over two steps; (c) PdCl2, 1:1
CH2Cl2/MeOH, rt, 84% (a/bZ1:1.5 as determined by 1H NMR analysis);
˚
(d) Cl3CCN, DBU, CH2Cl2, 0 8C, 53%; (e) CF3C(NPh)Cl, NaH, 4 A
molecular sieves, CH2Cl2, 0 8C, 74% (a/bZ3:1 as determined by 1H NMR
analysis).

E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
5441
Figure 2. Glycosyl acceptors and products of Table 1 (reaction conditions of the glycosidations are described therein).
Table 1. Glycosylations with D-Fucp3N trihaloacetimidate donors
Entry
Acceptor
Donor
Solvent
Activator
Yielda (a/b)
Product
1
2
3
4
5
6
6
7
6
6
7
7
5 (2.0 equiv)
5 (2.0 equiv)
5 (2.0 equiv)
8 (2.0 equiv)
8 (2.0 equiv)
8 (1.5 equiv)
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
Dioxane/DME/
toluene 4:1:1
Dioxane/DME/
toluene 4:1:1
CH2Cl2
TMSOTf
TMSOTf
BF3$OEt2
TMSOTf
TMSOTf
TMSOTf
Traces
Traces
No product
65% (62:38)b
61% (68:32)b
55% (88:12)b
9
10
—
9
10
10
7
18
8 (1.5 equiv)
TMSOTf
No product
—
8
9
19
19
8 (1.8 equiv)
8 (1.5 equiv)
TMSOTf
TMSOTf
70% (82:18)c
63% (89:11)c
20
20
Dioxane/DME/
toluene 4:1:1
a Isolated yield.
1
b Measured by H NMR.
c Measured after separation of the two anomers.
oligosaccharides. Among the several repeating units that
characterise each serotype of phytopathogenic lipopoly-
saccharides, the pentasaccharide repeating unit of the
major O-antigen component from P. syringae pv. holci
IMV 830010 was chosen (Fig. 1).
chosen for the synthesis of 11. It required the synthesis of
the rhamnosyl O-3 acceptor 15, whose position 2 would be
protected with an orthogonal protecting group. Firstly
levulinoyl (Lev) was chosen as protecting group for this
position. Thus, the known benzyl 3-O-allyl-4-O-benzoyl-a-
L-rhamnopyranoside 1617 was subjected to levulination with
LevOH in presence of N,N0-diisopropylcarbodiimide
(DIPC) and 4-dimethylaminopyridine (DMAP) (99%) and
subsequent de-O-allylation with PdCl2 (78%): no acyl
migration was observed during the allyl cleavage to obtain
18 (Scheme 3).27 Unfortunately, the coupling between 8
and 18 was unsuccessful, revealing that the coupling of the
D-Fucp3NAc donor 8 probably works only with armed
acceptors. Actually, when 8 was coupled with the armed
2-O-allylated rhamnosyl O-3 acceptor 19,28,29 disaccharide
20 was obtained in satisfying yield both in CH2Cl2 and in
dioxane/DME/toluene 4:1:1 (Table 1, entries 8 and 9).
In order to obtain a suitable disaccharide glycosyl acceptor,
20 was subjected to de-O-allylation to give 21 in high yield
(93%).
For the synthesis of the branched pentasaccharide 11, two
paths could be planned: retrosynthetic analysis suggested
either a (4C1) approach, involving the coupling between 8
and a linear rhamnosyl tetrasaccharide 12,17 or a (3C2)
strategy, in, which the key-glycosylation regards the
trisaccharide donor 1317 and the disaccharide acceptor 14,
which could be obtained by coupling 8 with a suitable
rhamnosyl O-3 acceptor 15 (Scheme 2).
In the synthesis of an analogous pentasaccharide, the major
component from P. syringae pv. ribicola NVPPB 1010, in
which the D-Fucp3N branch is replaced by a D-GlcpNAc
unit,26 a (4C1) strategy was chosen.17 It revealed that the
(4C1) key-coupling needed a large excess of the amino-
sugar donor, because of the very poor reactivity of the
acceptor 12 (with RZBz). Since donor 8 was quite
‘precious’, the other strategy, the (3C2) approach, was
The coupling between 21 and the trisaccharide trichloro-
acetimidate donor 13 was performed in CH2Cl2 with

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E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
Scheme 2. Retrosynthetic analysis of the methyl glycoside of the pentasaccharide repeating unit of the major O-antigen component from P. syringae pv. holci
IMV 8300.
BF3$OEt2 as activator, giving 22 in 51% yield. As expected,
the new glycosidic bond was formed with total a-stereo-
selectivity, as ascertained by the value of the heteronuclear
1JC,H coupling constant (1JC,HZ173 Hz),30 measured in a
coupled HMQC-COSY experiment. Besides, even if the 2-
OH group of the glycosyl acceptor 14 was considered to be
poorly reactive due to its steric hindrance, and therefore
susceptible to competition by the NHAc group as a
Scheme 3. Reagents and conditions: (a) LevOH, DIPC, DMAP, CH2Cl2, rt, 99%; (b) PdCl2, 3:2 CH2Cl2/MeOH, rt, 78%; (c) see Table 1, entries 7–9; (d) PdCl2,
˚
1:1 CH2Cl2/MeOH, rt, 93%; (e) BF3$OEt2, AW-300 4 A molecular sieves, CH2Cl2, K20 8C, 51%; (f) (i) Pd/C, 9:1 MeOH/HCOOH, ultrasound bath, rt,
(ii) 1 M NaOMe, MeOH, rt, 78% over two steps.

E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
5443
Figure 3. 1H NMR spectrum (D2O, 400 MHz) of the target pentasaccharide 11.
nucleophile in the glycosylation,31 no imidate adducts were
detected during the reaction course. Finally, a two-step
deprotection of 22 (debenzylation by transfer hydrogenation
under Perlin’s conditions,32 and subsequent de-O-acylation
with sodium methoxide) afforded the target pentasaccharide
11 in 78% yield (1H NMR spectrum of 11 reported in
Fig. 3).
(1H: 200 MHz, 13C: 50 MHz) or Bruker DRX-400 (1H:
400 MHz, 13C: 100 MHz) instruments in CDCl3 (CHCl3 as
internal standard, 1H: CHCl3 at d 7.26; 13C: CDCl3 at d 77.0)
and in D2O (acetone as internal standard, 1H: (CH3)2CO at d
2.05; 13C: (CH3)2CO at d 31.5). Assignment of proton
chemical shifts were based on 1D HOHAHA and COSY
experiments. For pentasaccharides 11 and 22, 2D NMR
experiments such as TOCSY, NOESY, HSQC and HMQC-
COSY were also performed to assign proton and carbon
chemical shifts. Positive ESI-MS spectra were recorded on a
Finnigan LCQ-DECA ion trap mass spectrometer. IR
spectra were recorded on a JASCO-FT/IR-430 spectro-
meter. Optical rotations were measured on a JASCO P-1010
polarimeter. Analytical thin layer chromatographies (TLC)
were performed on aluminium plates precoated with Merck
Silica Gel 60 F254 as the adsorbent. The plates were
developed with 5% H2SO4 ethanolic solution and then
heating to 130 8C. Column chromatographies were per-
formed on Merck Kieselgel 60 (63–200 mesh), except
where differently specified. Gel-filtration chromatography
was performed on a Sephadex G-10 column (1.0!20 cm)
with water as eluant.
3. Summary
The study on the glycosylation reaction involving a
D-Fucp3N donor here reported revealed that the N-phenyl
trifluoroacetimidate of D-Fucp3N gives good yields with
several armed rhamnosyl acceptors and a high a-stereo-
selectivity is achievable by using a ternary mixture
(dioxane/DME/toluene 4:1:1) as solvent. This study opens
a route to the synthesis of a-D-Fucp3NAc containing
oligorhamnans, that are interesting molecules for studying
the effects of O-antigen model oligosaccharides on the
modulation of plant response to bacteria. An example of the
synthetic accessibility to these molecules is the first reported
synthesis of an a-D-Fucp3NAc containing oligosaccharide,
the methyl glycoside of the pentasaccharide repeating
unit of the major O-antigen component from P. syringae
pv. holci IMV 8300.
4.1.1. Allyl 2-O-benzyl-3-deoxy-4,3-(2-trichloromethyl-
1-oxa-3-azaprop-2-eno)-a-D-fucopyranoside (2). A solu-
tion of 1 (903 mg, 2.74 mmol) in DMF (20 mL) was treated
with BnBr (3.4 mL, 28.6 mmol) and NaH (60% oil
suspension; 353 mg, 14.7 mmol). The solution was stirred
at rt for 90 min, the solution was then diluted with CH2Cl2
(300 mL) and washed with water (300 mL). The organic
layer was collected, dried and concentrated to give a residue
that, after chromatography (11:1 petroleum ether/EtOAc),
afforded pure 2 (840 mg, 68%) as a yellowish oil. [a]D
4. Experimental
4.1. General methods
1H and 13C NMR spectra were recorded on Varian XL-200

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E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
C70.2 (c 1.0, CH2Cl2). IR (thin film, NaCl) 3035, 2944,
(d, 1H, J4,3Z2.8 Hz, H-4a), 5.21 (d, 1H, J4,3Z2.8 Hz,
H-4b), 5.01–4.83 (m, 4H, H-1b, NHa, NHb, OCHHPh), 4.76
1
1677, 1266 cmK1; H NMR (CDCl3, 200 MHz) d 7.36 (m,
5H, H-Ar), 5.91 (m, 1H, OCH2CH]CH2), 5.32 (dd, 1H,
JvicZ17.2 Hz, JgemZ1.6 Hz, OCH2CH]CHH trans), 5.20
(dd, 1H, JvicZ10.4 Hz, JgemZ1.6 Hz, OCH2CH]CHH
cis), 4.85 (d, 1H, JgemZ12.0 Hz, OCHHPh), 4.76–4.69
(m, 3H, H1, H4, OCHHPh), 4.55 (dd, 1H, J3,4Z9.0 Hz,
J3,2Z5.4 Hz, H3), 4.30 (m, 2H, H5, OCHHCH]CH2), 4.05
(m, 1H, OCHHCH]CH2), 3.77 (dd, 1H, J2,3Z5.4 Hz,
J2,1Z4.0 Hz, H2), 1.33 (d, 3H, J6,5Z6.6 Hz, H6);
(CDCl3, 50 MHz) d 164.1 (C]N), 138.0 (Cipso), 134.0
(OCH2CH]CH2), 128.5 (C-Ar), 117.2 (OCH2CH]CH2),
96.1 (C1), 84.7 (C4), 74.0, 73.8, 68.7, 66.8, 64.2 (C2, C3, C5,
OCH2CH]CH2, OCH2Ph), 16.1 (C6). ESI-MS for
C18H20Cl3NO4 (m/z): Mr (calcd) 419.05, Mr (found)
442.28 (MCNa)C. Anal. Calcd: C, 51.39; H, 4.79; N,
3.33. Found: C, 51.55; H, 4.70; N, 3.32.
(d, 1H, JgemZ12.0 Hz, OCHHPh), 4.68 (d, 1H, JgemZ
12.0 Hz, OCHHPh), 4.53 (m, 2H, H-3a, OCHHPh), 4.38
(q, 1H, J5,6Z6.6 Hz, H-5a), 4.17 (m, 1H, H-3b), 3.84 (q, 1H,
J5,6Z6.6 Hz, H-5b), 3.63 (dd, 1H, J2,3Z10.2 Hz, J2,1
Z
3.6 Hz, H-2a), 3.33 (dd, 1H, J2,3Z10.2 Hz, J2,1Z7.2 Hz,
H-2b), 2.08 (s, 3H, OAc), 2.04 (s, 3H, OAc), 1.84 (s, 3H,
NAc), 1.79 (s, 3H, NAc), 1.13 (d, 3H, J6,5Z6.6 Hz, H-5b),
1.07 (d, 3H, J6,5Z6.6 Hz, H-5a); 13C NMR (CDCl3,
50 MHz) d 170.0 (4 COCH3), 138.1 (Cipso), 137.4 (Cipso),
128.4 (C-Ar), 98.0 (C-1a), 90.5 (C-1b), 76.0, 73.7, 72.8,
72.1, 71.9, 70.2, 65.0, 60.4 (C-2a, C-2b, C-4a, C-4b, C-5a,
C-5b, 2 OCH2Ph), 52.0, 47.8 (C-3a, C-3b), 23.2 (2 COCH3),
21.0, 20.7 (2 COCH3), 16.5, 16.3 (C-6a, C-6b). ESI-MS for
C17H23NO6 (m/z): Mr (calcd) 337.15, Mr (found) 360.22
(MCNa)C. Anal. Calcd: C, 60.52; H, 6.87; N, 4.15. Found:
C, 60.89; H, 6.80; N, 4.00.
4.1.2. Allyl 4-O-acetyl-3-acetamido-2-O-benzyl-a-D-
fucopyranoside (3). To a solution of 2 (689 mg,
1.64 mmol) in THF (10 mL), 1 M HCl was added
(1.57 mL). The mixture was vigorously stirred at rt for
30 min, after that 1 M NaHCO3 (200 mL) was added.
Stirring was continued for additional 10 min, then EtOAc
(200 mL) was added. The organic layer was collected, dried
and concentrated to afford an oily residue that was
subsequently dissolved in pyridine (3 mL). The solution
was treated with acetic anhydride (3 mL) and stirred at rt
overnight. The solution was then concentrated and the
residue dissolved in CH2Cl2 (100 mL) and extracted with
1 M HCl (100 mL) and water (100 mL). The organic layer
was collected, dried and concentrated to afford a residue,
that, after chromatography (3:2 petroleum ether/EtOAc),
gave pure 3 (403 mg, 63%) as a white foam. [a]D C126.8
(c 1.0, CH2Cl2). IR (thin film, NaCl) 3055, 2951, 1735,
4.1.4. 4-O-Acetyl-3-acetamido-2-O-benzyl-a-D-fucopyra-
nosyl trichloroacetimidate (5). Compound 4 (77 mg,
0.22 mmol) was dissolved in CH2Cl2 (3.0 mL) under an
argon atmosphere and to the 0 8C cooled solution Cl3CCN
(115 mL, 1.21 mmol) and DBU (3.3 mL, 6.6 mmol) were
added. The solution was stirred at 0 8C for 4 h and then
concentrated. The resulting residue was chromatographed
(1:1 petroleum ether/EtOAc) over neutral alumina gel to
afford 5 (57 mg, 53%) as a white foam. [a]D C99.2 (c 0.8,
CH2Cl2). IR (thin film, NaCl) 3022, 2979, 1739, 1671 cmK1
;
1H NMR (CDCl3, 200 MHz) d 8.60 (s, 1H, NHCCl3), 7.36
(m, 5H, H-Ar), 6.60 (d, 1H, J1,2Z3.4 Hz, H1), 5.41 (d, 1H,
J4,3Z2.4 Hz, H4), 5.02 (d, 1H, JH,NHZ6.6 Hz, NH), 4.75
(d, 1H, JgemZ12.0 Hz, OCHHPh), 4.55 (m, 1H, H3), 4.46
(d, 1H, JgemZ12.0 Hz, OCHHPh), 4.33 (q, 1H, J5,6
6.6 Hz, H5), 3.81 (dd, 1H, J2,3Z11.4 Hz, J2,1Z3.4 Hz),
2.08 (s, 3H, OAc), 1.84 (s, 3H, NAc), 1.09 (d, 3H, J6,5
Z
1
1664, 1259 cmK1; H NMR (CDCl3, 200 MHz) d 7.36 (m,
Z
5H, H-Ar), 5.897 (m, 1H, OCH2CH]CH2), 5.35–5.14 (m,
4H, H4, NH, OCH2CH]CH2), 4.95 (d, 1H, J1,2Z2.7 Hz,
H1), 4.65 (d, 1H, JgemZ12.0 Hz, OCHHPh), 4.53 (m, 1H,
H3), 4.47 (d, 1H, JgemZ12.0 Hz, OCHHPh), 4.13 (m, 2H,
H5, OCH2CH]CH2), 3.97 (m, 2H, OCH2CH]CH2), 3.67
(dd, 1H, J2,3Z11.4 Hz, J2,1Z2.7 Hz, H2), 2.06 (s, 3H,
OAc), 1.79 (s, 3H, NAc), 1.03 (d, 3H, J6,5Z6.6 Hz, H6);
13C NMR (CDCl3, 50 MHz) d 170.0 (2 COCH3), 138.0
(Cipso), 133.7 (OCH2CH]CH2), 128.5 (C-Ar), 117.8
(OCH2CH]CH2), 95.4 (C1), 73.1, 72.7, 71.6, 68.4, 64.8
(C2, C4, C5, OCH2CH]CH2, OCH2Ph), 48.2 (C3), 23.0,
20.6 (2 COCH3), 16.1 (C6). ESI-MS for C20H27NO6 (m/z):
Mr (calcd) 377.18, Mr (found) 400.37 (MCNa)C. Anal.
Calcd: C, 63.64; H, 7.21; N, 3.71. Found: C, 63.80; H, 7.00;
N, 3.65.
6.6 Hz, H6); 13C NMR (CDCl3, 50 MHz) d 170.1, 169.9 (2
COCH3), 161.4 (Cl3CC]NH), 137.4 (Cipso), 128.3 (C-Ar),
93.5 (C-1), 72.0, 71.9, 71.8, 67.8 (C2, C4, C5, OCH2Ph),
48.7 (C3), 23.1, 20.6 (2 COCH3), 16.3 (C6). ESI-MS for
C19H23Cl3N2O6 (m/z): Mr (calcd) 480.06, Mr (found) 513.30
(MCNa)C. Anal. Calcd: C, 47.37; H, 4.81; N, 5.81. Found:
C, 47.60; H, 4.89; N, 5.75.
4.1.5. 4-O-Acetyl-3-acetamido-2-O-benzyl-D-fucopyra-
nosyl N-phenyl-trifluoroacetimidate (8). A mixture of 4
˚
(251 mg, 0.72 mmol) and freshly powdered 4 A molecular
sieves was suspended under argon in CH2Cl2 (5 mL) and
cooled to 0 8C under stirring. CF3C(NPh)Cl (53 mL,
0.42 mmol) and NaH (60% oil suspension; 17 mg,
0.42 mmol) were added and stirred was continued at 0 8C
for 3 h, after that the mixture was filtered over Celite and the
filtrate concentrated. Neutral alumina (Brockman grade 1)
column chromatography (3:2 petroleum ether/EtOAc) on
the residue, afforded 8 (277 mg, 74%; a/bZ3:1) as a
colourless oil. IR (thin film, NaCl) 3040, 1738, 1670, 1656,
1260 cmK1; 1H NMR NMR (CDCl3, 200 MHz) (a-anomer)
4.1.3. 4-O-Acetyl-3-acetamido-2-O-benzyl-D-fucopyra-
nose (4). A suspension of 3 (357 mg, 0.92 mmol) and
PdCl2 (27 mg, 0.15 mmol) in 1:1 CH2Cl2/MeOH (10 mL)
was vigorously stirred at rt for 5 h. The mixture was filtered
over a Celite pad, then diluted with CH2Cl2 (150 mL) and
washed with 5 M NaCl (150 mL). The organic layer was
collected, dried and concentrated. The resulting residue was
chromatographed (1:1 petroleum ether/EtOAc) to afford 4
(270 mg, 84%; a/bZ1:1.5) as a yellowish oil. IR (thin film,
d 7.42–6.73 (H-Ar), 6.60 (m, 1H, H-1), 5.38 (d, 1H, J4,3
Z
2.4 Hz, H-4), 4.83 (m, 2H, NH, OCHHPh), 4.50 (m, 2H, H3,
OCHHPh), 4.28 (q, 1H, J5,6Z6.6 Hz, H-5), 3.75 (dd, 1H,
J2,3Z10.2 Hz, J2,1Z3.4 Hz, H-2), 2.07 (s, 3H, OAc), 1.84
(s, 3H, NAc), 1.11 (dd, 3H, J6,5Z6.6 Hz, H-6); 13C NMR
(CDCl3, 50 MHz) (a-anomer) d 170.1, 169.9 (2 COCH3),
NaCl) 3517, 3009, 1743, 1666, 1255 cmK1
;
1H NMR
(CDCl3, 200 MHz) d 5.40 (d, 1H, J1,2Z3.6 Hz, H-1a), 5.27

E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
5445
143.5, 137.4 (2 Cipso), 129.3–119.4 (C-Ar), 92.5 (C-1), 72.3,
71.9, 71.8, 67.9 (C2, C4 C5, OCH2Ph), 48.5 (C3), 23.2, 20.6
(2 COCH3), 16.4 (C6). ESI-MS for C25H27F3N2O6 (m/z): Mr
(calcd) 508.18, Mr (found) 531.38 (MCNa)C. Anal. Calcd:
C, 59.05; H, 5, 35; N, 5.51. Found: C, 59.10; H, 5.45; N,
5.43.
72.6, 71.5, 71.3, 71.2, 70.9, 70.5, 69.1, 69.0, 68.9, 67.3,
66.7, 65.1 (C-2aA, C-2Ab , C-2aB, C-2bB, C-3Aa, C-3Ab , C-4aA,
C-4bA, C-4Ba, C-4Bb , C-5aA, C-5bA, C-5Ba, C-5Bb ,
2
OCH2CH]CH2, 4 OCH2Ph,), 23.0, 22.9, 20.6, 20.4 (4
COCH3), 17.6, 17.5, 16.3, 16.1 (C-6aA, C-6bA, C-6aB, C-6Bb).
ESI-MS for C40H47NO11 (m/z): Mr (calcd) 717.31, Mr
(found) 740.51 (MCNa)C. Anal. Calcd: C, 66.93; H, 6.60;
N, 1.95. Found: C, 67.10; H, 6.47; N, 1.99.
4.2. General procedure for D-Fucp3NAc couplings in
CH2Cl2
4.3.2. Methyl(4-O-acetyl-3-acetamido-2-O-benzyl-D-
fucopyranosyl)-(1/3)-2,3-O-isopropylidene-a-L-rham-
nopyranoside (10). See the general procedure for D-Fucp3-
NAc couplings in CH2Cl2 and in dioxane/toluene/DME
4:1:1 v/v/v. IR (thin film, NaCl) 3042, 1748, 1680,
A mixture of donor 8 (37 mg, 0.074 mmol) and rhamnosyl
acceptor (0.037 mmol) was co-evaporated three times with
toluene, the residue was then mixed with freshly powdered
˚
AW-300 4 A molecular sieves and suspended under argon
1
1229 cmK1; H NMR (CDCl3, 400 MHz) d 7.41–7.26 (m,
in CH2Cl2 (1.0 mL). The mixture was cooled and stirred at
0 8C, TMSOTf (1.2 mL, 7.4 mmol) was added and the
temperature was allowed to gradually rise to rt. After
completion of the reaction (TLC analysis), the mixture was
neutralized by adding pyridine. The mixture was then
filtered over Celite and concentrated to give a residue, that
was purified by column chromatography.
10H, H-Ara,b), d 5.73 (d, 1H, J1,2Z3.5 Hz, H-1aB), 5.33 (d,
1H, J4,3Z2.2 Hz, H-4Ba), 5.14 (d, 1H, J4,3Z2.2 Hz, H-4bB),
4.86 (m, 5H, H-1Aa, H-1bB, NHa, 2 OCHHPh), 4.67–4.54
(m, 4H, H-1Bb, H-5Bb, NHb, OCHHPh), 4.44 (d, 1H, Jgem
12.0 Hz, OCHHPh), 4.40 (m, 1H, H-3aB), 4.31 (t, 1H, J4,3
Z
Z
J4,5Z7.1 Hz, H-3Ab ), 4.24 (t, 1H, J4,3Z J4,5Z7.1 Hz, H-3aA),
4.20–4.07 (m, 4H, H-2aA, H-2Ab , H-3Bb, H-5aB), 3.72 (m, 2H,
H-5aA, H-5Ab ), 3.65 (dd, 1H, J2,3Z11.4 Hz, J2,1Z3.5 Hz,
H-2aB), 3.56 (dd, 1H, J4,5Z9.9 Hz, J4,3Z7.1 Hz, H-4aA), 3.51
(dd, 1H, J4,5Z9.9 Hz, J4,3Z7.1 Hz, H-4bA), 3.36 (m, 7H,
H-2bB OMea, OMeb), 2.08 (2 s, 6H, 2 OAc), 1.85 (s, 3H,
NAc), 1.76 (s, 3H, NAc), 1.57 (s, 6H, 2 CH3), 1.36 (s, 6H, 2
4.3. General procedure for D-Fucp3NAc couplings in
dioxane/toluene/DME 4:1:1 v/v/v
A mixture of donor 8 (37 mg, 0.074 mmol) and rhamnosyl
acceptor (0.049 mmol) was co-evaporated three times with
toluene, the residue was then mixed with freshly powdered
CH3), 1.34 (d, 3H, J6,5Z6.2 Hz, H-6aA), 1.24 (d, 3H, J6,5
Z
6.6 Hz, H-6bB), 1.15 (d, 3H, J6,5Z6.2 Hz, H-6bA), 1.09 (d, 3H,
J6,5Z6.6 Hz, H-6aB); 13C NMR (CDCl3, 100 MHz) d 167.8
(COCH3), 137.6 (Cipso), 126.5–125.7 (C-Ar), 104.2 (C-1bB),
97.9 C-1aA, C-1Ab ), 94.5 (C-1aB), 82.2, 78.4, 78.2, 76.4, 76.0,
75.8, 75.2, 73.8, 72.3, 72.1, 71.2, 70.5, 67.3, 65.0, 63.7
(C-2aA, C-2bA, C-2Ba, C-2Bb, C-3Aa, C-3Ab , C-4Aa, C-4Ab , C-4Ba,
C-4bB, C-5aA, C-5Ab , C-5Ba, C-5bB, OCHHPh ), 54.5 (OMe),
51.8 (C-3bB), 47.9 (C-3Ba), 27.8 (CH3), 26.1 (CH3), 22.9,
22.8, 20.6, 20.5 (4 COCH3), 17.8, 17.5, 16.3, 15.9 (C-6aA,
C-6bA, C-6aB, C-6Bb). ESI-MS for C27H39NO10 (m/z): Mr
(calcd) 537.26, Mr (found) 538.20 (MCH)C. Anal. Calcd:
C, 60.32; H, 7.31; N, 2.61. Found: C, 60.40; H, 7.19; N,
2.51.
˚
AW-300 4 A molecular sieves and suspended under argon
in 4:1 dioxane/toluene (1.5 mL). The mixture was cooled
and stirred at 0 8C, a 0.025 M DME solution of TMSOTf
(0.3 mL, 7.4 mmol) was added and the temperature was
allowed to gradually raise to rt After completion of the
reaction (TLC analysis), the mixture was neutralized by
adding pyridine. The mixture was then filtered over Celite
and concentrated to give a residue, that was purified by
column chromatography.
4.3.1. Benzyl(4-O-acetyl-3-acetamido-2-O-benzyl-D-
fucopyranosyl)-(1/3)-3-O-allyl-4-O-benzoyl-a-L-rham-
nopyranoside (9). See the general procedure for D-Fucp3-
NAc couplings in CH2Cl2 and in dioxane/toluene/DME
4:1:1 v/v/v. IR (thin film, NaCl) 3025, 2980, 2933, 1744,
4.3.3. Benzyl 3-O-allyl-4-O-benzoyl-2-O-levulinoyl-a-L-
rhamnopyranoside (17). To a solution of 16 (152 mg,
0.382 mmol) in CH2Cl2 (3.0 mL), levulinic acid (245 mL,
2.28 mmol), DMAP (23 mg, 0.190 mmol) and then DIPC
(220 mL, 2.48 mmol) were added. After 4 h stirring at rt, the
mixture was filtered over a Celite pad, diluted with CH2Cl2
(50 mL) and washed with water (50 mL). The organic layer
was collected, dried and concentrated to give a residue,
which after chromatography (8:1 petroleum ether/EtOAc)
afforded 17 (187 mg, 99%) as an oil. [a]D K12.7 (c 1.0,
CH2Cl2). IR (thin film, NaCl) 3028, 2935, 1749, 1725,
1666 cmK1 1H NMR (CDCl3, 400 MHz) d 8.11–7.26
;
(m, 30H, H-Ar), 5.73 (m, 2H, 2 OCH2CH]CH2), 5.50 (t,
1H, J4,3ZJ4,5Z10.0 Hz, H-4bA), 5.41 (d, 1H, J4,3Z1.8 Hz,
H-4aB), 5.35 (t, 1H, J4,3ZJ4,5Z10.0 Hz, H-4aA), 5.20–5.10
(m, 5H, H-1bA, H-4Bb, OCHHPh, 2 OCH2CH]CHH trans),
5.08–4.97 (m, 4H, H-1Ba, NHa, 2 OCH2CH]CHH cis), 4.91
(bs, 1H, H-1aA), 4.77 (m, 4H, NHb, 3 OCHHPh), 4.65 (d, 1H,
J1,2Z7.4 Hz, H-1Bb), 4.61–4.50 (m, 6H, H-3Ba, H-5aB, 4
OCHHPh), 4.12–4.03 (m, 5H, H-2aA, H-2Ab , H-3Bb, 2
OCHHCH]CH2), 4.01–3.94 (m, 6H, H-3aA, H-3Ab , H-5Aa,
H-5bA, 2 OCHHCH]CH2), 3.78 (dd, 1H, J2,3Z10.3 Hz,
J2,1Z3.4 Hz, H-2Ba), 3.69 (q, 1H, J5,6Z6.4 Hz, H-5bB), 3.34
(dd, 1H, J2,3Z10.7 Hz, J2,1Z7.4 Hz, H-2bB), 2.078 (s, 3H,
OAc) 2.05 (s, 3H, OAc), 1.84 (s, 3H, NAc), 1.79 (s, 3H,
NAc), 1.29 (m, 6H, H-6aA, H-6Ab ), 1.01 (d, 3H, J6,5Z6.4 Hz,
H-6aB), 0.98 (m, 6H, J6,5Z6.4 Hz, H-6Bb); 13C NMR (CDCl3,
100 MHz) d 170.1, 169.9 (4 COCH3), 165.5, 165.4 (COPh),
134.4–128.1 (2 OCH2CH]CH2, C-Ar), 116.7, 116.6
(2 OCH2CH]CH2), 105.8 (C-1bB), 98.7, 96.6, 96.4 (C-1Aa,
C-1bA, C-1aB), 76.9, 76.0, 75.8, 74.4, 74.2, 73.6, 73.5, 73.4,
1
1255 cmK1; H NMR (CDCl3, 200 MHz) d 8.05–7.36 (m,
10H, H-Ar), 5.67 (m, 1H, OCH2CH]CH2), 5.36 (dd, 1H,
J2,3Z3.4 Hz, J2,1Z1.6 Hz, H2), 5.24 (t, 1H, J4,3Z J4,5
9.8 Hz, H4), 5.14 (d, 1H, JvicZ17.2 Hz, JgemZ1.8 Hz,
OCH2CH]CHH trans), 5.01 (d, 1H, JvicZ10.4 Hz, Jgem
Z
Z
1.8 Hz, OCH2CH]CHH cis), 4.88 (d, 1H, J1,2Z1.6 Hz,
H1), 4.72 (d, 1H, JgemZ12.0 Hz, OCHHPh), 4.54 (d, 1H,
JgemZ12.0 Hz, OCHHPh), 4.07–3.76 (m, 4H, H3, H5,
OCH2CH]CH2), 2.84–2.68 (m, 4H, CH2CH2), 2.20 (s,
3H, CH3CO), 1.24 (d, 3H, J6,5Z6.4 Hz, H6); 13C NMR

5446
E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
(CDCl3, 50 MHz) d 206.1 (CH3C]O), 171.7 (C]O Lev),
166.5 (C]O Bz), 136.4 (Cipso), 134.1 (OCH2CH]CH2),
133.2 (Cipso), 130.0–127.5 (C-Ar), 117.5 (OCH2CH]CH2),
97.6 (C-1), 74.8, 73.2, 70.9, 69.0, 68.9, 66.6 (C-2, C-3, C-4,
C-5, OCH2CH]CH2, OCH2Ph), 37.9, 29.8, 28.2 (CH2CH2,
CH3C]O), 17.5 (C-6). ESI-MS for C28H32O8 (m/z): Mr
(calcd) 496.21, Mr (found) 519.22 (MCNa)C. Anal. Calcd:
C, 67.73; H, 6.50. Found: C, 67.60; H, 6.65.
(MCNa)C. Anal. Calcd: C, 65.05; H, 7.23; N, 2.23. Found:
C, 65.20; H, 7.19; N, 2.32.
4.3.6. Methyl(4-O-acetyl-3-acetamido-2-O-benzyl-a-D-
fucopyranosyl)-(1/3)-4-O-benzyl-a-L-rhamnopyrano-
side (21). A mixture of compound 20-a (56 mg,
0.089 mmol) and PdCl2 (7.8 mg, 44 mmol) was suspended
in 1:1 CH2Cl2/MeOH (2.0 mL) under vigorous stirring.
After 4 h the mixture was filtered on a Celite pad, then
diluted with CH2Cl2 (25 mL) and washed with 5 M NaCl
(30 mL). The organic layer was collected, dried and
concentrated to give an oily residue that, after column
chromatography (1:2 petroleum ether/EtOAc) afforded 21
(49 mg, 93%) as an oil. [a]D C32.3 (c 1.0, CH2Cl2). IR (thin
film, NaCl) 3509, 3030, 1741, 1669, 1258 cmK1; 1H NMR
(CDCl3, 400 MHz) d 7.49–7.29 (m, 10H, H-Ar), 5.07 (d,
1H, J4,3Z3.0 Hz, H-4B), 5.04 (bs, 1H, H-1A), 4.80–4.71 (m,
4H, H-1B, 3 OCHHPh), 4.53 (m, 1H, H-3B), 4.44 (d, 1H,
JgemZ12.0 Hz, OCHHPh), 4.06 (q, 1H, J5,6Z6.6 Hz,
4.3.4. Benzyl 4-O-benzoyl-2-O-levulinoyl-a-L-rhamno-
pyranoside (18). Compound 17 (189 mg, 0.381 mmol)
was dissolved in 3:2 MeOH/CH2Cl2 (5.0 mL), PdCl2
(27 mg, 0.30 mmol) was then added and the mixture was
vigorously stirred at rt overnight, after that it was filtered
over a Celite pad, diluted with CH2Cl2 (50 mL) and washed
with 5 M NaCl (50 mL). The organic layer was collected,
dried and concentrated to give a residue, which, after
chromatography (4:1 petroleum ether/EtOAc), afforded 18
(135 mg, 78%) as an oil. [a]D K41.4 (c 1.0, CH2Cl2). IR
H-5B), 3.99 (m, 2H, H-2A, H-3A), 3.75 (dq, 1H, J5,4
Z
1
(thin film, NaCl) 3517, 3039, 1731, 1250 cmK1; H NMR
9.3 Hz, J5,6Z6.0 Hz, H-5A), 3.63 (dd, 1H, J2,3Z11.4 Hz,
J2,1Z3.3 Hz, H-2B), 3.52 (t, 1H, J4,3ZJ4,5Z9.3 Hz, H-4A),
3.36 (s, 3H, OMe), 2.05 (s, 3H, OAc), 1.79 (s, 3H, NAc),
1.38 (d, 3H, J6,5Z6.0 Hz, H-6A), 0.73 (d, 3H, J6,5Z6.6 Hz,
H-6B); 13C NMR (CDCl3, 100 MHz) d 169.9 (COCH3),
138.1, 137.1 (2 Cipso), 128.7–127.5 (C-Ar), 99.9 (C-1A),
93.3 (C-1B), 79.3, 77.1, 75.5, 73.1, 73.0, 72.7, 67.6, 67.2
(C-2A, C-2B, C-3A, C-4A, C-4B, C-5A, C-5B, 2 OCH2Ph),
54.6 (OMe), 48.1 (C-3B), 23.1, 20.5 (2 COCH3), 17.9
(C-6A), 15.8 (C-6B). ESI-MS for C31H41NO10 (m/z): Mr
(calcd) 587.27, Mr (found) 610.00 (MCNa)C. Anal. Calcd:
C, 63.36; H, 7.03; N, 2.38. Found: C, 63.55; H, 6.96; N,
2.34.
(CDCl3, 200 MHz) d 8.05–7.34 (m, 10H, H-Ar), 5.26 (dd,
1H, J2,3Z3.6 Hz, J2,1Z1.8 Hz, H2), 5.12 (t, 1H, J4,3
J4,5Z9.8 Hz, H4), 4.91 (d, 1H, J1,2Z1.8 Hz, H1), 4.74 (d,
1H, JgemZ12.0 Hz, OCHHPh), 4.55 (d, 1H, JgemZ12.0 Hz,
OCHHPh), 4.22 (dd, 1H, J3,4Z9.8 Hz, J2,1Z3.6 Hz, H3),
4.04 (dq, 1H, J5,4Z9.8 Hz, J5,6Z6.2 Hz, H5), 2.87–2.63 (m,
Z
4H, CH2CH2), 2.22 (s, 3H, CH3CO), 1.27 (d, 3H, J6,5
Z
6.2 Hz, H6); 13C NMR (CDCl3, 50 MHz) d 207.2
(CH3C]O), 172.2 (C]O Lev), 166.7 (C]O Bz), 136.8,
133.4 (2 Cipso), 129.8–127.8 (C-Ar), 96.9 (C-1), 75.1, 72.7,
69.6, 68.9, 66.4 (C-2, C-3, C-4, C-5, OCH2Ph), 38.2, 29.7,
28.2 (CH2CH2, CH3C]O), 17.5 (C-6). ESI-MS for
C25H28O8 (m/z): Mr (calcd) 456.18, Mr (found) 479.49
(MCNa)C. Anal. Calcd: C, 65.78; H, 6.18. Found: C,
65.78; H, 6.25.
4.3.7. Methyl(2,4-di-O-benzoyl-3-O-chloroacetyl-a-L-
rhamnopyranosyl)-(1/3)-(2,4-di-O-benzoyl-a-L-rham-
nopyranosyl)-(1/2)-(3,4-di-O-benzoyl-a-L-rhamnopyr-
anosyl)-(1/2)-[4-O-acetyl-3-acetylamino-2-O-benzyl-a-
D-fucopyranosyl-(1/3)]-4-O-benzyl-a-L-rhamnopyra-
noside (22). A mixture of 21 (20 mg, 34.1 mmol) and 13
(66 mg, 50.8 mmol) was co-evaporated three times with
toluene, the residue was then mixed with freshly powdered
4.3.5. Methyl(4-O-acetyl-3-acetamido-2-O-benzyl-a-D-
fucopyranosyl)-(1/3)-2-O-allyl-4-O-benzyl-a-L-rham-
nopyranoside (20). See the general procedure for D-Fucp3-
NAc couplings in CH2Cl2 and in dioxane/toluene/DME
4:1:1 v/v/v. (a-anomer). [a]D C20.4 (c 0.6, CH2Cl2). IR
1
(thin film, NaCl) 3019, 2956, 1747, 1665, 1253 cmK1; H
AW-300 4 A molecular sieves, suspended under argon in
˚
NMR (CDCl3, 400 MHz) d 7.42–7.27 (m, 10H, H-Ar), 5.87
(m, 1H, OCH2CH]CH2), 5.24 (dd, 1H, JvicZ17.3 Hz,
CH2Cl2 (2.0 mL) and stirred at K20 8C. BF3$OEt2 (3.2 mL,
25.4 mmol) was then added. After 24 h, an additional aliquot
of 13 (44 mg, 33.9 mmol) and BF3$OEt2 (2.1 mL,
16.9 mmol) was added. After an additional day the reaction
was quenched with a drop of Et3N. After filtration over a
Celite pad, the mixture was concentrated to give a residue,
that, after column chromatography (1:1 petroleum ether/
EtOAc), afforded 22 (30 mg, 51%) as a white foam. [a]D
C113.3 (c 1.0, CH2Cl2). IR (thin film, NaCl) 3052, 3028,
JgemZ1.7 Hz, OCH2CH]CHH trans), 5.21 (d, 1H, J1,2
Z
3.4 Hz, H-1B), 5.14 (dd, 1H, JvicZ10.2 Hz, JgemZ1.7 Hz,
OCH2CH]CHH cis), 5.07 (d, 1H, J4,3Z3.0 Hz, H-4B),
4.86 (d, 1H, JgemZ10.5 Hz, OCHHPh), 4.81–4.60 (m, 5H,
H-1A, H-3B, NH, 2 OCHHPh), 4.43 (d, 1H, JgemZ12.0 Hz,
OCHHPh), 4.27–4.09 (m, 3H, H-5B, OCH2CH]CH2), 4.05
(dd, 1H, J3,4Z8.7 Hz, J3,2Z2.7 Hz, H-3A), 3.79 (bs, 1H,
1
H-2A), 3.71 (m, 2H, H-2B, H-5A), 3.61 (t, 1H, J4,3Z J4,5
Z
1739, 1656, 1249 cmK1; H NMR (CDCl3, 400 MHz) d
9.3 Hz, H-4A), 3.33 (m, 3H, OMe), 2.04 (s, 3H, OAc), 1.79
(s, 3H, NAc), 1.37 (d, 3H, J6,5Z6.0 Hz, H-6A), 0.78 (d, 3H,
J6,5Z6.6 Hz, H-6B); 13C NMR (CDCl3, 100 MHz) d 169.9
(COCH3), 138.1, 138.0 (2 Cipso), 134.9 (OCH2CH]CH2),
129.6–127.7 (C-Ar), 117.2 (OCH2CH]CH2), 98.9 (C-1A),
93.6 (C-1B), 79.8, 75.5, 74.4, 72.9, 72.8, 72.2, 71.6, 68.1,
68.0, 65.1 (C-2A, C-2B, C-3A, C-4A, C-4B, C-5A, C-5B,
OCH2Ph, OCH2CH]CH2), 54.7 (OMe), 48.1 (C-3B), 23.1,
20.6 (2 COCH3), 18.1, 15.9 (C-6A, C-6B). ESI-MS for
C34H45NO10 (m/z): Mr (calcd) 627.72, Mr (found) 650.50
8.18–7.10 (m, 40H), 5.83 (dd, 1H, J3,4Z9.6 Hz, J3,2Z
2.8 Hz, H-3B), 5.72 (d, 1H, J2,3Z3.0 Hz, H-2C), 5.59 (t, 1H,
J4,3ZJ4,5Z10.0 Hz, H-4B), 5.56 (t, 1H, J4,3ZJ4,5Z9.6 Hz,
H-4C), 5.44 (dd, 1H, J3,4Z9.8 Hz, J3,2Z2.8 Hz, H-3D), 5.34
(m, 2H, H-1B, H-4D), 5.18 (m, 3H, H-1D, H-1E, H-2D), 5.11
(d, 1H, J4,3Z2.8 Hz, H-4E), 5.06 (bs, 1H, H-1C), 4.90 (d,
1H, JgemZ10.8 Hz, OCHHPh), 4.87 (d, 1H, JgemZ12.0 Hz,
OCHHPh), 4.84 (bs, 1H, H-1A), 4.76 (d, 1H, JgemZ10.8 Hz,
OCHHPh), 4.63 (m, 2H, H-3C, NH), 4.50 (m, 1H, H-3E),
4.42 (d, 1H, JgemZ12.0 Hz, OCHHPh), 4.34 (bs, 1H, H-2B),

E. Bedini et al. / Tetrahedron 61 (2005) 5439–5448
5447
4.30–4.20 (m, 4H, H-5B, H-5C, H-5D, H-5E), 4.13 (dd, 1H,
J3,4Z9.6 Hz, J3,2Z2.8 Hz, H-3A), 4.08 (bs, 1H, H-2A),
3.79–3.64 (m, 5H, H-2E, H-4A, H-5A, CH2Cl), 3.37 (s, 3H,
OMe), 1.96 (s, 3H, OAc), 1.54 (s, 3H, NAc), 1.42 (d, 3H,
J6,5Z6.0 Hz, H-6A), 1.33 (m, 6H, H-6B, H-6C), 1.18 (d, 3H,
J6,5Z6.2 Hz, H-6D), 0.77 (d, 3H, J6,5Z6.6 Hz, H-6E); 13C
NMR (CDCl3, 100 MHz) d 166.9 (COCH2Cl), 165.4–164.5
(COCH3, COPh), 138.2, 137.1 (2 Cipso), 133.4–128.0
Dr. Alfonso Iadonisi for the several fruitful conversations
and advices. The NMR spectra were performed at CIMCF
(Centro di Metodologie Chimico-Fisiche) of University
‘Federico II’ of Naples.
1
(C-Ar), 100.5 (C-1B), 99.8 (C-1C, JC,HZ173 Hz), 99.6
References and notes
(C-1A), 98.9 (C-1E), 94.2 (C-1E), 79.8 (C-4A), 78.7 (C-2B),
76.6 (C-2A), 75.7 (C-3A), 75.5 (OCH2Ph), 74.4 (C-3C), 73.5
(C-4C), 72.7 (C-4E), 72.2 (C-2E), 72.0 (C-4B), 71.8 (C-2C),
71.5 (C-4D, OCH2Ph), 70.4 (C-3B), 70.3 (C-3D), 68.2
(C-5A), 67.8–67.2 (C-5B, C-5C, C-5D, C-5E), 55.0 (OMe),
48.1 (C-3E), 40.2 (COCH2Cl), 22.9, 20.4 (2 COCH3), 18.1
(C-6A), 17.7 (C-6B, C-6C), 17.3 (C-6D), 15.8 (C-6E). ESI-
MS for C93H96ClNO29 (m/z): Mr (calcd) 1725.58, Mr
(found) 1748.05 (MCNa)C. Anal. Calcd: C, 64.67; H,
5.60; N, 0.81. Found: C, 64.57; H, 5.80; N, 0.75.
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6.5 Hz, H-5E), 4.25 (dd, 1H, J3,2Z11.1 Hz, J3,4Z2.9 Hz,
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3.6 Hz, J2,1Z1.6 Hz, H-2D), 4.04 (dd, 1H, J2,3Z3.6 Hz,
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H-4C), 3.49 (t, 1H, J4,3ZJ4,5Z9.8 Hz, H-4B), 3.46 (t, 1H,
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Z
6.2 Hz, H-6B, H-6D), 1.26 (d, 3H, J6,5Z6.2 Hz, H-6C), 1.18
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165.5 (COCH3), 102.4 (C-1D), 101.8 (C-1C), 100.5 (C-1B),
99.4 (C-1A), 94.5 (C-1E), 78.5 (C-2B), 78.0 (C-3C), 75.0
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