Synthesis of a bicyclic analog of l-iduronic acid adopting the biologically relevant 2S0 conformation

Article abstract of DOI:10.1016/j.carres.2007.02.025

The synthesis of a bicyclic analogue of the naturally occurring α-l-iduronic acid locked in a biologically active ²S₀ skewboat conformation is disclosed. The desired ²S₀ conformation has been obtained by tetheri

Full text of DOI:10.1016/j.carres.2007.02.025

Carbohydrate Research 342 (2007) 1876–1887
Synthesis of a bicyclic analog of L-iduronic acid adopting
2
the biologically relevant S0 conformation
Antonio J. Herrera,a,b, Marita T. Beneitez,a,b, Luis Amorim,a,b, F. Javier Canada,c
˜
c
a,b
a,b,
*
´
´
Jesu´s Jimenez-Barbero, Pierre Sinay and Yves Bleriot
¨
aEcole Normale Supe´rieure, De´partement de Chimie, UMR 8642 Associe´e au CNRS, 24 rue Lhomond, 75231 Paris Cedex 05, France
bInstitut de Chimie Mole´culaire (FR 2769), Universite´ Pierre et Marie Curie-Paris 6, 75005 Paris, France
cCentro de Investigaciones Biologicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
Received 30 January 2007; received in revised form 14 February 2007; accepted 21 February 2007
Available online 25 February 2007
Abstract—The synthesis of a bicyclic analogue of the naturally occurring a-L-iduronic acid locked in a biologically active 2S0 skew-
boat conformation is disclosed. The desired 2S0 conformation has been obtained by tethering the C-2 and C-5 carbon atoms of the
sugar ring with a dimethyloxy bridge and confirmed by NMR and molecular modeling. The new mimic displays the exact hydroxyl
pattern of a-L-iduronic acid, a major monosaccharide component of glycosaminoglycans and thus represents a closer mimic of the
latter, compared to previously reported bicyclic analogs.
OTs
O
O
HO
HO
BnO
HO2C
HO
HO
HO2C
R'O
HO
Diacetone
glucose
O
OR
O
O
O
OH
L-iduronic acid mimic
OH
OH
BnO
L-iduronic acid unit
in the biologically active
2S0 conformation
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Conformation; Glycosaminoglycans; Heparin; Iduronic acid; Scaffold
1. Introduction
properties of GAGs containing L-iduronic acid.4 More
specifically, NMR studies5 on the synthetic pentasaccha-
ride 16 (Fig. 1), representing the antithrombin binding
site of heparin and containing only one L-iduronic acid
residue, suggested a large contribution of the unusual
2S0 skewboat conformer7 in such a pentamer where it
is adjacent to a 3-O-sulfonated aminosugar residue.4a
To establish a correlation between conformation and
antithrombotic activity, the total synthesis of the three
pentasaccharides 2–4 was achieved,8 in which the L-idu-
ronic acid residue was conformationally locked, either in
The conformation of L-iduronic acid residues in glycos-
aminoglycans (GAGs) such as heparin, heparan sulfate,
and dermatan sulfate was earlier the cause of a long con-
troversy.1,2 Thanks to the availability of well defined
synthetic oligosaccharides, it has been unambiguously
demonstrated that such residues are in equilibrium
1
4
2
between three conformations: C4, C1, and S0.3 This
unique conformational flexibility emerged as a new
concept for explaining the recognition and biological
1
4
2
a C4 , C1 or S0 form. In these compounds, several
hydroxyl groups and all the N-sulfonates were replaced
by methoxy groups and O-sulfonates, respectively, a
change that greatly simplified the synthetic route but
*
Corresponding author. E-mail: yves.bleriot@ens.fr
These three authors contributed equally to this work.
0008-6215/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2007.02.025

A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
1877
-
ketone, which was directly used without purification
and treated with vinyl magnesium bromide to afford
the allylic alcohol 10 as a single product in 75% yield,
the stereochemistry at C-2 for this compound being
not firmly established at this stage.à Ozonolysis
followed by reduction with NaBH4 yielded diol 11
(37% yield over two steps, unoptimized). Regioselective
tosylation at the primary position afforded tosylate 12,
from which the isopropylidene group was removed
under mild acidic conditions to furnish triol 13 in
excellent yield.
OSO3
O
OH
-
OSO3
OMe
NHSO3
O
-
O
O
COO-
OH
-
OSO3
OSO3
O
COO-
-
O
O
-
-
OSO3
O
NHSO3
OH
OH
OH
O
L-iduronic
acid unit
-
OH
NHSO3
essential groups
contributing groups
The key cyclization step was then achieved by treat-
ment of triol 13 under basic conditions with NaH in
dry DMF to afford 14 in a modest 20% yield along with
more polar unidentified products. Its structure was
firmly established as follows: hydrogenolysis of the benz-
yl groups and subsequent per-acetylation of the crude
compound afforded a crystalline compound 15, the X-
ray structure of which was solved (Fig. 3).§ The struc-
ture of tetracetate 15 clearly indicates that the bicyclic
compound 14 arises from displacement of the tosyl
group at C-2 in 13 by the OH group at C-4. This in
turn demonstrates addition of the Grignard reagent
from the a-face of the transient ketone yielding the
undesired D-manno configured isomer, 10. As described
by Ley and co-workers in a paper that appeared after
we undertook this research,15 the stereoselectivity of
the addition of the Grignard reagent can be rational-
ized by the b-configuration of the anomeric substituent
in the ketone favoring a trans addition at C-2 (see
Scheme 1).
Figure 1. Structure of pentasaccharide 1 with essential and contri-
buting groups (reproduced from Petitou and van Boeckel).12b
which did not affect their biological activity.9,10 It was
concluded that antithrombin-bound L-iduronic acid
adopts the 2S0 skewboat conformation, which thus
governs the antithrombotic activity of heparin (Fig. 2).
Another pentasaccharide, 5, containing a slightly more
flexible L-iduronic acid unit was later prepared.11 In
these first- and second-generation pentamers 3 and 5,
respectively, and as the logical result of the selected syn-
thetic strategy, the hydroxyl group at C-2 of the parent
L-iduronic acid was missing. In the specific case of anti-
thrombin mediated activity, this substituent was shown
not to be essential, albeit contributing to an increase
of the activity;12 actually, the effect of the missing substi-
tuent is compensated by the sulfate group located at C-3
of the D-glucosamine unit.13 In the more general context
of GAGs biological studies, the synthesis of a closer
2
mimic of L-iduronic acid locked around the S0 confor-
mation and retaining all the hydroxyl groups is of interest
and is disclosed in this piece of work. Our selected
new third-generation scaffold 6 has its oxygen atom of
the bridging unit moved one atom away from C-2, to
generate a stable structure of ether type (Fig. 2).
2.2. Second approach
Another route, based on the dihydroxylation of an
exomethylene installed at C-2, was envisioned to provide
the desired D-gluco configured stereoisomer (Scheme 2).
Cis dihydroxylation of C-alkylidene carbohydrates with
OsO4 has been shown to proceed from the less hindered
face of the olefin.16 In our case, the isopropylidene
group and the b-anomeric isopropyl group should favor
a dihydroxylation from the a face of the sugar ring to
produce the desired D-gluco stereoisomer.
2. Results and discussion
2.1. First approach
The first approach started from the known D-glucose
derivative 714 available from diacetone glucose. The
choice of the isopropyl group as the anomeric substitu-
ent was imposed by the poor glycosylation step of the
thiophenyl glycosyl donor with methanol. Alkene 7
was ozonolyzed and further reduced with LiAlH4 to
yield primary alcohol 8 in 70% yield. O-Benzylation fol-
lowed by silyl group removal with TBAF afforded alco-
hol 9. The required stereoselective installation of a
latent leaving group at position 2 while retaining a D-
gluco configured scaffold having two extra substituents
at positions 2 and 5 was performed as follows. Swern
oxidation of alcohol 9 furnished the corresponding
à NOE experiments gave ambiguous results on this structure.
§ Selected crystal structure data for 15; crystal system orthorhombic;
space group P212121; Z = 4; cell parameters: a = 10.485(5),
b = 14.231(10), c = 14.836(10), a = 90, b = 90, c = 90; radiation
˚
(Mo Ka) k = 0.71069 A; 193 variables for 1169 reflections; final
R = 0.1142, RW = 0.1327; crystallographic data (excluding structure
factors) have been deposited at the Cambridge Crystallographic Data
Centre as Supplementary Publication No. CCDC 604630. Copies of
the data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK [fax: (internat.) +44-1223/
336-033; e-mail: deposit@ccdc.cam.ac.uk].

1878
A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
NaO3SO
NaO3SO
O
OMe
MeO
O
OSO3Na
OMe
MeO
O
MeO
MeO
L-iduronic acid
analogs 2,3,4,5
O
O
O
O
NaOOC
NaO3SO
OSO3Na
OSO3Na
NaO3SO
O
OMe
O
O
O
O
O
-OOC
MeO
O
-OOC
MeO
-OOC
MeO
-OOC
O
OMe
4 (4C1)
OMe
2 (1C4)
3 (2S0)
5 (2S0)
O
HOOC
HO
OiPr
O OH
HO
6
Figure 2. Structure of pentasaccharides 2–5 and new L-iduronic acid mimic 6.
followed by subsequent intramolecular opening with
the alkoxide at C-6. Finally, hydrogenolysis of the
benzyl groups followed by chemoselective oxidation of
the primary alcohol with TEMPO18 afforded the corre-
sponding crude carboxylic acid, which was protected
as its benzyl ester 21 (75% yield over three steps) for ease
of purification. Hydrogenolysis of the benzyl group
furnished the desired a-L-iduronic acid analog 6 in pure
form and excellent yield. Several attempts to crystallize
derivatives of 6 were unsuccessful.
However, the 2S0 skewboat conformation of com-
pound 6 was confirmed by NMR and molecular model-
ing (Table 1). L-Iduronic acid mimic 6 exists as an
2
equilibrium between two S0-like skewboat conformers,
Figure 3. X-ray structure of compound 15.
A and B, that simply differ by the orientation of the
bridged oxygen which is pointing either towards the
anomeric oxygen or toward the carboxylic group,
respectively. For each conformer, there is a slight differ-
ence in the shape of the six-membered ring, as deduced
from the expected J3,4 coupling values for the two con-
formers (which only differ by 0.3 kJ/mol according to
MM3* calculations). According to the MM3* energies
and, more importantly, to the experimental NOEs
(Table 1), conformer A is predominant (Fig. 4). Due
to the flexibility of the three atom bridge in compound
6 and as observed in bicycle 5,11 5S1 and 1,5B conforma-
tions cannot be excluded for the pyranose ring of 6.
In conclusion, the synthesis of a a-L-iduronic acid
mimic 6 locked in the biologically relevant 2S0 skewboat
conformation and displaying the full hydroxyl pattern
of L-iduronic acid has been achieved for the first time.
Fine tuning of the biological activities of GAGs frag-
ments may result from a freezing of appropriate locked
conformations of their residues. In this respect, the
availability of this third generation L-iduronic acid scaf-
fold is of interest.
Starting from alcohol 9, Wittig olefination of the tran-
sient ketone described above furnished the C-2 methyl-
ene glycoside 16 in 86% yield17 which, upon
dihydroxylation, gave a single diol 17 in 85% yield. A
sequence similar as the one described above was then
applied. Regioselective tosylation of the primary alcohol
yielded tosylate 18 in 83% yield and subsequent removal
of the isopropylidene group under mild acidic condi-
tions afforded triol 19 in 96% yield. Comparison of the
spectroscopic data obtained for the new diol 17, tosyl
derivative 18 and triol 19 with the previous D-manno
configured diol 11, tosyl derivative 12 and triol 13
showed significant discrepancies that confirmed the
D-gluco configuration for the molecules obtained with
the second route.
The key cyclization of triol 19 under basic conditions
smoothly afforded a less polar compound 20, the NMR
data of which were in accordance with the expected
bicyclic structure. This cyclization step may possibly
occur via transient spiroepoxide formation at C-2

A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
1879
O
O
ref. 14
1) BnBr, NaH, DMF, rt
2) TBAF, THF, rt
O
O
Diacetone glucose
O
O
OiPr
OTBDMS
OiPr
BnO
BnO
BnO
R
OH
96%
9
7 : R = CH=CH2
8 : R = CH2OH
1) O3, CH2Cl2, -78 °C
2) LiAlH4, THF, 0 °C
1) (COCl)2, DMSO
Et3N, CH2Cl2, -78 °C
70%
2) CH2=CHMgBr, THF, -78 °C
74%
OH
HO
OH
O
OH
O
O
O
1) O3, CH2Cl2, -78 °C
CSA, MeOH, rt
O
HO
OiPr
O
O
OiPr
OiPr
BnO
BnO
BnO
BnO
2) NaBH4, MeOH, rt
37%
93%
BnO
BnO
OR
OTs
10
13
- only one isomer formed
- stereochemistry at C-2
undetermined at this point
11 : R = H
TsCl, pyr.
DMAP, rt
12 : R = Ts
NaH, DMF, 70 °C
74%
20%
OAc
OiPr
OH
1) H2, 10% Pd/C
MeOH/AcOEt, rt
OiPr
OH
AcO
OH
O
OAc
BnO
OBn
O
O
O
OAc
O
OiPr
BnO
BnO
10
2) Ac2O, pyr.
DMAP, rt
O
O
15
70%
14
Scheme 1.
1) (COCl)2, DMSO
Et3N, CH2Cl2 , -78 °C
OsO4, NMO
acetone/H2O, rt
OH
O
O
O
O
O
O
O
O
O
OiPr
OiPr
OiPr
BnO
BnO
BnO
BnO
BnO
BnO
2) PPh3CH2Br, BuLi,
0 °C to rt
OH
OH
17
16
9
85%
86%
TsCl, pyr.
DMAP, rt
83%
OTs
O
OTs
HO
HO
BnO
BnO
HO
O
O
NaH, DMF, 70 °C
CSA, MeOH, rt
96%
O
OiPr
O
OiPr
OH
OiPr
BnO
BnO
O
71%
BnO
OH
BnO
OH
20
19
18
1) H2, 10% Pd/C, EtOAc, rt
2) TEMPO, KBr, NaOCl, CH2Cl2, rt
3) BnBr, KHCO3, Bu4NI, DMF, rt
75%
H2, Pd black
MeOH, rt
O
O
BnO2C
HO2C
HO
HO
OiPr
OH
OiPr
OH
HO
O
O
HO
quant.
6
21
Scheme 2.
3. Experimental
3.1. General methods
Ar, unless stated. Melting points were recorded on a
Buchi 535 and are uncorrected. Optical rotations were
¨
measured on a Perkin–Elmer 241 digital polarimeter
with a path length of 1 dm. Mass spectra were recorded
on a JMS-700 spectrometer, using chemical ionization
with ammonia or FAB. NMR spectra were recorded
Solvents were freshly distilled from Na/benzophenone
(THF), or P2O5 (CH2Cl2). Reactions were carried under

1880
A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
used a double pulse field gradient spin echo22 for selec-
tion of the chosen resonance followed by the corre-
sponding mixing sequence.
Table 1. Experimental and calculated NMR data for L-iduronic acid
analog 6a
Experimental
Calculated (MM/MC/MD)
Molecular mechanics calculations were performed
using the MacroModel/Batchmin23 package (version
7.0) and the MM3* force field.24 Bulk water solvation
was simulated using MacroModel’s generalized Born
GB/SA continuum solvent model.25 Energy minimiza-
tions were conducted using the conjugate gradient
method until convergence according to the internal
criterion of the program. Experimental and expected J
and NOE data were compared as described.26 J Values
were estimated from the MM3* geometries by applying
the generalized Karplus equation proposed by Altona
and co-workers.27
Conformer A
Conformer B
3JH,H (Hz)
3JH,H (Hz)
J3,4 2.0
NOE
3JH,H (Hz)
J3,4 0.7
Key interproton distancesb (A)
J3,4 4.0
˚
Proton pair
H1/H3
H3/H4
H1/CH isopropyl
H7/CH isopropyl
CH isopropyl/H1
Intensity
s
mw
s
mw
w
2.5
2.9
2.5
3.0
3.2
2.5
3.0
2.5
3.8
3.2
a Experimental and calculated J34 values and experimental (s, strong,
m, medium and w, weak) NOEs observed for compound 6.
b Key interproton distances that may be correlated with the experi-
mental NOEs.
3.3. Structure numbering
1
on a Bruker DRX-400 (400 and 100.6 MHz, for H and
The following numberings by analogy with the parent
sugars were used:
13C, respectively) or a Bruker AC-250 (250 and 63 MHz,
for 1H and 13C, respectively). TLC was performed on sil-
ica gel 60 F254 (Merck) and developed by charring with
H2SO4 in ethanol. Flash column chromatography was
performed using silica gel 60 (230–400 mesh, Merck).
OAc
8
6
OTs
O
6
5
OiPr
6
7
HO
8
AcO
OAc
O
5
7
O
1
BnO
HO
4
5
HO
OiPr
2
1
7
OiPr
OAc
1
BnO
2
4
3
4
3
O
2
8
3
OH
OH
BnO
BnO
O
3.2. NMR and molecular modeling of 6
NMR spectra were recorded at 298 K in D2O on Bruker
AVANCE 500 MHz spectrometers. TOCSY19 and
HSQC20 experiments were performed using the standard
sequences. Selective 1D and 2D NOESY21 were per-
formed with mixing times of 350, 500, and 600 ms.
The selective 1D NOESY versions of the experiments
3.4. NMR Assignments
Assignment of protons and carbons at C-6, C-7, and C-8
for some compounds proved to be difficult and these
signals are therefore sometimes not unambiguously
assigned.
Conformer B
Conformer A
6
6
O
O
7
7
HOOC
HO4
HO2C
HO
HO
5
2
5
O
O
1
4
1
O
3
O
2
OH
3
HO
OH
Figure 4. Conformations A and B adopted by L-iduronic acid mimic 6.

A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
1881
3.5. Isopropyl 3-O-benzyl-2-O-tert-butyldimethylsilyl-
4,6-O-isopropylidene-5-C-hydroxymethyl-b-D-gluco-
pyranoside (8)
which was directly dissolved in dry THF (10 mL) under
argon. Tetrabutylammonium fluoride (8.0 mL, 8.0
mmol, 1 M in THF) was added and the reaction mixture
was stirred overnight at rt and then quenched by the
addition of water and extracted with EtOAc. The com-
bined organic layers were washed with water and brine,
dried over MgSO4 and concentrated. Purification by
flash column chromatography (cyclohexane–EtOAc,
4:1) afforded alcohol 9 (1.20 g, 96%) as a white crystal-
line compound. [a]D ꢀ17 (c 0.8, CHCl3); mp 97–98 ꢁC
(EtOAc–n-pentane); 1H NMR (CDCl3, 400 MHz): d
7.40–7.30 (m, 10H, 2 · Ph), 4.87 (d, H, J = 11.8 Hz,
CH2Ph), 4.85 (d, H, J = 7.8 Hz, H-1), 4.76 (d, H,
J = 11.8 Hz, CH2Ph), 4.68 (d, 1H, J = 11.9 Hz, CH2Ph),
4.61 (d, 1H, J = 11.9 Hz, CH2Ph), 4.00 (sept.,
J = 6.1 Hz, CH isopropyl), 3.96 (d, 1H, J = 10.7 Hz,
H-6), 3.95 (d, 1H, J = 10.6 Hz, H-4), 3.94 (d, 1H,
J = 10.7 Hz, H-7), 3.90 (d, 1H, J = 10.7 Hz, H-60),
3.84 (dd, 1H, J = 8.2 Hz, 10.6 Hz, H-3), 3.69 (d, 1H,
J = 10.7 Hz, H-70), 3.55 (dt, 1H, J = 2.8 Hz,
J = 7.8 Hz, H-2), 2.50 (d, 1H, J = 2.8 Hz, OH), 1.52
(s, 3H, CH3 isopropylidene), 1.45 (s, 3H, CH3 isopropyl-
idene), 1.27 (d, 3H, J = 6.1 Hz, CH3 isopropyl), 1.21 (d,
3H, J = 6.1 Hz, CH3 isopropyl); 13C NMR (CDCl3,
100 MHz): d 138.85, 137.84 (2 · Cipso), 128.38–127.49
(2 · Ph), 100.31 (C isopropylidene), 97.92 (C-1), 77.52
(C-3), 75.85 (C-4), 75.37 (C-2), 73.96, 73.63
(2 · CH2Ph), 71.95 (CH isopropyl), 70.56 (C-5), 66.17
(C-6), 65.73 (C-7), 29.33 (CH3 isopropylidene), 23.32
(CH3 isopropyl), 21.92 (CH3 isopropyl), 19.01 (CH3
isopropylidene); m/z (CI, NH3): 490 ([M+NH4]+,
100%), 473 ([M+H]+, 10%); HRMS (CI, NH3):
calcd for C27H40NO7 [M+NH4]+: 490.2805. Found:
490.2807.
Vinyl derivative 7 (450 mg, 0.9 mmol) was dissolved in
CH2Cl2 (15 mL) and the solution was cooled to
ꢀ78 ꢁC. Ozone was bubbled through the solution under
stirring until persistence of a pale blue color (10 min).
Excess of ozone was quenched by the addition of
Me2S and the reaction mixture was stirring for 1 h and
allowed to reach rt. The solvent was removed under re-
duced pressure and the crude aldehyde was directly used
for the next reaction. The crude aldehyde was dissolved
in dry THF (35 mL) under argon and the solution was
cooled to ꢀ10 ꢁC. Lithium aluminum hydride (34 mg,
0.9 mmol) was added slowly and the reaction mixture
was stirred for 1 h and warmed to 0 ꢁC. The reaction
was quenched at 0 ꢁC by adding a few drops of water
followed by a few drops of a 15% w/v solution of
NaOH. After stirring for 5 min at 0 ꢁC and 30 min at
rt, a white precipitate was formed and filtered off. The
filtrate was concentrated and the residue was purified
by flash column chromatography (cyclohexane–EtOAc,
4:1) to afford alcohol 8 (312 mg, 0.63 mmol, 70%) as a
white solid. [a]D ꢀ59 (c 1.0, CHCl3); mp 78–79 ꢁC
1
(EtOAc–cyclohexane); H NMR (CDCl3, 400 MHz): d
7.36–7.30 (m, 5H, Ph), 4.81 (d, 1H, J = 11.0 Hz,
CH2Ph), 4.77 (d, 1H, J = 7.1 Hz, H-1), 4.67 (d, 1H,
J = 11.0 Hz, CH2Ph), 4.13 (m, H-7), 4.07–4.00 (m, 3H,
H-4, H-70, CH isopropyl), 3.97 (d, J = 10.7 Hz, H-6),
3.63 (dd, J = 7.5 Hz, J = 10.2 Hz, H-3), 3.62 (dd,
J = 0.8 Hz, J = 10.7 Hz, H-60), 3.56 (t, 1H, J = 7.1 Hz,
H-2), 1.49 (s, 3H, CH3 isopropylidene), 1.44 (s, 3H,
CH3 isopropylidene), 1.28 (d, 3H, J = 6.2 Hz, CH3 iso-
propyl), 1.23 (d, 3H, J = 6.2 Hz, CH3 isopropyl), 0.93
(s, 9H, t-Bu), 0.12 (s, 3H, SiCH3), 0.08 (s, 3H, SiCH3);
13C NMR (CDCl3, 100 MHz): d 138.76 (Cipso), 128.09–
127.36 (Ph), 100.23 (C isopropylidene), 97.77
(C-1), 78.76 (C-3), 75.93 (C-2), 75.85 (C-4), 74.34
(CH2Ph) 70.93 (CH isopropyl), 70.53 (C-5), 64.83
(C-6), 57.73 (C-7), 29.32 (CH3 isopropylidene), 25.86
(t-Bu), 23.46, 21.45 (2 · CH3 isopropyl), 18.95 (CH3
isopropylidene), ꢀ4.22, ꢀ4.41 (2 · SiCH3); m/z (CI,
NH3): 514 ([M+NH4]+, 100%); HRMS (CI, NH3): calcd
for C26H48NO7Si [M+NH4]+: 514.3200. Found:
514.3204.
3.7. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-4,6-O-
isopropylidene-2-C-vinyl-b-D-mannopyranoside (10)
Oxalyl chloride (1.17 mL, 13.7 mmol) was added drop-
wise under argon to a stirred solution of dry DMSO
(1.62 mL, 22.8 mmol) in dry CH2Cl2 (10 mL) cooled to
ꢀ78 ꢁC, and the reaction mixture was stirred for
30 min at ꢀ78 ꢁC. A solution of alcohol 9 (2.15 g,
4.56 mmol) in dry CH2Cl2 (20 mL) was added dropwise
to the solution and the reaction mixture was stirred for
1 h at ꢀ78 ꢁC. Triethylamine (3.8 mL, 27.4 mmol) was
added and the reaction mixture was warmed to rt for
30 min. The reaction mixture was diluted with CH2Cl2
and washed with water. The organic layer was dried
over MgSO4 and concentrated to afford the rather
unstable ketone that was dissolved in dry THF
(20 mL) under argon. This solution was cooled to
ꢀ78 ꢁC and vinyl magnesium bromide (16 mL,
16 mmol, 1 M solution in THF) was added and the reac-
tion mixture was stirred for 4 h at ꢀ78 ꢁC under argon.
Ammonium chloride (satd aq solution) was added to
3.6. Isopropyl 3-O-benzyl-4,6-O-isopropylidene-5-C-benz-
yloxymethyl-b-D-glucopyranoside (9)
Alcohol 8 (1.30 g, 2.62 mmol) and BnBr (0.6 mL,
5.2 mmol) were dissolved in dry DMF (26 mL) under
argon. NaH (209 mg, 5.2 mmol) was added by portions
at 0 ꢁC. After stirring for 90 min at rt, the reaction mix-
ture was quenched by the addition of MeOH (5 mL). The
solvent was evaporated to afford the crude benzyl ether,

1882
A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
quench the reaction and the reaction mixture was
extracted with EtOAc. The organic layer was dried over
MgSO4 and concentrated. Purification by flash column
chromatography (cyclohexane–EtOAc, 5:1 then 3:1)
afforded alcohol 10 (1.67 g, 3.36 mmol, 74%) as a solid.
[a]D ꢀ31 (c 1.0, CHCl3); mp 81–82 ꢁC (EtOAc–cyclo-
CH2Ph), 4.48 (d, 1H, J = 10.4 Hz, H-4), 4.02–3.88 (m,
5H, H-3, H-6, H-60, H-7, CH isopropyl), 3.77 (d, 1H,
J = 10.6 Hz, H-70), 3.46 (m, 2H, H-8, H-80), 1.58 (s,
3H, CH3 isopropylidene), 1.48 (s, 3H, CH3 isopropyl-
idene), 1.24 (d, 3H, J = 6.1 Hz, CH3 isopropyl), 1.13
(d, 3H, J = 6.1 Hz, CH3 isopropyl); 13C NMR (CDCl3,
100 MHz): d 138.19, 137.90 (2 · Cipso), 128.85–127.36
(2 · Ph), 100.49 (C isopropylidene), 94.82 (C-1), 76.91
(C-3), 74.85 (C-2), 74.16 (C-4), 74.08 (CH2Ph), 73.70
(CH2Ph), 71.20 (CH isopropyl), 70.88 (C-5), 66.80 (C-
6), 65.82 (C-7), 62.89 (C-8), 29.52 (CH3 isopropylidene),
23.17 (CH3 isopropyl), 21.55 (CH3 isopropyl),
19.33 (CH3 isopropylidene); m/z (CI, NH3): 520
([M+NH4]+, 100%); HRMS (CI, NH3): calcd for
C28H42O8N [M+NH4]+: 520.2910. Found: 520.2914.
1
hexane); H NMR (CDCl3, 400 MHz): d 7.38–7.31 (m,
10H, 2 · Ph), 5.63 (dd, 1H, J = 10.7 Hz, J = 17.3 Hz,
CH@), 5.36 (dd, 1H, J = 1.3 Hz, J = 17.3 Hz, @CH2),
5.23 (dd, 1H, J = 1.3 Hz, J = 10.7 Hz, @CH2), 4.93 (s,
1H, H-1), 4.78 (d, 1H, J = 11.6 Hz, CH2Ph), 4.65 (d,
1H, J = 12.0 Hz, CH2Ph), 4.63 (d, 1H, J = 11.6 Hz,
CH2Ph), 4.58 (d, 1H, J = 12.0 Hz, CH2Ph), 4.42 (d,
1H, J = 10.2 Hz, H-4), 4.09 (d, 1H, J = 10.7 Hz, H-6),
3.95 (d, 1H, J = 10.2 Hz, H-3), 3.90 (sept., J = 6.1 Hz,
CH isopropyl), 3.87 (d, 1H, J = 10.7 Hz, H-60), 3.79
(s, 2H, H-7, H-70), 2.75 (s, 1H, OH), 1.57 (s, 3H, CH3
isopropylidene), 1.48 (s, 3H, CH3 isopropylidene), 1.23
(d, 3H, J = 6.1 Hz, CH3 isopropyl), 1.09 (d, 3H,
J = 6.1 Hz, CH3 isopropyl); 13C NMR (CDCl3,
100 MHz): d 139.04 (CH@), 138.42, 137.77 (2 · Cipso),
128.34–127.42 (2 · Ph), 116.13 (CH2@), 100.51 (C iso-
propylidene), 97.13 (C-1), 77.29 (C-2), 76.02 (C-3),
74.62 (CH2Ph), 73.90 (C-4), 73.75 (CH2Ph), 72.03 (CH
isopropyl), 70.04 (C-5), 68.44 (C-6), 66.22 (C-7), 29.47
(CH3 isopropylidene), 23.06 (CH3 isopropyl), 21.56
(CH3 isopropyl), 19.29 (CH3 isopropylidene); m/z (CI,
NH3): 516 ([M+NH4]+, 100%); HRMS (CI, NH3):
calcd for C29H42O7N [M+NH4]+: 516.2961. Found:
516.2963.
3.9. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-4,6-O-
isopropylidene-2-C-tosyloxymethyl-b-D-mannopyranoside
(12)
Diol 11 (497 mg, 1 mmol) was dissolved in dry pyridine
(2 mL) under argon and TsCl (570 mg, 0.3 mmol) fol-
lowed by a catalytic amount of DMAP were added.
The reaction mixture was stirred for 24 h and more TsCl
(570 mg, 0.3 mmol) was added to complete the reaction.
After 48 h, the reaction was quenched by the addition of
water and extracted with EtOAc. The solvents were
removed under reduced pressure and the residue purified
by flash column chromatography (cyclohexane–EtOAc,
2:1) to afford tosylate 12 (484 mg, 0.73 mmol, 74%) as
a solid along with starting material 11 (122 mg,
0.24 mmol). [a]D ꢀ19 (c 1.0, CHCl3); mp 91–92 ꢁC
3.8. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-4,6-O-
isopropylidene-2-C-hydroxymethyl-b-D-mannopyranoside
(11)
1
(EtOAc–cyclohexane); H NMR (CDCl3, 400 MHz): d
7.78 (d, 2H, CH aromatic), 7.44–7.22 (3 · Ph), 5.13 (s,
1H, H-1), 4.80 (d, 1H, J = 10.9 Hz, CH2Ph), 4.66 (m,
2H, CH2Ph), 4.44 (d, 1H, J = 10.9 Hz, CH2Ph), 4.34
(d, 1H, J = 10.3 Hz, H-3), 4.13 (d, 1H, J = 10.3 Hz,
H-4), 4.11 (d, 1H, J = 8.9 Hz, H-8), 3.99 (d, 1H,
J = 10.8 Hz, H-6), 3.93 (d, 1H, J = 8.9 Hz, H-80), 3.90
(d, 1H, J = 10.8 Hz, H-60), 3.89 (sept., 1H, J = 6.1 Hz,
CH isopropyl), 3.88 (d, 1H, J = 10.6 Hz, H-7), 3.72 (d,
1H, J = 10.6 Hz, H-70), 2.72 (s, 1H, OH), 2.44 (s, 3H,
CH3 tosyl), 1.52 (s, 3H, CH3 isopropylidene), 1.43 (s,
3H, CH3 isopropylidene), 1.19 (d, 3H, J = 6.1 Hz,
CH3 isopropyl), 1.07 (d, 3H, J = 6.1 Hz, CH3 isopro-
pyl); 13C NMR (CDCl3, 100 MHz): d 145.09, 138.11,
137.83, 132.40 (4 · Cipso), 129.89–127.62 (3 · Ph),
100.47 (C isopropylidene), 93.63 (C-1), 75.02 (CH2Ph),
74.48 (C-2), 74.02 (C-3), 73.62 (CH2Ph), 72.75 (C-4),
72.39 (CH isopropyl), 70.02 (C-5), 67.04 (C-8), 66.41
(C-6), 65.68 (C-7), 29.38 (CH3 isopropylidene), 23.11
(CH3 isopropyl), 21.55 (CH3 isopropyl, CH3 tosyl),
19.24 (CH3 isopropylidene); m/z (CI, NH3): 674
([M+NH4]+, 28%), 502 (100%); HRMS (CI, NH3): calcd
for C35H48O10NS [M+NH4]+: 674.2999. Found:
674.2997.
Vinyl derivative 10 (1.67 g, 3.36 mmol) was dissolved in
CH2Cl2 (300 mL) and the solution was cooled to
ꢀ78 ꢁC. Ozone was bubbled through the solution under
stirring until persistence of a pale blue color (10 min).
Excess of ozone was quenched by the addition of
Me2S and the reaction mixture was stirring for 1 h and
allowed to reach rt. The solvent was removed under
reduced pressure and the crude aldehyde was directly used
for the next reaction. The crude aldehyde was dissolved
in MeOH (35 mL) and the solution was cooled to 0 ꢁC.
Sodium borohydride (255 mg, 6.74 mmol) was added
and the reaction mixture was stirred for 3 h at rt and
then concentrated. Purification of the residue by flash
column chromatography (cyclohexane–EtOAc, 3:1)
afforded the corresponding diol 11 (625 mg, 1.24 mmol,
37% over two steps, unoptimized) as a solid. [a]D +17 (c
1
1.0, CHCl3); mp 131–132 ꢁC (EtOAc–cyclohexane); H
NMR (CDCl3, 400 MHz): d 7.41–7.30 (m, 10H,
2 · Ph), 5.02 (s, 1H, H-1), 4.88 (d, 1H, J = 11.7 Hz,
CH2Ph), 4.65 (d, 1H J = 11.7 Hz, CH2Ph), 4.64 (d,
1H, J = 11.6 Hz, CH2Ph), 4.61 (d, 1H, J = 11.6 Hz,

A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
1883
3.10. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-2-C-
tosyloxymethyl-b-D-mannopyranoside (13)
H-80), 3.20 (br s, 1H, OH), 1.33 (d, 3H, J = 6.1 Hz,
CH3 isopropyl), 1.26 (d, 3H, J = 6.1 Hz, CH3 isoprop-
yl); 13C NMR (CDCl3, 400 MHz): d 138.34, 137.89
(2 · Cipso), 128.75–127.18 (2 · Ph), 100.13 (C-1), 78.99
(C-3 or C-4), 78.52, 78.50 (C-2, C-5), 73.85 (C-3 or
C-4), 73.64 (CH2Ph), 70.25 (CH isopropyl), 72.68, 72.35,
64.12 (C-6, C-7, C-8), 72.29 (CH2Ph), 23.43, 21.39
(2 · CH3 isopropyl); m/z (CI, NH3): 445 ([M+H]+,
15%), 462 ([M+NH4]+, 76%); HRMS (CI, NH3): calcd
for C25H36NO7 [M+NH4]+: 462.2495. Found: 462.2492.
Tosyl derivative 12 (392 mg, 0.60 mmol) was dissolved
in MeOH (5 mL) and camphorsulfonic acid (10 mg)
was added. The reaction mixture was stirred for
90 min, quenched by the addition of Amberlite IRA-
400 resin, filtered and the solvent was evaporated under
reduced pressure. Purification of the residue by flash col-
umn chromatography (cyclohexane–EtOAc, 2:1) affor-
ded triol 13 (344 mg, 0.56 mmol, 93%) as a colorless
syrup. [a]D ꢀ38 (c 1.0, CHCl3); 1H NMR (CDCl3,
400 MHz): d 7.74 (d, 2H, Ts), 7.45–7.19 (3 · Ph), 5.11
(s, 1H, H-1), 4.76 (d, 1H, J = 11.0 Hz, CH2Ph), 4.61
(d, 1H, J = 12.1 Hz, CH2Ph), 4.48 (d, 1H, J = 12.1 Hz,
CH2Ph), 4.38 (d, 1H, J = 11.0 Hz, CH2Ph), 4.22 (d,
1H, J = 9.7 Hz, H-4), 4.03 (d, 1H, J = 9.7 Hz, H-3),
4.11 (d, 1H, J = 8.9 Hz, H-7), 3.92 (d, 1H, J = 8.9 Hz,
H-70), 3.81 (sept., 1H, J = 6.1 Hz, CH isopropyl), 3.78
(d, 1H, J = 10.8 Hz, H-8), 3.55 (m, 3H, H-6, H-60, H-
80), 3.30–3.12 (br, 3H, 3 · OH), 2.39 (s, 3H, CH3 Ts),
1.13 (d, 3H, J = 6.1 Hz, CH3 isopropyl), 1.03 (d, 3H,
J = 6.1 Hz, CH3 isopropyl); 13C NMR (CDCl3,
100 MHz): d 145.01, 137.99, 137.48, 132.13 (4 · Cipso),
129.79–127.57 (3 · Ph), 93.88 (C-1), 77.50 (C-3), 77.48
(C-2), 75.40 (CH2Ph), 74.09 (C-5), 73.71 (CH2Ph),
72.15 (C-4), 69.88 (C-8), 69.20 (CH isopropyl), 67.00
(C-7), 64.33 (C-6), 23.10 (CH3 isopropyl), 21.59 (CH3
isopropyl); m/z (CI, NH3): 634 ([M+NH4]+, 70%);
HRMS (CI, NH3): calcd for C32H44O10NS
[M+NH4]+: 634.2686. Found: 634.2690.
3.12. Isopropyl 2-C-4-O-anhydro-2,3,6-tri-O-acetyl-5-C-
acetoxymethyl-2-C-hydroxymethyl-b-D-mannopyranoside
(15)
Compound 14 (25 mg, 0.056 mmol) was dissolved in
MeOH–EtOAc (2 mL, 1:1) and Pd/C (10 mg) was
added. The reaction vessel was purged from air and
the reaction mixture was stirred overnight under hydro-
gen, filtered through a Celite plug eluted with MeOH.
The solvent was removed under reduced pressure and
the crude oil was dissolved in dry pyridine (1 mL). The
solution was cooled to 0 ꢁC and Ac2O (0.5 mL) followed
by a catalytic amount of DMAP were added under
argon. The reaction mixture was stirred at rt overnight
and concentrated. Purification of the residue by flash
column chromatography (cyclohexane–EtOAc, 1:1)
afforded tetracetate 15 (17 mg, 0.039 mmol, 70%) as
colorless crystals. [a]D ꢀ40 (c 0.2, CHCl3); mp 120–
121 ꢁC (EtOAc–cyclohexane); 1H NMR (CDCl3,
400 MHz): d 5.56 (d, 1H, J = 1.0 Hz, H-1), 5.51 (dd,
1H, J = 1.0 Hz, J = 5.6 Hz, H-3), 4.63 (d, 1H,
J = 8.9 Hz, H-6 or H-7 or H-8), 4.56 (s, 2H, H-6 or
H-7 or H-8), 4.32 (d, 1H, J = 10.9 Hz, H-6 or H-7 or
H-8), 4.28 (d, J = 5.6 Hz, H-4), 4.19 (d, 1H,
J = 10.9 Hz, H-6 or H-7 or H-8), 3.97 (sept., 1H,
J = 6.2 Hz, CH isopropyl), 3.91 (d, 1H, J = 8.9 Hz, H-
6 or H-7 or H-8), 2.16, 2.11, 2.09, 2.07 (4 · s, 12H,
4 · OAc), 1.26 (d, 3H, J = 6.2 Hz, CH3 isopropyl),
1.11 (d, 3H, J = 6.2 Hz, CH3 isopropyl); 13C NMR
(CDCl3, 100 MHz): d 170.36, 170.31, 170.10, 170.00
(4 · C@O), 97.40 (C-1), 78.01, 76.51 (C-2, C-5), 71.30,
71.13, 70.49 (C-3, C-4, CH isopropyl), 71.02, 63.58,
62.43 (C-6, C-7, C-8), 23.01, 21.01 (2 · CH3 isopropyl),
20.92, 20.81, 20.74, 20.68 (4 · CH3CO). Anal. Calcd
for C19H28O11: C, 52.77, H, 6.53. Found, C, 52.74, H,
6.59.
3.11. Isopropyl 2-C-4-O-anhydro-3-O-benzyl-5-C-benzyl-
oxymethyl-2-C-hydroxymethyl-b-D-mannopyranoside
(14)
Sodium hydride (60 mg, 0.90 mmol, 60% in oil) was
added to
a solution of compound 13 (185 mg,
0.30 mmol) in very dry DMF (8 mL) under argon. The
reaction mixture was heated at 70 ꢁC and stirred for
2 h. The reaction was quenched by the addition of
MeOH and concentrated. The residue was purified by
flash column chromatography (cyclohexane–EtOAc,
5:1 then 2:1) to afford bicyclic compound 14 (27 mg,
0.06 mmol, 20%) as a colorless syrup. [a]D ꢀ22 (c 0.5,
1
CHCl3); H NMR (CDCl3, 400 MHz): d 7.40–7.25 (m,
10H, 2 · Ph), 5.18 (s, 1H, H-1), 4.92 (d, 1H,
J = 11.6 Hz, CH2Ph), 4.79 (d, 1H, J = 11.6 Hz, CH2Ph),
4.76 (d, 1H, J = 10.9 Hz, CH2Ph), 4.65 (d, 1H,
J = 10.9 Hz, CH2Ph), 4.48 (m, 2H, H-3, H-4), 4.39 (d,
1H, J = 11.4 Hz, H-6 or H-7 or H-8), 4.21 (d,
1H, J = 11.4 Hz, H-60 or H-70 or H-80), 4.09 (d, 1H,
J = 7.8 Hz, H-6 or H-7 or H-8), 4.08 (sept., 1H,
J = 6.1 Hz, CH isopropyl), 3.89 (d, 1H, J = 7.8 Hz,
H-60 or H-70 or H-80), 3.80 (d, 1H, J = 8.5 Hz, H-6 or
H-7 or H-8), 3.58 (d, 1H, J = 8.5 Hz, H-60 or H-70 or
3.13. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-4,6-O-
isopropylidene-2-C-methylene-b-D-arabinoside (16)
Anhydrous DMSO (1.5 mL, 20.0 mmol) was added
dropwise to a solution of oxalyl chloride (1.2 mL,
13.3 mmol) in dry CH2Cl2 (13 mL) under argon and stir-
red for 30 min at ꢀ60 ꢁC. The reaction mixture was
cooled to ꢀ78 ꢁC and a solution of alcohol 9 (2.10 g,

1884
A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
4.45 mmol) in dry CH2Cl2 (32 mL) was added slowly via
a dropping funnel. After stirring for 90 min at ꢀ78 ꢁC,
Et3N (3.7 mL, 26.7 mmol) was added and the reaction
mixture was stirred for 30 min at ꢀ78 ꢁC and then al-
lowed to reach rt for 15 min. The reaction mixture was
then diluted with CH2Cl2, washed with water and brine,
and dried over MgSO4. The organic extracts were evap-
orated to afford crude ketone, which was directly en-
gaged in the next step. n-Butyl lithium (5.3 mL,
13.3 mmol, 2.5 M solution in THF) was added dropwise
to a solution of Ph3PCH2Br (4.8 g, 13.3 mmol) in dry
THF (25 mL) at 0 ꢁC under argon. The reaction mixture
was stirred for 30 min at 0 ꢁC until persistence of a pale
orange color. A solution of the crude ketone in THF
(20 mL) was transferred by cannula into the solution
and the reaction mixture was stirred overnight at rt.
The reaction was quenched by the addition of satd aq
NH4Cl and extracted with EtOAc. The combined organic
layers were washed with water and brine, dried over
MgSO4 and concentrated. Purification by flash column
chromatography (cyclohexane–EtOAc, 9:1) afforded
exomethylene derivative 16 (1.80 g, 86%) as a solid.
[a]D ꢀ36 (c 1.0, CHCl3); mp 83–84 ꢁC (EtOAc–cyclo-
quenched by adding an excess of a saturated solution
of Na2S2O3. The reaction mixture was stirred for
30 min, extracted with EtOAc, dried over MgSO4, and
concentrated. Purification by flash column chromato-
graphy (cyclohexane–EtOAc, 4:1) afforded diol 17
(438 mg, 85%) as a yellow syrup. [a]D ꢀ41 (c 0.7,
1
CHCl3); H NMR (CDCl3, 250 MHz): d 7.40–7.30 (m,
10H, 2 · Ph), 4.95 (s, 1H, H-1), 4.80 (s, 2H, CH2Ph),
4.69 (d, 1H, J = 10.0 Hz, CH2Ph), 4.61 (d, 1H,
J = 10.0 Hz, CH2Ph), 4.12 (d, 1H, J = 11.5 Hz, H-8),
4.03–3.92 (m, 6H, H-3, H-6, H-60, H-7, H-80, CH iso-
propyl), 3.85 (d, 1H, J = 10.9 Hz, H-4), 3.65 (d, 1H,
J = 10.2 Hz, H-70), 2.90 (br s, 2H, 2 · OH), 1.51 (s,
3H, CH3 isopropylidene), 1.43 (s, 3H, CH3 isopropyl-
idene), 1.24 (d, 3H, J = 6.1 Hz, CH3 isopropyl), 1.19
(d, 3H, J = 6.1 Hz, CH3 isopropyl); 13C NMR (CDCl3,
62.9 MHz): d 138.79, 137.76 (2 · Cipso), 128.42–127.45
(2 · Ph), 100.47 (C isopropylidene), 100.37 (C-1), 79.24
(C-3), 75.40 (C-2), 75.15 (CH2Ph), 74.30 (C-4), 73.77
(CH2Ph), 72.63 (CH isopropyl), 70.40 (C-5), 66.12
(C-7), 65.81 (C-6), 60.83 (C-8), 29.38 (CH3 isopropyl-
idene), 23.31 (CH3 isopropyl), 21.68 (CH3 isopropyl),
19.14 (CH3 isopropylidene); m/z (CI, NH3): 520
([M+NH4]+, 100%); HRMS (CI, NH3): calcd for
C28H42O8N [M+NH4]+: 520.2910. Found: 520.2906.
1
hexane); H NMR (CDCl3, 400 MHz): d 7.42–7.31 (m,
10H, 2 · Ph), 5.51 (m, 1H, @CH2), 5.46 (m, 1H,
@CH2), 5.38 (s, 1H, H-1), 4.83 (d, 1H, J = 12.3 Hz,
CH2Ph), 4.76 (d, 1H, J = 12.3 Hz, CH2Ph), 4.67 (d,
1H, J = 12.3 Hz, CH2Ph), 4.62 (d, 1H, J = 12.3 Hz,
CH2Ph), 4.33 (dt, 1H, J = 1.8 Hz, J = 10.0 Hz, H-3),
4.20 (d, 1H, J = 10.0 Hz, H-4), 4.06 (sept., 1H,
J = 6.1 Hz, CH isopropyl), 4.01 (d, 1H, J = 10.6 Hz,
H-6), 3.95 (d, 1H, J = 10.5 Hz, H-7), 3.90 (d, 1H,
J = 10.5 Hz, H-70), 3.70 (d, 1H, J = 10.6 Hz, H-60),
1.53 (s, 3H, CH3 isopropylidene), 1.48 (s, 3H, CH3 iso-
propylidene), 1.33 (d, 3H, J = 6.1 Hz, CH3 isopropyl),
1.22 (d, 3H, J = 6.1 Hz, CH3 isopropyl); 13C NMR
(CDCl3, 100 MHz): d 142.83 (C-2), 138.88, 138.09
(2 · Cipso), 128.27–127.30 (2 · Ph), 113.52 (@CH2),
100.19 (C isopropylidene), 96.07 (C-1), 76.80 (C-4),
74.56 (C-3), 73.56 (CH2Ph), 72.30 (CH2Ph), 70.84 (CH
isopropyl), 70.41 (C-5), 67.44 (C-6), 65.83 (C-7), 29.34
(CH3 isopropylidene), 23.37 (CH3 isopropyl), 21.73
(CH3 isopropyl), 19.02 (CH3 isopropylidene); m/z (CI,
NH3): 486 ([M+NH4]+, 10%), 426 (Mꢀisopropyl,
100%); HRMS (CI, NH3): calcd for C28H40O6N
[M+NH4]+: 486.2856. Found: 486.2857.
3.15. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-4,6-O-
isopropylidene-2-C-tosyloxymethyl-b-D-glucopyranoside
(18)
To a solution of diol 17 (1.80 g, 3.58 mmol) in dry pyr-
idine (7 mL) was added at 0 ꢁC under argon recrystal-
lized TsCl (2.0 g, 10.7 mmol) and a catalytic amount
of DMAP. The reaction mixture was stirred overnight
at rt, quenched by the addition of ice, stirred for another
20 min and extracted with EtOAc. The solvents were
removed under reduced pressure and the residue was
purified by flash column chromatography (cyclohexane–
EtOAc, 9:1) to afford tosylate 18 (1.95 g, 2.97 mmol,
83%) as a white solid. [a]D ꢀ56 (c 0.6, CHCl3); mp
117–118 ꢁC (EtOAc–cyclohexane); 1H NMR (CDCl3,
400 MHz): d 7.90–7.00 (m, 14H, 3 · Ph), 4.87 (s, 1H,
H-1), 4.80–4.60 (m, 5H, 2 · CH2Ph, H-4), 4.50 (d, 1H,
J = 9.8 Hz, H-6), 4.22 (d, 1H, J = 10.3 Hz, H-7), 4.20
(d, 1H, J = 9.8 Hz, H-60), 4.05 (d, 1H, J = 10.1 Hz, H-
3), 3.95 (sept., 1H, J = 6.2 Hz, CH isopropyl), 3.66 (d,
1H, J = 10.6 Hz, H-8), 3.64 (d, 1H, J = 10.6 Hz, H-80),
3.60 (d, 1H, J = 10.3 Hz, H-70), 2.50 (s, 3H, CH3 tosyl),
1.80 (s, 1H, OH), 1.48 (s, 3H, CH3 isopropylidene), 1.38
(s, 3H, CH3 isopropylidene), 1.24 (d, 3H, J = 6.2 Hz,
CH3 isopropyl), 1.15 (d, 3H, J = 6.2 Hz, CH3 iso-
propyl); 13C NMR (CDCl3, 100 MHz): d 144.40, 138.42,
136,74, 132.95 (4 · Cipso), 129.61–127.49 (3 · Ph),
100.71 (C isopropylidene), 99.55 (C-1), 80.02 (C-3),
75.21 (C-2), 75.04 (CH2Ph), 73.54 (CH2Ph), 73.03 (C-
4), 71.62 (C-5), 70.58 (C-8), 70.43 (CH isopropyl),
3.14. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-2-C-
hydroxymethyl-4,6-O-isopropylidene-b-D-glucopyran-
oside (17)
Exomethylene derivative 16 (467 mg, 1 mmol) was dis-
solved in a mixture of acetone–water (5:1, 2 mL) and
NMO (270 mg, 2.0 mmol) followed by OsO4 (2.5% in
t-BuOH, 0.1 mL, 0.02 mmol) were added. The reaction
mixture was stirred for 2 days under argon and

A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
1885
69.71 (C-6), 68.08 (C-7), 29.20 (CH3 isopropylidene),
23.46 (CH3 isopropyl), 21.57 (CH3 tosyl), 21.15 (CH3
isopropyl), 19.14 (CH3 isopropylidene); m/z (CI, NH3):
674 ([M+NH4]+, 22%), 502 (100%); HRMS (CI, NH3):
calcd for C35H48O10NS [M+NH4]+: 674.2999. Found:
674.2995.
J = 12.0 Hz, CH2Ph), 4.83 (s, 1H, H-1), 4.76 (d, 1H,
J = 12.0 Hz, CH2Ph), 4.59 (d, 1H, J = 12.0 Hz, CH2Ph),
4.54 (d, 1H, J = 12.0 Hz, CH2Ph), 4.45 (app. t, 1H,
J = 3.5 Hz, H-4), 4.19 (d, 1H, J = 10.9 Hz, H-6), 4.02
(sept., 1H, J = 6.1 Hz, CH isopropyl), 4.00 (d, 1H,
J = 12.7 Hz, H-7), 3.85 (d, 1H, J = 12.7 Hz, H-70),
3.67 (d, 1H, J = 10.9 Hz, H-60), 3.59 (d, 1H,
J = 3.5 Hz, H-3), 3.53 (d, 1H, J = 9.2 Hz, H-8), 3.21
(d, 1H, J = 9.2 Hz, H-80), 2.37 (d, 1H, J = 3.9 Hz,
OH-4), 2.35 (s, 1H, OH-2), 1.26 (d, 3H, J = 6.1 Hz,
CH3 isopropyl), 1.18 (d, 3H, J = 6.1 Hz, CH3 isoprop-
yl); 13C NMR (CDCl3, 100 MHz): d 138.09, 137.17
(2 · Cipso), 128.62–127.73 (2 · Ph), 99.98 (C-1), 85.05
(C-3), 82.28 (C-2), 74.71 (C-5), 73.94 (C-4), 73.64
(CH2Ph), 73.22 (C-7), 72.24 (CH2Ph), 69.92 (CH iso-
propyl), 69.84 (C-8), 67.25 (C-6), 23.60 (CH3 isopropyl),
21.53 (CH3 isopropyl); m/z (CI, NH3): 462 ([M+NH4]+,
100%); HRMS (CI, NH3): calcd for C25H36O7N
[M+NH4]+: 462.2486. Found: 462.2490.
3.16. Isopropyl 3-O-benzyl-5-C-benzyloxymethyl-2-C-
tosyloxymethyl-b-D-glucopyranoside (19)
A catalytic amount of camphorsulfonic acid was added
to
a stirred solution of compound 18 (460 mg,
0.70 mmol) in MeOH (7 mL). After 90 min, the reaction
was quenched by adding slowly solid NaHCO3 at 0 ꢁC
until neutral pH of the solution. The reaction mixture
was diluted with EtOAc and filtered through a Celite
plug. The solvent was evaporated and the residue was
purified by flash column chromatography (cyclohexane–
EtOAc, 3:2) to afford triol 19 (422 mg, 0.68 mmol, 96%)
as a white solid. [a]D ꢀ35 (c 0.8, CHCl3); mp 85–86 ꢁC
1
(EtOH); H NMR (CDCl3, 400 MHz): d 7.73 (d, 2H,
3.18. Isopropyl 6-O-benzoate-2-C-5-C-dimethyloxy-a-L-
iduronic acid (21)
J = 8.2 Hz, Ts), 7.27–7.15 (m, 12H, 3 · Ph), 4.96 (s,
1H, H-1), 4.85 (d, 1H, J = 11.6 Hz, CH2Ph), 4.65 (d,
1H, J = 11.6 Hz, CH2Ph), 4.58 (d, 1H, J = 12.0 Hz,
CH2Ph), 4.53 (d, 1H, J = 12.0 Hz, CH2Ph), 4.34 (d,
1H, J = 10.0 Hz, H-6), 4.31 (d, 1H, J = 10.0 Hz, H-60),
3.95–3.88 (m, 3H, H-3, H-4, CH isopropyl), 3.82 (d,
1H, J = 10.5 Hz, H-7), 3.70 (d, 1H, J = 11.4 Hz, H-8),
3.62 (d, 1H, J = 11.4 Hz, H-80), 3.60 (d, 1H,
J = 10.5 Hz, H-70), 2.45 (s, 3H, CH3 tosyl), 1.20 (d,
3H, J = 6.2 Hz, CH3 isopropyl), 1.14 (d, 3H,
J = 6.2 Hz, CH3 isopropyl); 13C NMR (CDCl3,
100 MHz): d 144.67, 138.12, 137.33, 132.77 (4 · Cipso),
129.67–127.70 (3 · Ph), 98.19 (C-1), 81.75 (C-3 or C-
4), 77.46 (C-2), 74.72 (CH2Ph), 74.15 (C-5), 73.82
(CH2Ph), 71.52 (C-3 or C-4), 70.28 (C-7), 68.96 (CH iso-
propyl), 67.92 (C-6), 65.04 (C-8), 23.09 (CH3 isopropyl),
21.59 (CH3 tosyl), 21.46 (CH3 isopropyl); m/z (CI,
NH3): 634 ([M+NH4]+, 35%); HRMS (CI, NH3): calcd
for C32H44O10NS [M+NH4]+: 634.2686. Found:
634.2687.
Compound 20 (450 mg, 1.0 mmol) was dissolved in
EtOAc (35 mL) and 10% Pd/C (50 mg) was added.
The reaction mixture was stirred for 3 h under H2 atmo-
sphere and filtered through a Celite plug eluted with
MeOH. The solvent was removed under reduced
pressure to afford a tetrol (267 mg, quant.) as an oil. This
tetrol was directly engaged in the next oxidation reaction.
The tetrol (267 mg, 1.0 mmol) was suspended in CH2Cl2
(3 mL) and TEMPO (2.4 mg) followed by a saturated
solution of NaHCO3 (2.2 mL), KBr (11.2 mg) and n-
Bu4NCl (17 mg) were added at rt. The reaction mixture
was cooled to 0 ꢁC and a saturated solution of NaHCO3
(1.1 mL), brine (2.2 mL) and NaClO (1.5 mL, bleach
commercial solution) were added dropwise and stirred
for 30 min. The two layers were separated and the or-
ganic phase was extracted with water and the combined
aqueous extracts were acidified to pH ꢁ 4 with aq HCl.
The aqueous extracts were concentrated and the crude
acid was dissolved in DMF (20 mL) and KHCO3
(683 mg, 5.5 mmol) followed by n-Bu4NI (2.0 g,
5.5 mmol) and BnBr (0.7 mL, 5.5 mmol) were added at
rt under argon. The reaction mixture was stirred over-
night. After completion of the reaction, DMF was
removed under reduced pressure and the residue was
dissolved in EtOAc and washed with a satd aq Na2S2O3
and brine. The organic layer was concentrated and puri-
fication by flash column chromatography (cyclohexane–
EtOAc, 1:1 then 1:4) afforded the benzyl ester 21
(280 mg, 0.75 mmol, 75%) as a colorless oil. [a]D ꢀ24
3.17. Isopropyl 3,6-O-dibenzyl-2-C-5-C-dimethyloxy-a-L-
idopyranoside (20)
Sodium hydride (19 mg, 0.49 mmol) was added to a
solution of compound 19 (86 mg, 0.14 mmol) in very
dry DMF (10 mL) under argon. The reaction mixture
was introduced immediately in a preheated bath at
70 ꢁC and stirred for 90 min. The reaction was quenched
by the addition of MeOH and concentrated. The residue
was purified by flash column chromatography (cyclo-
hexane–EtOAc, 9:1 then 4:1) to afford bicyclic com-
pound 20 (63 mg, 0.10 mmol, 71%) as a colorless
syrup. [a]D ꢀ3 (c 0.8, CHCl3); 1H NMR (CDCl3,
400 MHz): d 7.45–7.30 (m, 10H, 2 · Ph), 5.01 (d, 1H,
1
(c 1.0, CHCl3); H NMR (CDCl3, 400 MHz): d 7.30
(m, 5H, Ph), 5.21 (d, 1H, J = 12.4 Hz, CH2Ph), 5.19
(d, 1H, J = 12.4 Hz, CH2Ph), 4.98 (s, 1H, H-1), 4.60
(s, 1H, OH), 4.45 (br s, 1H, H-4), 4.30 (br s, 1H, OH),

1886
A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
4.20 (d, 1H, J = 12.8 Hz, H-8), 4.19–4.10 (m, 2H, H-7,
CH isopropyl), 3.99 (d, 1H, J = 12.8 Hz, H-80), 3.85
(br s, 1H, H-3), 3.72 (d, 1H, J = 11.2 Hz, H-70), 3.50
(br s, 1H, OH), 1.29 (d, 3H, J = 6.1 Hz, CH3 isopropyl),
1.19 (3H, d, J = 6.1 Hz, CH3 isopropyl); 13C NMR
(CDCl3, 100 MHz): d 169.41 (C@O), 135.15 (Cipso),
128.53–128.05 (Ph), 99.89 (C-1), 86.67 (C-2), 79.77
(C-3), 76.25 (C-4), 75.03 (C-5), 73.69 (C-6), 70.85 (CH
isopropyl), 67.48 (CH2Ph), 66.65 (C-7), 23.58 (CH3
isopropyl), 21.67 (CH3 isopropyl); m/z (CI, NH3): 386
([M+NH4]+, 100%); HRMS (CI, NH3): calcd for
C18H28NO8 [M+NH4]+: 386.1815. Found: 386.1818.
References
1. Rees, D. A.; Morris, E. R.; Stoddart, J. F.; Stevens, E. S.
Nature 1985, 317, 480.
2. Casu, B.; Choay, J.; Ferro, D. R.; Gatti, G.; Jacquinet,
J.-C.; Petitou, M.; Ragazzi, A. M.; Sinay, P.; Torri, G.
¨
Nature 1986, 322, 215–216.
3. Ferro, D. R.; Provasoli, A.; Ragazzi, M.; Torri, G.; Casu,
B.; Gatti, G.; Jacquinet, J.-C.; Sinay, P.; Petitou, M.;
¨
Choay, J. J. Am. Chem. Soc. 1986, 108, 6773–6778.
4. (a) Casu, B.; Petitou, M.; Provasoli, A.; Sinay, P. Trends
¨
Biochem. Sci. 1988, 13, 221–225; (b) Canales, A.; Angulo,
J.; Lozano, R.; Ojeda, R.; Fayos, R.; Martın-Lomas, M.;
Gimenez-Gallego, G.; Nieto, P. M.; Jimenez-Barbero, J.
J. Am. Chem. Soc. 2005, 127, 5778–5779.
´
´
´
5. Torri, G.; Casu, B.; Gatti, G.; Petitou, M.; Choay, J.;
3.19. Isopropyl 2-C-5-C-dimethyloxy-a-L-iduronic acid
(6)
Jacquinet, J.-C.; Sinay, P. Biochem. Biophys. Res. Com-
¨
mun. 1985, 128, 134–140.
6. Sinay, P.; Jacquinet, J.-C.; Petitou, M.; Duchaussoy, P.;
¨
Benzyl ester 21 (64 mg, 0.174 mmol) was dissolved in
MeOH (3 mL) and Pd black (7 mg) was added. The
reaction vessel was purged from air and stirred over-
night under a hydrogen atmosphere. Filtration through
a Celite plug eluted with MeOH and concentration
Lederman, I.; Choay, J.; Torri, G. Carbohydr. Res. 1984,
132, C5–C9.
7. For a discussion on the emergence of S0 or S2 confor-
2
0
´
mation in the idopyranose series, see: Auge, J.; David, S.
Tetrahedron 1984, 40, 2101–2106.
8. (a) Das, S. K.; Mallet, J.-M.; Esnault, J.; Driguez, P.-A.;
´
Duchaussoy, P.; Sizun, P.; Herault, J.-P.; Herbert, J.-M.;
afforded the L-iduronic acid analog
6
(48 mg,
Petitou, M.; Sinay, P. Angew. Chem., Int. Ed. 2001, 40,
1670–1673; (b) Das, S. K.; Mallet, J.-M.; Esnault, J.;
Driguez, P.-A.; Duchaussoy, P.; Sizun, P.; Herbert, J.-M.;
¨
0.173 mmol, quant.) as an oil. [a]D ꢀ41 (c 1.0, CH3OH);
1H NMR (CDCl3, 400 MHz): d 4.88 (s, 1H, H-1), 4.27
(d, 1H, J = 13.1 Hz, H-6), 4.26 (d, 1H, J = 3.4 Hz, H-
4), 4.11 (sept., 1H, J = 6.2 Hz, CH isopropyl), 4.08 (d,
1H, J = 11.3 Hz, H-8), 3.93 (d, 1H, J = 13.1 Hz, H-60),
3.67 (d, 1H, J = 11.3 Hz, H-80), 3.66 (d, 1H,
J = 3.4 Hz, H-3), 1.24 (d, 3H, J = 6.2 Hz, CH3 iso-
propyl), 1.16 (d, 3H, J = 6.2 Hz, CH3 isopropyl); 13C
NMR (CDCl3, 100 MHz): d 172.70 (C@O), 99.81 (C-
1), 87.13 (C-2), 79.36 (C-3), 76.04 (C-4), 75.24 (C-5),
74.13 (C-6), 71.79 (CH isopropyl), 66.23 (C-8), 22.85
(CH3 isopropyl), 20.95 (CH3 isopropyl); m/z (CI,
NH3): 296 ([M+NH4]+, 100%); HRMS (CI, NH3):
calcd for C11H22O8N [M+NH4]+: 296.1345. Found:
296.1348.
Petitou, M.; Sinay, P. Chem. Eur. J. 2001, 7, 4821–4833.
¨
9. Westerduin, P.; van Boeckel, C. A. A.; Basten, J. E. M.;
Broekhoven, M. A.; Lucas, H.; Rood, A.; van der
Heijden, H.; van Amsterdam, R. G. M.; van Dinther, T.
G.; Meuleman, D. G.; Visser, A.; Vogel, G. M. T.; Damm,
J. B. L.; Overklift, G. T. Bioorg. Med. Chem. 1994, 2,
1267–1280.
´
10. Herbert, J. M.; Herault, J. P.; Bernat, A.; van Amsterdam,
R. G. M.; Lormeau, J. C.; Petitou, M.; van Boeckel, C. A.
A.; Hoffmann, P.; Meuleman, D. G. Blood 1998, 91, 4197–
4205.
11. Kovensky, J.; Mallet, J.-M.; Esnault, J.; Driguez, P.-A.;
´
Sizun, P.; Herault, J.-P.; Herbert, J.-M.; Petitou, M.;
Sinay, P. Eur. J. Org. Chem. 2002, 3595–3603.
¨
12. (a) van Boeckel, C. A. A.; Petitou, M. Angew. Chem., Int.
Ed. Engl. 1993, 32, 1671–1690; (b) Petitou, M.; van
Boeckel, C. A. A. Angew. Chem., Int. Ed. 2004, 43, 3118–
3133.
13. (a) Desai, U. R.; Petitou, M.; Bjo¨rk, I.; Olson, S. T.
Biochemistry 1998, 37, 13033–13041; (b) Desai, U. R.;
Petitou, M.; Bjo¨rk, I.; Olson, S. T. J. Biol. Chem. 1998,
273, 7478–7487.
Acknowledgements
A.J.H., M.T.B. and L.A. thank the European Commu-
nity Network ‘Glycidic Scaffold’ (HPRN-CT-2002-
00173) for financial support. C. Duhayon (Centre de
´
14. Bleriot, Y.; Vadivel, S. K.; Herrera, A. J.; Grieg, I. R.;
Kirby, A. J.; Sinay, P. Tetrahedron 2004, 60, 6813–6828.
¨
´
Resolution des Structures, Paris VI University) is grate-
15. Cleator, E.; McCusker, C. F.; Steltzer, F.; Ley, S. V.
Tetrahedron Lett. 2004, 45, 3077–3080.
fully acknowledged for solving the structure of com-
´
pound 15 and Y. Poncel (Ecole Normale Superieure)
16. (a) Walker, D. L.; Fraser-Reid, B. J. Am. Chem. Soc.
1975, 97, 6251–6253; (b) Yoshimura, J.; Matsuzawa, M.
Carbohydr. Res. 1981, 96, 7–20; (c) Dyong, I.; Weygand,
J.; Meyer, W. Tetrahedron Lett. 1981, 22, 2969–2970; (d)
Zagar, C.; Scharf, H.-D. Liebigs Ann. Chem. 1992, 693–
697.
for his contribution to this work.
Supplementary data
1H and 13C NMR spectra for compounds 6, 8–20; crys-
tallographic information file for 15. Supplementary data
associated with this article can be found, in the online
version, at doi:10.1016/j.carres.2007.02.025.
17. These conditions of methylenation compete well with the
use of Lombardo reagent. See: Hollingworth, G. J.;
Pattenden, G. Tetrahedron Lett. 1998, 39, 703–706; For
Lombardo reagent, see: Lombardo, L. Tetrahedron Lett.
1982, 23, 4293–4296.

A. J. Herrera et al. / Carbohydrate Research 342 (2007) 1876–1887
1887
18. (a) Anelli, P. L.; Biffi, C.; Montanari, F.; Quici, S. J. Org.
Chem. 1987, 52, 2559–2562; (b) Anelli, P. L.; Banfi, S.;
Montanari, F.; Quici, S. J. Org. Chem. 1989, 54, 2970–
2972; (c) Siedlecka, R.; Skarzewski, J.; Mlochowski, J.
Tetrahedron Lett. 1990, 31, 2177–2180; (d) Davis, N. J.;
Flitsch, S. L. Tetrahedron Lett. 1993, 34, 1181–1184; (e)
De Nooy, A. E. J.; Besemer, A. C. Carbohydr. Res. 1995,
269, 89–98; (f) Haller, M.; Boons, G.-J. J. Chem. Soc.,
Perkin Trans. 1 2001, 814–822; (g) Litjens, R. E. J. N.; Den
Heeten, R.; Timmer, M. S. M.; Overkleeft, H. S.; Van der
Marel, G. A. Chem. Eur. J. 2005, 11, 1010–1016.
19. Braunschweiler, L.; Ernst, R. R. J. Magn. Res. 1983, 53,
521–527.
21. Macura, S.; Ernst, R. R. Mol. Phys. 1980, 41, 95–108.
22. Hwang, T. L.; Shaka, A. J. J. Am. Chem. Soc. 1992, 114,
3157–3158.
23. Mohamadi, F.; Richards, N. G. J.; Guida, W. C.;
Liskamp, R.; Lipton, M.; Caufield, C.; Chang, G.;
Hendrickson, T.; Still, W. C. J. Comp. Chem. 1990, 11,
440–467.
24. Allinger, N. L.; Yuh, Y. H.; Lii, J. H. J. Am. Chem. Soc.
1989, 111, 8551–8559.
25. Still, W. C.; Tempzyk, A.; Hawley, R.; Hendrickson, T. J.
Am. Chem. Soc. 1990, 112, 6127–6129.
´
26. Poveda, A.; Asensio, J. L.; Martın-Pastor, M.; Jimenez-
Barbero, J. J. Biomol. NMR 1997, 10, 29–43.
27. Haasnoot, C. A. G.; de Leeuw, F. A. A. M.; Altona, C.
Tetrahedron 1980, 36, 2783–2794.
20. Bodenhausen, G.; Reuben, D. J. Chem. Phys. Lett. 1980,
69, 185–189.