From d-glucuronic acid to l-iduronic acid derivatives via a radical tandem decarboxylation-cyclization

Article abstract of DOI:10.1016/j.carres.2014.01.006

A synthesis to l-iduronic derivatives, major components of heparin derived pentasaccharides was accomplished by formal inversion of configuration at C-5 of a d-glucuronic acid derivative through radical formation at C-5 using Barton decarboxylation followed by intramolecular radical addition on an acetylenic tether at O-4 giving exclusively a bicyclic sugar of l-ido configuration. Oxidation and ring opening of this bicyclic sugar led to a l-iduronate. This method opens the way to short syntheses of pentasaccharidic moiety of Idraparinux and congeners.

Full text of DOI:10.1016/j.carres.2014.01.006

Carbohydrate Research 386 (2014) 99–105
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
From D-glucuronic acid to L-iduronic acid derivatives via a radical
tandem decarboxylation–cyclization
Stéphane Salamone a,b, Michel Boisbrun a,b, Claude Didierjean c,d, Yves Chapleur a,b,
⇑
a Université de Lorraine, SRSMC, UMR 7565, BP 70239, F-54506 Vandœuvre-lès-Nancy, France
b CNRS, SRSMC, UMR 7565, BP 70239, F-54506 Vandœuvre-lès-Nancy, France
c Université de Lorraine, CRM2, UMR 7036, BP 70239, F-54506 Vandœuvre-lès-Nancy, France
d CNRS, CRM2, UMR 7036, BP 70239, F-54506 Vandœuvre-lès-Nancy, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A synthesis to
plished by formal inversion of configuration at C-5 of a
mation at C-5 using Barton decarboxylation followed by intramolecular radical addition on an acetylenic
tether at O-4 giving exclusively a bicyclic sugar of -ido configuration. Oxidation and ring opening of this
bicyclic sugar led to a -iduronate. This method opens the way to short syntheses of pentasaccharidic
moiety of Idraparinux and congeners.
L
-iduronic derivatives, major components of heparin derived pentasaccharides was accom-
Received 22 November 2013
Received in revised form 30 December 2013
Accepted 8 January 2014
D-glucuronic acid derivative through radical for-
L
Available online 15 January 2014
L
Keywords:
Ó 2014 Elsevier Ltd. All rights reserved.
L
-Idose
C-5 inversion
Radical decarboxylation
Radical cyclization
1. Introduction
L
-iduronic moiety G which is needed for biological activity of the
oligosaccharides and which is challenging in terms of synthesis.
-hexoses are rare sugars from natural sources and are often bio-
synthetized by epimerization of -sugars as it is the case for -idu-
ronic acid.6 However the chemical synthesis of the
-idoA moiety is
L-Iduronic acid (
L
-idoA) is a major constituent of heparin, a
L
highly sulfated linear polysaccharide belonging to the family of
glycosaminoglycans, extensively used for its anticoagulant proper-
ties.1,2 Structural elucidation of the active domain of heparin, a
pentasaccharide referred to as DEFGH, along with SAR studies led
to chemically defined synthetic heparin analogues such as Fonda-
parinux (1), the only commercial ultra low molecular weight hep-
arin and Idraparinux (2), a more potent and easier to prepare
analogue which is O-sulfated and O-methylated (Fig. 1).3 Idrapari-
nux, a long acting antithrombin-mediated inhibitor of factor Xa, is
an efficient anticoagulant in deep venous thrombosis. Idraparinux
binds to antithrombin more strongly than Fondaparinux because of
a higher number of hydrophobic interactions due to extensive
methylation. More complex constructions involving Idraparinux
and thrombin inhibitors have been proposed. Biotinylated deriva-
tives of these antithrombotics have been elaborated to allow their
neutralization by injection of avidin.4
D
L
L
more complex and remains the limiting step of the preparation of
these pentasaccharides. Although chemoenzymatic syntheses have
recently emerged,7 efficient chemical syntheses of
L
-idose deriva-
-glucose are epimers, differing only
in their configuration at C-5, therefore, most of the strategies ex-
plored to reach -idoA made use of a -glucose derivative as start-
tives are needed. L-idose and D
L
D
ing material and proceeded via basic or radical epimerizations of
pyranose derivatives,8 diastereoselective hydroboration of 5,6
exo-glycals,9 nucleophilic substitution10 or nucleophilic addition
on furanose aldehyde derivatives.11 However, these strategies of-
ten suffer from modest diastereoselectivity affording mixtures of
L-ido and
D-gluco derivatives.
Examination of former syntheses of DEFGH pentasaccharides
shows that a widely used strategy is the assembly of two blocks
DEF and GH,5 the DEF block being obtained from two other build-
ing blocks D and EF. It is clear that in these target structures GH
and EF differ only by the stereochemistry at C-5 of G. Being able
to prepare GH from EF in a completely stereospecific manner
would be of tremendous interest in the context of a multistep syn-
thesis. We attempted to tackle this problem in a model study and
we report here some of our results obtained on a monosaccharide.
Many chemical syntheses of pentasaccharides related to hepa-
rin have been reported.5 All synthetic approaches required the
preparation of at least five monosaccharide building blocks often
referred to as DEFGH (Fig. 1). One important building block is the
⇑
Corresponding author. Tel.: +33 383 68 47 73; fax: +33 383 68 47 80.
E-mail address: yves.chapleur@univ-lorraine.fr (Y. Chapleur).
0008-6215/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.carres.2014.01.006

100
S. Salamone et al. / Carbohydrate Research 386 (2014) 99–105
D
OSO3
O
E
F
G
H
the next step. Two methods of radical decarboxylation were envi-
sioned, the first used a classical Barton ester,13 the second went
through a stable N-(acyloxy)phthalimide activated ester as de-
scribed by Okada et al.15 The Barton decarboxylation method was
eventually selected since it gave in our hands slightly better yields
and easier purifications. Thus, acid 10 was converted to a mixed
anhydride by treatment with isobutyl chloroformate (IBCF) in the
presence of N-methyl-morpholine, then 2-mercaptopyridine
N-oxide sodium salt was added to afford the Barton ester which
was submitted to UV irradiation in the presence of tert-butylthiol,
leading to the expected 5-exo dig cyclization adduct 11 in 44% yield
from alcohol 9, along with 5% of the reduced compound 12
(Scheme 2).
-
-
OSO3
-
OSO3
O
COO-
-OOC
O
HO
HO
OH
O
O
O
O
O
-O3SHN
O
HO
-O3SHN
HO
-O3SO
-O3SHN
OMe
HO
-O3SO
1
-
OSO3
-
OSO3
O
-
O
OSO3
COO-
O
-OOC
O
MeO
MeO
OMe
O
O
O
O
-O3SO
MeO
O
-O3SO
MeO
-O3SO
OMe
MeO
-O3SO
MeO
2
Figure 1. Structures of two synthetic heparin analogue pentasaccharides, Fonda-
parinux (1), and Idraparinux (2).
The moderate yield of the reaction was considered acceptable
over 3 steps and it is worth noting that a single diastereomer
was isolated. Yet, the configuration of the newly formed sugar
could not be ascertained by NMR using the proton coupling con-
stants due to a distortion of the carbohydrate ring (see Section 4).
Hence, alkene 11 was submitted to ozonolysis and the resulting
ketone 13 was condensed with 2,4-dinitrophenylhydrazine
(2,4-DNPH) giving rise to the hydrazone 14. Subsequent purifica-
tions and recrystalizations gave suitable crystals for X-ray
diffraction analysis (Fig. 2).
2. Results and discussion
It was reasoned that the inversion at C-5 would be better
achieved on a pyranose structure owing to the strong tendency
of
L
-idose derivative to exist as furanose derivatives. Basic epimer-
-glucuronic acid or ester is difficult to drive to the -ido
ization of
D
L
derivative and b-elimination is often a side-reaction. Hydrobora-
tion of 5,6 exo-glycals is strongly dependent of the substrate in par-
ticular of the anomeric configuration, the b anomer (like in GH)
X-ray crystallographic data showed the distorted 4C1 conforma-
tion adopted by the carbohydrate, corroborating the observed cou-
pling constants, and confirmed the desired stereochemistry at C-5
giving mostly the D
-gluco configuration.9a,c,d
and consequently the
(Fig. 2).
L-ido configuration of the cyclization product
Radical cyclization forming five-membered rings has been
introduced by Stork et al. as an efficient way to control the stereo-
chemistry of the newly formed C–C bond.12a,b This has been use-
fully applied to carbohydrate12c–h and carbocyclic chemistry.12i,j
On the basis of our previous work on radical cyclization on sugar
templates,12c–e we anticipated that a kinetically favoured 5-exo
dig cyclization between a radical generated at C-5 and a suitable
tether at O-4 would lead exclusively to a 4,5-cis fused-ring system,
The opening of the oxolan ring and further excision of one car-
bon were attempted on ketone 13. Enolization of this ketone was
improductive, the equatorial H-5 proton being preferentially ab-
stracted with LDA or weaker bases. Not unexpectedly Baeyer–Vil-
liger oxidation of 13 gave the corresponding lactone with oxygen
insertion between C-5 and C-6. We then attempted to reverse this
situation by changing the methylene group of the five-membered
ring for an acetal. For that purpose, the alkene 11 was efficiently
transformed into its isomer 15 by treatment with dichlorotris(tri-
phenylphosphine)ruthenium(II) catalyst in the presence of diiso-
propylethylamine in toluene at 80 °C. Treatment of 15 with NBS
in the presence of ethanol gave the bromoacetal 16 as a single ste-
reoisomer in 87% yield. On treatment with DBU in refluxing tolu-
ene for 4 days, the latter gave the alkene 17 in modest yield
(29%) together with its 5,6 isomer (43% not shown). Finally, ozon-
olysis of 17 gave the expected ketone 18 in 80% yield. Gratifyingly,
Baeyer Villiger oxidation of this ketone using m-CPBA and sodium
bicarbonate in dichloromethane gave the expected unstable lac-
tone which was not isolated since it cleaved spontaneously
giving access to the desired L-ido configuration only. Moreover, the
formation of a radical at C-5 has been invented by Barton et al. by
decarboxylation of uronic acid via the corresponding thiohydroxa-
mate, the so-called Barton ester.13
A
D
-glucuronic acid was thus a good starting point for our inves-
tigations. Starting from methyl -glucopyranoside, the known
a
-D
4,6-diol 6 was obtained in good yield on multi-gram scale, using
only recrystallizations as a mean of purification. Selective protec-
tion of the primary hydroxyl group as a trityl ether followed by
propargylation at O-4 and detritylation afforded alcohol 9 in excel-
lent yield (Scheme 1).
Even though no selective oxidation was required, the primary
alcohol was oxidized using the TEMPO/NaBr/NaOCl system allow-
ing to work in water,14 to give the corresponding carboxylic acid 10
which was just cleared of the inorganic salts and used as such in
in situ to provide the L-iduronic acid 19 and the carbonate 21
according to proton NMR and mass spectrometry analyses on the
crude mixture (see Supporting information). The presence of the
ethoxycarbonate might result from a second Baeyer–Villiger reac-
tion on the orthoester prior to decomposition, due to the slight ex-
cess of m-CPBA used.16 The mixture was heated under reflux with a
small amount of TsOH to cleave the carbonate group affording a
single uronic acid 19 which was esterified under basic conditions
to avoid furanose formation providing the methyl ester 20 in 56%
yield from 18 (Scheme 3).
We then modified our route to 19 by installing the ethylacetal
function as the tether earlier in the synthesis (Scheme 4). The eth-
oxypropyne group was introduced by a transacetalation reaction
under acidic conditions. Hence, diol 6 was selectively oxidized with
TEMPO14 and the resulting carboxylic acid was protected as the
methyl ester 22. Transacetalation with 3,3-diethoxy-1-propyne
OH
O
PhCHO
ZnCl2
NaH, MeI
THF
0°C --> r.t.
88%
Ph
O
Ph
O
O
O
HO
HO
O
O
MeO
HO
72%
HO
HO
MeO
OMe
OMe
OMe
3
4
5
OH
O
OTr
O
Propargyl bromide
NaH, DMF
,
TsOH
TrCl, DMAP
MeOH
Pyridine
HO
MeO
HO
MeO
90%
0°C --> r.t.
91%
MeO
MeO
94%
6
7
OMe
OMe
OTr
OH
O
TsOH
O
O
O
MeOH
MeO
MeO
MeO
90%
MeO
OMe
OMe
gave the fully protected
D-glucuronate 23 as a 2:1 mixture of
8
9
diastereomers which was submitted to saponification to give car-
Scheme 1. Synthesis of alcohol 9.
boxylic acid 24. The radical tandem decarboxylation–cyclization

S. Salamone et al. / Carbohydrate Research 386 (2014) 99–105
101
IBCF, NMM then
S
2-mercaptopyridine
CO2H
O
TEMPO, NaBr
NaOCl
N
N-oxide sodium salt
O
O
O
9
MeO
O
O
THF, 0°C
H2O, 0°C
MeO
MeO
OMe
10
MeO
OMe
O
O
O3, PPh3
CH2Cl2
t-BuSH
hν
O
OMe
OMe
H
O
OMe
OMe
O
O
+
MeO
O
-78°C --> r.t.
89%
MeO
OMe
OMe
OMe
13
12
11
(5% from 9)
(
44% from 9)
NO2
H
N
2,4-DNPH
N
Dowex, MeOH
O
OMe
OMe
O2N
Reflux
41%
O
14
OMe
Scheme 2. Radical tandem decarboxylation–cyclization.
(1)
TEMPO, NaBr
CO2Me
O
CO2Me
O
, P O
OEt
NaOCl, H2O, 0°C
EtO
2
5
HO
6
EtO
EtO
O
MeO
MeO
CHCl3, 60°C
67%
(2) TsOH
, MeOH
MeO
OMe
MeO
reflux
89%
OMe
23
22
(1) IBCF, NMM then
2-mercaptopyridine
N-oxide sodium salt
THF, 0°C
O
OMe
OMe
NaOH
EtOH/H2O
CO2H
O
EtO
O
O
MeO
95%
(2) t-BuSH, hν
MeO
OMe
OMe
48%
17
24
Scheme 4. Improved route to acetal 17.
was performed on the crude acid resulting in the fused-ring com-
pound 17, in a yield that was comparable to the one observed with
the propargylic ether. Eventually the remaining steps were per-
Figure 2. Crystal structure of hydrazone 14. For clarity, (1) only one of the two
independent molecules is shown and (2) only polar and methine hydrogen atoms
are shown.
formed on the mixture of diastereomers and furnished the L-idur-
onate in similar yields as previously described. This early
functionalization allowed us to cut three steps in the synthesis,
including the dehydrohalogenation which had the lowest yield
(29%).
Br
RuCl2(PPh3)3
DIPEA
NBS, EtOH
CH2Cl2
O
OMe
OMe
O
OMe
OMe
EtO
EtO
11
Toluene 80°C
84%
The
was unambiguously confirmed by comparison of its proton cou-
pling constants with those of the corresponding -glucuronate 22
L-ido configuration of the newly formed methyl uronate 20
O
-30°C --> r.t.
87%
O
OMe
16
OMe
15
D
and those of a known yet differently protected methyl
L-iduro-
O
O3, DMS
CH2Cl2
nate17 (Table 1).
O
OMe
O
OMe
OMe
DBU,Tol.
EtO
110°C
4 days, 29%
O
-78°C --> r.t.
80%
O
OMe
3. Conclusions
OMe
OMe
17
18
In conclusion, a new stereoselective method to reach an
L-idoA
O
derivative from its -gluco counterpart has been achieved in five
D
m-CPBA
NaHCO3
(1)
TsOH,
O
OMe
OMe
OMe
O
MeOH reflux
steps, the inversion of configuration being made during a tandem
process involving the formation of a radical at C-5. Our method
compares well with existing methods of epimerization involving
O
RO2C
OMe
(2) MeI, Et3N
DMF
CH2Cl2, 0°C
EtO
O
HO
19 R = H
20 R = Me (56%)
OMe
OMe
a C-5 radical which always gave a mixture of
derivatives depending on the solvent.8d,e The method described
here offers the advantage of giving only the -ido configuration.
D-gluco and L-ido
OMe
HO2C
EtO
OMe
O
L
These results pave the way to a new process for the preparation
of synthetic heparin analogues by direct transformation of EF
building blocks into GH building blocks saving about ten steps of
synthesis.
O
OMe
21
O
Scheme 3. First synthesis of
L-iduronate 20.

102
S. Salamone et al. / Carbohydrate Research 386 (2014) 99–105
Table 1
J(H,H) coupling constants of methyl uronates (in Hz)
OMe
O
CO2Me
OBn
O
MeO2C
OAc
O
MeO2C
HO
OMe
HO
MeO
HO
OAc
Ref. 17
MeO
OMe
OMe
22
20
J1,2
J2,3
J3,4
J4,5
0.9
3.5
3.5
1.6
3.4
9.3
9.5
9.6
1.4
3.3
3.3
1.8
74.08; H: 6.82. Found: C: 74.23; H: 6.88; MS (ESI): 525
[M+Na]+.
4. Experimental
4.1. General methods
4.3. Methyl 2,3-di-O-methyl-4-O-propargyl-a-D-glucopy
ranoside (9)
All commercial reagents were used as received. THF was dis-
tilled from sodium/benzophenone under argon, dichloromethane
from P2O5, then calcium hydride and methanol from magnesium.
DMF was stored over 4 Å MS. Pyridine and triethylamine were
stored over KOH. TLC was performed on silica gel 60 F254, pre-
coated plates. Compounds were visualized using UV254 and 30%
H2SO4 MeOH with charring. Column chromatographies were per-
To a solution of 8 (2.00 g, 3.98 mmol) in methanol (40 mL) was
added TsOH (80 mg, 0.42 mmol, 0.1 equiv). After 5 h at room tem-
perature, sodium carbonate (78 mg) was added and stirring was
continued for 15 min. After filtration through CeliteÒ and concen-
tration the residue was purified by chromatography (hexane/
EtOAc 70:30), recrystallized in Et2O, and washed with Et2O/hexane
(1:1). The filtrate was recrystallized twice from Et2O to afford 9 as
formed using 63–200 lM or 40–63 lM or 5–40 lM silica gel.
NMR spectra were recorded at 303 K at 250 or 400 MHz for 1H
and 62.9 or 100.6 MHz for 13C. The chemical shifts are reported
in ppm (d) relative to residual solvent peak. Elucidations of chem-
ical structures were based on 1H, COSY, HSQC, 13C, HMBC experi-
ments. Mass spectra (MS) were recorded in ESI mode on
quadrupole spectrometer or ESI/QqTOF spectrometer for HRMS.
Optical rotations were obtained using sodium D line at rt. Melting
points were determined in capillaries and are uncorrected. Infrared
spectra were recorded on NaCl window. Compounds 4,18 5,19 6,20
721 and 2222 have been prepared according to literature
procedures.
white crystals (936 mg, 3.60 mmol, 90%). Mp 97–98 °C; ½a D20
ꢁ
191.7
(c 1.0; CHCl3); IR (film) 3477 cmꢂ1 1H NMR (CDCl3, 400 MHz): d
;
4.81 (d, J1–2 = 3.6 Hz, 1H, H-1), 4.44, 4.39 (ABX system, JAB = 15.3 -
Hz, JAX = JBX = 2.4 Hz, 2H, CH2), 3.84–3.80 (m, 2H, H-6, H-60), 3.60
(s, 3H, OCH3), 3.60–3.54 (m, 2H, H-3, H-5), 3.50 (s, 3H, OCH3),
3.44–3.41 (m, 1H, H-4), 3.39 (s, 3H, OCH3), 3.18 (dd, J2–3 = 9.6 Hz,
J1–2 = 3.6 Hz, 1H, H-2), 2.47 (t, J = 2.4 Hz, 1H, C„CAH), 1.97 (t,
JCH–OH = 6.6 Hz, 1H, OH); 13C NMR (CDCl3, 100.6 MHz): d 97.5 (C-
1), 83.7 (C-3), 82.1 (C-2), 80.3 (HAC„CA), 76.7 (C-4), 74.5
(HAC„CA), 70.4 (C-5), 61.9 (C-6), 61.1 (OCH3), 59.8 („CACH2),
59.1, 55.3 (2ꢀOCH3); Anal. Calcd for C12H20O6 C: 55.37; H: 7.74.
Found: C: 55.69; H: 7.45; MS (ESI): 283 [M+Na]+.
4.2. Methyl 2,3-di-O-methyl-4-O-propargyl-6-O-triphenyl
methyl-a-
D
-glucopyranoside (8)
4.4. Methyl 4,7-anhydro-6-deoxy-6-methylene-2,3-di-O-
methyl-b-L-ido-heptopyranoside (11)
To
a
solution of alcohol 7 (9.72 g, 20.9 mmol) in DMF
(100 mL), under argon at 0 °C, was added portionwise sodium
hydride (60% in mineral oil, 1.26 g, 31.5 mmol, 1.5 equiv). After
30 min, propargyl bromide (4.5 mL, 41.8 mmol, 2.0 equiv) was
added. After stirring for 17 h at room temperature, methanol
(20 mL) was added to the reaction mixture then water
(250 mL). The aqueous phase was extracted with Et2O
(4 ꢀ 120 mL) the combined organics were washed with water
(100 mL), dried (MgSO4), filtered, and concentrated. The residue
was purified by column chromatography (hexane/EtOAc 90:10)
to afford fully protected 8 as white solid (9.53 g, 19.0 mmol,
To a solution of alcohol 9 (2.05 g, 7.88 mmol) in water (55 mL)
were added NaBr (162 mg, 1.58 mmol, 0.2 equiv) and TEMPO
(49 mg, 0.31 mmol, 0.04 equiv). The reaction mixture was cooled
to 0 °C then a NaOCl aqueous solution (13% v/v, 18 mL, 31.4 mmol,
4.0 equiv) was added. After 5 h at 0 °C ethanol was added (96% v/v,
18 mL), the pH was reduced to 2–3 by the addition of 1 N HCl. The
volatiles were removed in vacuo and the residue suspended in
methanol, filtered to remove salts, and washed with dichlorometh-
ane and methanol. The filtrate was concentrated, dissolved in
anhydrous THF (80 mL) under argon IBCF (1.00 mL, 7.72 mmol,
1.0 equiv) and N-methylmorpholine (0.87 mL, 7.91 mmol,
1.0 equiv) were added at 0 °C. After 20 min, the flask was covered
with aluminum foil, 2-mercaptopyridine N-oxide sodium salt
(2.35 g, 15.76 mmol, 2.0 equiv) was added, and the reaction mix-
ture was stirred at rt. After 40 min anhydrous THF (200 mL) and
tert-butylthiol (1.35 mL, 12.60 mmol, 1.6 equiv) were added. The
foil was removed and the reaction mixture irradiated and heated
with a UV lamp (300 W) for 30 min. The thiol excess was neutral-
ized with a NaOCl aqueous solution (13% v/v, 20 mL). The reaction
mixture was concentrated then dissolved in EtOAc (150 mL),
91%). Mp 120–121 °C; ½a D20
ꢁ
91.5 (c 1.0; CHCl3); IR (film) 3293
cmꢂ1
;
1H NMR (CDCl3, 400 MHz): d 7.50–7.48 (m, 6H, HAr),
7.32–7.21 (m, 9H, HAr), 4.91 (d, J1–2 = 3.6 Hz, 1H, H-1), 4.22,
4.14 (ABX system, JAB = 15.3 Hz, JAX = JBX = 2.4 Hz, 2H, CH2),
0
3.70 (ddd, J4–5 = 9.8 Hz, J5–6 = 5.0 Hz, J5–6 = 1.5 Hz, 1H, H-5),
3.62 (s, 3H, OCH3), 3.57–3.43 (m, 3H, H-3, H-4, H-60), 3.55 (s,
3H, OCH3), 3.47 (s, 3H, OCH3), 3.29 (dd, J2–3 = 9.5 Hz, J1–
0
2 = 3.6 Hz, 1H, H-2), 3.13 (dd, J6–6 = 10.2 Hz, J5–6 = 5.0 Hz, 1H,
H-6), 2.21 (t, J = 2.4 Hz, 1H, C„CAH); 13C NMR (CDCl3,
100.6 MHz): d 144.2, 128.9, 127.9, 127.1 (18 ꢀ CAr), 97.3 (C-1),
86.5 (C-Ph3), 83.8 (C-3), 82.1 (C-2), 78.0 (HAC„CA), 77.7 (C-
4), 74.1 (HAC„CA), 69.9 (C-5), 63.0 (C-6), 61.2 (OCH3), 59.7
(„CACH2), 59.1, 55.1 (2ꢀOCH3); Anal. Calcd for C31H34O6 C:
washed successively with
a 5% NaHCO3 aqueous solution
(2 ꢀ 25 mL), and brine (2 ꢀ 25 mL), then the aqueous layer was ex-
tracted with dichloromethane (2 ꢀ 20 mL). The combined organics

S. Salamone et al. / Carbohydrate Research 386 (2014) 99–105
103
were dried (MgSO4), filtered, and concentrated. Column chroma-
tography (CH2Cl2/EtOAc 98:2) afforded the alkene 11 as (790 mg,
3.43 mmol, 44%) and the reduced 12 as colorless oils (90 mg,
lized first in methanol to provide 14 as yellow crystals (56 mg,
0.14 mmol, 41%). Suitable crystals for X-ray diffraction analysis
were obtained from ethanol, mp 134–135 °C; ½a D20
ꢂ602.1 (c 0.4;
ꢁ
0.39 mmol, 5%). ½a D20
ꢁ
ꢂ38.0 (c 1.0; CHCl3); 1H NMR (CDCl3,
CHCl3); IR (film) 3282 cmꢂ1; 1618 (C@N); 1519; 1505 (N@O);
1337; 1313 (N@O); 1H NMR (CDCl3, 400 MHz): d 12.03 (s, 1H,
NH), 9.13 (d, J = 2.4 Hz, 1H, HAr), 8.32 (dd, J = 9.6 Hz, J = 2.4 Hz,
1H, HAr), 7.90 (d, J = 9.6 Hz, 1H, HAr), 5.05 (dd, J4–5 = 8.4 Hz,
J5–7 = 1.6 Hz, 1H, H-5), 4.95 (d, J1–2 = 2.7 Hz, 1H, H-1), 4.63 (dd,
Jgem = 14.7 Hz, J5–7 = 1.6 Hz, 1H, H-70), 4.42 (m, 2H, H-4, H-7), 3.81
(dd, J2–3 = 9.6 Hz, J3–4 = 6.4 Hz, 1H, H-3), 3.63 (s, 3H, OCH3), 3.54
(s, 3H, OCH3), 3.36 (s, 3H, OCH3), 3.25 (dd, J2–3 = 9.6 Hz,
J1–2 = 2.7 Hz, 1H, H-2); 13C NMR (CDCl3, 100.6 MHz): d 158.8
(C-6), 145.0 (6 ꢀ CAr), 138.5, 130.2, 129.9, 123.6, 116.2, 99.7
(C-1), 80.6 (C-4), 79.2 (C-2), 76.8 (C-3), 70.1 (C-5), 66.5 (C-7),
60.2, 59.4, 58.3 (3 ꢀ OCH3); Anal. Calcd for C16H20N4O9: C: 46.60;
H: 4.89; N: 13.59, found: C: 46.66; H: 4.89; N: 13.64; MS (ESI):
m/z 435 [M+Na]+.
400 MHz): d 5.30 (dd, Jgem = 4.1 Hz, J = 2.0 Hz, 1H, C@CHaHb), 5.09
(dd, Jgem = 4.1 Hz, J = 2.0 Hz, 1H, C@CHaHb), 4.69 (d, J1–2 = 2.4 Hz,
1H, H-1), 4.63–4.54 (m, 2H, H-5, H-70), 4.27 (td, Jgem = 13.3 Hz,
J = 2.0 Hz, 1H, H-7), 3.99 (br t, J = 5.4 Hz, 1H, H-4), 3.71 (dd,
J2–3 = 7.5 Hz, J3–4 = 5.4 Hz, 1H, H-3), 3.56 (s, 3H, OCH3), 3.52
(s, 3H, OCH3), 3.42 (s, 3H, OCH3), 3.24 (dd, J2–3 = 7.5 Hz,
J1–2 = 2.4 Hz, 1H, H-2); 13C NMR (CDCl3, 100.6 MHz): d 147.5
(C-6), 108.0 (C@CH2), 99.1 (C-1), 79.6 (C-4), 78.5 (C-2), 77.0 (C-3),
75.2 (C-5), 68.8 (C-7), 59.5, 59.4, 56.7 (3 ꢀ OCH3); MS (HR-ESI)
for C11H18O5Na [M+Na]+: 253.1052, found: 253.1063.
4.5. Methyl 2,3-di-O-methyl-4-O-propargyl-a-D-xylopyranoside
(12)
IR (film) 3251 cmꢂ1
;
1H NMR (CDCl3, 400 MHz):
d
4.76
4.8. Methyl-4,7-anhydro-6-deoxy-6-methyl-2,3-di-O-methyl-b-
(d, J1–2 = 3.5 Hz, 1H, H-1), 4.35, 4.29 (ABX system, JAB = 15.8 Hz,
L-ido-hepto-6-enopyranoside (15)
0
0
JAX = JBX = 2.4 Hz, 2H, CH2), 3.73 (dd, J5–5 = 10.5 Hz, J4–5 = 4.9 Hz,
1H, H-50), 3.61 (s, 3H, OCH3), 3.51 (s, 3H, OCH3), 3.62–3.42
(m, 3H, H-3, H-4, H-5), 3.40 (s, 3H, OCH3), 3.16 (dd, J2–3 = 9.0 Hz,
J1–2 = 3.5 Hz, 1H, H-2), 2.45 (t, J = 2.4 Hz, 1H, C„CAH); 13C NMR
(CDCl3, 100.6 MHz): d 97.6 (C-1), 82.9 (C-3), 81.9 (C-2), 80.1
(HAC„CA), 77.6 (C-4), 74.5 (HAC„CA), 61.2 (OCH3), 59.8 (C-5),
To a solution of alkene 11 (900 mg, 3.91 mmol) in anhydrous
toluene (20 mL), under argon, were added diisopropylethylamine
(0.65 mL, 3.91 mmol, 1.0 equiv) and tris(triphenylphosphine)
ruthenium dichloride (750 mg, 0.78 mmol, 0.2 equiv). The mixture
was heated at 80 °C for 15 h then the volatiles were evaporated.
The residue was purified by column chromatography (CH2Cl2/
EtOAc 90:10) to afford alkene 15 as a green oil (760 mg, 3.30 mmol,
84%). 1H NMR (CDCl3, 400 MHz): d 6.19 (s, 1H, H-7), 4.74–4.71 (m,
2H, H-5, H-1), 4.23 (dd, J4–5 = 7.8 Hz, J3–4 = 3.0 Hz, 1H, H-4), 3.81
(dd, J2–3 = 7.4 Hz, J3–4 = 3.0 Hz, 1H, H-3), 3.52 (s, 6H, 2 ꢀ OCH3),
3.42 (s, 3H, OCH3), 3.31 (dd, J2–3 = 7.4 Hz, J1–2 = 2.2 Hz, 1H, H-2),
1.74 (s, 3H, CH3); 13C (CDCl3, 100.6 MHz): d 143.1 (C-7), 112.3
(C-6), 98.2 (C-1), 81.7 (C-4), 78.8 (C-3), 78.2 (C-2), 77.5 (C-5),
59.2, 58.3, 56.3 (3 ꢀ OCH3), 9.1 (CH3); MS (HR-ESI) for C11H18O5Na
[M+Na]+: 253.1052, found: 253.1057.
59.2 (OCH3), 58.9 („CACH2), 55.3 (OCH3); MS (ESI): 253 [M+Na]+
.
4.6. Methyl 4,7-anhydro-2,3-di-O-methyl-b-L-ido-heptopyr
anosid-6-ulose (13)
Through a solution of alkene 11 (900 mg, 3.91 mmol) in anhy-
drous dichloromethane (20 mL), under argon and cooled to
ꢂ78 °C, was bubbled ozone (0.2 L/min, 110 V). When the solution
had turned dark blue, oxygen was bubbled through until the solu-
tion became colorless. Triphenylphosphine (1.14 g, 4.35 mmol,
1.1 equiv) was added and the solution was brought to room tem-
perature for 1h30 and the reaction mixture was concentrated. Col-
umn chromatography (CH2Cl2/EtOAc 95:5) afforded 13 as colorless
oil (807 mg, 3.48 mmol, 89%) which turned into a white solid at
ꢂ18 °C. It was recrystallized from Et2O/hexane, mp 66–67 °C;
4.9. Methyl-4,7-anhydro-6-bromo-6-deoxy-6-methyl-7-ethoxy-
2,3-di-O-methyl-b-L-ido-heptopyranoside (16)
To a solution of alkene 15 (151 mg, 0.66 mmol) in dichloro-
methane (5 mL) was added under argon, anhydrous ethanol
(0.12 mL, 2.0 mmol, 3.0 equiv). The reaction mixture was cooled
to ꢂ30 °C then N-bromosuccinimide (130 mg, 0.73 mmol,
1.1 equiv) was added. After 1h30 the mixture was kept at rt for
18 h then diluted with dichloromethane (25 mL) and washed with
water (2 ꢀ 10 mL). The organic layer was dried (MgSO4), filtered,
and concentrated. The residue was purified by column chromatog-
raphy (CH2Cl2/EtOAc 90:10) to afford 16 as a white solid (206 mg,
0.58 mmol, 87%).1H NMR (CDCl3, 400 MHz): d 5.26 (s, 1H, H-7),
4.64 (d, J1–2 = 2.4 Hz, 1H, H-1), 4.39 (dd, J4–5 = 4.0 Hz, J3–4 = 2.8 Hz,
1H, H-4), 4.30 (d, J4–5 = 4.0 Hz, 1H, H-5), 3.79–3.71 (m, 2H, H-3,
OCHaHbCH3), 3.51–3.48 (m, 1H, OCHaHbCH3), 3.50 (s, 3H, OCH3),
3.49 (s, 3H, OCH3), 3.45 (s, 3H, OCH3), 3.29 (dd, J2–3 = 6.4 Hz,
J1–2 = 2.4 Hz, 1H, H-2), 1.87 (s, 3H, CH3), 1.18 (t, J = 6.8 Hz, 3H,
OCH2CH3); 13C (CDCl3, 100.6 MHz): d 109.9 (C-7), 98.9 (C-1), 80.3
(C-5), 79.4 (C-4), 78.4 (C-3), 77.0 (C-2), 69.9 (C-6), 64.0 (OCH2CH3),
59.1, 58.3, 56.5 (3 ꢀ OCH3), 21.2 (CH3), 15.1 (OCH2CH3); MS
(HR-ESI) for C13H23O6BrNa [M+Na]+: 377.0575 Found: 377.0548.
½
a 2D0
ꢁ
ꢂ80.6 (c 1.0; CHCl3); IR (film)): 1772 cmꢂ1
;
1H NMR (CDCl3,
400 MHz): d 4.76 (d, J1–2 = 2.8 Hz, 1H, H-1), 4.46 (dd, J4–5 = 9.3 Hz,
J3–4 = 7.3 Hz, 1H, H-4), 4.28 (br d, J4–5 = 9.3 Hz, 1H, H-5), 4.11,
4.03 (ABX system, JAB = 17.4 Hz, JAX = 1.2 Hz, JBX = 0 Hz, 2H, H-7,
H-70), 3.73 (dd, J2–3 = 10.0 Hz, J3–4 = 7.3 Hz, 1H, H-3), 3.63 (s, 3H,
OCH3), 3.50 (s, 3H, OCH3), 3.37 (s, 3H, OCH3), 3.14 (dd,
J2–3 = 10.0 Hz, J1–2 = 2.8 Hz, 1H, H-2); 13C NMR (CDCl3,
100.6 MHz): d 210.4 (C-6), 98.9 (C-1), 79.7 (C-2), 79.2 (C-4), 76.9
(C-3), 72.5 (C-5), 66.9 (C-7), 60.4, 59.3, 57.0 (3 ꢀ OCH3); Anal. Calcd
for C10H16O6: C: 51.72; H: 6.94, found: C: 51.80; H: 6.97; MS (ESI)
255 [M+Na]+; 287 [M+Na+MeOH]+.
4.7. Methyl 4,7-anhydro-2,3-di-O-methyl-b-L-ido-heptopyr
anosid-6-ulose 2,4-dinitrophenyl osazone (14)
To a solution of ketone 13 (396 mg, 0.96 mmol) in methanol
(10 mL) were added 2,4-dinitrophenylhydrazine (66%, 356 mg,
1.20 mmol, 1.3 equiv) and DowexÒ 50X8 (100 mg), then the reac-
tion mixture was heated under reflux. After 4 h the reaction mix-
ture was filtered and the precipitate washed with methanol. The
filtrate was concentrated, the resulting residue dissolved in EtOAc
(60 mL), and successively washed with a 5% NaHCO3 aqueous solu-
tion (2 ꢀ 20 mL) and water (1 ꢀ 20 mL). The organic layer was
dried (MgSO4), filtered, and concentrated. The residue was purified
by column chromatography (CH2Cl2/EtOAc 95:5) then recrystal-
4.10. Methyl 4,7-anhydro-6-deoxy-6-methylene-7-ethoxy-2,3-
di-O-methyl-b-L-ido-hepto pyranoside (17)
From 16: To a solution of bromoacetal 16 (99 mg, 0.28 mmol) in
toluene (5 mL) was added DBU (0.13 mL, 0.87 mmol, 3.0 equiv).
After 36 h another batch of toluene (2 mL) and DBU (0.13 mL,

104
S. Salamone et al. / Carbohydrate Research 386 (2014) 99–105
0.87 mmol, 3.0 equiv) was added. After 2 days at reflux the vola-
tiles were evaporated. The residue was then dissolved in EtOAc
(30 mL) and successively washed with a 5% aqueous citric acid
(1 ꢀ 10 mL), a saturated aqueous NaHCO3 (1 ꢀ 10 mL), and brine
(1 ꢀ 10 mL). The aqueous phase was extracted with dichlorometh-
ane (2 ꢀ 20 mL) then the combined organics were dried (MgSO4),
filtered, and concentrated. The residue was purified by column
chromatography (CH2Cl2/EtOAc 98:2) to afford 17 as colorless oil
(22 mg, 0.08 mmol, 29%). 1H NMR (CDCl3, 400 MHz): d 5.44 (t,
J = 2.8 Hz, 1H, AC@CHaHb), 5.34–5.32 (m, 2H, H-7, AC@CHaHb),
4.79 (d, J1–2 = 2.8 Hz, 1H, H-1), 4.73 (td, J4–5 = 7.6 Hz, J = 2.8 Hz,
1H, H-5), 4.02 (t, J3–4 = J4–5 = 7.6 Hz, 1H, H-4), 3.95 (dd,
J2–3 = 9.6 Hz, J3–4 = 7.6 Hz, 1H, H-3), 3.89–3.81 (m, 1H, OCHaHbCH3),
3.63 (s, 3H, OCH3), 3.62–3.57 (m, 1H, OCHaHbCH3), 3.50 (s, 3H,
OCH3), 3.41 (s, 3H, OCH3), 3.13 (dd, J2–3 = 9.6 Hz, J1–2 = 2.8 Hz, 1H,
H-2), 1.23 (t, J = 7.2 Hz, 3H, OCH2CH3); 13C (CDCl3, 100.6 MHz): d
147.4 (C-6), 111.6 (AC@CH2), 103.0 (C-7), 99.5 (C-1), 80.0 (C-2),
79.7 (C-4), 79.0 (C-3), 74.1 (C-5), 63.3 (OCH2CH3), 60.3, 59.0, 56.5
(3xOCH3), 15.3 (OCH2CH3).
From 24: Radical cyclization was carried out as described for 11
using acid 24 (1.89 g, 5.92 mmol) to afford 17 as colorless oil
(218 mg, 0.79 mmol, 48%), in a 2:1 mixture of diastereomers as
seen from 1H NMR; 1H NMR (CDCl3, 400 MHz): d 5.57–5.35 (m,
3H, H-7, AC@CH2), 4.79 (d, J1–2 = 3.0 Hz, 1H, H-1m), 4.73 (td,
J4–5 = 7.9 Hz, J = 2.6 Hz, 1H, H-5m), 4.62 (d, J1–2 = 1.7 Hz, 1H,
H-1M), 4.59 (br d, J4–5 = 4.0 Hz, 1H, H-5M), 4.07–3.93 (m, 2H,
H-3, H-4), 3.90–3.78 (m, 1H, OCHaHbCH3), 3.72 (dd, J2–3 = 5.0 Hz,
J3–4 = 2.8 Hz, 1H, H-3M), 3.61–3.55 (m, 1H, OCHaHbCH3), 3.53
(s, 3H, OCH3M), 3.50 (s, 3H, OCH3), 3.47 (s, 3H, OCH3M), 3.41 (s,
3H, OCH3m), 3.30 (dd, J2–3 = 5.0 Hz, J1–2 = 1.6 Hz, 1H, H-2M), 3.13
(dd, J2–3 = 9.6 Hz, J1–2 = 3.0 Hz, 1H, H-2m), 1.23 (t, J = 7.1 Hz, 3H,
OCH2CH3); 13C NMR (CDCl3, 100.6 MHz): d 148.1 (C-6M), 147.4
(C-6m), 115.2 (AC@CH2M), 111.6 (AC@CH2m), 103.0 (C-7m),
102.2 (C-7M), 99.5 (C-1m), 99.3 (C-1M), 80.1 (C-2m), 79.7 (C-4m),
79.0 (C-3m), 77.7 (C-2M), 77.0 (C-4M), 76.4 (C-3M), 74.7 (C-5M),
74.2 (C-5m), 63.8 (OCH2CH3M), 63.3 (OCH2CH3m), 60.3 (OCH3m),
59.9 (OCH3M), 59.1 (OCH3m), 58.6 (OCH3M), 56.8 (OCH3M), 56.5
(OCH3m), 15.4 (OCH2CH3M), 15.3 (OCH2CH3m); MS (HR-ESI): m/z
calcd for C13H22O6Na [M+Na]+: 297.1309, found: m/z = 297.1318.
C-3m), 79.4 (C-3M), 79.2 (C-4m), 75.9 (C-4M), 72.4 (C-5m), 70.2
(C-5M), 65.5 (OCH2CH3), 65.0 (OCH2CH3), 60.6 (OCH3), 59.8
(OCH3), 59.3 (OCH3M), 57.2 (OCH3m), 56.7 (OCH3m), 15.2 (OCH2-
CH3M), 15.1 (OCH2CH3m). MS (ESI): 299 [M+Na]+; 331
[M+Na+MeOH]+.
4.12. Methyl (methyl 2,3-di-O-methyl-b-L-idopyranosid)uronate
(20)
To a solution of ketone 18 (50 mg, 0.18 mmol) in dichlorometh-
ane (3 mL), under argon and cooled to 0 °C, were added m-CPBA
(77%, 120 mg, 0.54 mmol, 3.0 equiv) and NaHCO3 (20 mg,
0.23 mmol, 1.3 equiv). After 3 h stirring the volatiles were removed
under vacuum. The resulting residue was dissolved in EtOAc
(30 mL), extracted with distilled water, (2 ꢀ 10 mL) and the aque-
ous phase was concentrated. The crude mixture was dissolved in
methanol (10 mL), TsOH was added (4 mg, 0.02 mmol, 0.1 equiv)
then the reaction mixture was heated under reflux and the reaction
monitored by 1H NMR in deuterated methanol to check the disap-
pearance of the carbonate. After 8 h the volatiles were evaporated.
The residue was dissolved in DMF (5 mL) then triethylamine
(28 lL, 0.20 mmol, 1.1 equiv) and methyl iodide (56 lL, 0.90 mmol,
5.0 equiv) were added. After 3h30 stirring at room temperature the
reaction mixture was concentrated, dissolved in EtOAc (30 mL),
and the organic phase was washed with a 5% NaHCO3 aqueous
solution (2 ꢀ 10 mL),
a
5% citric acid aqueous solution
(2 ꢀ 10 mL), and brine (1 ꢀ 10 mL). The aqueous phase was ex-
tracted with dichloromethane (5 ꢀ 10 mL) and the combined
organics were dried (MgSO4), filtered, and concentrated. Column
chromatography (CH2Cl2/EtOAc 85:15) afforded 20 as colorless
oil (25 mg, 0.10 mmol, 56%). ½a D20
ꢁ
118.5 (c 0.4; CHCl3); IR (film)
3491 cmꢂ1; 1765 (C@O); 1H NMR (CDCl3, 400 MHz): d 4.61
(d, J1–2 = 0.9 Hz, 1H, H-1), 4.42 (d, J4–5 = 1.6 Hz, 1H, H-5), 3.97
(m, 1H, H-4), 3.80 (s, 3H, OCH3), 3.78–3.75 (m, 1H, OH), 3.69 (t,
J2–3 = J3–4 = 3.5 Hz, 1H, H-3), 3.57 (s, 3H, OCH3), 3.56 (s, 3H,
OCH3), 3.47 (s, 3H, OCH3), 3.41 (br d, J2–3 = 3.5 Hz, 1H, H-2). 13C
NMR (CDCl3, 100.6 MHz): d 169.6 (C@O), 100.9 (C-1), 77.5 (C-3),
77.2 (C-2), 74.8 (C-5), 67.7 (C-4), 60.8, 58.4, 57.5, 52.4 (4ꢀOCH3);
Anal. Calcd for C10H18O7: C: 48.00; H: 7.25, found: C: 47.62; H:
7.15; MS (ESI): 272 [M+Na]+.
4.11. Methyl 4,7-anhydro-7-ethoxy-2,3-di-O-methyl-b-L-ido-
heptopyranosid-6-ulose (18)
4.13. Methyl [methyl 4-O-(10-ethoxy-20-propyn-10-yl)-2,3-di-O-
methyl-a-D-glucopyranosid] uronate (23)
Through a solution of alkene 17 (449 mg, 1.64 mmol) in anhy-
drous dichloromethane (10 mL), under argon and cooled to
ꢂ78 °C, was bubbled ozone (0.2 L/min, 110 V). When the solution
had turned dark blue, oxygen was bubbled through in order to re-
move the excess ozone. When the solution became colorless
dimethylsulfide (5 drops) was added and the solution was brought
to room temperature. After 1h15 the reaction mixture was concen-
trated. Column chromatography (CH2Cl2/EtOAc 95:5) afforded 16
as white solid (364 mg, 1.32 mmol, 80%), in a mixture of diastereo-
mers (4:1) (the relative composition of the mixture was deter-
mined by 1H NMR from integrations of protons H-2); IR (film)
To a solution of methyl uronate 22 (4.56 g, 18.2 mmol) in chlo-
roform (200 mL) were added, under argon, P2O5 (5.31 g,
36.3 mmol, 2.0 equiv), and propargylaldehyde diethylacetal
(5.2 mL, 36.3 mmol, 2.0 equiv), then the reaction mixture was
heated at 60 °C. After 4 h stirring, the cooled reaction mixture
was filtered through a pad of CeliteÒ then the volatiles were re-
moved under vacuum. The crude mixture was suspended in EtOAc
(300 mL), washed with a 5% NaHCO3 aqueous solution (1 ꢀ 30 mL),
and brine (1 ꢀ 30 mL). The organic layer was dried (MgSO4), fil-
tered, and concentrated. Column chromatography (hexane/EtOAc
80:20) afforded fully protected 23 as colorless oil (4.07 g,
12.2 mmol, 67%) in a diastereomeric mixture (2:1) determined by
1H NMR from integrations of EtO-CH signal, along with some unre-
acted 20 (1.17 g, 4.7 mmol, 26%). IR (film) 1752 cmꢂ1; 3266
(„CAH); 1H NMR (CDCl3, 400 MHz): d 5.58 (d, J = 1.7 Hz, 1H,
EtO-CHM), 5.35 (d, J = 1.7 Hz, 1H, EtO-CHm), 4.88–4.86 (m, 1H,
H-1), 4.18 (d, J4–5 = 10.0 Hz, 1H, H-5m), 4.15 (d, J4–5 = 10.0 Hz, 1H,
H-5M), 3.86–3.78 (m, 1H, H-4), 3.80 (s, 3H, OCH3m), 3.78 (s, 3H,
OCH3M), 3.73–3.65 (m, 1H, OCHaHbCH3), 3.62 (s, 3H, OCH3M),
3.62–3.47 (m, 2H, H-3, OCHaHbCH3), 3.59 (s, 3H, OCH3m), 3.50 (s,
3H, OCH3), 3.44 (s, 3H, OCH3m), 3.43 (s, 3H, OCH3M), 3.31–3.26
(m, 1H, H-2), 2.56 (m, 1H, HAC„CA), 1.25–1.18 (m, 3H, OCH2CH3);
1783 cmꢂ1 1H NMR (CDCl3, 400 MHz): d 4.93 (br s, 1H, H-7M),
;
4.89 (d, J = 1.1 Hz, 1H, H-7m), 4.79 (d, J1–2 = 2.9 Hz, 1H, H-1m),
4.76 (d, J1–2 = 2.8 Hz, 1H, H-1M), 4.50 (dd, J3–4 = 9.5 Hz,
J4–5 = 6.2 Hz, 1H, H-4M), 4.44–4.39 (m, 2H, H-4m, H-5M), 4.34
(d, J4–5 = 9.1 Hz, 1H, H-5m), 4.07 (dd, J2–3 = 10.2 Hz, J3–4 = 7.7 Hz,
1H, H-3m), 3.10 (dd, J2–3 = 10.2 Hz, J1–2 = 2.9 Hz, 1H, H-2), 3.95–
3.77 (m, 2H, OCHaHbCH3), 3.73–3.48 (m, 3H, H-3M, OCHaHbCH3),
3.66 (s, 3H, OCH3m), 3.63 (s, 3H, OCH3M), 3.50 (s, 3H, OCH3),
3.42 (s, 3H, OCH3m), 3.38 (s, 3H, OCH3M), 3.17 (dd, J2–3 = 9.4 Hz,
J1–2 = 2.8 Hz, 1H, H-2M), 1.28–1.24 (m, 3H, OCH2CH3); 13C NMR
(CDCl3, 100.6 MHz): d 205.6 (C-6M), 205.3 (C-6m), 99.0 (C-1m),
98.7 (C-1M), 97.2 (C-7m), 96.1 (C-7M), 80.2 (C-2m), 79.8 (C-2M,

S. Salamone et al. / Carbohydrate Research 386 (2014) 99–105
105
13C NMR (CDCl3, 100.6 MHz): d 169.9 (C@O), 169.6 (C@OM), 98.0
(C-1M), 97.9 (C-1m), 92.6 (EtO-CH), 82.9 (C-3M), 81.9 (C-3m),
81.8 (C-2m), 81.5 (C-2M), 78.9 (HAC„CM), 78.6 (HAC„Cm),
76.7 (C-4M), 76.4 (C-4m), 74.2 (HAC„Cm), 74.0 (HAC„CM),
70.2 (C-5M), 70.1 (C-5m), 61.4 (OCH3), 61.3 (OCH2CH3m), 60.4
(OCH2CH3M), 59.3 (OCH3m), 59.2 (OCH3M), 55.8 (OCH3), 52.7
(OCH3m), 52.6 (OCH3M), 15.0 (OCH2CH3); Anal. Calcd for
3. (a) Petitou, M.; Duchaussoy, P.; Lederman, I.; Choay, J.; Jacquinet, J. C.; Sinaÿ, P.;
Torri, G. Carbohydr. Res. 1987, 167, 67–75; (b) Petitou, M.; van Boeckel, C. A. A.
Angew. Chem., Int. Ed. 2004, 43, 3118–3133.
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C
15H24O8: C: 54.21; H: 7.28, found: C: 54.17; H: 7.13; MS (ESI):
355 [M+Na]+.
4.14. 4-O-(10-Ethoxy-20-propyn-10-yl)-1,2,3-tri-O-methyl-
a-D-
glucopyranosiduronic acid (24)
To a solution of methyl uronate 23 (1.12 g, 3.37 mmol) in EtOH/
H2O (3:1 v/v, 100 mL) was added sodium hydroxide (156 mg,
3.90 mmol, 1.3 equiv). After 5 h stirring at room temperature the
volatiles were evaporated. The residue was dissolved in water
(50 mL), the pH was reduced to 2–3 with a 5% citric acid aqueous
solution, then the aqueous layer was saturated with sodium chlo-
ride before extraction with dichloromethane (10 ꢀ 20 mL). If nec-
essary the pH was adjusted by the addition of more citric acid
aqueous solution. The combined organics were dried (MgSO4), fil-
tered, and concentrated to afford 24 without further purification
as colorless oil (1.02 g, 3.20 mmol, 95%), in a mixture of diastereo-
mers (3:1) as seen from 1H NMR spectra; IR (film)) 1751 cmꢂ1
;
3268 („CAH); 1H NMR (CDCl3, 400 MHz): d 5.63 (d, J = 1.6 Hz,
1H, EtO-CHM), 5.45 (br s, 1H, EtO-CHm), 4.90–4.88 (m, 1H, H-1)
(diastereomeric mixture), 4.18–4.13 (m, 1H, H-5), 3.87–3.81 (m,
1H, H-4), 3.77–3.68 (m, 1H, OCHaHbCH3), 3.62 (s, 3H, OCH3),
3.62–3.54 (m, 2H, H-3, OCHaHbCH3), 3.51 (s, 3H, OCH3), 3.44 (s,
3H, OCH3), 3.33–3.25 (m, 1H, H-2), 2.62 (br s, 1H, HAC„Cm),
2.59 (d, J = 1.6 Hz, 1H, HAC„CM), 1.24–1.16 (m, 3H, OCH2CH3);
13C NMR (CDCl3, 100.6 MHz): d 174.0 (C@Om), 173.8 (C@OM),
98.0 (C-1M), 97.8 (C-1m), 92.5 (EtO-CH), 82.9 (C-3), 81.8 (C-3M),
81.7 (C-2m), 81.4 (C-2M), 78.8 (HAC„CM), 78.5 (HAC„Cm),
76.4 (C-4M), 75.7 (C-4m), 74.8 (HAC„CM), 74.3 (HAC„Cm),
70.1 (C-5), 61.3 (OCH3M), 61.2 (OCH3m), 60.7 (OCH2CH3), 59.3
(OCH3M), 59.2 (OCH3m), 55.9 (OCH3),14.9 (OCH2CH3); MS (ESI):
341 [M+Na]+.
Acknowledgments
We gratefully acknowledge Sanofi for a Ph.D. fellowship to S.S.
Many thanks go to Bertrand Castro, Patrick Trouilleux, and Gino
Ricci (Sanofi) for helpful discussions.
Supplementary data
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.carres.
2014.01.006.
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