Synthesis of octahydropyrano[3,2-b]pyrrole-2-carboxylic acid derivatives from d-mannose

Article abstract of DOI:10.1016/j.carres.2008.03.017

Bicyclic amino acids are useful building blocks in synthesizing biologically active molecules and peptidomimetics. 2-Carboxy-6-hydroxyloctahydroindole (Choi) is a novel bicyclic amino acid found in the marine natural products aeruginosins. Many compounds in the aeruginosin family exhibit inhibition activities toward serine proteases including thrombin and trypsin. The unique Choi structure is the common feature of this family of oligopeptides and this motif is important for their observed biological activities. To better understand the influence of the stereochemistry of the Choi core structure on the inhibition activities, we have previously synthesized ring-oxygenated variants from glucose. The preparation of octahydro-pyrano[3,2-b]pyrrole 2-carboxylic acids from d-mannose is reported here. These novel bicyclic amino acids can be used in the preparation of aeruginosin analogs, as well as conformationally constrained peptidomimetics or other biologically active molecules.

Full text of DOI:10.1016/j.carres.2008.03.017

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 1743–1753
Synthesis of octahydropyrano[3,2-b]pyrrole-2-carboxylic
acid derivatives from D-mannose
Jean-Rene Ella-Menye, Xiaoping Nie and Guijun Wang*
Department of Chemistry, University of New Orleans, New Orleans, LA 70148, United States
Received 25 November 2007; received in revised form 6 March 2008; accepted 10 March 2008
Available online 15 March 2008
Abstract—Bicyclic amino acids are useful building blocks in synthesizing biologically active molecules and peptidomimetics.
2-Carboxy-6-hydroxyloctahydroindole (Choi) is a novel bicyclic amino acid found in the marine natural products aeruginosins.
Many compounds in the aeruginosin family exhibit inhibition activities toward serine proteases including thrombin and trypsin.
The unique Choi structure is the common feature of this family of oligopeptides and this motif is important for their observed bio-
logical activities. To better understand the influence of the stereochemistry of the Choi core structure on the inhibition activities, we
have previously synthesized ring-oxygenated variants from glucose. The preparation of octahydro-pyrano[3,2-b]pyrrole
2-carboxylic acids from D-mannose is reported here. These novel bicyclic amino acids can be used in the preparation of aeruginosin
analogs, as well as conformationally constrained peptidomimetics or other biologically active molecules.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Aerguginosin; Octahydroindole 2-carboxylic acid; Rigid conformation; Thrombin inhibitor
1. Introduction
5 is the core structure of similar natural products, dysin-
osins (Chart 3).12,13
Structurally constrained bicyclic amino acids are useful
building blocks for the preparation of peptidomimetics
and other biologically important molecules.1–3 Several
examples of these types of compounds (1–5) are shown
in Chart 1. The conformationally constrained synthetic
bicyclic amino acids 1–3 has been used in the prepara-
tion of thrombin inhibitors such as 6–8 (Chart 2).4–6
2-Carboxy-6-hydroxyloctahydroindole (Choi) 4 is an-
other conformationally rigid amino acid, which is the
core structure present in the marine natural products
called aeruginosins.7–11 The dihydroxylated compound
A majority of the naturally occurring aeruginosins
share the same stereochemistry and substitution pattern
although some exceptions have been reported. Several
structures of aeruginosins and related compounds
(9–12) are shown in Chart 3.11,12 Many aeruginosins
are found to be inhibitors of serine proteases including
blood coagulation factors, such as thrombin and factor
VIIa. The unusual octahydroindole core structure is
important for their observed biological activities. Direct
inhibition of thrombin has demonstrated utility in
treating thrombosis-related disorders;13 however, more
S
HN
OH
O
HO
HO
OH
O
N
N
N
H2N
H2N
N
H
HO
N
H
O
OH
OH
O
O
OH
O
O
O
5
4
1
2
3
Chart 1. Structures of bicyclic amino acids that are useful building blocks.
*
Corresponding author. Tel.: +1 504 280 1258; fax: +1 504 280 6860; e-mail addresses: gwang2@uno.edu; wangguij@yahoo.com
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.03.017

1744
J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
HN NH2
H
H
H
S
N
O
S
O
N
N
NH2
NH
N
H
N
NH
Ph
N
N
O
O
O
S
O
H2N
NHSO2Bn
N
O
N
H
O
O
HN NH2
8
6
7
Chart 2. Structures of thrombin inhibitors containing fused amino acids.
HO
HO
O
NH
N
N
O
N
HN
HN
NH2
H
N
O
NH2
NH
HO
N
H
O
O
HO
O
OH
NH
HO
Oscillarin
Aeruginosin 298-A
10
9
OH
HO
O
HO
NH2
NH2
O
N
N
N
N
HN
H
HO
OH
O
N
NH2
O
O
HO
O
H
OSO3
Aeruginosin EI 461
Dysinosin A
11
12
Chart 3. Structures of aeruginosins and related compounds.
efficient oral anticoagulants remain elusive. In this
regard, aeruginosins are promising natural products that
can be explored and optimized to obtain potent and
selective thrombin inhibitors.
shown in Figure 1.25,29 Sugars are readily available
renewable resources, and they contain abundant chiral
centers that can be used as chiral pool starting materials
for the synthesis of more complex molecules. We have
also synthesized the bicyclic amino acid 16 using L-glu-
cose as the starting material and tetrapeptides contain-
ing the Choi variant 16.29 We envisioned that by using
a different monosaccharide such as D-mannose as the
starting material, bicyclic amino acids 17 and 18 can
be prepared using a similar method for the preparation
of 14 and 15. Similarly, if D-galactose is used as the
starting material, the trans O-Choi analogs 19 can
be synthesized. These ring-oxygenated variants of
2-carboxy-6-hydroxyoctahydroindole can be used as
surrogates of Choi in the design and synthesis of
Because of the biological importance of this class of
molecules, the total synthesis of Aeruginosin 298-A
(Chart 3),14–17 Aeruginosin EI461,18 Oscillarin,11 and
Dysinosins19,20 have been accomplished by a few
research groups. Several syntheses of the Choi fragment
and analogs have also been reported.21–25 In addition,
aeruginosin analogs have also been designed and synthe-
sized in the search for improved thrombin inhibitors.26–28
We were intrigued by this unusual amino acid and
developed an efficient method to synthesize protected
ring-oxygenated variants (14, 15) from D-glucose 13 as
OH
O
O
O
OEt
OEt
HO
N
H
N
H
HO
BnO
O
O
BnO
OH
OH
OBn
OBn
13
15
14
O
O
OH
OH
O
O
OH
OH
*
N
N
H
O
HO
HO
O
N
H
N
H
HO
O
HO
O
H
OH
OH
OH
17
16
18
19
Figure 1. O-Choi analogs that can be synthesized from monosaccharides.

J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
1745
aeruginosin-based thrombin inhibitors. These com-
pounds can also be used in synthesizing peptidomi-
metics with particular conformational features. We
report here the progress on the preparation of Choi ana-
logs using D-mannose and D-galactose as the starting
materials.
ing products 27 and 28, in which only the five membered
rings were reductively opened. The mixture of these two
intermediates was then benzylated to give the only
dibenzylated product, 29.
The dibenzylated compound 29 was then successfully
converted to the protected O-Choi analogs 36 and 37 as
shown in Scheme 2. The benzylidene acetal in intermedi-
ate 29 was quantitatively hydrolyzed using concentrated
acetic acid to afford diol 30. Dimesylation of both
hydroxyl groups was achieved in good yield by reacting
30 with methanesulfonyl chloride in dichloromethane.
Selectively substituting the primary mesylate in 31 with
bromide using sodium bromide and a catalytic amount
of tetrabutylammonium bromide afforded compound
32. Displacement of the 6-bromide with N-Boc pro-
tected diethylaminomalonate under basic conditions
gave compound 33, which was decarboxylated in very
good yield to give intermediate 34 as a 1:1 ratio of
diastereomers. N-Boc deprotection of 34 afforded 35
and subsequent intramolecular cyclization led to the
protected ring-oxygenated Choi analogs 36 and 37 in
good yield. These two compounds can be separated
via chromatography and can be deprotected or used
2. Results and discussion
To synthesize the O-Choi analogs from D-mannose, a
modified route of our previous approach using D-glu-
cose as the starting material was used.25 As shown in
Schemes 1 and 2, D-mannose (20) was smoothly con-
verted to 1,5-anhydro-mannitol 24 in four steps using
our previous procedure.25 Because the hydroxyl groups
at C-2 and C-3 in compound 24 are cis, selective protec-
tion of the C-4 and C-6 hydroxyl groups as an acetal
proved to be difficult, so the corresponding diacetals
were synthesized instead (Scheme 1). The diastereomeric
acetals 25 and 26 were obtained in approximately a 1:1
ratio. Selective reduction of this diacetal mixture under
carefully monitored conditions afforded the ring open-
AcO
AcO
AcO
OAc
O
HO
HO
HO
OH
AcO
AcO
AcO
OAc
O
AcO
AcO
AcO
OAc
O
Bu3SnH, AIBN
100%
HBr-AcOH
Ac2O, BF3.Et2O
0 oC-RT
O
99%
OAc
OH
Br
96%
22
23
20
21
H
Ph
O
H
O
Ph
O
HO
OH
O
Ph
Ph
Ph
PhCH(OMe)2
81%
NaOMe, MeOH
97%
O
HO
O
O
O
O
+
HO
O
O
24
25
26
29
OBn
O
OH
O
O
O
O
OBn
O
Ph
Ph
O
LiAlH4-AlCl3
85%
O
+
BnBr, NaH
75%
O
HO
BnO
BnO
27
28
Scheme 1. Preparation of the protected 1,5-anhydro-D-mannitol intermediate 29.
OMs
Br
OBn
OBn
O
OBn
HO
HO
BnO
O
NaBr, TBAB
78%
O
MsCl, DIPEA
85%
AcOH (80%)
100%
MsO
MsO
BnO
29
BnO
30
31
32
CO2Et
CO2Et
CO2Et
CO2Et
H2N
BocHN
CO2Et
BocHN
BocHN CO2Et
OBn
O
TEA/Tol
reflux
TFA/DCM
96%
NaOH
Tol, heat MsO
91%
OBn
O
OBn
MsO
BnO
O
NaH, Tol
51%
MsO
BnO
BnO
33
34
35
O
O
O
O
OEt
OEt
OEt
O
OEt
O
Pd(OH)2/C
+
N
N
N
H
O
N
H
HO
BnO
BnO
O
HO
H
H
OH
OBn
OBn
OH
36 (48%)
37 (50%)
39
38
Separate diastereomers
Scheme 2. Synthesis of dihydroxyl O-Choi variants from D-mannose.

1746
J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
OAc
O
OAc
O
OH
OH
HO
OAc
AcO
OAc
AcO
OAc
O
OAc
AcO
O
Ac2O, NaOAc
OH 70%
33% HBr-HOAc
Bu3SnH
Benzene
95%
OH
40
AcO
41
AcO
42
91%
OAc
Br
OAc
43
Ph
Ph
O
O
OH
OH
HO
OH
BnO
OH
O
H+
O
PhCH(OMe)2
BnBr, NaH
96%
O
O
NaOMe
O
O
HBF4, DMF
92%
MeOH
100%
95%
OH
HO
OBn
BnO
OH
OBn
47
45
46
44
OMs
Br
OMs
O
OMs
NaBr
X
DMSO
OH
MsCl, Py
93%
*
O
O
N
H
HO
O
BnO
BnO
OBn
OBn
OH
49
48
19
Scheme 3. Synthesis of intermediate 48 from D-galactose.
CO2Et
H2N CO2Et
OH
BnO
OH
O
OMs
OTr
O
OTr
O
OH
BnO
OTr
O
H
N
MsCl, Py
BnO
EtO2C
EtO2C BnO
TrCl, Py
94%
85%
OBn
OBn
OBn
OBn
50
52
51
47
Scheme 4. An alternative route for converting D-galactose derivatives to Choi analogs.
directly in coupling reactions with other compounds. In
the decarboxylation, there is no diastereoselectivity for
the stereocenter generated, and a 1:1 ratio of diastereo-
mers of 34 was obtained. If the decarboxylation reaction
is executed after the cyclization, there will be a facial
selectivity favoring one isomer over the other. However,
it is also possible to epimerize this position if needed.
The work described above and our previous studies
have shown that we can successfully prepare Choi ana-
logs from D-glucose and D-mannose. However, we have
encountered problems when using D-galactose (40) to
prepare Choi analogs with trans ring junctures. Initially,
we had hoped that the synthesis could be accomplished
by a method similar to the one starting from D-mannose.
To this end, as shown in Scheme 3, we could successfully
prepare dimesylate 48. However, the 6-mesylate group
in 48 could not be converted to the corresponding bro-
mide due to steric hindrance posed by the axial group
at 4-position.
Therefore, a modified route was explored in which the
alkylation sequence was switched. As shown in Scheme
4, this approach involves the protection of the 6-hydro-
xyl group in 47 with a protecting group such as trityl
and displacement of the 4-mesylate group to give the
key intermediate 52. Compound 51 can be prepared
smoothly; however, several attempts to displace the 4-
mesylate group in 51 with diethylaminomalonate proved
problematic. The use of a smaller or electron withdraw-
ing protecting group on O-6, instead of trityl, may give
positive results and we are currently exploring alterna-
tive routes to synthesize trans-fused Choi analogs.
In conclusion, we have efficiently synthesized octa-
hydro-pyrano[3,2-b]pyrrole-2-carboxylic acid derivatives
starting from D-mannose. The synthesis of trans-fused
bicyclic amino acids from D-galactose cannot be
achieved using a similar method due to steric hindrance
at the 4-position, which prevents a key substitution reac-
tion. Therefore, alternative approaches are necessary to
complete the synthesis of these bicyclic amino acids
from D-galactose. The readily available monosaccha-
rides including D-glucose, D-mannose, and D-galactose
are useful chiral pool materials and they are stereo-
isomers in which the configuration of one hydroxyl
group differs from each other. From the data presented
above, this difference significantly affects the reaction
outcome. The conformationally rigid bicyclic amino
acids synthesized here can be used in the synthesis of
aeruginosin analogs or peptidomimetics with special
structural requirement.
3. Experimental
3.1. General methods
All reagents, solvents, and starting materials were
purchased from Aldrich or Lancaster unless otherwise
specified. Anhydrous solvents were purchased from

J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
1747
Aldrich in sure-seal bottles and used directly without
3.4. 2,3,4,6-Tetra-O-acetyl-1,5-anhydro-D-mannitol (23)
further treatment. 1H and 13C NMR spectra were
acquired on Varian 400 MHz NMR spectrometer. Melt-
ing points were measured using a Fisher–Jones melting
point apparatus. Typically thin layer chromatography
Compound 22 (16.8 g, 40.9 mmol) was dissolved in
anhydrous benzene (20.0 mL). Tributyltin hydride
(11.0 mL, 41.5 mmol) and AIBN (a few mg) were added
to the solution and the mixture was refluxed for 1.5 h.
The mixture was then cooled to room temperature and
diluted with diethyl ether (100 mL). Potassium fluoride
(7.20 g, 124 mmol in 30 mL of water) was added to the
mixture and stirred for 2 h. The precipitated Bu3SnF
was filtered out and the water phase separated from
the ether. The organic phase was washed with water
and dried over Na2SO4. After filtration, concentration,
and drying under high vacuum, the product was
obtained as a light yellow oil in quantitative yield
(13.6 g, 40.9 mmol). 1H NMR (CDCl3, 400 MHz); d
5.27 (br s, 1H), 5.24 (t, 1H, J = 10.2 Hz), 5.01 (dd,
1H, J = 10.0, 3.5 Hz), 4.19 (dd, 1H, J = 12.3, 5.6 Hz),
4.08 (dd, 1H, J = 12.2, 2.0 Hz), 4.01 (dd, 1H, J = 13.2,
1.8 Hz), 3.64 (d, 1H, J = 13.2 Hz), 3.55 (m, 1H), 2.12
(s, 3H), 2.06 (s, 3H), 2.00 (s, 3H), 1.96 (s, 3H). 13C
NMR (CDCl3, 100 MHz); d 170.6, 170.3, 170.0, 169.5,
76.6, 71.5, 68.5, 68.0, 66.0, 62.6, 20.8, 20.7, 20.6, 20.5.
HRMS calcd for C14H20O9Na [M+Na]+ 355.1005,
found 355.1015.
˚
(60 A pore, UV254, phosphomolybdic acid as the stain-
ing agent) was used to monitor reactions. Silica Gel
(230–400 meshes) was used for flash chromatography.
Solvents were generally removed under reduced pressure
using a rotary evaporator (Buchi rotavapor R200).
3.2. 1,2,3,4,6-Penta-O-acetyl-a-D-mannopyranose (21)
D-Mannose 20 (19.0 g, 106 mmol) was dissolved in Ac2O
(55.0 mL, 582 mmol) and the mixture was cooled to 0 °C.
Boron trifluoride diethyletherate (8.00 mL, 64.0 mmol)
was added dropwise at 0 °C and the mixture was stirred
at room temperature for 1.5 h. The mixture was poured
into a beaker containing 200 mL of ice and stirred for
1 h. The product was extracted three times using CH2Cl2,
the organic phase was washed with saturated NaHCO3
and water and then dried over Na2SO4. After filtration,
concentration, and drying under vacuum, the product
was obtained as a brown oil in 96% yield (39.9 g,
102 mmol). 1H NMR (CDCl3, 400 MHz); d 5.86 (d,
1H, J = 1.0 Hz), 5.49 (dd, 1H, J = 3.2, 0.9 Hz), 5.29 (t,
1H, J = 9.9 Hz), 5.13 (dd, 1H, J = 9.9, 3.3 Hz), 4.31
(dd, 1H, J = 12.4, 5.4 Hz), 4.14 (dd, 1H, J = 12.4,
2.3 Hz), 3.80 (m, 1H), 2.22 (s, 3H), 2.10 (s, 3H), 2.09 (s,
3H), 2.05 (s, 3H), 2.01 (s, 3H). 13C NMR (CDCl3,
100 MHz); d 170.2, 169.8, 169.4, 169.3, 168.0, 90.1,
72.8, 70.3, 67.9, 65.2, 61.8, 20.4. HRMS calcd for
C16H22O11Na [M+Na]+ 413.1060, found 413.1055.
3.5. 1,5-Anhydro-D-mannitol (24)
Compound 23 (15.5 g, 46.7 mmol) was dissolved in
anhydrous MeOH (20.0 mL). Sodium methoxide
(0.252 g, 4.67 mmol) was added to the solution and the
mixture was stirred for 16 h at room temperature. The
MeOH was evaporated under vacuum and the crude
mixture was co-distilled with anhydrous toluene. After
drying under high vacuum, the product was obtained
without purification as a viscous yellow oil in 97% yield
3.3. 2,3,4,6-Tetra-O-acetyl-a-D-mannopyranosyl bromide
(22)30
1
(7.40 g, 45.1 mmol). H NMR (D2O, 400 MHz); d 3.83
Compound 21 (19.8 g, 51.0 mmol) was mixed with Ac2O
(14.4 mL, 152 mmol) and the mixture was cooled to 0 °C.
HBr (33% in acetic acid, 45.0 mL, 2.57 mmol) was added
to the solution, which was stirred at room temperature
for 4.5 h. The mixture was then poured into a beaker
containing about 200 mL of ice, stirred for 10 min, and
extracted with dichloromethane. The organic phase was
washed with saturated NaHCO3 and water and then dried
over Na2SO4. After filtration and concentration, the crude
mixture was dried under high vacuum and the product was
obtained as a light yellow oil in 99% yield (20.9 g,
(m, 1H), 3.77 (t, 2H, J = 12.9 Hz), 3.54 (dd, 1H,
J = 12.2, 6.5 Hz), 3.51 (m, 1H), 3.48 (dd, 1H, J = 7.5,
3.2 Hz), 3.43 (pseudo d, 1H, J = 9.5 Hz), 3.15 (pseudo
t, 1H, J = 7.0 Hz). 13C NMR (D2O, 100 MHz); d 81.9,
74.9, 71.2, 70.5, 68.7, 62.7. HRMS calcd for C6H12O5Na
[M+Na]+ 187.0582, found 187.0584.
3.6. 1,5-Anhydro-(2S)-2,3:4,6-di-O-benzylidene-D-manni-
tol (25) and 1,5-anhydro-(2R)-2,3:4,6-di-O-benzylidene-D-
mannitol (26)
1
50.8 mmol). H NMR (CDCl3, 400 MHz); d 6.29 (br s,
Compound 24 (0.157 g, 0.958 mmol) was dissolved in
anhydrous DMF (2.00 mL). p-Toluenesulfonic acid
(0.055 g, 0.289 mmol) and benzaldehyde dimethyl acetal
(0.580 mL, 3.86 mmol) were added to the solution and
the mixture was stirred at 60 °C for 24 h. The solution
was cooled to room temperature, diluted with dichloro-
methane, and then cooled to 0 °C. The reaction was
quenched by the addition of saturated NaHCO3. The
1H), 5.71 (dd, 1H, J = 10.2, 3.4 Hz), 5.44 (dd, 1H,
J = 3.4, 1.6 Hz), 5.36 (t, 1H, J = 10.2 Hz), 4.32 (dd, 1H,
J = 12.5, 4.9 Hz), 4.21 (m, 1H), 4.13 (dd, 1H, J = 12.4,
2.1 Hz), 2.17 (s, 3H), 2.09 (s, 3H), 2.07 (s, 3H), 2.00 (s,
3H). 13C NMR (CDCl3, 100 MHz); d 170.5, 169.7, 169.6,
169.7, 83.0, 72.8, 72.1, 67.9, 65.3, 61.4, 20.8, 20.7, 20.6,
20.5.

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J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
organic phase was separated from the water layer and
washed three times with 60 mL of H2O. After drying
on sodium sulfate, the CH2Cl2 was evaporated and the
product was dried under high vacuum without further
purification to afford a light yellow solid containing
both endo- and exo-isomers (0.264 g, 0.776 mmol) in
81% overall yield. Compounds 25 and 26 can be sepa-
rated by recrystallization in ethanol or by flash chroma-
79.7, 76.7, 72.1, 71.8, 71.4, 68.5, 67.8. HRMS calcd for
C20H22O5Na [M+Na]+ 365.1365, found 365.1365. Com-
pound 28: 1H NMR (CDCl3, 400 MHz); d 7.56–7.32 (m,
10H), 5.64 (s, 1H), 4.89 (d, 1H, J = 12.0 Hz), 4.77 (d,
1H, J = 12.0 Hz), 4.33 (dd, 1H, J = 10.4, 4.9 Hz), 4.13
(t, 1H, J = 9.4 Hz), 4.10 (dd, 1H, J = 12.7, 1.6 Hz),
4.00 (m,1H), 3.84 (t, 1H, J = 10.3 Hz), 3.69 (dd, 1H,
J = 9.4, 3.5 Hz), 3.56 (dd, 1H, J = 12.7, 1.5 Hz), 3.35
(dt, 1H, J = 9.8, 4.9 Hz), 2.79 (br s, 1H). 13C NMR
(CDCl3, 100 MHz); d 137.8, 137.5, 128.8, 128.3, 128.1,
127.8, 127.7, 125.9, 101.3, 78.9, 77.4, 72.5, 71.6, 70.1,
68.4, 68.2. HRMS calcd for C20H22O5Na [M+Na]+
365.1365, found 365.1365.
1
tography if necessary. Compounds 25 (exo isomer): H
NMR (CDCl3, 400 MHz); d 7.58–7.33 (m, 10H), 6.00
(s, 1H), 5.54 (s, 1H), 4.51 (m, 1H), 4.37 (m, 2H), 4.20
(dd, 1H, J = 5.3, 2.2 Hz), 3.93 (m, 1H), 3.78 (m, 2H),
3.32 (dt, 1H, J = 9.9, 5.2 Hz). 13C NMR (CDCl3,
100 MHz); d 138.9, 137.1, 129.3, 128.9, 128.4, 128.1,
126.5, 126.1, 104.2, 101.6, 81.3, 76.4, 74.7, 69.1, 68.6,
66.8. HRMS calcd for C20H21O5 [M+H]+ 341.1389,
found 341.1378. Compound 26 (endo isomer): 1H
NMR (CDCl3, 400 MHz); d 7.58–7.33 (m, 10H), 6.35
(s, 1H), 5.65 (s, 1H), 4.51 (m, 1H), 4.37 (m, 2H), 4.20
(dd, 1H, J = 5.3, 2.2 Hz), 3.93 (m, 1H), 3.78 (m, 2H),
3.32 (td, 1H, J = 9.9, 5.2 Hz). 13C NMR (CDCl3,
100 MHz); d 138.9, 137.2, 129.3, 129.0, 128.3, 128.2,
126.2, 125.9, 103.0, 101.8, 78.2, 76.0, 73.5, 69.2, 68.6,
67.1. HRMS calcd for C20H21O5 [M+H]+ 341.1389,
found 341.1378.
3.8. 1,5-Anhydro-2,3-di-O-benzyl-4,6-O-benzylidene-D-
mannitol (29)
A 1:1 mixture of compounds 27 and 28 (155 mg,
0.453 mmol) was dissolved in anhydrous DMF
(2.50 mL). The solution was cooled to 0 °C and sodium
hydride (54.4 mg, 2.27 mmol) was added to the reaction
flask under anhydrous conditions. The mixture was left
stirring at room temperature for 30–35 min, after which
benzyl bromide (0.220 mL, 1.85 mmol) was added to the
mixture and the reaction was left stirring for another
12 h. The solution was cooled to 0 °C and diluted with
CH2Cl2, then quenched with ice. After stirring for an-
other 15 min the organic phase was separated from the
water layer and washed with saturated NH4Cl and then
with H2O three times. After drying over Na2SO4, the
CH2Cl2 was evaporated and the crude mixture was puri-
fied on SiO2 gel with a gradient of solvent system, hex-
ane to hexane/CH2Cl2/THF 15:1:1. The pure product
was obtained as a white solid with a 75% yield
(146 mg, 0.338 mmol). Mp: 84–85 °C 1H NMR (CDCl3,
400 MHz); d 7.55–7.24 (m, 15H), 5.67 (s, 1H), 4.81
(m,3H), 4.77 (d, 2H, J = 12.4 Hz), 4.29 (m, 2H), 4.08
(dd, 1H, J = 12.6, 1.9 Hz), 3.87 (t, 1H, J = 10.3 Hz),
3.81 (m, 1H), 3.69 (dd, 1H, J = 9.8, 3.3 Hz), 3.45
(d, 1H, J = 12.6 Hz), 3.36 (dt, 2H, J = 9.9, 4.9 Hz).
13C NMR (CDCl3, 100 MHz); d 138.5, 138.2, 137.7,
128.8, 128.4, 128.3, 128.2, 128.0, 127.7, 127.5, 125.9,
101.3, 79.2, 78.5, 74.3, 72.6, 72.4, 72.2, 68.9, 68,6.
HRMS calcd for C27H28O5Na [M+Na]+ 455.1834,
found 455.1827.
3.7. 1,5-Anhydro-2-O-benzyl-4,6-O-benzylidene-D-manni-
tol (27) and 1,5-anhydro-3-O-benzyl-4,6-O-benzylidene-
D-mannitol (28)
A 1:1 mixture of diacetals 25 and 26 (0.207 g,
0.608 mmol) was dissolved in a 1:1 mixture of anhy-
drous CH2Cl2 and ether (2.00 mL). The solution was
cooled to 0 °C and carefully protected from moisture
in the air, aluminum chloride (0.081 mg, 0.607 mmol)
and lithium aluminum hydride (0.023 g, 0.606 mmol)
were added to the reaction mixture. After stirring at
room temperature for 30 min, the solution was cooled
to 0 °C and the reaction was quenched by ice. The solu-
tion was diluted with CH2Cl2 and the two phases were
separated. The organic phase was washed with a solu-
tion of saturated NaHCO3 and with H2O. After drying
on Na2SO4, the organic phase was evaporated and the
product was obtained as a colorless oil in 85% yield
(0.176 g, 0.514 mmol). The product is composed of a
mixture of the 2-OBn and 3-OBn isomers. A portion
of the mixture was purified on silica gel with a gradient
of solvent system using hexane to hexane/EtOAc 3:1 to
give the isolated compounds 27 and 28. Compound 27:
1H NMR (CDCl3, 400 MHz); d 7.52–7.29 (m, 10H),
5.58 (s, 1H), 4.79 (d, 1H, J = 12.1 Hz), 4.62 (d, 1H,
J = 12.1 Hz), 4.29 (dd, 1H, J = 10.4, 4.9 Hz), 4.16 (dd,
1H, J = 12.9, 1.6 Hz), 3.85 (m, 4H), 3.51 (dd, 1H,
J = 12.9, 0.7 Hz), 3.35 (td, 1H, J = 10.4, 4.9 Hz), 2.29
(br s, 1H). 13C NMR (CDCl3, 100 MHz); d 137.6,
137.3, 129.1, 128.6, 128.2, 128.0, 127.9, 126.3, 102.0,
3.9. 1,5-Anhydro-2,3-di-O-benzyl-D-mannitol (30)
Compound 29 (1.71 g, 3.95 mmol) was dissolved in ace-
tic acid (80% in H2O, 20.0 mL). The solution was stirred
at 45–50 °C for 12 h and cooled to 0 °C. The reaction
mixture was neutralized with satd aq NaHCO3 solution
and water was then removed under reduced pressure.
The crude mixture was taken up in EtOAc and the
organic phase was washed with H2O and dried over
Na2SO4. After filtration and drying under high vacuum,

J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
1749
product 30 was obtained without further purification as
a white solid in quantitative yield (1.36 g, 3.95 mmol).
Mp: 82–83 °C 1H NMR (CDCl3, 400 MHz); d 7.41–
7.25 (m, 10H), 4.73 (d, 1H, J = 12.4 Hz), 4.61 (t, 2H,
J = 11.8 Hz), 4.46 (d, 1H, J = 11.8 Hz), 4.11 (dd, 1H,
J = 12.8, 2.0 Hz), 4.00 (t, 1H, J = 9.5 Hz), 3.89 (dd,
1H, J = 11.8, 3.3 Hz), 3.79 (d, 1H, J = 5.6 Hz), 3.76
(m, 1H), 3.39 (dd, 1H, J = 9.4, 3.2 Hz), 3.35 (d, 1H,
J = 12.7 Hz), 3.26 (m, 3H). 13C NMR (CDCl3,
100 MHz); d 138.0, 137.8, 128.5, 128.4, 128.3, 128.0,
127.9, 127.8, 127.7, 127.6, 82.2, 80.1, 71.9, 71.3, 71.1,
67.5, 67.1, 62.9. HRMS calcd for C20H24O5Na
[M+Na]+ 367.1521, found 367.1517.
6:1. The pure product was obtained as a light yellow so-
lid in 78% yield (0.691 g, 1.42 mmol). Mp: 74–75 °C H
1
NMR (CDCl3, 400 MHz); d 7.39–7.27 (m, 10H), 4.77
(m, 1H), 4.74 (m, 2H), 4.59 (t, 1H, J = 12.5 Hz), 4.39
(d, 1H, J = 11.3 Hz), 4.22 (dd, 1H, J = 12.9, 2.3 Hz),
3.86 (m, 1H), 3.81 (dd, 1H, J = 10.9, 1.8 Hz), 3.63 (dd,
1H, J = 9.4, 3.2 Hz), 3.52 (m, 2H), 3.36 (d, 1H,
J = 12.9 Hz), 2.93 (s, 3H). 13C NMR (CDCl3,
100 MHz); d 137.5, 136.8, 128.6, 128.5, 128.3, 127.9,
79.3, 79.0, 78.5, 71.7, 71.1, 71.0, 66.4, 38.6, 31.7. HRMS
calcd for C21H25BrO6SNa [M+Na]+ 507.0453, found
507.0471.
3.12. Diethyl 2-(((2R,3R,4R,5R)-4,5-bis(benzyloxy)-3-
(methylsulfonyloxy)tetrahydro-2H-pyran-2-yl)methyl)-2-
(tert-butoxycarbonylamino)malonate (33)
3.10. 1,5-Anhydro-2,3-di-O-benzyl-4,6-di-O-methanesul-
fonyl-D-mannitol (31)
A solution of compound 30 (1.08 g, 3.14 mmol) in
dichloromethane (15.0 mL) was cooled to 0 °C. Meth-
anesulfonyl chloride (0.980 mL, 12.6 mmol) and Et3N
(3.00 mL, 21.5 mmol) were added to the reaction mix-
ture. This solution was left stirring at 0 °C for 30 min
and then at room temperature 14 h. The solution was
then diluted with CH2Cl2 and the reaction was quenched
with ice. After separating the phases, the organic phase
was washed with water and dried on Na2SO4. The sol-
vent was evaporated and the crude mixture was purified
on SiO2 gel using a gradient of hexane to hexane/EtOAc
2:1. The pure product was obtained as a light brown
N-Boc-diethylaminomalonate (0.426 g, 1.55 mmol) was
dissolved in anhydrous toluene (1 mL). After cooling
to 0 °C, sodium hydride (57–63% in mineral oil,
65.3 mg, 1.55 mmol) was added and the solution was
stirred for 45 min. Compound 32 (0.146 g, 0.301 mmol)
in 1.00 mL of anhydrous toluene and TBAI (34.4 mg,
0.093 mmol) were added to the mixture and the solution
was stirred under reflux for 14 h. The solution was
cooled to room temperature, diluted with CH2Cl2, and
quenched with ice. After separating the phases, the or-
ganic phase was washed twice with water and dried over
Na2SO4. After filtration and concentration, the crude
mixture was purified on SiO2 gel using a gradient of sol-
vent of hexane to hexane/EtOAc 6:1. The pure product
was obtained as a white solid in 51% yield (104 mg,
0.153 mmol). Mp: 41–42 °C 1H NMR (CDCl3,
400 MHz); d 7.37–7.25 (m, 10H), 6.03 (br s, 1H), 4.79–
4.50 (m, 5H), 4.17 (m, 5H), 3.80 (m, 2H), 3.55 (d, 1H,
J = 8.3 Hz), 3.39 (t, 1H, J = 9.9 Hz), 3.15 (d, 1H,
J = 12.8 Hz), 2.93 (m, 3H), 2.54 (dd, 1H, J = 14.9,
10.8 Hz), 1.42 (s, 9H), 1.22 (t, 6H, J = 6.7 Hz). 13C
NMR (CDCl3, 100 MHz); d (major rotomer) 168.4,
153.9, 137.8, 128.4, 128.3, 127.9, 127.6, 81.6, 79.5,
74.7, 72.5, 71.2, 71.1, 66.3, 64.2, 62.5, 38.9, 35.0, 28.1,
13.7. (Minor rotomer) 167.8, 153.5, 137.3, 128.4,
128.3, 127.9, 127.6, 81.6, 79.3, 74.7, 72.4, 71.4, 70.9,
66.1, 64.2, 62.0, 38.6, 35.1, 27.8, 13.8. HRMS calcd for
C33H45NO12SNa [M+Na]+ 702.2560, found 702.2571.
1
semi-solid in 85% yield (1.34 g, 2.68 mmol). H NMR
(CDCl3, 400 MHz); d 7.38–7.24 (m, 10H), 4.84 (t, 1H,
J = 9.6 Hz), 4.69 (d, 1H, J = 12.2 Hz), 4.59 (m, 2H),
4.44 (d, 1H, J = 11.3 Hz), 4.36 (dd, 1H, J = 11.5,
5.7 Hz), 4.14 (d, 1H, J = 12.9 Hz), 3.88 (br s, 1H), 3.68
(dd, 1H, J = 9.4, 2.8 Hz), 3.62 (m, 1H), 3.37 (d, 1H,
J = 12.9 Hz), 3.01 (s, 3H), 2.93 (s, 3H). 13C NMR
(CDCl3, 100 MHz); d 137.5, 136.7, 128.4, 128.3, 127.9,
127.8, 127.7, 127.6, 79.1, 76.2, 71.7, 71.0, 70.9, 68.4,
66.3, 38.4, 37.3. HRMS calcd for C22H28O9S2Na
[M+Na]+ 523.1072, found 523.1087.
3.11. 1,5-Anhydro-2,3-di-O-benzyl-6-bromo-6-deoxy-4-
O-methanesulfonyl-D-mannitol (32)
Compound 31 (0.920 g, 1.84 mmol) was dissolved in
anhydrous DMSO (10.0 mL). Sodium bromide (1.14 g,
11.1 mmol)
and
tetrabutylammonium
bromide
3.13. Ethyl 3-((2R,3R,4R,5R)-4,5-bis(benzyloxy)-3-
(methylsulfonyloxy)tetrahydro-2H-pyran-2-yl)-2-(tert-
butoxycarbonylamino)-propanoate (34)
(0.178 g, 0.552 mmol) were added to the solution and
the mixture was stirred at 60 °C for 36 h. The reaction
mixture was stirred under nitrogen atmosphere for 1–
2 h, some DMSO was evaporated during this process,
and the crude residue was taken up in CH2Cl2. The or-
ganic phase was washed three times with H2O, dried
over Na2SO4. The solvent was then removed under re-
duced pressure. The crude product was purified on
SiO2 gel using a gradient of hexane to hexane/EtOAc
A solution of compound 33 (220 mg, 0.324 mmol) in
5.00 mL of ethanol was treated with 1 N NaOH
(5 mL), the reaction mixture was stirred at 40–50 °C
for about 10 h. The solution was washed with ether sev-
eral times, then the combined ether phases were
extracted with water twice. The aqueous solution was

1750
J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
combined and acidified with 1 N HCl to pH 2–3, then
extracted with chloroform several times, the combined
chloroform solution was dried over Na2SO4, and con-
centrated. The residue was then subjected to decarboxyl-
ation reaction in refluxing toluene overnight. The
reaction mixture was evaporated under reduced pressure
to remove toluene, the residue was purified by flash
chromatography on silica gel using hexane/ethyl acetate
from 9:1 to 5:1 ratio. Product 34 was obtained as a col-
MeOH in EtOAc to give pure diastereomers 36 and 37
as a colorless oil. Compound 36 was obtained in a
48% yield (25.0 mg, 0.061 mmol). 1H NMR (CDCl3,
400 MHz);
d 7.41–7.27 (m, 10H), 4.77 (d, 1H,
J = 12.5 Hz), 4.76 (m, 2H), 4.65 (d, 1H, J = 12.2 Hz),
4.17 (q, 2H, J = 7.0 Hz), 4.14 (d, 1H, J = 8.1 Hz), 4.03
(d, 1H, J = 12.6 Hz), 3.94 (m, 1H), 3.69 (m, 2H), 3.52
(m, 1H), 3.27 (d, 1H, J = 12.7 Hz), 2.26 (dd, 1H,
J = 13.9, 8.7 Hz), 2.09 (m, 1H), 1.29 (m, 3H). 13C
NMR (CDCl3, 100 MHz); d 175.3, 138.2, 138.1, 128.4,
128.3, 127.8, 127.7, 127.6, 127.5, 79.6, 73.6, 72.7, 72.3,
69.1, 67.1, 60.7, 60.6, 58.5, 37.4, 14.1. HRMS calcd for
C24H30NO5 [M+H]+ 412.2124, found 412.2133. Com-
pound 37 was obtained in a 50% yield (26.0 mg,
0.063 mmol). 1H NMR (CDCl3, 400 MHz); d 7.49–
7.26 (m, 10H), 4.81 (d, 1H, J = 12.5 Hz), 4.75 (d, 1H,
J = 12.5 Hz), 4.69 (d, 1H, J = 12.5 Hz), 4.63 (d, 1H,
J = 12.5 Hz), 3.82 (m, 2H), 3.72 (m, 2H), 3.23 (d, 2H,
J = 12.7 Hz), 2.27 (m, 1H), 2.08 (dd, 1H, J = 14.3,
4.5 Hz), 1.19 (t, 3H, J = 7.1 Hz). 13C NMR (CDCl3,
100 MHz); d 173.3, 138.3, 138.1, 128.3, 128.2, 127.8,
127.6, 127.5, 127.4, 78.8, 73.8, 72.2, 71.9, 69.3, 66.9,
61.7, 60.9, 59.3, 38.1, 14.0. HRMS calcd for
C24H30NO5 [M+H]+ 412.2124, found 412.2112.
1
orless semi-solid in 91% yield (180 mg, 0.296 mmol). H
NMR (CDCl3, 400 MHz); d 7.39–7.25 (m, 10H), 5.33
(m, 1H), 4.80–4.46 (m, 5H), 4.38 (m, 2H), 4.16 (m,
3H), 3.83 (d, 1H, J = 15.8 Hz), 3.58 (m, 1H), 3.46–3.29
(m, 1H), 3.27 (m, 1H), 2.91–2.85 (m, 3H), 2.11 (m,
1H), 1.44 (s, 9H), 1.28–1.23 (m, 3H). 13C NMR (CDCl3,
100 MHz); d (major isomer): 172.3, 155.6, 137.5, 136.7,
128.4, 128.3, 127.8, 79.8, 79.5, 75.7, 72.1, 71.9, 71.1,
70.8, 66.6, 61.1, 50.6, 38.5, 33.9, 28.1, 13.9. (Minor iso-
mer): 172.1, 155.0, 137.6, 136.8, 128.4, 128.2, 127.8,
79.8, 79.3, 75.6, 72.1, 71.9, 71.1, 70.9, 66.3, 61.1, 50.9,
38.5, 33.9, 28.1, 13.8. Yield: 91%. HRMS calcd for
C30H41NO10SNa [M+Na]+ 630.2349, found 630.2346.
3.14. Ethyl 2-amino-3-((2R,3R,4R,5R)-4,5-bis(benzyl-
oxy)-3-(methylsulfonyloxy) tetrahydro-2H-pyran-2-
yl)propanoate (35)
3.16. 1,2,3,5,6-Penta-O-acetyl-a-D-galactopyranose (41)
Compound 34 (80 mg, 0.132 mmol) was treated with
1.00 mL TFA and 4.00 mL CH2Cl2 at 0 °C for 4–5 h.
The solvent was evaporated under reduced pressure,
and saturated NaHCO3 (15.0 mL) and EtOAc
(25.0 mL) were added to the residue. The aqueous layer
was extracted three times with EtOAc. The combined
organic layer was dried over Na2SO4. Solvent was re-
moved using a rotovap and intermediate 35 was ob-
tained as a yellow oil without further purification in a
96% yield (64.0 mg, 0.126 mmol). Compound 35 was
used directly for the next cyclization step. 1H NMR
(CDCl3, 400 MHz); d 7.43–7.22 (m, 10H), 4.70 (m,
2H), 4.57 (m, 2H), 4.39 (d, 1H, J = 11.1 Hz), 4.19 (m,
4H), 3.86 (s, 1H), 3.65 (m, 2H), 3.41 (m, 1H), 2.89 (s,
3H), 2.38 (m, 2H), 1.26 (m, 3H).
Sodium acetate (9.15 g, 112 mmol) was dissolved in
Ac2O (105 mL, 1.11 mol). The solution was heated to re-
flux temperature and D-galactose (40, 20.0 g, 111 mmol)
was added in portions. The solution was stirred at
145 °C for 3 h, cooled to room temperature, and poured
into a beaker containing 200 mL of ice H2O. After stir-
ring in water for 2 h, the product crystallized out and
was filtered through a Buchner funnel. The solid prod-
uct was washed thoroughly with cold water and recrys-
tallized in EtOH to afford a white crystalline solid in
70% yield (30.3 g, 77.6 mmol). 1H NMR (CDCl3,
400 MHz) d 5.69 (d, 1H, J = 8.3 Hz), 5.42 (d, 1H,
J = 3.0 Hz), 5.33 (dd, 1H, J = 10.4, 8.3 Hz), 5.07 (dd,
1H, J = 10.4, 3.4 Hz), 4.14 (m, 2H), 4.05 (t, 1 H,
J = 6.6 Hz), 2.16 (s, 3H), 2.12 (s, 3H), 2.04 (br s, 6H),
1.99 (s, 3H). 13C NMR (CDCl3, 100 MHz) d 169.9,
169.8, 169.5, 168.9, 168.6, 91.7, 71.3, 70.4, 67.6, 66.6,
60.8, 20.2.
3.15. (2S,3aR,6R,7S,7aS)-ethyl 6,7-bis(benzyloxy)octa-
hydropyrano[3,2-b]pyrrole-2-carboxylate (36) and
(2R,3aR,6R,7S,7aS)-ethyl 6,7-bis(benzyloxy)-octahydro-
pyrano[3,2-b]pyrrole-2-carboxylate (37)
3.17. 2,3,4,6-Tetra-O-acetyl-a-D-galactopyranosyl bro-
mide (42)31
The crude product 35 (64 mg, 0.126 mmol) was dis-
solved in 5.00 mL of toluene, and 1.5 equiv of DIEA
(0.236 mmol) was added to the reaction flask. The mix-
ture was brought to refluxing for 2–3 h to give the cyc-
lized products. The solvent was removed under
reduced pressure and the crude products were purified
by flash chromatography using a gradient of solvent sys-
tems of hexane/EtOAc from 3:1 to 1:1, then to 2%
A mixture of compound 41 (18.9 g, 48.3 mmol) and
Ac2O (14.0 mL, 148 mmol) was cooled to 0 °C and
hydrobromic acid (33% in acetic acid, 42.4 mL,
242 mmol) was added to the reaction mixture. After stir-
ring at room temperature for 90 min, the solution was
poured into 200 mL of ice-water and stirred for
15 min. The product was extracted from the aqueous

J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
1751
phase using EtOAc. The organic phase was then washed
two to three times with saturated NaHCO3 and three
times with H2O. After drying with Na2SO4 overnight,
the solvent was evaporated on a rotovap and the crude
residue was dried under high vacuum to afford a light
yellow powder in 91% yield (18.1 g, 44.0 mmol). 1H
NMR (CDCl3, 400 MHz) d 6.69 (d, 1H, J = 3.9 Hz),
5.51 (m, 1H), 5.39 (dd, 1H, J = 10.6, 3.3 Hz), 5.04 (dd,
1H, J = 10.6, 3.9 Hz), 4.48 (t, 1H, J = 6.5 Hz), 4.18
(dd, 1H, J = 11.4, 6.4 Hz), 4.09 (dd, 1H, J = 11.4,
6.7 Hz), 2.14 (s, 3H), 2.10 (s, 3H), 2.05 (s, 3H), 2.00 (s,
3H). 13C NMR (CDCl3, 100 MHz) d 170.3, 170.1,
169.9, 169.8, 88.1, 71.0, 67.9, 67.7, 66.9, 60.8, 20.7,
20.6, 20.5, 20.4.
5.6 Hz), 3.79 (m, 1H), 3.67 (td, 1H, J = 10.3, 5.5 Hz),
3.55 (m, 2H), 3.41 (m, 2H), 3.03 (t, 1H, J = 10.8 Hz).
13C NMR (D2O, 100 MHz) d 80.4, 75.1, 70.2, 70.1,
67.7, 62.4.
3.20. 1,5-Anhydro-4,6-O-benzylidene-D-galactitol (45)
Compound 44 (2.34 g, 14.3 mmol) was dissolved in
anhydrous DMF (10.0 mL) and the solution was cooled
to 0 °C. Benzaldehyde dimethyl acetal (3.22 mL,
21.5 mmol) and tetrafluoroboric acid (50% w/v in
Et2O, 0.750 mL, 17.1 mmol) were added and the solu-
tion was stirred at 0 °C for 15 min and at room temper-
ature for 12–15 h. Et3N (1.20 mL, 8.60 mmol) was
added to the mixture and the solution was stirred at
room temperature for 15 min. DMF was evaporated
and the crude product was recrystallized in EtOAc to
give the pure product as a white solid in 92% yield
(3.32 g, 13.9 mmol). 1H NMR (CDCl3, 400 MHz) d
7.49 (m, 2H), 7.38 (m, 3H), 5.56 (s, 1H), 4.31 (dd, 1H,
J = 12.6, 1.4 Hz), 4.26 (m, 1H), 4.15 (dd, 1H, J = 11.2,
5.2 Hz), 4.05 (dd, 1H, J = 12.6, 1.8 Hz), 3.98 (td, 1H,
J = 10.2, 5.2 Hz), 3.55 (m, 1H), 3.43 (m, 1H), 3.25 (t,
1H, J = 11.0 Hz). 13C NMR (CDCl3, 100 MHz) d
137.4, 129.3, 128.3, 126.3, 101.5, 75.8, 74.8, 70.4, 69.7,
69.2, 68.2. HRMS calcd for C13H16O5 [M]+ 252.0999,
found 252.0998.
3.18. 2,3,4,6-Tetra-O-acetyl-1,5-anhydro-D-galactitol
(43)
Compound 42 (9.23 g, 22.4 mmol) was dissolved in
anhydrous benzene (20.0 mL). Tributyltin hydride
(5.95 mL, 22.4 mmol) and AIBN (a few mg) were added
to the solution and the reaction was refluxed at 90 °C for
75 min. The solution was cooled to room temperature
and diluted with Et2O. Potassium fluoride (4.00 g,
68.8 mmol) dissolved in 30.0 mL of H2O was added
and the mixture was stirred at room temperature over-
night and a white precipitate of Bu3SnF was formed.
The solid residue was filtered out and the organic phase
was separated from the aqueous phase and dried over
Na2SO4. The ether was evaporated using a rotavap
and the product was dried under high vacuum to afford
a white solid in 95% yield (7.09 g, 21.3 mmol). 1H NMR
(CDCl3, 400 MHz) d 5.44 (d, 1H, J = 3.3 Hz), 5.22 (td,
1H, J = 10.3, 5.5 Hz), 5.04 (dd, 1H, J = 10.2, 3.4 Hz),
4.19 (dd, 1H, J = 11.2, 5.5 Hz), 4.06 (d, 2H,
J = 6.4 Hz), 3.81 (t, 1H, J = 6.4 Hz), 3.28 (t, 1H,
J = 10.9 Hz), 2.14 (s, 3H), 2.05 (s, 3H), 2.04 (s, 3H),
2.00 (s, 3H). 13C NMR (CDCl3, 100 MHz) d 170.3,
170.0, 169.9, 169.8, 74.7, 71.3, 67.6, 66.9, 66.2, 61.8,
20.6, 20.5, 20.4, 20.3. HRMS calcd for C14H21O9
[M+H]+ 333.1186, found 333.1174.
3.21. 1,5-Anhydro-2,3-di-O-benzyl-4,6-O-benzylidene-D-
galactitol (46)
Sodium hydride (1.60 mmol, 65.0 mg of 60% dispersed
in mineral oil) was added to a magnetically stirring
solution of compound 45 (0.100 g, 0.396 mmol) in
2.00 mL DMF and 1.00 mL toluene at 0 °C. The mix-
ture was left stirring at room temperature for 1 h after
which benzyl bromide (0.200 mL, 1.64 mmol) was
added dropwise and the reaction was left stirring over-
night under anhydrous conditions. The reaction mix-
ture was then poured into ice water, extracted 4–5
times with ethyl acetate. The combined organic phase
was washed with water and brine and dried over
Na2SO4. The solvent was removed under reduced pres-
sure and the residue purified by flash chromatography
to give the pure product 46 as white plate-like crystals
3.19. 1,5-Anhydro-D-galactitol (44)
Compound 43 (7.78 g, 23.4 mmol) was dissolved in
anhydrous MeOH (30.0 mL). Sodium methoxide
(127 mg, 2.35 mmol) was added to the solution and
the reaction was stirred at room temperature for 16 h.
The MeOH was evaporated under vacuum and the
crude mixture was taken up in H2O and neutralized to
pH 5–6 with diluted HCl. The aqueous phase was
washed two to three times with hexane and then concen-
trated on a rotovap, with co-distillation with toluene.
The product was then dried under high vacuum to afford
1
in 96% yield (0.165 g, 0.381 mmol). H NMR (CDCl3,
400 MHz) d 7.56–7.26 (m, 15H), 5.50 (s, 1H), 4.86 (d,
1H, J = 11.5 Hz), 4.80 (m, 2H), 4.67 (d, 1H,
J = 11.5 Hz), 4.26 (dd, 1H, J = 12.4, 1.3 Hz), 4.21 (d,
1H, J = 3.5 Hz), 4.18–4.05 (m, 2H), 3.98 (dd, 1H,
J = 12.4, 1.6 Hz), 3.58 (dd, 1H, J = 9.1, 3.6 Hz), 3.27
(m, 1H), 3.24 (t, 1H, J = 10.6 Hz). 13C NMR (CDCl3,
100 MHz) d 138.6, 138.5, 137.7, 128.9, 128.4, 128.3,
128.1, 127.8, 127.7, 127.6, 127.5, 126.3, 101.3, 80.9,
74.4, 74.0, 73.8, 71.5, 70.3, 69.7, 68.4. HRMS calcd
for C27H28O5 [M]+ 433.2015, found 433.2000.
1
a yellow semi-solid in 94% yield (3.62 g, 22.1 mmol). H
NMR (D2O, 400 MHz) d 3.84 (dd, 1H, J = 11.1,

1752
J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
3.22. 1,5-Anhydro-2,3-di-O-benzyl-D-galactitol (47)
12 h. The solution was diluted with CH2Cl2 and
quenched with ice water. The organic phase was washed
2–3 times with water and dried over Na2SO4. After fil-
tration and concentration, the crude product was puri-
fied on SiO2 gel using a solvent system of hexane/
EtOAc 10:1. The pure product was obtained as a white
solid in 94% yield (0.842 g, 1.44 mmol). 1H NMR
(CDCl3, 400 MHz) d 7.49–7.21 (m, 25H), 4.78 (m,
3H), 4.65 (d, 1H, J = 11.6 Hz), 4.08 (m, 1H), 4.05 (dd,
1H, J = 11.2, 5.5 Hz), 3.89 (td, 1H, J = 10.0, 5.5 Hz),
3.49 (dd, 1H, J = 9.1, 3.2 Hz), 3.37 (m, 3H), 3.15 (t,
1H, J = 10.9 Hz). 13C NMR (CDCl3, 100 MHz) d
143.8, 138.4, 138.1, 128.7, 128.5, 128.4, 127.9, 127.8,
127.7, 127.6, 127.5, 127.0, 86.9, 81.9, 77.6, 74.5, 73.5,
72.1, 68.4, 67.5, 63.0.
Compound 46 (0.165 g, 0.381 mmol) was dissolved in
50% acetic acid (10.0 mL). Sulfuric acid (10%,
3.00 mL) was added and the reaction was stirred at
55 °C for 12 h. The solution was neutralized with satu-
rated NaHCO3 and the solvent was evaporated. The
crude residue was taken up in EtOAc and the solid salts
were filtered out. After concentration of the organic
phase, the crude mixture was purified on SiO2 gel using
a gradient of hexane/EtOAc 4:1 to 1:1. The pure prod-
uct was obtained as a colorless oil in 95% yield
1
(0.125 g, 0.363 mmol). H NMR (CDCl3, 400 MHz) d
7.40–7.28 (m, 10H), 4.76 (m, 3H), 4.64 (d, 1H,
J = 11.6 Hz), 4.08 (dd, 1H, J = 11.2, 5.5 Hz), 4.05 (d,
1H, J = 3.3 Hz), 3.91 (td, 1H, J = 10.2, 5.5 Hz), 3.90
(dd, 1H, J = 11.7, 6.4 Hz), 3.74 (dd, 1H, J = 11.6,
4.6 Hz), 3.50 (dd, 1H, J = 9.1, 3.3 Hz), 3.35 (t, 1H,
J = 5.5 Hz), 3.18 (t, 1H, J = 11.0 Hz), 2.98 (br s, 2H).
13C NMR (CDCl3, 100 MHz) d 138.2, 137.8, 128.4,
128.3, 127.8, 127.7, 127.6, 81.6, 78.3, 74.3, 73.3, 71.9,
68.1, 67.6, 62.5. HRMS calcd for C20H25O5 [M+H]+
345.1702, found 345.1686.
3.25. 1,5-Anhydro-2,3-di-O-benzyl-4-O-methanesulfonyl-
6-O-trityl-D-galactitol (51)
Compound 50 (0.480 g, 0.818 mmol) was dissolved in
anhydrous CH2Cl2 (3.00 mL). Methanesulfonyl chloride
(0.130 mL, 1.67 mmol) and pyridine (0.133 mL,
1.64 mmol) were added to the solution and the reaction
was stirred at room temperature for 18 h. The solution
was diluted with CH2Cl2 and quenched with ice H2O.
The organic phase was washed with saturated NaHCO3
and with H2O 2–3 times. After drying with Na2SO4, fil-
tration and concentration, the crude mixture was puri-
fied on SiO2 gel with a gradient of solvent system of
hexane/EtOAc 10:1 to 7:1. The pure product was ob-
tained as a light yellow solid in 85% yield (0.460 g,
3.23. 1,5-Anhydro-2,3-di-O-benzyl-4,6-di-O-methanesul-
fonyl-D-galactitol (48)
Compound 47 (0.125 g, 0.363 mmol) was dissolved in
anhydrous dichloromethane (2.00 mL). Methanesulfonyl
chloride (0.110 mL, 1.42 mmol) and pyridine (2.00 mL,
24.7 mmol) were added to the solution and the reaction
was stirred at room temperature for 14 h. The solution
was diluted with CH2Cl2 and washed 3–4 times with
H2O. After drying on Na2SO4, the organic phase was con-
centrated and the crude mixture was purified on SiO2 gel
using a gradient of hexane/EtOAc 4:1 to 3:1. The pure
product was obtained as a light yellow oil in 93% yield
1
0.692 mmol). H NMR (CDCl3, 400 MHz) d 7.47–7.21
(m, 25H), 5.25 (m, 1H), 4.88 (d, 1H, J = 11.2 Hz),
4.75 (d, 1H, J = 11.6 Hz), 4.69 (d, 1H, J = 11.2 Hz),
4.63 (d, 1H, J = 11.6 Hz), 4.00 (dd, 1H, J = 11.3,
5.5 Hz), 3.76 (td, 1H, J = 10.1, 5.5 Hz), 3.47 (m, 2H),
3.27 (m, 2H), 3.11 (t, 1H, J = 11.1 Hz), 2.87 (s, 3H).
13C NMR (CDCl3, 100 MHz) d 143.6, 138.1, 137.5,
128.7, 128.4, 128.3, 128.2, 127.9, 127.8, 127.7, 127.6,
127.2, 87.4, 80.5, 77.4, 76.5, 73.9, 73.6, 72.7, 68.5, 62.4,
38.9.
1
(0.168 g, 0.336 mmol). H NMR (CDCl3, 400 MHz) d
7.41–7.27 (m, 10H), 5.21 (m, 1H), 4.82 (d, 1H,
J = 10.9 Hz), 4.77 (d, 1H, J = 11.7 Hz), 4.73 (d, 1H,
J = 10.9 Hz), 4.66 (d, 1H, J = 11.7 Hz), 4.37 (dd, 1H,
J = 10.5, 6.6 Hz), 4.23 (dd, 1H, J = 10.5, 6.2 Hz), 4.09
(dd, 1H, J = 11.5, 5.4 Hz), 3.81 (m, 2H), 3.63 (dd, 1H,
J = 9.4, 3.0 Hz), 3.24 (t, 1H, J = 11.3 Hz), 3.07 (s, 3H),
3.02 (s, 3H). 13C NMR (CDCl3, 100 MHz) d 137.8,
137.0, 128.6, 128.5, 128.3, 128.2, 127.9, 127.8, 79.9, 76.6,
74.8, 73.7, 73.5, 73.2, 68.4, 67.1, 39.0, 37.5. HRMS calcd
for C22H28O9S2Na [M+Na]+ 523.1072, found 523.1046.
Acknowledgments
We are grateful to the financial support from the Amer-
ican Heart Association (Grant # 043285N). We would
also like to thank Branden Hopkinson and Jiang Qian
for their help in synthesizing several intermediates.
3.24. 1,5-Anhydro-2,3-di-O-benzyl-6-O-trityl-D-galactitol
(50)
Supplementary data
Compound 47 (0.530 g, 1.54 mmol) was dissolved in
anhydrous CH2Cl2 (5.00 mL). Trityl chloride (0.495 g,
3.41 mmol) and pyridine (0.240 mL, 2.97 mmol) were
added to the solution and the reaction was stirred for
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.carres.
2008.03.017.

J.-R. Ella-Menye et al. / Carbohydrate Research 343 (2008) 1743–1753
1753
Med. Chem. 2004, 11, 2297–2321; (d) Srivastava, S.;
Goswami, L. N.; Dikshit, D. K. Med. Res. Rev. 2005, 25,
66–92.
References
1. (a) Murphy, P. V.; Dunne, J. L. Curr. Org. Synth. 2006, 3,
403–437; (b) Perdih, A.; Kikelj, D. Curr. Med. Chem.
2006, 13, 1525–1556.
2. Sakai, R.; Koike, T.; Sasaki, M.; Shimamoto, K.; Oiwa,
C.; Yano, A.; Suzuki, K.; Tachibana, K.; Kamiya, H. Org.
Lett. 2001, 3, 1479–1482.
14. Wipf, P.; Methot, J. L. Org. Lett. 2000, 2, 4213–4216.
15. (a) Valls, N.; Lopez-Canet, M.; Vallribera, M.; Bonjoch, J.
J. Am. Chem. Soc. 2000, 122, 11248–11249; (b) Valls, N.;
Lopez-Canet, M.; Vallribera, M.; Bonjoch, J. Chem. Eur.
J. 2001, 7, 3446–3460.
16. (a) Ohshima, T.; Gnanadesikan, V.; Shibuguchi, T.;
Fukuta, Y.; Nemoto, T.; Shibasaki, M. J. Am. Chem.
Soc. 2003, 125, 11206–11207; (b) Fukuta, Y.; Ohshima, T.;
Gnanadesikan, V.; Shibuguchi, T.; Nemoto, T.; Kisugi,
T.; Okino, T.; Shibasaki, M. Proc. Natl. Acad. Sci. U.S.A.
2004, 101, 5433–5438; (c) Ohshima, T. Chem. Pharm. Bull.
2004, 52, 1031–1052.
17. Hanessian, S.; Margarita, R.; Hall, A.; Johnstone, S.;
Tremblay, M.; Parlanti, L. Pure Appl. Chem. 2003, 75,
209–221.
18. Valls, N.; Vallribera, M.; Carmeli, S.; Bonjoch, J. Org.
Lett. 2003, 5, 447–450.
19. Hanessian, S.; Margarita, R.; Hall, A.; Johnstone, S.;
Tremblay, M.; Parlanti, L. J. Am. Chem. Soc. 2002, 124,
13342–13343.
3. (a) Sun, H.; Nikolovska-Coleska, Z.; Yang, C.-Y.; Xu, L.;
Liu, M.; Tomita, Y.; Pan, H.; Yoshioka, Y.; Krajewski,
K.; Roller, P. P.; Wang, S. J. Am. Chem. Soc. 2004, 26,
16686–16687; (b) Sun, H.; Nikolovska-Coleska, Z.; Yang,
C.-Y.; Xu, L.; Tomita, Y.; Krajewski, K.; Roller, P. P.;
Wang, S. J. Med. Chem. 2004, 47, 4147–4150.
4. (a) Tamura, S. Y.; Goldman, E. A.; Brunck, T. K.; Ripka,
W. C.; Semple, J. E. Bioorg. Med. Chem. Lett. 1997, 3,
331; (b) Fobian, Y. M.; d’Avignon, D. A.; Moeller, K. D.
Bioorg. Med. Chem. Lett. 1996, 6, 315–318; (c) Bachand,
B.; Tarazi, M.; St-Denis, Y.; Edmunds, J. J.; Winocour, P.
D.; Leblond, L.; Siddiqui, M. A. Bioorg. Med. Chem. Lett.
2001, 11, 287–290.
´
5. (a) St-Denis, Y.; Levesque, S.; Bachand, B.; Edmunds, J.
´
J.; Leblond, L.; Preville, P.; Tarazi, M.; Winocour, P. D.;
20. Hanessian, S.; Del-Valle, J. R.; Xue, Y. J. Am. Chem. Soc.
2006, 128, 10491–10495.
Siddiqui, A. M. Bioorg. Med. Chem. Lett. 2002, 12, 1181–
1184; (b) St-Denis, Y.; Augelli-Szafran, C. E.; Bachand,
B.; Berryman, K. A.; DiMaio, J.; Doherty, A. M.;
Edmunds, J. J.; Leblond, L.; Levesque, S.; Narasimhan,
L. S.; Penvose-Yi, J. R.; Rubin, R.; Tarazi, M.; Winocour,
P. D.; Siddiqui, A. Bioorg. Med. Chem. Lett. 1998, 8,
3193–3198; (c) Levesque, S.; St-Denis, Y.; Bachand, B.;
21. Bonjoch, J.; Catena, J.; Isabal, E.; Lopez-Canet, M.; Valls,
N. Tetrahedron: Asymmetry 1996, 7, 1899–1902.
22. (a) Hanessian, S.; Tremblay, M. Org. Lett. 2004, 6, 4683–
4686; (b) Hanessian, S.; Tremblay, M.; Marzi, M.; Del
Valle, J. R. J. Org. Chem. 2005, 70, 5070–5085.
23. Toyoka, N.; Okumura, M.; Himiyama, T.; Nakazawa, A.;
Nemoto, H. Synlett 2003, 55–58.
24. (a) Valls, N.; Borregan, M.; Bonjoch, J. Tetrahedron Lett.
2006, 47, 3701–3704; (b) Valls, N.; Vallribera, M.; Font-
Bard, M.; Solansb, X.; Bonjoch, J. Tetrahedron: Asym-
metry 2003, 14, 1241–1244.
25. Nie, X.; Wang, G. J. Org. Chem. 2005, 70, 8687–8692.
26. Doi, T.; Hoshina, Y.; Mogi, H.; Yamada, Y.; Takahashi,
T. J. Comb. Chem. 2006, 8, 571–582.
27. Hanessian, S.; Guillemette, S.; Ersmark, K. Chimia 2007,
61, 361–367.
´
Preville, P.; Leblond, L.; Winocour, P. D.; Edmunds, J. J.;
Rubin, J. R.; Siddiqui, M. A. Bioorg. Med. Chem. Lett.
2001, 11, 3161–3164.
6. Hanessian, S.; Balaux, E.; Musil, D.; Olsson, L. L.;
Nilsson, I. Bioorg. Med. Chem. Lett. 2000, 10, 243–247.
7. Ishida, K.; Okita, Y.; Matsuda, H.; Okino, T.; Murakami,
M. Tetrahedron 1999, 55, 10971–10988.
8. Kodani, S.; Ishida, K.; Murakami, M. J. Nat. Prod. 1998,
61, 1046–1048.
9. Ploutno, A.; Shoshan, M.; Carmeli, S. J. Nat. Prod. 2002,
65, 973–978.
10. Shin, H. J.; Matsuda, H.; Murakami, M.; Yamaguchi, K.
J. Org. Chem. 1997, 62, 1810–1813.
28. Hanessian, S.; Ersmark, K.; Wang, X.; Valle, J. R. D.;
Blomberg, N.; Xue, Y.; Fjellstrom, O. Bioorg. Med. Chem.
Lett. 2007, 3480–3485.
29. Nie, X.; Wang, G. Tetrahedron 2008, accepted for
publication.
11. Hanessian, S.; Tremblay, M.; Petersen, J. F. W. J. Am.
Chem. Soc. 2004, 126, 6064–6071.
12. (a) Carroll, A. R.; Pierens, G. K.; Fechner, G.; de Almeida
Leone, P.; Ngo, A.; Simpson, M.; Hyde, E.; Hooper, J. N.
A.; Bostrom, S. L.; Musil, D.; Quinn, R. J. J. Am. Chem.
Soc. 2002, 124, 13340–13341; (b) Carroll, A. R.; Bucha-
nan, M. S.; Edser, A.; Hyde, E.; Simpson, M.; Quinn, R. J.
J. Nat. Prod. 2004, 67, 1291–1294.
13. Recent reviews on thrombin inhibitors: (a) Linkins, L.-A.;
Weitz, J. I. Curr. Pharm. Des. 2005, 11, 3877–3884; (b)
Peterlin-Masic, L.; Cesar, J.; Zega, A. Curr. Pharm. Des.
´
30. (a) Nobrega, C.; Vazquez, J. T. Tetrahedron: Asymmetry
2003, 14, 2793–2801; (b) Timmons, S. C.; Jakeman, D. L.
Org. Lett. 2007, 9, 1227–1230.
31. (a) Maier, M. A.; Yannopoulos, C. G.; Mohamed, N.;
Roland, A.; Fritz, H.; Mohan, V.; Just, G.; Manoharan,
M. Bioconjugate Chem. 2003, 14, 18–29; (b) Ladmiral, V.;
Mantovani, G.; Clarkson, G. J.; Cauet, S.; Irwin, J. L.;
Haddleton, D. M. J. Am. Chem. Soc. 2006, 128, 4823–
4830.
2006, 12, 73–91; (c) Steinmetzer, T.; Sturzebecher, J. Curr.
¨