Synthesis of 2-amido, 2-amino, and 2-azido derivatives of the nitrogen analogue of the naturally occurring glycosidase inhibitor salacinol and their inhibitory activities against O-GlcNAcase and NagZ enzymes

Article abstract of DOI:10.1016/j.carres.2008.02.027

Seven 2-substituted derivatives of the nitrogen analogue of salacinol, a naturally occurring glycosidase inhibitor, were synthesized for structure-activity studies with hexosaminidase enzymes. The target zwitterionic compounds were synthesized by means of

Full text of DOI:10.1016/j.carres.2008.02.027

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 1766–1777
Synthesis of 2-amido, 2-amino, and 2-azido derivatives of
the nitrogen analogue of the naturally occurring glycosidase
inhibitor salacinol and their inhibitory activities against
O-GlcNAcase and NagZ enzymes
Niloufar Choubdar, Ramakrishna G. Bhat, Keith A. Stubbs, Scott Yuzwa
and B. Mario Pinto*
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
Received 9 February 2008; received in revised form 28 February 2008; accepted 29 February 2008
Available online 7 March 2008
Abstract—Seven 2-substituted derivatives of the nitrogen analogue of salacinol, a naturally occurring glycosidase inhibitor, were
synthesized for structure–activity studies with hexosaminidase enzymes. The target zwitterionic compounds were synthesized by
means of nucleophilic attack of the 2-azido-1,4-dideoxy-1,4-imino-D-arabinitol at the least hindered carbon atom of 2,4-O-benzyl-
idene-L-erythritol-1,3-cyclic sulfate. Hydrogenation of the azido zwitterionic compound in methanol resulted in the reduction of the
azide and subsequent methylation of the resulting amine in one pot. A similar reaction, with ethanol as the solvent, gave the N-ethyl
derivative. The 2-amino analogues were finally obtained by the reduction of the azide function using triphenylphosphine. Acylation
of the amine using acetic, propionic, or valeric anhydride afforded the corresponding 2-amido derivatives. Deprotection of the acyl-
ated, coupled products using 80% trifluoroacetic acid proceeded smoothly. Unlike their sulfonium ion counterparts, these
compounds were stable and did not undergo ring opening. We also report the synthesis of the parent nitrogen heterocycles,
N-Boc-1,2,4-trideoxy-2-amino-1,4-imino-D-arabinitol, and 1,2,4-trideoxy-2-acetamido-1,4-imino-D-arabinitol and its corresponding
N-Boc protected compound. The 2-substituted analogues and the parent iminoalditol showed marginal activity (<33% at 250 lM)
against human O-GlcNAcase and Vibrio cholerae NagZ enzymes.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Glycosidase inhibitors; Salacinol; 1,2,4-Trideoxy-2-amido-1,4-imino-D-arabinitol derivatives; Ammonium sulfates; Cyclic sulfates;
O-GlcNAcase and NagZ inhibition
1. Introduction
and 1-deoxynojirimycin 3, of which 1 has been used
for the oral treatment of type II diabetes.6–9 Swainso-
nine 2 is an inhibitor of Golgi a-mannosidase II (GMII),
which is a key enzyme in the N-glycosylation pathway.10
Deoxynojirimycin 3 is a powerful glucosidase inhibitor
and its derivatives have been used in the treatment of
diabetes, Gaucher’s disease, and viral infections.11–16
Salacinol 4 and kotalanol 5 are two naturally occur-
ring glycosidase inhibitors which are extracted from
roots and stems of a Sri Lankan plant, Salacia reticul-
ata.17–24 These compounds are unique in having a sulfo-
nium salt along with a sulfate counter ion. The
permanent positive charge on the sulfur atom is thought
to mimic the oxacarbenium ion-like transition state for
Glycosidases are involved in many biological processes
such as cell–cell or cell–virus recognition, immune
responses, cell growth, and viral and parasitic infec-
tions.1,2 The controlled inhibition of glycosidases has
potential for the treatment of many diseases such as dia-
betes, viral infections, and cancer.3–5
There are several naturally occurring glycosidase
enzyme inhibitors such as acarbose 1, swainsonine 2,
*
Corresponding author. Tel.: +1 778 782 4152; fax: +1 778 782
4860; e-mail: bpinto@sfu.ca
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.02.027

N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
1767
the glycosidase-mediated hydrolysis reactions.25–27 It
has been suggested that the counterion sulfate is impor-
tant for the interaction of this compound with the active
site of the enzyme,25,28,29 although this conclusion has
been brought into question recently.30
synthesized, in turn, from the commercially available
L-glutamic acid (Scheme 2).
N-Boc-1,2,4-trideoxy-2-azido-1,4-imino-D-arabinitol
29 was synthesized from L-glutamic acid in 8 steps
according to a literature procedure.33–35 The Boc pro-
tecting group was then removed under acidic conditions
to give the desired azido iminoalditol 24 in 72% yield
(Scheme 3).
The alkylation reaction of 24 with 2,4-O-benzylidene-
L-erythritol-1,3-cyclic sulfate (25) in acetonitrile in a
sealed tube afforded the desired coupled product 23 in
68% yield. The benzylidene protecting group was then
removed using trifluoroacetic acid (TFA, 80%) to afford
the desired product 10 in 73% yield (Scheme 4).
It was of interest to design compounds that might
function as inhibitors of the hexosaminidase enzymes
that cleave the b-glycosidic linkage of 2-acetamido-2-
deoxy-b-D-glycopyranosides. Our initial foray into this
area involved the attempted synthesis of 2-acetamido-
and 2-amino derivatives of salacinol 4. The benzyli-
dene-protected 3,5-O-benzyl-2-acetamido- 6 and the
2-amino- 7 substituted analogues of salacinol were
found to undergo ring opening reactions by nucleophilic
participation of the amide or amine moieties to give
acyclic amido 8 or ammonium sulfates 9, respectively
(Scheme 1).31 We were intrigued by this result because
it seemed to suggest that irreversible inhibition of
enzymes might occur through nucleophilic participation
of active-site residues. We further questioned whether
this type of reactivity would be general with the 2-amino
and 2-amido compounds, and whether the correspond-
ing nitrogen analogues of salacinol containing such func-
tionalities at C-2 would be stable. We report herein the
synthesis of seven target compounds 10–16 containing
acetamido, amino, azido, and longer-chain amido sub-
stituents at C-2.
Hydrogenation of compound 23 in methanol at 70 psi
did not yield the expected compound 11 (Scheme 5).
Instead, we observed a very interesting result, namely
the one-pot reduction of the azide to the amine followed
by N,N-dimethylation, while the benzylidene protecting
group remained intact (see 30, Scheme 6). A 1D-
NOESY experiment of compound 30 showed correla-
tions between N(CH3)2 and H-2 and H-3 which
confirmed that methylation of the amine had occurred.
Also, correlations were observed between the H-1b res-
onance and H-10b and H-4. Treatment of this compound
with trifluoroacetic acid (80%) afforded the 2-N,N-
dimethylamino analogue 15. To explore this chemistry
further, the hydrogenation reaction was then performed
at 70 psi H2 in the presence of Pd/C in ethanol; the N-
ethylamino derivative 31 was isolated. Treatment of this
compound with trifluoroacetic acid (80%) afforded the
2-N-ethylamino analogue (16) (Scheme 6). These com-
pounds presumably result from the formation of formal-
dehyde or acetaldehyde on the catalyst surface. Reaction
with the amines, after hydrogenation of the azides,
would then give the imines which undergo further
hydrogenation to yield the N-alkylamino derivatives.
Reduction of the azido compound 23 to the amine 32
was accomplished using PPh3, following a literature pro-
cedure.36,37 Deprotection of the benzylidene protecting
group afforded the desired 2-amino derivative 11 in
76% yield (Scheme 7). The stereochemistry at the ring
nitrogen center of 11 was confirmed by means of a
1D-NOESY experiment. Thus, irradiation of the H-10b
resonance showed correlations to H-4, H-1b, and
H-1a, and irradiation of H-4 showed correlations to
H-10b, H-1b, and H-10a. Correlations between H-10
and H-4 indicated that H-10 and H-4 are on the same
face, and correlations between H-1 and H-4 indicated
that the ring was intact and had not opened.
A very recent report describing the activity of the
parent iminoalditol 17, its enantiomer 18, and the corre-
sponding N-benzyl derivatives 19, 20 against
a
D-hexosaminidase enzyme indicated that whereas the
D-isomers are weak competitive inhibitors, the L-isomers
are potent, non-competitive inhibitors.32 Accordingly,
we report also our own syntheses of the parent
compounds, the iminoarabinitol 17, N-Boc-1,2,4-tride-
oxy-2-amino-1,4-imino-D-arabinitol 21, and N-Boc-
1,2,4-trideoxy-2-acetamido-1,4-imino-D-arabinitol 22.
Finally, we report the enzyme inhibitory activities of
compounds 10–16 (Scheme 2), their parent 2-acetamido
(17) and 2-azido (24) iminoalditols, N-Boc protected 2-
acetamido (22) and 2-amino (21) compounds against
two enzymes that cleave the b-glycosidic linkage of 2-
acetamido-2-deoxy-b-D-glycopyranosides.
2. Results and discussion
Retrosynthetic analysis indicated that the target com-
pounds 10–16 could be synthesized by the reduction of
the 2-azido function, its subsequent acylation, and the
removal of the benzylidene protecting group in com-
pound 23. Compound 23 could be synthesized, in turn,
by nucleophilic attack of the azido compound 24 at
the less hindered carbon of 2,4-O-benzylidene-L-erythri-
tol-1,3-cyclic sulfate (25). Compound 24 could be
synthesized from the epoxide 26 that could be
Treatment of compound 32 with acetic, propionic, or
valeric anhydride in methanol afforded the correspond-
ing amides 33–35 in 54–89% yield. Removal of the
benzylidene group in each of these compounds then
afforded the corresponding ammonium salts 12–14
(Scheme 8).

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N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
OH
HO
HO
N
HO
HO
CH3
OH
O
NH
OH
HN
HO
HO
HO
H
OH
OH
OH
OH
HO
3
O
O
2
HO
OH
HO
O
O
OH
HO
1
HO
OH
OH
OH
-
OH
4'
OH
3'
1'
OH
2'
-
5
S + OSO3
S
+
OSO
3OH
1
2
OH
HO
4
3
HO
HO
OH
4
5
Ph
Ph
O
O
O
O
-
-
S+
S
OSO3
OSO3K+
OH
BnO
BnO
BnO
NHCOCH3
OH
BnO
NHCOCH3
6
8
OH
OH
OH
-
-
S + OSO3
S
OSO3
CH3
HO
HO
HO
HO
NH2
NH3+
9
7
OH
OSO3
-OH
NH+
HO
X
HO
10 : X = N3
11 : X = NH2
12 : X = NHCOCH3
13 : X = NHCOCH2CH3
14 : X = NHCOCH2CH2CH2CH3
15 : X = N(CH3)2
16 : X = NHCH2CH3
R
R
R
N
N
N
HO
HO
HO
HO
NHCOCH3
HO
NHCOCH3
HO
X
18 : R = H
20 : R = CH2C6H5
17 : R = H
19 : R = CH2C6H5
21 : R = Boc, X = NH2
22 : R = Boc, X = NHCOCH3
Scheme 1.
To obtain the parent iminoarabinitol, the azide 29 was
amine 21 in 92% yield. The 13C NMR spectrum of this
first reduced using triphenylphosphine to afford the
compound at ambient temperature showed two sets of

N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
1769
Ph
OH
O
O
OH
-
-
OSO3
NH+
NH
OSO3
NH+
O
O
O
HO
HO
Ph
HO
O
+
O
S
O
X
HO
HO
N3
HO
N3
25
24
10 : X = N3
Ph = C6H5
11 : X = NH2
23
12 : X = NHCOCH3
13 : X = NHCOCH2CH3
14 : X = NHCOCH2CH2CH2CH3
15 : X = N(CH3)2
COO-
NH
16 : X = NHCH2CH3
+H3N
HO
COOH
L- Glutamic acid
O
26
Scheme 2.
Ph
Ph
N
COO-
N
O
O
Ref 33-35
BH3.THF
HO
O
+H3N
COOH
O
55%
27
28
H
N
Boc
N
Ref 34
HCl
HO
HO
MeOH
HO
N3
HO
N3
72%
29
24
Scheme 3.
Ph
OH
O
O
- OH
H
N
-
NH+
NH+
OSO3
OSO3
Cyclic sulfate (25)
K2CO3, CH3CN
TFA (80%)
HO
HO
HO
N3
N3
HO
HO
N3
HO
68%
23
73%
10
24
Scheme 4.
peaks due to restricted rotation about the carbamate;
the 13C NMR spectrum at 70 °C using D2O as the sol-
vent revealed one set of peaks above coalescence. The
amine 21 was then acetylated using acetic anhydride in
methanol to afford the corresponding amide 22 in 90%
yield; the 13C NMR spectrum of this compound was
also obtained at 70 °C in D2O. Deprotection of 22 with
HCl afforded, after neutralization, the desired 1,2,4-tri-
deoxy-2-acetamido-1,4-imino-D-arabinitol (17) in 84%
yield (Scheme 9).
Compounds 10–16, their parent 2-acetamido (17) and
2-azido (24) iminoalditols, N-Boc protected-2-acet-
amido (22) and 2-amino (21) compounds were tested
against two enzymes that cleave the b-glycosidic linkage

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N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
dues from glycoconjugates.38–44 exo-b-N-Acetylglucos-
Ph
aminidases from family 3, of which Vibrio cholerae
NagZ (VCNagZ) is a member, uses a catalytic mecha-
nism involving the formation and breakdown of a cova-
lent glycosyl-enzyme intermediate.41 The enzymes from
family 2038,39 and more recently, 84,42–44 of which
human O-GlcNAcase is a member, have been shown
to differ in that they use a catalytic mechanism involving
assistance from the 2-acetamido group of the substrate.
The percent inhibition of enzyme activity in each case,
at an inhibitor concentration of 250 lM, is shown in
Scheme 10. Among the ammonium ions, compounds
15 and 16 showed the highest activities, with 15 and
16 showing 33% and 27% inhibition of O-GlcNAcase,
respectively, and 13% and 23% inhibition of NagZ,
respectively. These results likely reflect better hydropho-
bic contacts within the active site of the enzyme by the
non-polar methyl and ethyl groups on C-2; compound
11, with the 2-amino group, showed the lowest (1%)
O
O
OH
OH
-
-
OSO3
NH+
OSO3
NH+
HO
HO
H2 (70 psi)
Pd/C, MeOH
HO
N3
HO
NH2
11
23
Scheme 5.
of 2-acetamido-2-deoxy-b-D-glycopyranosides. There
are two main enzyme-catalyzed hydrolytic mechanisms
known for cleaving this linkage. Examples of these
two mechanistic classes include the exo-b-N-acetylglu-
cosaminidases from family 3, and those from families
20 and 84 of the glycoside hydrolases, all of which are
functionally related in that they catalyze the release of
terminal 2-acetamido-2-deoxy-b-D-glycopyranose resi-
Ph
Ph
O
2'
O
O
4'
O
OH
1'
3'
OH
-
-
-
5
OSO3
NH+
OSO3
NH+
OSO3
NH+
1
HO
HO
TFA (80%)
HO
H2 (70 psi), Pd/C
MeOH
4
2
3
HO
N(CH3)2
HO
N3
HO
N(CH3)2
68%
23
61%
30
15
H2 (70 psi), Pd/C
EtOH
Ph
O
OH
O
OH
-
-
OSO3
OSO3
NH+
NH+
HO
HO
TFA (80%)
HO
NHCH2CH3
60%
31
HO
NHCH2CH3
70%
16
Scheme 6.
Ph
OH
O
O
4'
1'
3
3'
2'
- OH
-
NH+
NH+
5
OSO3
OSO3
1
2
PPh3
MeOH/H2O (8:1)
TFA (80%)
4
HO
23
HO
NH2
NH2
HO
HO
85%
76%
11
32
Scheme 7.

N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
1771
Ph
Ph
OH
O
O
O
O
-OH
OSO3
NH+
-
NH+
-
NH+
OSO3
OSO3
MeOH
(RCO)2O
R = -CH3
TFA (80%)
HO
HO
HO
HO
NHCOR
HO
NHCOR
NH2
HO
32
-CH2CH3
-(CH2)3CH3
33 : R = -CH3 (68%)
12 : R = -CH3 (95%)
34 : R = -CH2CH3 (54%)
35 : R = -(CH2)3CH3 (89%)
13 : R = -CH2CH3 (62%)
14 : R = -(CH2)3CH3 (70%)
Scheme 8.
H
N
Boc
N
Boc
N
Boc
N
PPh3
MeOH
Ac2O
HO
HCl (conc.)
HO
HO
HO
MeOH
HO
HO
HO
NHCOCH3
HO
NHCOCH3
N3
NH2
92%
21
90%
22
84%
17
29
Scheme 9.
Scheme 10.
activity. Among the parent iminoalditols, the 2-acetam-
ido derivatives 17 and 22 showed the highest inhibition
of the enzymes.
salacinol were synthesized. Nucleophilic attack of 2-
azido-1,4-iminoarabinitol at the less hindered carbon
of a benzylidene-protected L-erythritol-1,3-cyclic sulfate
proceeded smoothly and afforded the desired coupled
products. These compounds are quite stable at room
temperature in contrast to their sulfur congeners
in which ring opening reactions were observed. The
parent compound, 2-acetamido-1,2,4-trideoxy-1,4-imino-
3. Conclusions
Seven 2-N-substituted derivatives of the nitrogen ana-
logue of the naturally occurring glucosidase inhibitor

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N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
D-arabinitol, was also prepared from the N-Boc, 2-azido
derivative. A one-pot reduction and alkylation of the
coupled azido derivatives was observed in hydrogenation
reactions at 70 psi of the azide in methanol or ethanol
containing Pd/C as a catalyst. The inhibitory activities
of seven 2-substituted analogues of the nitrogen analogue
of salacinol along with four of their iminoalditol parent
compounds were tested against two enzymes that cleave
the b-glycosidic linkage of 2-acetamido-2-deoxy-b-D-gly-
copyranosides, namely O-GlcNAcase and NagZ; the
compounds showed marginal inhibitory activity (<33%
at 250 lM).
in the assays using p-nitrophenyl GlcNAc as a substrate
(0.25 mM for O-GlcNAcase, 0.5 mM for VCNagZ). All
inhibitors were tested at a concentration of 250 lM. The
progress of the reaction at the end of 30 min was deter-
mined by measuring the extent of 4-nitrophenolate liber-
ated, as determined by absorbance measurements at
400 nm. The absorbance measurements were averaged
to give a final result.
4.3. General procedure for trifluoroacetic acid treatment
The coupled compound (0.1 mmol) was dissolved in tri-
fluoroacetic acid (2 mL, 80%) and the solution was stir-
red at room temperature for 1 h. The solvent was
removed under reduced pressure and the crude product
was collected.
4. Experimental
4.1. General methods
1
Optical rotations were measured at 21 °C. H and 13C
4.4. General procedure for amide formation
NMR were recorded with frequencies of 500 and
125 MHz, respectively. All assignments were confirmed
To a solution of amine 32 (0.1 mmol) in MeOH (10 mL),
the desired anhydride (acetic, propionic, or valeric)
(1.5 equiv) was added. The mixture was stirred at room
temperature for 4 h and the solvent was removed under
reduced pressure to afford the crude product.
1
1
with the aid of two-dimensional H, H (gCOSY) and
1H, 13C (gHMQC) experiments using standard Varian
pulse programs. Processing of the data was performed
with MestRec software. 1D-NOESY experiments were
recorded at 295 K on a 500 MHz spectrometer. For each
1D-NOESY spectrum, 512 scans were acquired with Q3
Gaussian Cascade pulse. A mixing time of 800 ms was
used in all the 1D-NOESY experiments. Analytical
thin-layer chromatography (TLC) was performed on
aluminum plates precoated with Silica Gel 60F-254 as
the adsorbent. The developed plates were air-dried,
exposed to UV light, and/or sprayed with a solution
containing 3% ninhydrin in EtOH and heated. Column
chromatography was performed with Silica Gel 60
(230–400 mesh). High resolution mass spectra were
obtained by the electrospray ionization (ESI) technique,
using a ZabSpec OA TOF mass spectrometer at
10,000 RP.
4.5. 10-((2-Azido-1,4-imino-1,2,4-trideoxy-D-arabinitol)-
4-N-ammonium)-20,40-O-benzylidene-10-deoxy-L-erythri-
tol-30-sulfate (23)
Compound 24 (200 mg, 1.0 mmol), 2,4-benzylidene-L-
erythritol-1,3-cyclic sulfate (25) (413 mg, 1.2 equiv),
and K2CO3 (80 mg) were dissolved in CH3CN–MeOH
(5:1). The mixture was stirred in a sealed tube in an oil
bath at 78 °C for 16 h. K2CO3 was removed by filtration
and the solvent was removed under reduced pressure.
Flash chromatography of the crude product [EtOAc–
MeOH, 10:1] afforded compound 23 as a solid
(374 mg, 68%). Mp 110–112 °C; [a]D +93 (c 0.3,
1
MeOH); H NMR (CD3OD) d 7.41–7.30 (5H, m, Ar),
0
0
5.58 (1H, s, CHPh), 4.39 (1H, dd, J4 b;4 a ¼ 11:0,
4.2. Kinetic analysis of O-GlcNAcase and NagZ
J3 ;4 a ¼ 5:4 Hz, H-40a), 4.09 (1H, ddd, J2 ;3 ¼ 9:9 Hz,
0
0
0
0
H-30), 3.95 (1H, ddd, J1 b;2 ¼ 8:4 Hz, H-20), 3.84 (1H,
0
0
All assays were carried out in triplicate at 37 °C for
30 min by using a stopped assay procedure in which
the enzymatic reactions (50 lL) were quenched by the
addition of a 4-fold excess (200 lL) of quenching buffer
(200 mM glycine, pH 10.75). Assays were initiated by
the addition, via syringe, of enzyme (5 lL), and in all
cases the final pH of the resulting quenched solution
was greater than 10. The time-dependent assay of
human O-GlcNAcase45 and V. cholerae (VC) NagZ46
enzymes revealed that both enzymes were stable over
this period in the assay buffer: 50 mM NaH2PO4,
100 mM NaCl, 0.1% BSA, pH 7.4. The enzymes
O-GlcNAcase and VCNagZ were used at a concentra-
tion of 0.16 lg lLꢀ1 and 0.053 lg lLꢀ1, respectively,
dd, J2,3 = 2.8 Hz, H-3), 3.82 (1H, ddd, J1a,2 = 1.4,
0
0
J1b,2 = 5.8 Hz, H-2), 3.78 (1H, dd, J3 ;4 ¼ 10:6 Hz,
H-40b), 3.58 (1H, dd, J5b,5a = 9.1, J4,5a = 7.2 Hz,
H-5a), 3.57 (1H, dd, J4,5b = 6.4 Hz, H-5b), 3.29 (1H,
dd, J1 b;1 a ¼ 14:2 Hz, H-10a), 3.08 (1H, dd, J2,1a = 1.4,
0
0
J1b,1a = 11.6 Hz, H-1a), 2.79 (1H, dd, J2,1b = 5.8 Hz,
H-1b), 2.54 (1H, dd, H-10b), 2.50 (1H, ddd, J3,4
=
3.4 Hz, H-4); 13C NMR (CD3OD) d 138.0, 128.7,
127.9, 126.1 (6C, Ph), 100.9 (CHPh), 80.0 (C-3), 76.6
(C-20), 73.3 (C-4), 69.3 (C-40), 68.3 (C-30), 66.2 (C-2),
59.7 (C-5), 57.7 (C-1), 54.9 (C-10). Anal. Calcd for
C16H22N4O8S: C, 44.65; H, 5.15; N, 13.02. Found: C,
44.28; H, 4.94; N, 12.72.

N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
1773
4.6. 10-((2-Azido-1,4-imino-1,2,4-trideoxy-D-arabinitol)-
H2O, 5:3:1] to afford compound 11 as a white solid
(77 mg, 76%). Mp 210–212 °C (dec); [a]D +40 (c 0.1,
4-N-ammonium)-10-deoxy-L-erythritol-30-sulfate (10)
MeOH); 1H NMR (D2O) d 4.27 (1H, ddd, J2 ;3
¼
0
0
H-30),
4.02
(1H,
ddd,
J1 b;2 ¼ 6:9,
0
0
Compound 23 (50 mg, 0.1 mmol) was subjected to trifluo-
roacetic acid treatment and the crude product was
purified by flash chromatography [EtOAc–MeOH, 7:1]
to afford compound 10 as a syrup (29 mg, 73%). [a]D
5:2 Hz,
J1 a;2 ¼ 6:6 Hz, H-20), 4.01 (1H, dd, J4,3 = 4.6 Hz,
0
0
0
0
0
0
H-3), 3.74 (1H, dd, J4 b;4 a ¼ 12:6, J3 ;4 a ¼ 3:4 Hz,
H-40a), 3.67 (1H, dd, J3 ;4 b ¼ 5:6 Hz, H-40b), 3.64
(1H, dd, J5b,5a = 12.2, J4,5a = 3.1 Hz, H-5a), 3.58 (1H,
dd, J4,5b = 2.7 Hz, H-5b), 3.47 (1H, ddd, J1a,2 = 2.0,
J3,2 = 2.0 Hz, H-2), 3.14 (1H, dd, J1b,1a = 11.5 Hz,
0
0
1
+50 (c 0.02, MeOH); H NMR (CD3OD) d 4.35 (1H,
ddd, J2 ;3 ¼ 9:4, J4 a;3 ¼ 4:65 Hz, H-30), 3.99 (1H, ddd,
0
0
0
0
J1 a;2 ¼ 5:5 Hz, H-20), 3.98 (1H, dd, J3,2 = 5.1 Hz,
0
0
H-2), 3.91 (1H, dd, J4 b;4 a ¼ 12:0 Hz, H-40a), 3.81 (1H,
H-1a), 2.92 (1H, dd, J1 b;1 a ¼ 13:2 Hz, H-10a), 2.83
0
0
0
0
0
0
dd, J4,3 = 2.2 Hz, H-3), 3.80 (1H, dd, J3 ;4 b ¼ 5:0 Hz,
H-40b), 3.71 (1H, dd, J5b,5a = 11.7, J4,5a = 4.6 Hz,
H-5a), 3.66 (1H, dd, J4,5b = 4.0 Hz, H-5b), 3.28 (1H,
dd, J1b,1a = 11.1, J2,1a = 2.6 Hz, H-1a), 3.21 (1H, dd,
(1H, dd, J2,1b = 5.9 Hz, H-1b), 2.51 (1H, ddd, H-4),
13
2.42 (1H, dd, H-10b); C NMR (D2O) d 81.2 (C-30),
75.0 (C-3), 72.3 (C-4), 69.4 (C-20), 59.5 (C-40), 58.9
(C-5), 55.8 (C-2), 55.3 (C-1), 55.0 (C-10). Anal. Calcd
for C9H20N2O8S: C, 34.17; H, 6.37; N, 8.86. Found:
C, 34.38; H, 6.41; N, 8.75.
J1 b;1 a ¼ 13:2 Hz, H-10a), 2.95 (1H, dd, J2,1b = 6.6 Hz,
0
0
0
0
H-1b), 2.57 (1H, m, H-4), 2.56 (1H, dd, J2 ;1 b
¼
13
6:9 Hz, H-10b); C NMR (CD3OD) d 80.8 (C-30),
76.8 (C-3), 73.3 (C-4), 69.8 (C-20), 66.3 (C-2), 60.9
(C-5), 60.2 (C-4), 57.4 (C-1), 57.2 (C-10). HRMS:
[M+H]+ calcd for C9H19O8N4S, 343.0924; found,
343.0972.
4.9. 10-((2-Acetamido-1,4-imino-1,2,4-trideoxy-D-arabini-
tol)-4-N-ammonium)-20,40-O-benzylidene-10-deoxy-L-
erythritol-30-sulfate (33)
Compound 32 (34 mg, 0.08 mmol) was subjected to the
amidation conditions using Ac2O and the crude product
was purified by flash chromatography [EtOAc–MeOH,
3:1] to afford 33 as a syrup (25 mg, 68%). [a]D ꢀ17 (c
4.7. 10-((2-Amino-1,4-imino-1,2,4-trideoxy-D-arabinitol)-
4-N-ammonium)-20,40-O-benzylidene-10-deoxy-L-erythri-
tol-30-sulfate (32)
1
0.1, MeOH); H NMR (CD3OD) d 7.48–7.29 (5H, m,
0
0
To a solution of 23 (100 mg, 0.2 mmol) in MeOH–H2O
(15:1, 15 mL) was added PPh3 (63 mg, 1.2 equiv). The
mixture was stirred at room temperature overnight.
The solvent was removed under reduced pressure and
the crude product was purified by flash chromatography
[EtOAc–MeOH, 3:1] to afford 32 as a syrup (80 mg,
85%). [a]D +21 (c 0.1, MeOH); 1H NMR (D2O) d
7.41–7.29 (5H, m, Ar), 5.61 (1H, s, CHPh), 4.39 (1H,
Ar), 5.58 (1H, s, CHPh), 4.52 (1H, dd, J4 b;4 a ¼ 10:9,
J3 ;4 a ¼ 5:4 Hz, H-40a), 4.24 (1H, ddd, J4 b;3 ¼ 9:8,
0
0
0
0
J2 ;3 ¼ 9:7 Hz, H-30), 4.07 (1H, ddd, J1 b;2 ¼ 7:6,
0
0
0
0
J1 a;2 ¼ 3:3 Hz, H-20), 4.03 (1H, dd, J4,3 = 8.5, J2,3
=
0
0
3.1 Hz, H-3), 4.01 (1H, ddd, J1a,2 = 3.0 Hz, H-2), 3.83
(1H, dd, J5b,5a = 12.1, J4,5a = 3.3 Hz, H-5a), 3.77 (1H,
dd, H-40b), 3.69 (1H, dd, J4,5b = 2.8 Hz, H-5b), 3.58
(1H, dd, J1 b;1 a ¼ 12:4 Hz, H-10a), 3.31 (1H, dd, H-1a),
3.21 (1H, dd, J1a,1b = 11.9, J2,1b = 6.2 Hz, H-1b), 2.92
(1H, dd, H-10b), 2.80 (1H, dd, H-4), 1.96 (1H, s, CH3);
13C NMR (D2O) d 174.8 (CO), 136.0, 130.1, 128.9,
126.3 (6C, Ph), 101.0 (CHPh), 75.3 (C-30), 73.6 (C-3),
72.5 (C-4), 68.4 (C-40), 68.1 (C-20), 57.8 (C-1), 56.1
(C-5), 54.7 (C-10), 54.3 (C-2). Anal. Calcd for
C18H26N2O9S: C, 48.42; H, 5.87; N, 6.27. Found: C,
48.20; H, 5.96; N, 6.19.
0
0
dd, J3 ;4 a ¼ 5:4, J4 b;4 a ¼ 11:0 Hz, H-40a), 4.16 (1H,
0
0
0
0
ddd, J2 ;3 ¼ 9:8, J4 b;3 ¼ 9:9 Hz, H-30), 3.99 (1H, dd,
0
0
0
0
0
0
J2,3 = 2.8, J4,3 = 4.8 Hz, H-3), 3.95 (1H, ddd, J1 a;2
¼
1:9 Hz, H-20), 3.77 (1H, dd, H-40b), 3.67 (1H, dd,
J4,5a = 3.1, J5b,5a = 12.3 Hz, H-5a), 3.55 (1H, dd,
J4,5b = 2.4 Hz, H-5b), 3.43 (1H, m, H-2), 3.16 (1H, dd,
J1 b;1 a ¼ 14:4 Hz, H-10a), 3.11 (1H, dd, J2,1a = 0.8,
0
0
J1b,1a = 11.7 Hz, H-1a), 2.93 (1H, dd, J2,1b = 6.2 Hz,
H-1b), 2.64 (1H, dd, J2 ;1 b ¼ 7:5 Hz, H-10b), 2.56 (1H,
ddd, H-4); 13C NMR (D2O) d 136.4, 129.9, 128.9,
126.2 (6C, Ph), 101.1 (CHPh), 79.0 (C-20), 75.1 (C-3),
71.9 (C-4), 68.9 (C-30), 68.6 (C-40), 58.7 (C-5), 56.0
(C-1), 55.8 (C-2), 53.4 (C-10). HRMS: [M+H]+ calcd
for C16H25O8N2S, 405.1331; found, 405.1337.
0
0
4.10. 10-((2-Acetamido-1,4-imino-1,2,4-trideoxy-D-ara-
binitol)-4-N-ammonium)-10-deoxy-L-erythritol-30-sulfate
(12)
Compound 33 (26 mg, 0.06 mmol) was subjected to tri-
fluoroacetic acid treatment and the crude product was
purified by flash chromatography [EtOAc–MeOH, 2:1]
to afford compound 12 as a syrup (20 mg, 95%). [a]D
4.8. 10-((2-Amino-1,4-imino-1,2,4-trideoxy-D-arabinitol)-
4-N-ammonium)-10-deoxy-L-erythritol -30-sulfate (11)
1
+50 (c 0.1, MeOH); H NMR (CD3OD) d 4.48 (1H,
ddd, J2 ;3 ¼ 4:6 Hz, H-30), 4.06 (1H, ddd, J1 b;2
¼
0
0
0
0
Compound 32 (130 mg, 0.3 mmol) was subjected to tri-
fluoroacetic acid treatment and the crude product was
purified by flash chromatography [EtOAc–MeOH–
6:3 Hz, H-20), 3.96 (1H, ddd, J3,2 = 4.9 Hz, H-2), 3.93
(1H, dd, J3 ;4 a ¼ 4:1 Hz, H-40a), 3.91 (1H, dd, J4,3
0
0
=

1774
N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
J2 ;1 b ¼ 5:9 Hz, H-10b), 2.39 (1H, ddd, H-4), 2.23 (2H,
q, JCH ;CH ¼ 7:6 Hz, CH2), 1.12 (3H, t, CH3); 13C
0
0
0
0
0
0
3.4 Hz, H-3), 3.82 (1H, dd, J4 a;4 b ¼ 12:0, J3 ;4 b
¼
5:1 Hz, H-40b), 3.72 (1H, dd, J5b,5a = 11.8, J4,5a
3.9 Hz, H-5a), 3.63 (1H, dd, J4,5b = 3.3 Hz, H-5b),
3.15 (1H, dd, J1b,1a = 10.1 Hz, H-1a), 3.11 (1H, dd,
J1 b;1 a ¼ 12:7, J2 ;1 a ¼ 7:5 Hz, H-10a), 2.85 (1H, dd,
J2,1b = 6.1 Hz, H-1b), 2.53 (1H, dd, H-10b), 2.45 (1H,
ddd, H-4), 1.96 (3H, s, CH3); 13C NMR (CD3OD) d
172.0 (CO), 80.9 (C-30), 78.0 (C-3), 73.7 (C-10), 69.7
(C-20), 60.9 (C-40), 60.5 (C-5), 57.3 (C-4), 57.1 (C-1),
56.5 (C-2), 21.4 (CH3). HRMS: [M+H]+ calcd for
C11H23O9N2S, 359.1124; found, 359.1122.
=
3
2
NMR (CD3OD) d 175.7 (CO), 80.9 (C-30), 78.2 (C-3),
73.8 (C-4), 69.9 (C-20), 60.9 (C-40), 60.7 (C-5), 57.3
(C-1), 57.2 (C-10), 56.4 (C-2), 28.9 (CH2), 9.3 (CH3).
HRMS: [M+H]+ calcd for C12H25O9N2S, 373.1281;
found, 373.1295.
0
0
0
0
4.13. 10-((1,4-Imino-2-pentanamido-1,2,4-trideoxy-D-ara-
binitol)-4-N-ammonium)-20,40-O-benzylidene-10-deoxy-L-
erythritol-30-sulfate (35)
4.11. 10-((1,4-Imino-2-propionamido-1,2,4-trideoxy-D-
arabinitol)-4-N-ammonium)-20,40-O-benzylidene-10-
deoxy-L-erythritol-30-sulfate (34)
Compound 32 (13 mg, 0.03 mmol) was subjected to the
amidation conditions using valeric anhydride and the
crude product was purified by flash chromatography
[EtOAc–MeOH, 6:1] to afford 35 as a syrup (14 mg,
89%). [a]D +85 (c 0.04, MeOH); H NMR (CD3OD) d
7.39–7.20 (5H, m, Ar), 5.47 (1H, s, CHPh), 4.46 (1H,
1
Compound 32 (65 mg, 0.16 mmol) was subjected to the
amidation conditions using propionic anhydride and
the crude product was purified by flash chromatography
[EtOAc–MeOH, 3:1] to afford 34 as a syrup (40 mg,
dd, J4 b;4 a ¼ 10:9, J3 ;4 a ¼ 5:4 Hz, H-40a), 4.16 (1H,
0
0
0
0
ddd, J4 b;3 ¼ 9:8, J2 ;3 ¼ 5:5 Hz, H-30), 3.89 (1H, ddd,
H-20), 3.86 (1H, ddd, J3,2 = 5.5 Hz, H-2), 3.83 (1H, dd,
H-3), 3.68 (1H, dd, H-40b), 3.64 (1H, dd, J5b,5a = 11.7,
J4,5a = 6.1 Hz, H-5a), 3.52 (1H, dd, J4,5b = 1.5 Hz,
0
0
0
0
1
54%). [a]D +250 (c 0.1, MeOH); H NMR (CD3OD) d
7.51–7.31 (5H, m, Ar), 5.58 (1H, s, CHPh), 4.57 (1H,
dd, J4 b;4 a ¼ 10:9, J3 ;4 a ¼ 5:4 Hz, H-40a), 4.27 (1H,
0
0
0
0
ddd, J4 b;3 ¼ 9:8, J2 ;3 ¼ 9:7 Hz, H-30), 4.01 (1H, ddd,
H-5b), 3.24 (1H, dd, J1 b;1 a ¼ 13:7, J2 ;1 a ¼ 5:1 Hz,
0
0
0
0
0
0
0
0
J1 b;2 ¼ 6:7 Hz, H-20), 3.98 (1H, ddd, J3,2 = 5.4 Hz,
H-2), 3.95 (1H, dd, J4,3 = 3.8 Hz, H-3), 3.79 (1H, dd,
H-40b), 3.76 (1H, dd, J5b,5a = 11.5, J4,5a = 3.8 Hz,
H-5a), 3.64 (1H, dd, J4,5b = 2.6 Hz, H-5b), 3.37 (1H,
dd, J1b,1a = 13.6, J2,1a = 4.1 Hz, H-1a), 3.16 (1H, dd,
H-10a), 3.04 (1H, dd, J1b,1a = 9.8 Hz, H-1a), 2.79 (1H,
0
0
0
0
dd, J2,1b = 5.9 Hz, H-1b), 2.54 (1H, dd, J2 ;1 b
¼
6:8 Hz, H-10b), 2.34 (1H, ddd, J3,4 = 2.0 Hz, H-4), 2.10
(2H, dt, JCH ;CH ¼ 7:3; JNH;CH ¼ 2:6 Hz, CH2), 1.47
2
2
2
(2H, m, CH2), 1.23 (2H, m, CH2), 0.82 (3H, t,
J1 b;1 a ¼ 10:2 Hz, H-10a), 2.92 (1H, dd, H-10b), 2.68
(1H, dd, J2,1b = 6.7 Hz, H-1b), 2.49 (1H, ddd, H-4),
2.22 (2H, q, JCH ;CH ¼ 7:6 Hz, CH2), 1.11 (3H, t,
JCH ;CH ¼ 7:3 Hz, CH3); 13C NMR (CD3OD)
d
0
0
2
3
174.9 (CO), 138.1, 128.6, 127.9, 126.1 (4C, Ph), 100.9
(CHPh), 78.9 (C-20), 78.0 (C-3), 73.9 (C-4), 69.4 (C-30),
69.2 (C-40), 59.7 (C-5), 58.1 (C-1), 56.4 (C-2), 55.8
(C-40), 35.5, 28.0, 22.2 (3 ꢁ CH2), 12.9 (CH3). HRMS:
[M+H]+ calcd for C21H33O9N2S, 489.1907; found,
489.1923.
3
2
CH3); 13C NMR (CD3OD) d 175.7 (CO), 138.0, 128.7,
127.9, 126.1 (6C, Ph), 100.9 (CHPh), 78.7 (C-20), 77.9
(C-3), 73.9 (C-4), 69.4 (C-30), 69.2 (C-40), 59.5 (C-5),
57.9 (C-10), 56.3 (C-2), 55.8 (C-1), 28.9 (CH2), 9.2
(CH3). HRMS: [M+H]+ calcd for C19H29O9N2S,
461.1594; found, 461.1599.
4.14. 10-((1,4-Imino-2-pentanamido-1,2,4-trideoxy-D-ara-
binitol)-4-N-ammonium)-10-deoxy-L-erythritol-30-sulfate
(14)
4.12. 10-((1,4-Imino-2-propionamido-1,2,4-trideoxy-D-
arabinitol)-4-N-ammonium)-10-deoxy-L-erythritol-30-sul-
fate (13)
Compound 35 (14 mg, 0.03 mmol) was subjected to tri-
fluoroacetic acid treatment and the crude product was
purified by flash chromatography [EtOAc–MeOH, 3:1]
to afford compound 14 as a syrup (8 mg, 70%). [a]D
Compound 34 (20 mg, 0.08 mmol) was subjected to tri-
fluoroacetic acid treatment and the crude product was
purified by flash chromatography [EtOAc–MeOH, 3:1]
to afford compound 13 as a syrup (10 mg, 62%). [a]D
1
+60 (c 0.05, MeOH); H NMR (CD3OD) d 4.47 (1H,
ddd, J2 ;3 ¼ 9:3 Hz, H-30), 4.05 (1H, ddd, H-20), 3.97
0
0
1
0
0
+100 (c 0.02, MeOH); H NMR (CD3OD) d 4.49 (1H,
(1H, ddd, J1b,2 = 6.0 Hz, H-2), 3.92 (1H, dd, J4 b;4 a
¼
ddd, J2 ;3 ¼ 4:7 Hz, H-30), 4.05 (1H, ddd, H-20), 3.95
12:0, J3 ;4 a ¼ 4:2 Hz, H-40a), 3.90 (1H, dd, J4,3 = 3.6,
0
0
0
0
0
0
0
0
0
0
(1H, ddd, H-2), 3.92 (1H, dd, J4 b;4 a ¼ 11:9, J3 ;4 a
¼
J2,3 = 1.9 Hz, H-3), 3.82 (1H, dd, J3 ;4 b ¼ 5:1 Hz,
H-40b), 3.71 (1H, dd, J5b,5a = 11.7, J4,5a = 4.2 Hz,
H-5a), 3.63 (1H, dd, J4,5b = 3.6 Hz, H-5b), 3.15 (1H, dd,
4:2 Hz, H-40a), 3.89 (1H, dd, J4,3 = 3.5 Hz, H-3), 3.82
(1H, dd, J3 ;4 b ¼ 5:1 Hz, H-40b), 3.69 (1H, dd, J5b,5a
=
=
0
0
0
0
11.7, J4,5a = 4.1 Hz, H-5a), 3.61 (1H, dd, J4,5b
J1b,1a = 10.0 Hz, H-1a), 3.12 (1H, dd, J1 b;1 a ¼ 12:9,
J2 ;1 a ¼ 7:3 Hz, H-10a), 2.87 (1H, dd, H-1b), 2.54 (1H,
0
0
3.5 Hz, H-5b), 3.13 (1H, dd, J1b,1a = 10.0 Hz, H-1a),
3.08 (1H, dd, J1 b;1 a ¼ 12:8, J2 ;1 a ¼ 7:8 Hz, H-10a),
dd, J2 ;1 b ¼ 6:2 Hz, H-10b), 2.46 (1H, ddd, H-4), 2.22
0
0
0
0
0
0
2.81 (1H, dd, J2,1b = 5.9 Hz, H-1b), 2.49 (1H, dd,
(2H, dt, JCH ;CH ¼ 7:3; JNH;CH ¼ 0:8 Hz, CH2), 1.59
2
2
2

N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
1775
0
0
0
0
(2H, m, CH2), 1.36 (2H, m, CH2), 0.93 (3H, t,
J1 a;1 b ¼ 12:6, J2 ;1 b ¼ 5:9 Hz, H-10b); 13C NMR
(CD3OD) 80.2 (C-30), 73.3 (C-3), 72.9 (C-4), 71.2
(C-2), 69.6 (C-20), 60.6 (C-40), 58.9 (C-5), 55.9 (C-10),
54.7 (C-1), 41.7 (CH3). HRMS: [M+Na]+ calcd for
C11H24O8N2SNa, 367.1151; found, 367.1152.
JCH ;CH ¼ 7:3 Hz, CH3); 13C NMR (CD3OD) d 175.0
2
3
(CO), 80.9 (C-30), 78.1 (C-3), 73.8 (C-4), 69.7 (C-20),
60.9 (C-40), 60.6 (C-5), 57.4 (C-10), 57.2 (C-1), 56.4
(C-2), 35.6, 28.0, 22.2 (3 ꢁ CH2), 12.9 (CH3). HRMS:
[M+H] calcd for C14H29O9N2S, 401.1594; found,
401.1617.
4.17. 10-((2-N-Ethylamino-1,4-imino-1,2,4-trideoxy-D-
arabinitol)-4-N-ammonium)-20,40-O-benzylidene-10-
deoxy-L-erythritol-30-sulfate (31)
4.15. 10-((2-N,N-Dimethylamino-1,4-imino-1,2,4-tride-
oxy-D-arabinitol)-4-N-ammonium)-20,40-O-benzylidene-
10-deoxy-L-erythritol-30-sulfate (30)
Compound 23 (16.5 mg, 0.04 mmol) was dissolved in
EtOH (15 mL), Pd/C (60 mg) was added, and the mix-
ture was stirred under H2 (70 psi) overnight. The cata-
lyst was removed by filtration, the solvent was
removed under reduced pressure, and the crude product
was purified by flash chromatography [EtOAc–MeOH,
3:1] to afford compound 31 as a syrup (10 mg, 60%).
Compound 23 (100 mg, 0.23 mmol) was dissolved in
MeOH (20 mL), Pd/C (100 mg) was added, and the mix-
ture was stirred under H2 (70 psi) overnight. The cata-
lyst was removed by filtration and the solvent was
removed under reduced pressure. The crude product
was purified by flash chromatography [EtOAc–MeOH,
3:1] to afford compound 30 as a syrup (61 mg, 61%).
1
[a]D +43 (c 0.1, MeOH); H NMR (CD3OD) d 7.56–
7.29 (5H, m, Ar), 5.58 (1H, s, CHPh), 4.57 (1H, dd,
1
0
0
0
0
[a]D +80 (c 0.05, MeOH); H NMR (CD3OD) d 7.48–
J4 b;4 a ¼ 10:9, J3 ;4 a ¼ 5:4 Hz, H-40a), 4.37 (1H, ddd,
0
0
0
0
7.32 (5H, m, Ar), 5.59 (1H, s, CHPh), 4.59 (1H, dd,
J4 b;3 ¼ 9:8, J2 ;3 ¼ 9:7 Hz, H-30), 4.22 (1H, dd, J4,3
=
J4 b;4 a ¼ 10:9, J3 ;4 a ¼ 5:4 Hz, H-40a), 4.30 (1H, ddd,
3.6, J2,3 = 1.8 Hz, H-3), 3.94 (1H, ddd, J1 b;2 ¼ 5:7,
0
0
0
0
0
0
J4 b;3 ¼ 10:0, J2 ;3 ¼ 9:9 Hz, H-30), 4.23 (1H, dd,
J1 a;2 ¼ 4:3 Hz, H-20), 3.88 (1H, dd, J5b,5a = 11.7,
J4,5a = 2.3 Hz, H-5a), 3.78 (1H, dd, H-40b), 3.62 (1H,
dd, J4,5b = 1.9 Hz, H-5b), 3.41 (1H, dd, J1b,1a = 11.2 Hz,
H-1a), 3.33 (1H, ddd, J1a,2 = 1.0 Hz, H-2), 3.26 (1H, dd,
0
0
0
0
0
0
0
0
J4,3 = 5.8, J2,3 = 4.0 Hz, H-3), 3.94 (1H, ddd, J1 a;2
¼
3:2 Hz, H-20), 3.85 (1H, dd, J5b,5a = 12.1, J4,5a
=
2.7 Hz, H-5a), 3.78 (1H, ddd, H-40b), 3.63 (1H, dd,
J4,5b = 2.2 Hz, H-5b), 3.49 (1H, dd, J1b,1a = 11.6,
J2,1a = 2.2 Hz, H-1a), 3.30 (1H, dd, H-10a), 3.18 (1H,
ddd, H-2), 2.92 (1H, dd, J2,1b = 7.3 Hz, H-1b), 2.72
J1 b;1 a ¼ 13:8 Hz, H-10a), 3.11 (2H, m, CH2), 2.97 (1H,
dd, J2,1b = 5.2 Hz, H-1b), 2.78 (1H, dd, H-10b), 2.56
(1H, ddd, H-4), 1.29 (3H, t, JCH ;CH ¼ 7:3 Hz, CH3);
0
0
2
3
(6H, s, 2 ꢁ CH3), 2.68 (1H, dd, J2 ;1 b ¼ 6:1 Hz, H-10b),
2.51 (1H, ddd, H-4); 13C NMR (CD3OD) 137.9, 128.7,
127.9, 126.1 (4C, Ph), 101.1 (CHPh), 79.5 (C-20), 72.7
(C-3), 72.5 (C-4), 71.5 (C-2), 69.3 (C-30), 68.7 (C-40),
58.3 (C-5), 54.9 (C-1), 53.7 (C-10), 41.3 (CH3). Anal.
Calcd for C18H28N2O8S: C, 49.99; H, 6.52; N, 6.48.
Found: C, 50.35; H, 6.48; N, 6.53. HRMS: [M+H]+
calcd for C18H29O8N2S, 433.1645; found, 433.1645.
13C NMR (CD3OD) 138.0, 128.7, 127.9, 126.1 (6C,
Ph), 101.1 (CHPh), 78.8 (C-20), 73.8 (C-3), 73.4 (C-4),
69.3 (C-2), 69.2 (C-30), 62.9 (C-40), 58.7 (C-1), 55.2
(C-5), 54.4 (C-10), 41.1 (CH2), 10.5 (CH3). HRMS:
[M+H]+ calcd for C18H29O8N2S, 433.1645; found,
433.1638.
0
0
4.18. 10-((2-N-Ethylamino-1,4-imino-1,2,4-trideoxy-D-
arabinitol)-4-N-ammonium)-10-deoxy-L-erythritol-30-
sulfate (16)
4.16. 10-((2-N,N-Dimethylamino-1,4-imino-1,2,4-tride-
oxy-D-arabinitol)-4-N-ammonium)-10-deoxy-L-erythritol-
30-sulfate (15)
Compound 31 (10 mg, 0.02 mmol) was subjected to tri-
fluoroacetic acid treatment and the crude product was
purified by flash chromatography [EtOAc–MeOH, 3:1]
to afford compound 16 as a syrup (5.6 mg, 70%). [a]D
Compound 30 (28 mg, 0.06 mmol) was subjected to tri-
fluoroacetic acid treatment and the crude product was
purified by flash chromatography [EtOAc–MeOH, 3:1]
to afford compound 15 as a syrup (15 mg, 68%). [a]D
ꢀ9 (c 0.2, MeOH); 1H NMR (CD3OD) d 4.43 (1H,
1
+29 (c 0.04, MeOH); H NMR (CD3OD) d 4.37 (1H,
ddd, J2 ;3 ¼ 4:7 Hz, H-30), 4.04 (1H, dd, H-3), 3.98
0
0
(1H, ddd, J1 a;2 ¼ 8:3, J1 b;2 ¼ 5:2 Hz, H-20), 3.82 (1H,
0
0
0
0
ddd, J2 ;3 ¼ 4:7 Hz, H-30), 4.11 (1H, dd, J4,3 = 4.5 Hz,
dd, J4 b;4 a ¼ 11:9, J3 ;4 a ¼ 4:2 Hz, H-40a), 3.71 (1H, dd,
0
0
0
0
0
0
H-3), 4.06 (1H, ddd, H-20), 3.94 (1H, dd, J4 b;4 a
¼
¼
=
J3 ;4 b ¼ 5:1 Hz, H-40b), 3.69 (1H, dd, J5b,5a = 11.7,
J4,5a = 2.4 Hz, H-5a), 3.54 (1H, dd, J4,5b = 2.3 Hz,
H-5b), 3.27 (1H, dd, J1b,1a = 11.0 Hz, H-1a), 3.18 (1H,
ddd, J1b,2 = 5.3 Hz, H-2), 2.96 (2H, m, CH2), 2.94
0
0
0
0
11:9, J3 ;4 a ¼ 4:5 Hz, H-40a), 3.80 (1H, dd, J3 ;4 b
0
0
0
0
4:6 Hz, H-40b), 3.79 (1H, dd, J5b,5a = 11.7, J4,5a
3.9 Hz, H-5a), 3.65 (1H,dd, J4,5b = 3.0 Hz, H-5b), 3.42
(1H, dd, J1b,1a = 11.3, J2,1a = 3.0 Hz, H-1a), 3.11 (1H,
(1H, dd, J1 b;1 a ¼ 12:7 Hz, H-10a), 2.72 (1H,dd, H-1b),
2.41 (1H, dd, H-10b), 2.36 (1H, ddd, J3,4 = 4.5 Hz,
H-4), 1.19 (3H, t, JCH ;CH ¼ 7:2 Hz, CH3); 13C NMR
0
0
dd, J2 ;1 a ¼ 7:1 Hz, H-10a), 2.99 (1H, ddd, J3,2
=
0
0
0.3 Hz, H-2), 2.76 (1H, dd, J2,1b = 7.9 Hz, H-1b), 2.56
(6H, s, 2 ꢁ CH3), 2.43 (1H, ddd, H-4), 2.42 (1H, dd,
2
3
(CD3OD) 80.6 (C-30), 74.3 (C-3), 73.4 (C-4), 69.3

1776
N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
(C-20), 63.1 (C-2), 60.6 (C-40), 58.9 (C-5), 55.8 (C-10),
54.6 (C-1), 41.2 (CH2), 10.9 (CH3). HRMS: [M+Na]+
calcd for C11H24O8N2SNa, 367.1151; found, 367.1193.
[M+H]+ calcd for C5H11N4O2, 159.0882; found,
159.0884.
4.21. N-Boc-2-amino-1,4-imino-1,2,4-trideoxy-D-
arabinitol (21)
4.19. N-Benzyl-2,3-epoxy-1,4-imino-1,2,3,4-tetradeoxy-
D-ribitol (28)
To a solution of 29 (270 mg, 1.0 mmol) in MeOH–H2O
(20:1, 30 mL) was added triphenylphosphine (329 mg,
1.25 mmol). The mixture was stirred at room tempera-
ture overnight, the solvent was removed under reduced
pressure, and the crude product was purified by flash
chromatography [EtOAc–MeOH–H2O, 5:3:1] to afford
21 as an amorphous solid (223 mg, 92%). [a]D ꢀ58.82
To a solution of compound 27 (16.7 g, 76.7 mmol) in dry
THF (100 mL) was added BH3ꢂTHF (160 mL, 1 M solu-
tion) at 0 °C. The mixture was stirred under N2 over-
night. The reaction was quenched by slowly adding
MeOH until gas evolution had stopped. Additional
MeOH (50 mL) was added and the solvents were
removed under reduced pressure. The residue was dis-
solved in MeOH (200 mL), the mixture was heated to
reflux for 1 h, and the solvent was removed under
reduced pressure. MeOH (100 mL) was added and evap-
orated under reduced pressure. This procedure was
repeated twice. Diethyl ether (250 mL) and HCl
(250 mL, 0.5 M) were added and the layers were sepa-
rated. The organic layer was extracted with HCl
(250 mL, 0.5 M). The aqueous layers were combined
and adjusted to pH 11–12 with NaOH (10 M), and ex-
tracted with dichloromethane (300 mL). The organic
phase was dried over Na2SO4 and concentrated. The
crude product was purified by flash chromatography
[hexanes–EtOAc, 2:1] to afford 28 as a syrup (11.0 g,
1
(c 2.55, H2O); H NMR (CD3OD) d 4.01–3.95 (1H, m,
H-5a), 3.95–3.85 (1H, m, H-3), 3.77 (1H, m, H-1a),
3.67–3.60 (2H, m, H-5b, H-4), 3.26 (1H, m, H-2), 3.14
(1H, dd, J1b,1a = 11.4, J2,1b = 4.4 Hz, H-1b), 1.48 (9H,
s, C(CH3)3); 13C NMR (at 70 °C, D2O) d 156.8 (CO),
82.4 (C(CH3)3), 79.5 (C-3), 66.1 (C-4), 60.9 (C-5), 55.6
(C-5), 52.3 (C-2), 52.3 (C-1), 28.5 (CH3). HRMS:
[M+H]+ calcd for C10H21O4N2, 233.1501; found,
233.1490.
4.22. N-Boc-2-acetamido-1,4-imino-1,2,4-trideoxy-D-
arabinitol (22)
To a solution of 21 (50 mg, 0.2 mmol) in MeOH (15 mL)
was added Ac2O (0.2 mL, 10 equiv) and the mixture was
stirred for 2 h. The solvent was removed under reduced
pressure and the crude product was purified by flash
chromatography [EtOAc–MeOH, 5:1] to afford 22 as a
syrup (53 mg, 90%). [a]D +320 (c 0.125, H2O); 1H
NMR (CD3OD) d 4.26–4.06 (1H, m, H-3), 4.11 (1H,
m, H-2), 3.92–3.79 (2H, m, H-1a, H-5a), 3.72 (1H, dd,
J5a,5b = 11.0 Hz, H-5b), 3.57 (1H, m, H-4), 3.12 (1H,
dd, J1a,1b = 11.7, J2,1b = 4.6 Hz, H-1b), 1.95 (3H, s,
CH3), 1.48 (9H, s, C(CH3)3); 13C NMR (at 70 °C,
D2O) d 174.9 (CO), 156.8 (CO), 82.7 (C(CH3)3), 76.6
(C-3), 65.5 (C-4), 60.8 (C-5), 54.9 (C-2), 49.9 (C-1),
28.4 (CH3), 22.7 (CH3). HRMS: [M+H]+ calcd for
C12H23O5N2, 275.1607; found, 275.1610.
1
70%). [a]D ꢀ18 (c 2.9, MeOH); H NMR (CDCl3) d
7.34–7.22 (5H, m, Ph), 3.86, 3.79 (2H, d, Jgem = 13.4 Hz,
CH2Ph), 3.65 (1H, dd, J2,3 = 2.8, J2,1b = 0.5 Hz, H-2),
3.57 (1H, ddd, H-3), 3.48 (1H, dd, J5b,5a = 10.8,
J4,5a = 5.1 Hz, H-5a), 3.37 (1H, dd, J4,5b = 6.1 Hz,
H-5b), 3.24 (1H, ddd, H-4), 3.15 (1H, dd, J1b,1a
=
13.2, J2,1a = 1.2 Hz, H-1a), 2.93 (1H, dd, H-1b); 13C
NMR (CDCl3) 140.0, 128.76, 128.72, 127.4 (6C, Ph),
66.8 (C-4), 63.1 (CH2Ph), 61.5 (C-5), 60.2 (C-3), 57.9
(C-2), 54.4 (C-1). Anal. Calcd for C12H15NO2: C,
70.22; H, 7.37; N, 6.82. Found: C, 69.99; H, 7.33; N,
6.65.
4.20. 2-Azido-1,4-imino-1,2,4-trideoxy-D-arabinitol (24)
To a solution of compound 29 (1.67 g, 6.5 mmol) in
MeOH (100 mL) was added concentrated HCl
(1.2 mL). The mixture was stirred overnight. The solvent
was removed under reduced pressure and the crude
product was purified by flash chromatography
[EtOAc–MeOH, 3:1] to afford compound 24 as a syrup
(0.73 g, 72%). [a]D +1 (c 0.7, MeOH); 1H NMR
(CD3OD) d 4.23 (1H, ddd, J3,2 = 4.5 Hz, H-2), 4.12
4.23. 2-Acetamido-1,4-imino-1,2,4-trideoxy-D-arabinitol
(17)
To a solution of 22 (37 mg, 0.1 mmol) in MeOH (5 mL)
was added HCl (0.03 mL) and the mixture was stirred
for 3.5 h. The solvent was removed under reduced pres-
sure and the crude product was purified by flash chro-
matography [EtOAc–MeOH, 2:1] to afford 17 as a
syrup (24 mg, 84%). [a]D +4 (c 0.17, MeOH); 1H
NMR (D2O) d 4.15 (1H, ddd, H-2), 4.07 (1H, dd,
(1H, dd, H-3), 3.89 (1H, dd, J5b,5a = 11.8, J4,5a
=
4.2 Hz, H-5a), 3.76 (1H, dd, J4,5b = 7.5 Hz, H-5b),
3.64 (1H, dd, J1b,1a = 12.4, J2,1a = 6.5 Hz, H-1a), 3.52
J2,3 = 7.7 Hz, H-3), 3.81 (1H, dd, J5b,5a = 12.7, J4,5a
=
(1H, ddd, J3,4 = 5.4 Hz, H-4), 3.25 (1H, dd, J2,1b
=
3.2 Hz, H-5a), 3.71 (1H, dd, J4,5b = 5.7 Hz, H-5b),
3.60 (1H, dd, J1b,1a = 12.3, J2,1a = 8.6 Hz, H-1a), 3.45
4.6 Hz, H-1b); 13C NMR (CD3OD) d 74.5 (C-3), 66.7
(C-4), 65.3 (C-2), 58.4 (C-5), 47.2 (C-1). HRMS:
(1H, ddd, J3,4 = 8.1 Hz, H-4), 3.09 (1H, dd, J2,1b =

N. Choubdar et al. / Carbohydrate Research 343 (2008) 1766–1777
1777
7.6 Hz, H-1b), 1.86 (3H, s, CH3); 13C NMR (D2O) d
174.8 (CO), 73.1 (C-3), 63.9 (C-4), 57.7 (C-5), 54.5
(C-2), 46.4 (C-1), 22.0 (CH3). HRMS: [M+H]+ calcd
for C7H15O3N2, 175.1083; found, 175.1081.
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Acknowledgments
We are grateful to the Natural Sciences and Engineering
Research Council of Canada for financial support and
to Dr. D. J. Vocadlo for helpful discussion.
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