Synthesis and anomeric stability of (1→6)-thiourea-linked pseudooligosaccharides

Article abstract of DOI:10.1016/S0008-6215(99)00141-X

The synthesis of oligosaccharide mimics incorporating a thiourea intersaccharide bridge by coupling of mono- and disaccharide per-O-acetylated glycosyl isothiocyanates and methyl 6-amino-6-deoxy-α-D-glucopyranoside, is reported. An unexpected anomerizatio

Full text of DOI:10.1016/S0008-6215(99)00141-X

www.elsevier.nl/locate/carres
Carbohydrate Research 320 (1999) 37–48
Synthesis and anomeric stability of
(1“6)-thiourea-linked pseudooligosaccharides
Juan Manuel Benito a, Carmen Ortiz Mellet a, Kashinath Sadalapure b,
Thisbe K. Lindhorst b, Jacques Defaye c, Jose´ Manuel Garc´ıa Ferna´ndez d,*
a Departamento de Qu´ımica Orga´nica, Facultad de Qu´ımica, Uni6ersidad de Se6illa, Aptdo. 553,
E-41071 Se6illa, Spain
b Department of Organic Chemistry, Uni6ersity of Hamburg, Martin-Luther-King-Platz 6,
D-20416 Hamburg, Germany
c De´partement de Pharmacochimie Mole´culaire/Glucides, CNRS (EP 811) and Uni6ersite´ Joseph Fourier-Grenoble 1,
BP 138, F-38243 Meylan, France
d Instituto de In6estigaciones Qu´ımicas, CSIC, Ame´rico Vespucio s/n, E-41092 Se6illa, Spain
Received 20 April 1999; accepted 24 May 1999
Abstract
The synthesis of oligosaccharide mimics incorporating a thiourea intersaccharide bridge by coupling of mono- and
disaccharide per-O-acetylated glycosyl isothiocyanates and methyl 6-amino-6-deoxy-a-
D-glucopyranoside, is re-
ported. An unexpected anomerization reaction was observed, however, for a- and b- -mannopyranosylthioureido
D
derivatives upon Zemple´n deacetylation. Kinetics studies revealed that this anomerization process is base catalysed
and strongly dependent upon reaction temperature and reaction time. The fully unprotected compounds could be
obtained without epimerization by performing the last step at 0 °C. In all cases, the final pseudooligosaccharides were
stable in water solution at room temperature in the absence of base. © 1999 Elsevier Science Ltd. All rights reserved.
Keywords: Sugar thioureas; Sugar isothiocyanates; Carbohydrate mimics; Oligosaccharide mimics; Anomerization
with anomeric configuration control in gly-
coside bond-forming reactions and the
biodegradability of oligosaccharide structures
through the action of glycosidases. Replace-
ment of the glycosidic oxygen atom by other
achiral functional groups such as amide (car-
bopeptoids, saccharopeptides) [4–11] or phos-
phodiester (carbonucleotoids) [12], which can
be generated in high yield without affecting
the existing stereocenters, appears as a very
attractive alternative. Thiourea-bridged oligo-
saccharide mimics [13–15], accessible through
coupling reaction of readily available sugar
isothiocyanates [16–18] and amino sugars,
likewise comply with the above features. Re-
cently, this strategy was implemented with
1. Introduction
The growing awareness of the role of
oligosaccharides as carriers of biological infor-
mation has spurred an aggressive effort to-
wards the development of synthetic metho-
dologies suitable for the construction of glyco-
drugs [1–3]. Assembly of monosaccharides
through glycosidic linkages, as in the natural
compounds, suffers from two major disadvan-
tages, namely the complications associated
* Corresponding author. +34-95-448-9559; fax: +34-95-
446-0565.
E-mail address: jogarcia@cica.es (J. Garc´ıa Ferna´ndez)
0008-6215/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(99)00141-X

38
J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
the preparation of b-cyclodextrin-scaffolded
glycoclusters containing (1“6)-intersaccha-
ride thiourea bridges [19,20]. In the course of
this work, an unprecedented anomerization
configurational pattern (Scheme 1). However,
under identical reaction conditions, the a-
D-
mannopyranosylthioureido isomer 9 experi-
enced concomitant epimerization at the
anomeric C-1% center, leading to an insepara-
ble mixture of diastereomeric pseudooligosac-
charides. This result, in combination with our
previous observation in the cyclodextrin se-
ries, discards an essential contribution of the
aglyconic moiety in the anomerization pro-
cess, pointing to a particular reactivity of
mannopyranosylthiourea derivatives in alka-
line medium.
reaction
of
a- -mannopyranosylthiourea
D
derivatives upon base treatment was observed.
Since Zemple´n deacetylation of multivalent
a- -mannopyranosylthioureas had previously
D
been reported [21–24], several questions
arose: (1) Whether the epimerization process
was promoted by the cyclodextrin aglycon; (2)
whether this is an intrinsic limitation to the
synthesis of (1“6)-thiourea-tethered pseu-
dooligosaccharides; or (3) whether it is a gen-
eral aspect of the chemistry of fully
unprotected glycosylthioureas. We have now
investigated this problem by studying the
anomeric stability of a series of thiourea-
linked pseudooligosaccharides as well as sim-
In order to gain deeper insight into this
problem, a series of a- and b- -mannopyra-
D
nosylthioureas was prepared by reaction of
the respective per-O-acetylated a- (5) and b-
(28)
D
-mannopyranosyl isothiocyanates with
amino sugar 4, ethylamine hydrochloride or
benzylamine. The previously unreported 1,2-
cis configured isothiocyanate 28 was obtained
pler a- and b- -mannopyranosylthioureas
D
under various deacetylation reaction con-
ditions.
from b- -mannopyranosylamine (24) [28] in
D
four steps (20% overall yield) by transforma-
tion into the known enamine 26 [29], hydroly-
sis with chlorine in wet dichloromethane, and
further isothiocyanation of the resulting amine
hydrochloride 27 with thiophosgene (Scheme
2).
2. Results and discussion
Nucleophilic addition of methyl 6-amino-6-
deoxy-a-
acylated b-
b-lactosyl, and a-
D
-glucopyranoside (4) [25] to per-O-
When compounds 14, 16, 17, 20 and 21
were subjected to sodium methoxide-catalyzed
D
-glucopyranosyl, b-cellobiosyl,
D-mannopyranosyl isothio-
cyanates (1–3, 5) [16,26,27] in pyridine at
room temperature afforded the corresponding
partially protected adducts 6–9 in 85–90%
yield (Scheme 1). As previously observed for
the reaction of the same isothiocyanates with
6I-amino-6I-deoxy- and per(6-amino-6-deoxy)-
b-cyclodextrin precursors [19], addition of the
amino group to the central atom of the het-
eroallene group proceeded with total chemose-
lectivity and with no need for hydroxyl
protection in the acceptor moiety. Since the
anomeric CꢀN bond is not involved in forma-
tion of the intersaccharide thiourea bridge, the
anomeric configuration of the glycosyl sub-
stituent in 6–9 matched that of the isothio-
cyanate precursor, as confirmed by 1H and 13C
NMR data (Tables 1 and 2).
Conventional Zemple´n deacetylation of the
b-glycosylthioureido derivatives 6–8 led to the
expected fully unprotected compounds 10 [13],
11, and 12 with retention of the original
Scheme 1.

J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
39
deacetylation protocols. To ascertain this
point, the effects of a number of factors upon
the outcome of the reaction were investigated,
including substrate concentration, catalyst ra-
tio, quality of methanol, temperature, reaction
time, acidity of the resin, and time of contact
of the resin with the reaction mixture.
No definitive correlation was observed for
different concentrations of the starting
D
-
mannopyranosylthiourea (from 0.01 to 0.05
M) or sodium methoxide (from 0.1 to 0.5
equiv/mol of acetate). The results were also
largely independent of the use of either abso-
lute or commercial methanol and on the
strong (Amberlite IR-120) or weakly acidic
character (Amberlite IRC-50) of the resin that
was used for neutralization after complete de-
protection. When the deacetylation reaction of
N-ethyl-N%-(2,3,4,6-tetra-O-acetyl-a- -
D
mannopyranosyl)thiourea (16) was conducted
at 30 °C in methanol-d4 with deuterated
1
sodium methoxide and with monitoring by H
NMR spectroscopy, the presence of the b
anomer 19 was already detected after 10 min,
with a 1:3 a/b thermodynamic equilibrium for
18 and 19 being achieved within 4 h (Fig. 1).
An identical anomeric mixture was obtained
starting from 17 after prolonged reaction
times. We concluded, therefore, that the
Scheme 2.
deacetylation, partial anomerization likewise
occurred in both the a- and b-series. Yet, a
puzzling dependence of the final relative pro-
portion of anomers on the performer labora-
tory and hands, from almost undetectable to
major presence of the opposite configuration
at C-1, was evidenced, which probably ac-
counted for different ‘standard’ Zemple´n
anomerization of
D-mannopyranosylthioureas
is a base-catalyzed process, ruling out an alter-
native acid-promoted mechanism at the resin
surface. No changes in the composition of the
neutralized mixtures occurred after 24 h in
deuterium oxide or methanol-d4 solution at
room temperature1.
Reaction temperature was found to exert a
dramatic influence in the anomerization rate.
Thus, at 0 °C no epimerization was observed
after 1 h. At this temperature, deacetylation of
acetylated
D
-mannopyranosylthiourea deriva-
tives could be performed by using 0.02 M
solutions in analytical grade methanol con-
taining 0.5 equiv of sodium methoxide for 20
min. These conditions gave reproducible, vir-
tually quantitative yields of the anomerically
1 Partial anomerization occurred during the acquisition of
13C NMR spectra for fully unprotected configurationally pure
mannopyranosylthiourea derivatives in deuterium oxide solu-
tion at 70 °C overnight.
1
Fig. 1. Molar fractions (digital integration of H signals at
500 MHz) of 18 (ꢀ) and 19 (ꢁ) in the reaction mixture
arising from deacetylation of 16 (0.02 M in CD3OD) with
NaOCD3 (0.1 equiv per mol of acetate) at 300 K.

40
J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
Table 1
1H NMR data (500 MHz) for the new thiourea derivatives 6–9 and 11–23
Unit
Chemical shifts (l)
H-1
H-2
H-3
H-4
H-5
H-6a
H-6b
6 a,d
6 b,d
I
II
5.04d
6.08d
3.80dd
5.38dd
3.89t
5.67t
3.54t
5.35t
4.03m
4.35ddd
4.25m
4.58dd
4.03m
4.46dd
I
II
5.04d
5.68bs
3.48d
5.04t
3.72t
5.31t
3.24t
4.98t
3.64dt
3.83ddd
3.48m
4.28dd
3.48m
4.09dd
a,f
7
I
II
III
5.30d
6.28d
5.32d
4.08dd
5.58t
5.43t
4.18t
5.84t
5.78t
3.81t
4.55t
5.60t
4.27m
4.48m
4.51m
4.73m
5.01dd
4.88dd
4.72m
4.74m
4.70m
7 b,d
8 a,f
8 b,c
I
II
III
4.72d
5.55m
4.55d
3.47dd
4.94t
4.91dd
3.72t
5.26t
5.15t
3.22t
3.85t
5.06t
3.64ddd
3.74ddd
3.68ddd
3.67dd
4.43dd
4.34dd
3.45dd
4.23dd
4.07dd
I
II
III
5.31d
6.28d
5.27dd
4.07dd
5.57t
5.53dd
4.18t
5.83t
5.69dd
3.81t
4.56t
5.94d
4.27m
4.48ddd
4.80m
4.80m
5.01dd
4.80m
4.80m
4.80m
4.80m
I
II
III
4.73d
5.55m
4.52d
3.47dd
4.94t
5.10dd
3.71t
5.27t
4.98dd
3.22bt
3.88t
5.35dd
3.63dt
3.77m
3.89ddd
3.71m
4.40bd
4.15dd
3.45dd
4.27dd
4.08dd
9 a,f
I
II
5.18d
6.27m
3.93dd
5.74m
4.04t
5.74m
3.70t
5.62t
4.20ddd
4.48m
4.34m
4.79dd
4.12m
4.58dd
11 a,f
I
II
III
5.21d
5.75d
4.94d
3.97dd
3.92t
3.75dd
4.08t
4.15–4.07m
3.93t
3.74t
4.15–4.07m
3.84t
4.20m
4.15–4.07m
3.82ddd
4.35m
4.35dd
4.33dd
4.20m
4.23dd
4.15dd
12 a,f
I
II
III
5.19d
5.72bd
4.86d
3.96dd
3.90t
4.95dd
4.07t
4.06m
4.06dd
3.72t
4.06m
4.34d
4.19m
4.10m
4.12dd
4.35m
4.22dd
4.18m
4.19m
4.20dd
4.18m
13 a,e
14 a,e
15 a,e
I
II
5.37d
6.18m
4.08dd
4.55dd
4.19t
4.24dd
4.84t
4.19t
4.32m
3.98ddd
4.45m
4.41dd
4.32m
4.32m
I
II
5.21d
6.46m
3.97dd
5.96dd
4.08t
5.77dd
3.72t
5.64t
4.20m
4.50ddd
4.42m
4.97dd
4.20m
4.63dd
I
II
5.36d
6.11m
4.11dd
4.56dd
4.22t
4.27dd
3.87t
4.18t
4.30m
4.01ddd
4.47m
4.47dd
4.30m
4.30m
16 b,c
17 b,c
18 a,g
19 a,e
20 b,g
21 b,c
I
I
I
I
I
I
5.30m
5.90m
5.44bs
5.75m
5.38m
5.86bd
5.30m
5.43dd
4.04m
4.18m
5.38m
5.42dd
5.25dd
5.14dd
3.83dd
3.91dd
5.35m
5.13dd
5.20t
5.22t
3.65t
3.80t
5.23t
5.18t
4.08ddd
3.82ddd
3.53m
4.26dd
4.28dd
3.86dd
4.09dd
4.25dd
4.23dd
4.15dd
4.12dd
3.74dd
3.92dd
3.99dd
4.10dd
3.66ddd
4.10m
3.78ddd
22 a,e
23 a,c
I
I
5.97m
5.77m
4.45m
4.20m
4.24m
3.92dd
4.12t
3.83t
3.94m
3.68ddd
4.17m
4.11dd
4.17m
3.95dd

J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
41
Table 1 (Continued)
Coupling constants (Hz)
J1,2
J2,3
J3,4
J4,5
J5,6a
J5,6b
J6a,6b
a,d
6
I
II
3.7
6.5
9.5
9.4
9.5
9.4
9.5
9.4
–
4.3
–
2.2
–
12.6
6 b,d
7 a,f
I
II
3.7
9.4
9.5
9.4
9.5
9.4
9.5
9.4
–
4.3
–
2.2
–
12.6
I
II
III
3.9
9.1
7.9
9.4
9.1
9.2
9.4
9.1
9.2
9.4
9.1
9.2
–
1.6
–
–
–
–
–
12.1
–
7 b,d
8 a,f
8 b,c
I
II
III
3.8
9.4
7.9
9.6
9.4
9.3
9.6
9.4
9.3
9.6
9.4
9.3
3.2
1.8
4.4
4.5
5.4
2.4
–
12.1
12.4
I
II
III
3.9
9.4
7.9
9.8
9.4
10.3
9.8
9.4
3.3
9.8
9.4
0
–
2.2
–
–
5.1
–
–
12.4
–
I
II
III
3.7
9.4
7.9
9.4
9.4
10.3
9.4
9.4
3.4
9.4
9.4
0.9
2.4
2.0
6.2
3.6
5.6
7.5
–
10.8
11.1
9 a,f
I
II
3.8
–
9.4
–
9.4
8.7
9.4
8.7
2.8
5.1
6.5
2.7
–
12.5
11 a,f
I
II
III
4.0
9.1
8.0
9.9
9.1
9.4
9.9
–
9.4
9.9
–
9.4
–
0.8
2.2
–
2.0
5.5
–
12.7
12.4
12 a,f
I
II
III
4.0
9.0
7.8
9.9
9.0
7.8
9.9
–
3.6
9.9
–
0
–
1.2
–
–
2.0
–
–
11.8
–
13 a,e
14 a,e
15 a,e
I
II
3.3
2.3
9.7
3.3
9.7
9.5
9.7
9.5
–
2.5
–
4.8
–
12.3
I
II
3.8
1.0
9.3
3.2
9.3
10.0
9.3
10.0
–
4.2
–
2.3
–
12.6
I
II
3.7
1.3
9.2
3.1
9.2
9.6
9.2
9.6
–
2.0
–
5.6
–
12.2
16 b,c
17 b,c
18 a,g
19 a,e
20 b,g
21 b,c
22 a,e
23 a,c
I
I
I
I
I
I
I
I
–
3.0
3.2
3.2
3.2
–
8.8
10.0
9.6
9.3
9.2
9.9
9.5
9.7
8.8
10.0
9.6
9.3
9.2
9.9
9.5
9.7
6.2
5.4
2.1
2.2
6.0
5.7
–
2.5
2.3
6.6
5.8
2.0
2.5
–
12.3
12.3
12.3
12.3
12.2
12.3
–
1.0
–
–
–
1.0
–
3.1
–
–
2.8
1.9
5.8
12.2
a In D2O.
b In CDCl3.
c At 313 K.
d At 323 K.
e At 333 K.
f At 343 K.
g At 300 MHz.

42
J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
Table 2
13C NMR data (125.7 MHz) for the new thioureas 6–9 and 11–23
Unit
Chemical shifts (l)
C-1
C-2
C-3
C-4
C-5
C-6
6 a,d,f
6 b,c
7 a,e
I
II
99.9
82.9
71.9
71.3
73.6
74.2
71.9
69.0
71.5
73.3
46.0
62.7
I
II
99.6
82.9
70.5
72.1
73.9
73.0
71.0
68.5
70.6
73.5
45.0
62.0
I
II
III
99.9
82.5
100.5
71.9
72.0
72.5
73.8
74.5
74.2
71.9
76.4
68.8
71.5
73.5
71.8
45.6
63.0
62.6
7 b,d
8 a,e
8 b,c
I
II
III
99.6
82.7
100.4
72.7
70.6
71.0
72.9
72.2
72.9
71.9
76.0
68.0
70.0
74.8
71.6
44.9
61.8
61.6
I
II
III
99.8
82.3
100.3
71.8
73.2
71.1
73.6
74.2
71.5
71.8
75.8
68.6
70.5
74.5
71.9
45.7
63.0
60.7
I
II
III
99.6
82.8
100.7
72.3
71.2
69.2
72.9
72.2
70.9
70.7
75.8
66.7
70.0
74.8
70.7
44.8
61.9
60.7
9 a,e
I
II
100.0
80.3
71.9
69.8
73.6
69.5
71.8
67.2
70.3
70.2
45.8
62.7
9 b,c
11 a,e
I
II
99.7
80.7
72.1
69.0
73.4
68.5
72.1
66.2
69.5
70.2
45.6
62.3
I
II
III
99.9
84.0
103.1
71.9
72.6
73.9
73.6
76.7
76.3
72.0
79.2
70.3
70.4
75.7
76.6
45.9
60.9
61.4
12 a,e
I f
II
III
83.6
99.6
103.2
71.6
72.1
71.3
73.2
71.6
78.4
68.9
70.0
44.9
60.4
61.4
75.7 g
72.9
76.4
75.5 g
13 a,c
14 a,d
15 a,d
I
II
101.8
85.1
73.0
72.0
75.4
73.8 g
69.2
71.9
76.2
48.1
63.2
73.9 g
I
II
99.7
81.1
71.8
70.5
73.4
72.3
71.6
66.2
70.1
73.3
45.7
62.7
I
II
102.4
85.0
74.4
73.1
76.0
76.6
74.2
69.7
72.5
80.6
48.3
64.2
16 b,c
17 b,c
18 a,e
19 a,d
20 b,c
21 b,c
22 a,d
23 a,c
I
I
I
I
I
I
I
I
80.7
81.0
82.6
84.0
80.7
81.0
82.7
82.9
68.7
70.2
70.0
73.1
68.4
69.9
70.0
71.7
68.4
71.4
71.1
76.1
68.3
71.4
71.0
74.9
66.2
65.5
67.7
69.3
65.8
65.6
67.4
68.0
70.0
74.0
74.3
80.1
69.4
74.0
74.2
78.8
62.2
62.3
61.4
63.7
61.9
62.3
61.2
62.4
a In D2O.
b In CDCl3.
c At 313 K.
d At 333 K.
e At 343 K.
f At 75.5 MHz.
g Assignments may be reversed.

J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
43
nucleophilic displacement by azide anion in
DMF, and final Staudinger reduction of the
6-azido derivative with triphenylphosphine in
dioxane–MeOH, followed by in situ hydroly-
sis of the resulting phosphinimine with ammo-
nium hydroxide, as previously reported [25].
b-
D
-Mannopyranosylamine (24) [28] was pre-
-mannose in 85% yield by treat-
pared from
D
Scheme 3.
ment of a 0.2 M aq solution with ammoniun
hydrogencarbonate and concentrated ammo-
nia following the procedure reported by Lu-
bineau et al. [36].
pure deacetylated compounds 13, 15, 18, 19,
22 and 23. The anomeric configuration was
confirmed in all cases by JC-1,H-1 measurements
(164–168 Hz for a- and 152–155 Hz for b-
derivatives) [30].
A Perkin–Elmer model 141 MC polarime-
ter and 1 dm tubes were used for measurement
of specific rotations at 22 °C. Infrared spectra
were recorded on a Bomem Michelson MB-
At present, it is not clear why the manno-
configured glycopyranosylthioureas anomerize
upon treatment with base and the others do
not. Probably, anomerization proceeds
through an open-chain Schiff base-type inter-
mediate, whose formation must be favored by
the relatively acidic character of the glycosidic
thiourea NH proton [31], following a mecha-
nistic pattern analogous to that proposed for
the anomerization of glycosylamines [28,32,33]
(Scheme 3). One could expect that the elec-
tronic delocalization of p electrons in the
thiourea ground state, resulting in a positive
charge density at the NH region [34], would
then favor the equatorial orientation of
anomeric thioureido substituents by virtue of
the reverse anomeric effect [35].
1
120 FTIR spectrophotometer. H and 13C
NMR spectra were recorded at 500 (125.7)
and 300 (75.5) MHz with, respectively, Bruker
500 AMX and 300 AMX spectrometers.
Chemical shifts are given in ppm with refer-
ence to tetramethylsilane as internal standard.
1
Assignments of H and 13C signals were as-
sisted by 2D COSY and HETCOR experi-
ments. FAB mass spectra were obtained with
a Kratos MS-80 RFA instrument. The operat-
ing conditions were the following: the primary
beam consisted of Xe atoms with a maximum
energy of 8 keV; the samples were dissolved in
thioglycerol, and the positive ions were sepa-
rated and accelerated over a potential of 7 kV;
NaI was added as cationizing agent. TLC was
performed with E. Merck precoated TLC
plates, Silica Gel 30F-245, with visualization
by UV light and by charring with 10% H2SO4.
Column chromatography was carried out with
Silica Gel 60 (E. Merck, 230–400 mesh). Mi-
croanalyses were performed by the Instituto
de Investigaciones Qu´ımicas (CSIC, Sevilla).
General procedure for the preparation of par-
tially protected (6–9, 14) and fully unprotected
In conclusion, we have shown that coupling
of per-O-acetylated glycosyl isothiocyanates
and unprotected amino sugars, followed by
catalytic deacetylation, provides a convenient
access to thiourea-linked pseudooligosaccha-
rides. The anomerization side reaction previ-
ously observed for -mannopyranosylthiourea
D
derivatives can be totally avoided by perform-
ing the last step at 0 °C. In all cases, the final
compounds are configurationally stable in the
absence of base.
methyl 6-deoxy-6-glycosylthioureido-h-
copyranoside deri6ati6es (10–13, 15).—A solu-
tion of methyl 6-amino-6-deoxy-a- -gluco-
pyranoside [25] (4, 75 mg, 0.38 mmol) and the
corresponding per-O-acetylglycopyranosyl
D-glu-
D
3. Experimental
isothiocyanate 1–3, 5 [16,26,27] or 28 (0.38
mmol) in pyridine (2 mL) was stirred for 2 h
at room temperature (rt). The solvent was
evaporated and the residue was chro-
matographed (45:5:3 EtOAcꢀEtOHꢀH2O) to
afford the thiourea adducts 6–9 and 14, re-
Materials and methods.—Methyl 6-amino-
6-deoxy-a- -glucopyranoside (4) was pre-
D
pared from commercial grade methyl
a- -glucopyranoside in three steps, by direct
replacement of the primary OH-6 by iodine,
D

44
J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
spectively. Subsequent Zemple´n deacetylation
of 6–8 (0.2 mmol) in MeOH (10 mL) was
effected by treatment with methanolic
NaOMe (0.1 equiv per mol of acetate) at rt
for 3 h, giving the fully unprotected pseu-
dooligosaccharides 10–12. Under identical re-
action conditions, compounds 9 and 14 led to
a mixture of the a- and b-mannopyranosylth-
ioureido derivatives 13 and 15. Pure samples
of 13 and 15 were obtained by performing the
deacetylation step at 0 °C with 0.5 equiv of
MeOH per mol of acetate and further neutral-
ization (Amberlite IR-120 H+) at the same
temperature.
CDCl3, 313 K) Table 2 and l 184.7 (CꢁS),
170.9, 170.7, 170.3, 170.0, 169.3, 169.1, 168.8
(7 CO), 55.4 (OMe), and 20.5 (7 MeCO);
FABMS: m/z 893 (30%, [M+Na]+). Anal.
Calcd for C34H50N2O22S: C, 46.89; H, 5.78; N,
3.22. Found: C, 46.89; H, 5.75; N, 3.22.
Methyl 6-deoxy-6-(2,3,6,2%,3%,4%,6%-hepta-O-
acetyl-i-lactosylthioureido) - h -
D
- glucopyran-
oside (8).—Yield: 287 mg (85%); [h]D
−120.3° (c 1.1, CH2Cl2); Rf 0.50 (45:5:3
1
EtOAcꢀEtOHꢀwater); NMR: H (500 MHz,
D2O, 343 K) Table 1 and l 3.91 (s, 3 H,
OMe), 2.73, 2.68, 2.66, 2.65, 2.64, 2.62, and
1
2.54 (7 s, each 3 H, 7 MeCO); H (500 MHz,
CDCl3, 313 K) Table 1 and l 7.06 (bs, 2 H,
NH, N%H), 3.41 (s, 3 H, OMe), 2.11, 2.08,
2.06, 2.03, 2.02, and 1.97 (7 s, each 3 H, 7
Methyl 6-deoxy-6-(2,3,4,6-tetra-O-acetyl-
i -
D
- glucopyranosylthioureido) - h -
D
- gluco-
pyranoside (6).—Yield: 202 mg (90%); [h]D
13
MeCO); C (125.7 MHz, D2O, 343 K) Table
+27.3° (c 1.0, H2O); Rf 0.49 (9:1 CH2Cl2–
2 and l 184.5 (CꢁS), 174.1, 174.0, 173.4,
1
MeOH); NMR: H (500 MHz, D2O, 323 K)
174.3, 173.2, 173.0, 172.8 (7 CO), 55.6 (OMe),
Table 1 and l 3.63 (s, 3 H, OMe), 2.36, 2.35,
13
20.8, 20.7, 20.6, 20.5 and 20.4 (7 MeCO); C
1
2.34, and 2.32 (4 s, each 3 H, 4 MeCO); H
(125.7 MHz, D2O, 343 K) Table 2 and l 184.4
(CꢁS), 174.0, 173.7, 174.3, 173.2, 173.0, 172.8,
172.7 (7 CO), 55.5 (OMe), 20.6, 20.5 and 20.4
(7 MeCO); 13C (125.7 MHz, CDCl3, 313 K)
Table 2 and l 184.7 (CꢁS), 170.9, 170.7, 170.3,
170.0, 169.3, 169.1, 168.8 (7 CO), 55.4 (OMe),
20.7, 20.6, 20.4, and 20.3 (7 MeCO); FABMS:
m/z 893 (100%, [M+Na]+). Anal. Calcd for
C34H50N2O22S: C, 46.89; H, 5.78; N, 3.22.
Found: C, 46.72; H, 5.45; N, 3.22.
(500 MHz, CDCl3, 333 K) Table 1 and l 7.28
(bs, 2 H, NH, N%H), 3.40 (s, 3 H, OMe), 2.04,
2.03, 2.00, and 1.98 (4 s, each 3 H, 4 MeCO);
13C (125.7 MHz, D2O, 323 K) Table 2 and l
183.5 (CꢁS), 172.4, 172.3 (4 CO), 55.7 (OMe),
20.6 and 20.5 (4 MeCO); 13C (125.7 MHz,
CDCl3, 313 K) Table 2 and l 184.7 (CꢁS),
171.2, 170.8, 169.8, 169.6 (4 CO), 55.5 (OMe),
and 20.7 (4 MeCO). Anal. Calcd for
C22H34N2O14S: C, 45.36; H, 5.88; N, 4.81.
Found: C, 45.25; H, 5.98; N, 4.72.
Methyl 6-deoxy-6-(2,3,4,6-tetra-O-acetyl-h-
D
-mannopyranosylthioureido)-h- -glucopyran-
D
Methyl 6-deoxy-6-(2,3,6,2%,3%,4%,6%-hepta-O-
oside (9).—Yield: 196 mg (87%); [h]D +69.0°
(c 1.0, CH2Cl2); Rf 0.47 (45:5:3
acetyl-i-cellobiosylthioureido)-h- -glucopyran-
D
1
oside (7).—Yield: 300 mg (89%); [h]D
EtOAcꢀEtOHꢀwater); NMR: H (500 MHz,
D2O, 343 K) Table 1 and l 3.76 (s, 3 H,
OMe), 2.58, 2.51, 2.50, and 2.45 (4 s, each 3
−183.0° (c 1.1, CH2Cl2); Rf 0.34 (45:5:3
1
EtOAcꢀEtOHꢀwater); NMR: H (500 MHz,
1
D2O, 323 K) Table 1 and l 4.07 (s, 3 H,
OMe), 2.69, 2.68, 2.64, 2.63, 2.61, and 2.58 (7
H, 4 MeCO); H (500 MHz, CDCl3, 313 K)
Table 1 and l 7.65 (bs, 1 H, NH), 7.29 (bs, 1
H, N%H), 3.41 (s, 3 H, OMe), 2.20, 2.15, 2.12,
1
s, each 3 H, 7 MeCO); H (500 MHz, CDCl3,
13
313 K) Table 1 and l 6.95 (bs, 2 H, NH,
N%H), 3.41 (s, 3 H, OMe), 2.11, 2.08 2.06,
2.03, 2.02, and 1.97 (7 s, each 3 H, 7 MeCO);
13C (125.7 MHz, D2O, 343 K) Table 2 and l
184.5 (CꢁS), 174.1, 174.0, 173.4, 174.3, 173.2,
173.0, 172.8 (7 CO), 55.6 (OMe), 20.8, 20.7,
20.6, 20.5 and 20.4 (7 MeCO); 13C (125.7
MHz, CDCl3, 313 K) Table 2 and l 184.7
(CꢁS), 171.2, 170.8, 169.8, 169.6 (4 CO), 55.5
and 1.98 (4 s, each 3 H, 4 MeCO); C (125.7
MHz, D2O, 343 K) Table 2 and l 183.9 (CꢁS),
174.1, 173.2, 173.1, 173.0 (4 CO), 55.7 (OMe),
20.7, 20.6, 20.5 and 20.4 (4 MeCO); 13C (125.7
MHz, CDCl3, 313 K) Table 2 and l 184.3
(CꢁS), 170.6, 170.1, 169.9, 169.4 (4 CO), 55.4
(OMe), and 20.5 (4 MeCO); FABMS: m/z 605
(100%, [M+Na]+). Anal. Calcd for
C22H34N2O14S: C, 45.36; H, 5.88; N, 4.81.
Found: C, 45.14; H, 5.71; N, 4.80.
13
(OMe), and 20.7 (4 MeCO); C (125.7 MHz,

J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
45
Methyl
6-deoxy-6-(i-
D
-mannopyranosyl-
Methyl
thioureido)-h-
80 mg (96%); [h]D +42.5° (c 0.7, H2O); lit.
6-deoxy-6-(i-
-glucopyranoside (10).—Yield:
D
-glucopyranosyl-
thioureido)-h- -glucopyranoside (15).—Yield:
82 mg (99%); [h]D +40.7° (c 1.1, MeOH); Rf
0.53 (2:1:1 BuOHꢀAcOHꢀwater); NMR: H
D
D
1
1
13
[13] [h]D +42.8° (c 0.6, H2O). The H and C
NMR data were in full agreement with those
reported in the literature [13].
(500 MHz, D2O, 333 K) Table 1 and l 3.96 (s,
3 H, OMe); 13C (125.7 MHz, D2O, 323 K)
Table 2 and l 185.6 (CꢁS), 85.0 (C-1%, JC-1%,H-1%
152.1 Hz), and 58.2 (OMe); FABMS: m/z 415
(100%, [M+Na]+). Anal. Calcd for
C14H26N2O10S: C, 40.57; H, 6.32; N, 6.76.
Found: C, 40.34; H, 6.10; N, 6.41.
Methyl 6-deoxy-6-(i-cellobiosylthioureido)-
h- -glucopyranoside (11).—Yield: 112 mg
D
(98%); [h]D +22.0° (c 0.7, H2O); Rf 0.47
1
(2:1:1 BuOH–AcOH–water); NMR: H (500
MHz, D2O, 343 K) Table 1 and l 3.82 (s, 3 H,
13
N-Ethyl-N%-(h- and i- -mannopyranosyl)-
D
OMe); C (125.7 MHz, D2O, 343 K) Table 2
thioureas (16–19).—To a solution of ethy-
lamine hydrochloride (27 mg, 0.33 mmol) in
water (5 mL), satd aq NaHCO3 was added
until pH 10. A solution of 2,3,4,6-tetra-O-
and l 184.2 (CꢁS), and 55.7 (OMe); FABMS:
m/z 599 (10%, [M+Na]+). Anal. Calcd for
C20H36N2O15S: C, 41.66; H, 6.29; N, 4.86.
Found: C, 41.45; H, 6.32; N, 4.70.
acetyl-a(b)- -mannopyranosyl isothiocyanate
D
Methyl 6-deoxy-6-(i-lactosylthioureido)-h-
(5 or 28, 116 mg, 0.30 mmol) in CH2Cl2 (5
mL) was then added, and the biphasic reac-
tion mixture was vigorously stirred for 30 min.
The organic layer was separated, washed with
water (2×5 mL), dried (NaSO4), and concen-
trated, and the residue was purified by column
chromatography using 1:1 EtOAcꢀhexanes as
eluent to give thioureas 16 and 17, respec-
tively. Subsequent deacetylation was effected
at 0 °C as described above to afford the fully
unprotected mannopyranosylthioureas 18 and
19 in virtually quantitative yield.
D
-glucopyranoside (12).—Yield: 110 mg
(95%); [h]D +34.0° (c 1.1, H2O); Rf 0.42
(2:1:1 BuOH–AcOH–water); NMR: H (500
1
MHz, D2O, 343 K) Table 1 and l 3.79 (s, 3 H,
OMe); 13C (75.5 MHz, D2O, 313 K) Table 2
and l 184.8 (CꢁS), and 55.5 (OMe); FABMS:
m/z 599 (100%, [M+Na]+). Anal. Calcd for
C20H36N2O15S: C, 41.66; H, 6.29; N, 4.86.
Found: C, 41.64; H, 6.17; N, 4.87.
Methyl
6-deoxy-6-(h- -mannopyranosyl-
D
thioureido)-h- -glucopyranoside (13).—Yield:
80 mg (96%); [h]D +116.4° (c 2.2, MeOH); Rf
0.51 (2:1:1 BuOHꢀAcOHꢀwater); NMR: H
D
1
N-Ethyl-N%-(2,3,4,6-tetra-O-acetyl-h- -
D
mannopyranosyl)thiourea (16). Yield: 115 mg
(89%); [h]D +124.5° (c 1.1 CH2Cl2); Rf 0.23
(500 MHz, D2O, 333 K) Table 1 and l 3.92 (s,
3 H, OMe); 13C (125.7 MHz, D2O, 313 K)
Table 2 and l 184.6 (CꢁS), 81.1 (C-1%, JC-1%,H-1%
164.7 Hz), and 56.9 (OMe); FABMS: m/z 415
1
(1:1 EtOAcꢀhexanes); NMR: H (500 MHz,
CDCl3, 313 K) Table 1 and l 6.81 (bs, 1 H,
NH), 6.72 (bs, 1 H, N%H), 3.60 (m, 2 H,
CH2CH3), 2.13, 2.05, 2.03, 2.00 (4 s, each 3 H,
(20%,
[M+H]+).
Anal.
Calcd
for
C14H26N2O10S: C, 40.57; H, 6.32; N, 6.76.
Found: C, 40.35; H, 6.19; N, 6.42.
3
4 MeCO), and 1.22 (t, 3 H, JH,H 7.3 Hz,
Methyl 6-deoxy-6-(2,3,4,6-tetra-O-acetyl-
CH2CH3); 13C (125.7 MHz, CDCl3, 313 K)
Table 2 and l 183.8 (CꢁS), 170.2, 169.8, 169.5
(4 CO), 40.5 (CH2CH3), 20.6, 20.4, 20.3, 20.2
(4 MeCO), and 14.1 (CH2CH3); FABMS: m/z
457 (100%, [M+Na]+) and 435 (50%, [M+
H]+). Anal. Calcd for C17H26N2O9S: C, 35.05;
H, 4.50; N, 4.81. Found: C, 34.93; H, 4.31; N,
4.77.
i-
D
-mannopyranosylthioureido)-h- -glucopyr-
D
anoside (14).—Yield: 191 mg (85%); [h]D
−11.0° (c 0.5, CH2Cl2); Rf 0.41 (45:5:3
1
EtOAcꢀEtOHꢀwater); NMR: H (500 MHz,
D2O, 333 K) Table 1 and l 3.81 (s, 3 H,
OMe), 2.71, 2.56, 2.54, and 2.46 (4 s, each 3
H, 4 MeCO); 13C (125.7 MHz, D2O, 313 K)
Table 2 and l 184.2 (CꢁS), 174.0, 173.5, 173.3,
172.9 (4 CO), 55.6 (OMe), 20.6, 20.5, and 20.4
(4 MeCO); FABMS: m/z 605 (100%, [M+
Na]+). Anal. Calcd for C22H34N2O14S: C,
45.36; H, 5.88; N, 4.81. Found: C, 45.27; H,
5.66; N, 4.80.
N-Ethyl-N%-(2,3,4,6-tetra-O-acetyl-i- -
D
mannopyranosyl)thiourea (17). Yield: 110 mg
(85%); [h]D −16.0° (c 0.9, CH2Cl2); Rf 0.17
1
(1:1 EtOAcꢀhexanes); NMR: H (500 MHz,
CDCl3, 313 K) Table 1 and l 6.40 (bs, 1 H,
NH), 5.90 (bs, 1 H, N’H), 3.47 (bs, 2 H,

46
J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
NH, N%H), 4.76 (d, 2 H, 3JH,H 4.7 Hz, CH2Ph),
CH2CH3), 2.22, 2.09 2.05, 1.98 (4 s, each 3 H,
3
2.15, 2.05, 2.02, and 1.88 (4 s, each 3 H, 4
4 MeCO), and 1.22 (t, 3 H, JH,H 7.5 Hz,
13
CH2CH3); 13C (125.7 MHz, CDCl3, 313 K)
Table 2 and l 182.3 (CꢁS), 170.7, 170.6, 169.6
(4 CO), 39.4 (CH2CH3), 20.8, 20.7, 20.6, 20.4
(4 MeCO), and 13.8 (CH2CH3); FABMS: m/z
457 (100%, [M+Na]+). Anal. Calcd for
C17H26N2O9S: C, 35.05; H, 4.50; N, 4.81.
Found: C, 35.05; H, 4.48; N, 4.61.
MeCO); C (75.5 MHz, CDCl3) Table 2 and
l 184.3 (CꢁS), 170.4, 170.1, 169.5 (4 CO),
136.0, 128.7, 127.7, 127.5 (Ph), 49.4 (CH2Ph),
20.6, 20.5, and 20.3 (4 MeCO); FABMS: m/z
519 (100%, [M+Na]+). Anal. Calcd for
C22H28N2O9S: C, 53.21; H, 5.68; N, 5.64.
Found: C, 53.18; H, 5.55; N, 5.53.
N-Benzyl-N%-(2,3,4,6-tetra-O-acetyl-i- -
D
N-Ethyl-N%-(h- -mannopyranosyl)thiourea
D
mannopyranosyl)thiourea (21). Yield: 170 mg
(91%); [h]D −16.5° (c 1.0, CH2Cl2); Rf 0.31
(18). [h]D +78.9° (c 1.0, MeOH); Rf 0.65
1
(2:1:1 BuOHꢀAcOHꢀwater); NMR: H (500
1
(1:1 EtOAcꢀhexanes); NMR: H (500 MHz,
MHz, D2O, 333 K) Table 1 and l 3.90 (m, 2
3
CDCl3, 313 K) Table 1 and l 7.36–7.26 (m, 5
H, Ph), 6.53 (bs, 1 H, NH), 6.35 (d, 1 H, J1,N%H
8.1 Hz, N%H), 4.65 (bs, 2 H, CH2Ph), 2.12,
2.02, 1.99, and 1.96 (4 s, each 3 H, 4 MeCO);
13C (125.7 MHz, CDCl3, 313 K) Table 2 and l
182.9 (CꢁS), 170.4, 170.3, 169.5 (4 CO), 136.0,
128.9, 127.9, 127.5 (Ph), 48.6 (CH2Ph), 20.6,
20.4, 20.3, and 20.2 (4 MeCO); FABMS: m/z
519 (100%, [M+Na]+). Anal. Calcd for
C22H28N2O9S: C, 53.21; H, 5.68; N, 5.64.
Found: C, 53.25; H, 5.58; N, 5.64.
H, CH2CH3), and 1.53 (t, 3 H, JH,H 7.0 Hz,
CH2CH3); 13C (125.7 MHz, D2O, 333 K)
Table 2 and l 182.3 (CꢁS), 82.6 (C-1, JC-1,H-1
166.0 Hz), 40.5 (CH2CH3), and 13.8
(CH2CH3); FABMS: m/z 267 (100%, [M+
H]+). Anal. Calcd for C9H18N2O5S: C, 40.59;
H, 6.81; N, 10.52. Found: C, 49.49; H, 6.69;
N, 10.43.
N-Ethyl-N%-(i- -mannopyranosyl)thiourea
D
(19). [h]D −3.1° (c 0.8, MeOH); Rf 0.72 (2:1:1
1
BuOHꢀAcOHꢀwater); NMR: H (500 MHz,
N-Benzyl-N%-(h- -mannopyranosyl)thiourea
D
D2O, 333 K) Table 1 and l 3.72 (m, 2 H,
(22). [h]D +37.0° (c 0.9, MeOH); Rf 0.75
3
CH2CH3), and 1.37 (t, 3 H, JH,H 7.2 Hz,
1
(2:1:1 BuOHꢀAcOHꢀwater); NMR: H (500
CH2CH3); 13C (125.7 MHz, D2O, 333 K)
Table 2 and l 183.8 (CꢁS), 84.0 (C-1, JC-1,H-1
153.0 Hz), 39.8 (CH2CH3), and 15.9
(CH2CH3); FABMS: m/z 289 (90%, [M+
Na]+), 267 (100%, [M+H]+). Anal. Calcd
for C9H18N2O5S: C, 40.59; H, 6.81; N, 10.52.
Found: C, 40.37; H, 6.75; N, 10.33.
MHz, D2O, 333 K) Table 1 and l 7.85–7.75
(m, 5 H, Ph), 5.25 and 5.14 (2 d, each 1 H,
13
2JH,H 15.0 Hz, CH2Ph); C (125.7 MHz, D2O,
313 K) Table 2 and l 182.5 (CꢁS), 138.1,
129.2, 127.9, 127.6 (Ph), 82.7 (C-1, JC-1,H-1
165.6 Hz), and 48.5 (CH2Ph); FABMS: m/z
(40%, [M+Na]+), (100%, [M+H]+). Anal.
Calcd for C14H20N2O5S: C, 51.20; H, 6.14; N,
8.53. Found: C, 51.00; H, 6.05; N, 8.34.
N-Benzyl-N%-(h- and i-
thioureas (20–23).—To a solution of 2,3,4,6-
tetra-O-acetyl-a(b)- -mannopyranosyl isoth-
D
-mannopyranosyl)-
D
N-Benzyl-N%-(i- -mannopyranosyl)thiourea
D
iocyanate (5 or 28, 116 mg, 0.30 mmol) in
CH2Cl2 (5 mL), benzylamine (33 mL, 0.30
mmol) was added. The reaction mixture was
stirred for 15 min, then concentrated and
purified by column chromatography (1:1
EtOAcꢀhexanes) to give thioureas 20 and 21,
respectively. Subsequent deacetylation was ef-
fected at 0 °C as described above to afford the
fully unprotected mannopyranosylthioureas
22 and 23 in virtually quantitave yield.
(23). [h]D −8.0° (c 1.0, MeOH); Rf 0.80 (2:1:1
1
BuOHꢀAcOHꢀwater); NMR: H (500 MHz,
D2O, 313 K) Table 1 and l 7.66–7.53 (m, 5
13
H, Ph), and 4.99 (m, 2 H, CH2Ph); C (125.7
MHz, D2O, 313 K) Table 2 and l 183.7 (CꢁS),
139.0, 130.2, 129.0, 128.6 (Ph), 82.9 (C-1, JC-
1,H-1 155.2 Hz), and 49.2 (CH2Ph); FABMS:
m/z 351 (40%, [M+Na]+), 329 (100%, [M+
H]+). Anal. Calcd for C14H20N2O5S: C, 51.20;
H, 6.14; N, 8.53. Found: C, 51.03; H, 6.21; N,
8.30.
N-Benzyl-N%-(2,3,4,6-tetra-O-acetyl-h- -
D
mannopyranosyl)thiourea (20). Yield: 184 mg
(97%); [h]D +70.9° (c 1.0, CH2Cl2); Rf 0.26
N-(2,2-Diethoxycarbonyl6inyl)-i- -manno-
D
pyranosylamine (25).—Treatment of b- -
D
1
(1:1 EtOAcꢀhexanes); NMR: H (300 MHz,
mannopyranosylamine (24, 0.496 g, 2.72
CDCl3) Table 1 and l 7.36–7.17 (m, 7 H, Ph,
mmol) in dry MeOH (10 mL) with diethyl

J.M. Benito et al. / Carbohydrate Research 320 (1999) 37–48
47
ethoxymethylenemalonate (0.83 mL, 4.06
mmol) overnight, as reported [29], and column
chromatography (45:5:3 EtOAcꢀH2OꢀEtOH)
of the resulting reaction mixture afforded 25
(0.75 g, 71%), mp 205–206 °C, [h]D +81.1° (c
1, pyridine), Rf 0.46 (45:5:3 EtOAcꢀ
EtOHꢀwater); lit. [29]: mp 207–209 °C, [h]D
+83° (pyridine); 13C NMR (75.5 MHz,
CD3OD) l 169.0 (CꢁO chelated), 167.8 (CꢁO
free), 159.1 (ꢁCH), 92.8 (Cꢁ), 87.2 (C-1), 79.9
(C-5), 75.3 (C-3), 71.9 (C-2), 67.9 (C-4), 62.8
(C-6), 61.0 (2 CH2), and 14.7 (2 CH3).
61.7 (C-6), 21.2, 20.6, 20.5, and 20.4 (4
MeCO).
2,3,4,6-Tetra-O-acetyl-i- -mannopyranosyl
D
isothiocyanate (28).—To a mixture of 1:1
CH2Cl2–H2O (40 mL) were added 27 (0.25 g,
0.65 mmol), CaCO3 (195 mg, 3 equiv, 1.95
mmol) and CsCl2 (0.077 mL, 1.5 eq, 1 mmol).
The reaction mixture was vigorously stirred
for 2 h and then filtered. The organic phase
was separated, washed with water, and dried
(MgSO4), and the solvent was removed under
reduced pressure. The residue was purified by
column chromatography using 1:2 EtOAcꢀ
hexanes as eluent to give 28 (128 mg, 50%);
[h]D −65.6° (c 1.0, CH2Cl2); Rf 0.55 (1:1
EtOAcꢀhexanes); IR (film) 2955, 2016, 1750,
2,3,4,6-Tetra-O-acetyl-N-(2,2-diethoxycar-
bonyl6inyl)-i- -mannopyranosylamine (26).—
D
Conventional acetylation of 25 (0.75 g, 2.1
mmol) with 1:1 Ac2Oꢀpyridine (10 mL) and
column chromatography (1:1 EtOAcꢀhexanes)
of the resulting product yielded 26 (0.67 g,
60%), mp 57ꢀ58 °C, [h]D −23.1° (c 1.5,
CH2Cl2), Rf 0.46 (1:1 EtOAcꢀhexanes); lit.
[29]: mp 54–58 °C, [h]D −47° (CHCl3);
1
1373, 1213, and 1090 cm−1; NMR: H (300
MHz, CDCl3) l 5.49 (dd, 1 H, J1,2 1.4, J2,3 3.3
Hz, H-2), 5.23 (t, 1 H, J3,4=J4,5 10.0 Hz,
H-4), 5.05 (dd, 1 H, H-3), 4.94 (d, 1 H, H-1),
4.25 (dd, 1 H, J5,6a 5.6, J6a,6b 12.4 Hz, H-6a),
4.18 (dd, 1 H, J5,6b 2.7 Hz, H-6b), 3.71 (ddd, 1
H, H-5); 13C (75.5 MHz, CDCl3) l 171.3,
170.5, 169.8 (3 CO), 146.7 (NꢁCꢁS), 82.5 (C-
1), 74.5 (C-5), 70.5 (C-3), 69.0 (C-2), 65.0
(C-4), 62.1 (C-6), 20.7, 20.6, 20.5 (4 MeCO);
FABMS: m/z 412 (100%, [M+Na]+). Anal.
Calcd for C15H19NO9S: C, 46.27; H, 4.92; N,
3.60. Found: C, 46.45; H, 4.83; N, 3.64.
1
NMR: H (300 MHz, CDCl3) l 9.53 (dd, 1 H,
J1,NH 9.2 Hz, JꢁCH, NH 13.1 Hz, NH), 7.99 (d, 1
3
H, ꢁCH), 4.25, 4.17 (2 q, each 2 H, JH,H 7.0
Hz, CH2CH3), 5.45 (dd, 1 H, J1,2 1.4 Hz, J2,3
3.3 Hz, H-2), 5.23 (t, 1 H, J3,4 =J4,5 10.0 Hz,
H-4), 5.10 (dd, 1 H, H-3), 4.83 (dd, 1 H, H-1),
4.26 (dd, 1 H, J5,6a 5.4 Hz, J6a,6b 12.4 Hz,
H-6a), 4.18 (dd, 1 H, J5,6b 2.4 Hz, H-6b), 3.76
(ddd, 1 H, H-5), 2.20, 2.09, 2.04, 1.99 (4 s,
each 3 H, 4 MeCO), 1.32, and 1.29 (2 t, each
3 H, 2 CH2CH3); 13C (75.5 MHz, CDCl3) l
170.5, 170.1, 169.9, 169.4 (4 CO), 168.1 (CꢁO
chelated), 165.2 (CꢁO free), 156.9 (ꢁCH), 94.1
(ꢁC), 84.3 (C-1), 73.9 (C-5), 70.9 (C-3), 69.0
(C-2), 64.8 (C-4), 62.1 (C-6), 20.7, 20.6, 20.5 (3
MeCO), 14.2, and 14.1 (2 CH2CH3).
Acknowledgements
We thank the Direccio´n General de Inves-
tigacio´n Cient´ıfica y Te´cnica (grant no. PB
97/0747) and the Deutsche Forschungsgemein-
schaft (SFB 470) for financial support.
2,3,4,6-Tetra-O-acetyl-i- -mannopyranosy-
D
lamine hydrochloride (27).—Through an ice-
cooled solution of 26 (2.5 g, 4.83 mmol) in wet
CH2Cl2 (20 mL) chlorine was bubbled until
saturation. The reaction mixture was stirred
for 30 min, then evaporated under reduced
pressure and washed with diethyl ether to
afford 27 in virtually quantitative yield, as
seen by 13C NMR spectroscopy. Compound
27, isolated as a white amorphous solid, was
used in subsequent reactions without further
purification. FABMS: m/z 371 ([M+Na−
HCl]+); NMR: 13C (125.7 MHz, CDCl3) l
170.8, 170.7, 169.8, 169.4 (4 CO), 78.5 (C-1),
74.8 (C-5), 71.0 (C-3), 67.5 (C-2), 65.2 (C-4),
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