Chain-growth polyglycosylation: Synthesis of linker-equipped mannosyl oligomers

Article abstract of DOI:10.1016/j.carres.2014.06.021

Direct syntheses of acetylated poly-mannosides can be achieved in one-step starting from a fully acetylated thioglycoside mannosyl donor using a polymerization-type strategy under the correct conditions. Under conditions that allow polymer growth from non-reducing to reducing end (N→R), different acceptor alcohols can be used as the 'terminating acceptors' to install different linkers at the reducing terminus. The efficiency is dependent on substituents of the linker, its length, temperature and choice of Lewis acid activator.

Full text of DOI:10.1016/j.carres.2014.06.021

Carbohydrate Research xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Chain-growth polyglycosylation: synthesis of linker-equipped
mannosyl oligomers
⇑
Heiko J. Schuster, Balakumar Vijayakrishnan, Benjamin G. Davis
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, OX1 3TA Oxford, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history:
Direct syntheses of acetylated poly-mannosides can be achieved in one-step starting from a fully acety-
lated thioglycoside mannosyl donor using a polymerization-type strategy under the correct conditions.
Under conditions that allow polymer growth from non-reducing to reducing end (N?R), different accep-
tor alcohols can be used as the ‘terminating acceptors’ to install different linkers at the reducing terminus.
The efficiency is dependent on substituents of the linker, its length, temperature and choice of Lewis acid
activator.
Received 27 April 2014
Received in revised form 16 June 2014
Accepted 19 June 2014
Available online xxxx
Keywords:
Glycosylation
Ó 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/3.0/).
Polymerization
Regioselective synthesis
Stereoselective synthesis
Rearrangement
Mannosides
1. Introduction
of these latter reactions are often undesired side-reactions during
glycosylations leading to, for example, O-acetyl migration (trans-
As part of glycoproteins, so-called ‘high mannose’ glycans play
fundamental roles in cells such as during protein biosynthesis
(e.g., modulating folding, transport, enzymatic degradation) and
in interactions (e.g., mediating adhesion, signalling).1–4 These con-
tain oligosaccharidic mannosyl ‘arms’ or ‘caps’, often mannobioside
acetylation) from the donor to the acceptor.24–26 Nevertheless, we
considered that such orthoesters, if generated from the correspond-
ing thioglycosides in situ, theoretically showed a strong synthetic
potential for sequential glycosylation at position 2-OH given that
they and corresponding tri/dioxoleniums might act as both donors
and acceptors (electrophiles and nucleophiles). Control of these
ambident glycosyl moieties to show both of these characters under
the appropriate conditions, might therefore allow a possible poly-
merization-type manifold. In principle, such a manifold could be
made to ‘grow’27 sufficiently by requiring auto-activation to allow
the formation of poly-mannosides of controllable length before ter-
mination by a chosen reducing end alcohol that possesses only
acceptor ability. Here, we investigate the influence of the choice
of Lewis acid, donor–acceptor ratio and scope of alcohol ‘termina-
tors’ in first attempts to test this novel concept of what might be
termed ‘chain growth’27 polyglycosylation. In addition, an initial
systematic study of parameters offers first insights into the pro-
posed mechanism involved in the generation of an intermediate
O-2 mannosyl acceptor and observed acetyl transfer to alcohol.
(a-
D-Man-(1?2)-D-Man) and mannotrioside (a-D-Man-(1?2)-a-D-
Man-(1?2)- -Man) that are also determinants of pathogenicity of
D
viruses such as the human immunodeficiency virus 1 (HIV-1),5,6
bacteria (Mycobacterium tuberculosis) and protozoan parasites of
the genus Leishmania.7 Direct synthetic access to these fragments
can be more difficult since the hydroxyl at C-2 is not accessible8–
12 by regioselective glycosylations.13 Consequently, published syn-
theses typically require a minimum of 6–8 steps to form the man-
nosidic union between two moieties, often with bulky, atom-
inefficient O-benzyl protected disaccharides.14–19 A low yielding
enzymatic access (3%) has also been reported.20
Glycosyl donors with 2-O-acyl protection give di-/tri-oxolenium
ions upon activation (Fig. 1). These can, in principle, react directly
with a nucleophile to form glycoside or reaction may proceed via
an orthoester intermediate.21 Orthoesters can also be rearranged
to the desired glycosides or act as glycosyl donors themselves.22,23
Under certain circumstances, they can also open in such a fashion
that the 2-O-acyl group is transferred to the acceptor alcohol. Both
2. Results and discussion
2.1. Testing polymannosylation
Acetylated thioglycoside 1 was chosen as a model glycosyl
donor; such and similar donors have been reported to occasionally
⇑
Corresponding author. Tel.: +44 1865 275 652.
E-mail address: ben.davis@chem.ox.ac.uk (B.G. Davis).
http://dx.doi.org/10.1016/j.carres.2014.06.021
0008-6215/Ó 2014 The Authors. Published by Elsevier Ltd.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
Please cite this article in press as: Schuster, H. J.; et al. Carbohydr. Res. (2014), http://dx.doi.org/10.1016/j.carres.2014.06.021

2
H. J. Schuster et al. / Carbohydrate Research xxx (2014) xxx–xxx
path
b
(a)
H3C
H3C
AcO
H3C
AcO
O
O
R
R
OAc
O
AcO
AcO
AcO
O
O
O
LA
O
O
O
[LA]+
NIS/TfOH
- PhSI
R
OH
O
O
O
AcO
AcO
AcO
AcO
AcO
AcO
III'''
AcO
SPh
path
II
1
I
a
III
LA = H+ or III or activator
Nu = II or
LA
O
H3C
LA
H3C
AcO
O
R
R
R
OH
O
O
O
O
AcO
AcO
O
O
AcO
AcO
III'
III''
AcO
R
OH
R
OH
(b)
III'
III'. III''
III'. III''. III''
2
3
4
III'
Nu
polymerization
III' + II
I
1
II
III'''
III' + III" + II
III''
R
OH
IN GENERAL III'. [III'']n
X
2
LA = e.g. to
"TBSi+" or H+ as
initator of
here the glycosyl cation acts as
LA during polymerization to
form a species equivalent to III''
acetylated
LA
O
(c)
'trapping' alcohol
is released as a
marker of this step
H3C
AcO
R
polymerization
'terminating'
alcohol
HO
O
AcO
O
AcO
AcO
O
O
H3C
O
R
OAc
O
AcO
III'
R
R
AcO
AcO
H3C
O
O
R
O
AcO
AcO
or
H3C
O
O
O
AcO
AcO
AcO
O
O
R
AcO
III''
O
AcO
AcO
II continues
'chain-growth
polymerization'
II
O
R
OH
AcO
each such step returns alcohol to the carrier pool,
allowing substoichiometric amounts
II
Figure 1. Suggested mechanism for ‘chain growth polyglycosylation’ leading to the formation of the mannoside oligomers from fully acetylated thioglycoside donor 1. (a) The
initiation and the stabilization of key ambident intermediate III; (b) the overall polyglycosylation manifold leading to oligosaccharides (dotted box corresponds to dotted box
in panel (a)); (c) an example of one polymerization cycle. LA = Lewis acid; Nu = nucleophile.
produce 2-OH products28 or transacetylated acceptors alcohols.29
We reasoned that this implied orthoester formation and that this
donor was therefore be a putative source of the key intermediates
needed for the suggested approach. As expected, glycosylations
with an excess of primary alcohol acceptor (2 equiv), such as
typically used for discrete monomannoside syntheses, gave good
yields of the monosaccharide (Table 1). However, we were
delighted to see that glycosylation by thioglycoside 1 of function-
alized alkyl alcohols (ROH) under varied NIS/TfOH activator
conditions (Table 1 and Scheme 1) gave not only the expected
monosaccharide products but also varying amounts of disaccha-
ride and trisaccharide; this was a vital early sign that the polymer-
ization manifold was potentially accessible.
the incoming alcohol attacks the anomeric carbon of I or III then
that leads to the formation of glycoside, for example, monosaccha-
ride 2. When sufficient stabilization is provided through Lewis acid
coordination in intermediate III, we posited that a ‘chain growth
polyglycosylation’ (Fig. 1b and c) might be initiated leading to
the formation of disaccharide (3) and trisaccharide (4) et cetera.
This idea was further supported by the observation by us and
others22,23,30,31 of acetylated acceptor alcohol as a marker of glyco-
side formation (Fig. 1c).
Next, this hypothesis was tested experimentally by the addition
of varying equivalents of alcohol (as the putative terminator of
polyglycosylation, Fig. 1b and c). This had a direct and marked
effect on the formation of increased amount of mannoside oligo-
mers (Table 1). Polyglycosylation would be terminated by the addi-
tion of such an acceptor alcohol to the anomeric centre of the
intermediate III00, thereby eliminating the acetylated alcohol. Alter-
natively, this intermediate can be attacked by another orthoester II
leading to the formation of higher mannosides (e.g., trisaccharide
product 4) through a polymerization that continues to ‘grow’.
When the acceptor alcohol employed in the reaction was reduced
this second path is relatively favoured. Distributions obtained were
also consistent with this mechanism: even with majority di- or
tri-saccharide as product, traces of tetramannoside were also
observed by MS when less than stoichiometric quantities of accep-
tor alcohol were employed for the glycosylation reaction. The rate
of each individual pathway is directly determined by the amounts
2.2. Mechanistic analysis of the synthesis of mannoside
oligomers
A plausible, mechanistic explanation for the formation of the a-
1?2 linkage in oligomers (considered here for mannobiosides)
involves an orthoester II (Fig. 1). In the case of thioglycoside, inter-
mediate II may be formed from an attack of the acceptor alcohol
not at the anomeric centre (pathway a) but the central carbon of
the initially generated dioxolenium ion I (pathway b) (Fig. 1a). This
process is then likely reversible as the orthoester II can then be
attacked by the Lewis acid at the OR group or at O-1 leading to
the formation of intermediate III, which can collapse back to II. If
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H. J. Schuster et al. / Carbohydrate Research xxx (2014) xxx–xxx
3
Table 1
Systematic study with different chloroalcohols and temperaturesa
1)
HO
OAc
O
Cl
AcO
AcO
AcO
n
NIS (1.2 eq.), TfOH (0.2 eq.),
4
Ä
MS, CH2Cl2
SPh
2) Ac2O (2.0 eq.)
1
OAc
O
AcO
AcO
OAc
O
AcO
AcO
AcO
OAc
O
AcO
AcO
AcO
O
AcO
AcO
AcO
AcO
+
+
O
AcO
Cl AcO
AcO
O
O
O
AcO
AcO
AcO
O
n
Cl
n
O
2
O
3
Cl
n
O
4
Entry
ROHa
Equivalent
T (°C)
2 (%)
3 (%)
4 (%)
1
2
3
4
5
6
7
8
9
a n = 1
2.0
1.05
2.0
25
4
25
4
87
80
98
91
43
25
97
89
20
<5
<5
<5
n.d.
13
n.d.
<5
48
69
n.d.
10
70
51
31
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
<5
b n = 2
c n = 4
2.0
1.05
1.05
2.0
4
ꢀ2
25
4
ꢀ2
ꢀ2
ꢀ2
ꢀ2
2.0
1.05
0.8b
0.5b
0.3b
10
11
12
20
26c
36c
22
a
b
c
All reactions performed with 1 mmol of 1. Yields are calculated based on glycosyl donor ‘feedstock’ 1 not on alcohol acceptor.
5–15% tetra-O-acetyl-1-deoxy-N-succinimido- -mannopyranoside isolated.
Small amount of tetramannoside 5c also observed in mass spectrum; n.d. not detected.
a-D
NIS/TfOH
ROH
Table 2
Influence of the Lewis acid on reactions with 5-chloropentanola
OAc
O
OR'
O
AcO
AcO
AcO
AcO
AcO
AcO
Entry
Lewis acid
2c (%)
3c (%)
4c (%)
CH2Cl2
OR
α-D-mannosyl
1
2
3
4
5
TfOH
25
10
20
5
75
75
70
80
3
<5%
<5%
<5%
10%
n.d.
SPh
2 R' = Ac
3 R' = tetra-O-acetyl-
4 R' = hepta-O-acetyl-
TMSOTf
TIPSOTf
TBDMSOTf
BF3ꢁEt2Ob
1
α-D-mannobiosyl
96
Scheme 1. ‘Polyglycosylation’ giving direct access to mannoside oligomers.
a
With 1.05 equiv of 5-chloropentanol at ꢀ2 °C in CH2Cl2 and 1 mmol of 1,
0.2 equiv of Lewis acid, 1.2 equiv of NIS and addition of Ac2O after 1 h.
b
1.1 equiv used.
of acceptor alcohol and key components and conditions such as
Lewis acid, the coordination properties of Lewis acid and the
reaction temperatures.
various chain lengths and varying temperatures. The use of
2.0 equiv clearly favoured formation of the monosaccharides 2
and only at lower temperatures (4 °C) small amounts of disaccha-
rides 3 were found (entries 4, 8). The use of reduced, 1.05 equiva-
lents of alcohol led to predominant formation of 3. Moreover, a
further decrease in temperature to ꢀ2 °C (entries 6, 9) gave an even
higher ratio in favour of mannobiosides with formation of small
quantities of trimannosides 4. Further reducing the equivalent of
alcohol (entries 10, 11, 12) further increased the amount of triman-
noside formation and in some cases tetramannosides 5 were also
observed (entries 11, 12).
These results with different alcohol equivalents support the
existence of a mechanistic pathway generating the intermediates
of III (III0 or III00) which react rapidly with alternative nucleophiles
(e.g., alcohol or nucleophile). Thus, the terminating alcohol plays
an important role: propyl and longer alcohols seem to be of the
minimum length required to achieve significant mannobioside
formation. This can be attributed to a reduced nucleophilicity,
2.3. Variation of conditions
Following this initial survey that was supportive of the
proposed manifold, more detailed studies employed versatile chlo-
roalcohols which would allow a variety of subsequent modifica-
tions through divergent elaboration (e.g., azide introduction,32
elimination,33 or displacement by thiols). Furthermore, they
allowed investigation of the influence of chain length (ethyl, propyl
and pentyl) which directly affects the electronic properties of the
attacking alcohol. All reactions were performed on a millimolar
scale in dry dichloromethane and in the presence of molecular
sieves. The addition of acetic anhydride after 1 h served to quench
and to acetylate any residual acceptor alcohols which co-eluted
with the products during purification; additionally this served to
reprotect any side products formed by unwanted deacetylation.
Table 1 depicts the results of a first study using three alcohols of
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4
H. J. Schuster et al. / Carbohydrate Research xxx (2014) xxx–xxx
consistent with the eventual competition by even the poor nucle-
ophile succinimide at lower levels of alcohol (Table 1).
3. Conclusions
We have been able to develop a direct protocol leading to
mannobiosides and higher oligosaccharides from the acetylated
thiomannoside 1. We suggest a chain-growth mechanism that
involves polyglycosylation via an orthoester intermediate and
associated Lewis acid-activated species, which are generated dur-
ing glycosylations with 2-O-acetyl protecting groups, reacting in
an intermolecular fashion to generate 1?2 linkages. This process
is dependent on the type and molar equivalents of the alcohol,
the Lewis acid and reaction temperatures. The minimum length
acceptors requirement for efficient disaccharide formation are pro-
pyl alcohols as ‘terminating acceptors’ and the reaction seems to be
flexible in the nature of functional groups that these alcohols may
carry, thus allowing direct installation of ‘linkers’. The use of tri-
flate-based Lewis acids as promoters/initiators allows this polygly-
cosylation whereas BF3ꢁEt2O can be used to avoid it. Initial results
suggest that this protocol allows selective reaction to the corre-
sponding higher mannosides by varying the equivalents of the ter-
minating alcohol and lowering reaction temperatures.
The results we have obtained are consistent with a mechanism
(Fig. 1) that, to the best of our knowledge, has not previously been
readily exploited in preparative glycosylation chemistry: chain-
growth polyglycosylation that proceeds from the non-reducing to
reducing (N-to-R) terminus. Whilst other elegant strategies36–40
for polyglycosides have been explored using anhydrosugars and
glycosyl halides, these have relied upon direct step-growth poly-
merization, which as a general polymerization strategy tends to
allow less control and in the case of some polyglycosylations
requires extreme conditions of heat or vacuum. As well as poten-
tially allowing greater chain control, the resulting termination by
a derivatizable group is an advantage, as for chain growth polymer-
izations generally. We also suggest that the many suggested
(pre)equilibria are essential in allowing a productive outcome
based on an ambident reactivity of orthoester II as both nucleo-
phile and electrophile (via III); it may also be that this process is
selective for one diastereomer of II (and III) over another.
We did not observe exact stoichiometry between recovered acet-
ylated alcohol, formed as a result of alcohol ‘trapping’ acetyl
(Fig. 1c), and polyglycosylation product as a result of ‘termination’
by alcohol. Other nucleophiles may therefore also play the role of
‘trapper’ in the mechanism; indeed in crude product mixtures we
do observe putative succinimidyl conjugates. Alternative mecha-
nisms can also be envisaged; for example, in situ generation of
intermediates with free OH-2 might also be considered. Interest-
ingly, the formation of equivalent species and resulting transgly-
cosylations has also been reported for gluco- and galacto-sides41
that might also be interpreted through such a mechanism. Hence,
the potential for use of this process might be even more widespread.
We are therefore currently investigating if such a poly(self-)glyco-
sylation process can also be developed for other sugars, although
the mannobiosides are by far the most biologically-relevant 1?2
linked disaccharides. Another possibility is to use in situ generated
terminating sugar acceptors for a one-step synthesis delivering
mixed oligosaccharides bearing an alternative residue in the reduc-
ing terminus. With careful control, even ‘block polyglycosylations’
giving runs of one sugar type and then another type might be con-
sidered. Strategies towards these ends and towards control of
higher oligosaccharides are also currently being investigated.
2.4. Variation of activator
To investigate the influence of the coordinating initiator
(Fig. 1c), various Lewis acids were also tested. This also tested the
hypothesis of a necessary coordinating effect of a stabilizing
counterion. Four triflate-based Lewis acids and BF3ꢁEt2O—the
commonly used Lewis acids for activation of N-iodosuccinimide32
—
were tested under identical conditions with chloropentanol as
terminating nucleophile. As shown in Table 2, the use of TBDMSOTf
gave increased polymerization over the other triflate-based acids;
allowing the isolation of a small amount (10%) of the mannotrioside
4c. This may be a result of bulk allowing greater lifetime of all of the
intermediates of type III or may reflect differential reactivity of
intermediates III0 or III00; for example, greater bulk of LA (Fig. 1c)
might relatively favour initiating reaction of III0.
The direct involvement of any silyl electrophile remains unclear;
no intermediate 2-O-silyl species were isolated or detected in the
reaction solutions by mass spectrometry. The use of BF3ꢁEt2O led
almost exclusively to formation of monosaccharide 2c. Even at
lower temperatures no disaccharide formation was found (data
not shown), hence, its use would prevent polymerization if mono-
saccharides were desired targets. Again this favouring of directly
productive glycosylation without polymerization may reflect the
accessibility of BF3 as a Lewis acid to II and hence greater relative
reactivity of III00 where the less accessible O-2 is coordinated.
2.5. Synthesis of mannoside oligomers equipped with diverse
linkers
Finally, to further test the suitability of this synthetic approach
for preparing diverse mannooligosaccharides the reactions were
repeated with nitrogen-containing linkers (Table 3). Linkers con-
taining amines or masked amines, such as these, find widespread
use in immobilization to solid surfaces and conjugation to biomol-
ecules. An efficient approach to higher mannosides with these link-
ers would provide rapid access to these biologically-relevant
glycans, for use in for example, immobilization to array surfaces,34
preparation of glycoprotein conjugates,19,35 and affinity-based
chromatography for identifying mannose-binding proteins. The
successful outcome of these reactions confirmed the versatility of
this approach. The reactions with the Cbz- and Boc-protected
aminopentanols gave mannobiosides 3d, e as the major products
and traces of trisaccharides 4d, e were only detected by mass spec-
trometric analysis. Azidopentanol gave only 15% of the monosac-
charide 2f and 17% mannotrioside 4f in addition to the major
mannobioside 3f.
Table 3
Synthesis of mannobiosides with different masked-amine linkersa
HO
X
1)
3
OR
NIS (1.2 eq.), TfOH (0.2 eq.),
AcO
AcO
AcO
O
4 MS, CH2Cl2
Ä
1
2) Ac2O (2.0 eq.)
O
X
3
2d,e,f R = Ac
3d,e,f R = tetra-O-acetyl-
α
-D
-mannosyl
α-D-mannobiosyl
4d,e,f R = hepta-O-acetyl-
4. Experimental section
4.1. General methods
Entry
Alcohol
2 (%)
3 (%)
4 (%)
1
2
3
d X = NHCbz
e X = NHBoc
f X = N3
23
10
15
65
75
41
<5%
<5%
17
Chemicals were purchased from Sigma–Aldrich and used as
supplied, unless otherwise stated. Anhydrous solvents were
a
With 1.05 equiv of 5-chloropentanol at ꢀ2 °C in CH2Cl2 and 1 mmol of 1.
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H. J. Schuster et al. / Carbohydrate Research xxx (2014) xxx–xxx
5
purchased from Fluka or Acros. All other solvents were used as
supplied (analytical or HPLC grade) without prior purification. ‘Pet-
rol’ refers to the fraction of light petroleum ether boiling in the
range of 40–60 °C. All reactions using anhydrous conditions were
performed using flame-dried apparatus under an atmosphere of
argon or nitrogen. Proton nuclear magnetic resonance (1H NMR)
spectra were recorded on a Mercury VX 400 (400 MHz) spectrom-
eter, as indicated. Carbon nuclear magnetic resonance (13C NMR)
spectra were recorded on a Varian Mercury VX 400 (100.6 MHz)
spectrometer, as indicated. NMR spectra were fully assigned using
COSY, HSQC and HMBC correlation experiments. All chemical shifts
are quoted on d scale in ppm using residual solvent as the internal
standard. Coupling constants (J) are reported in Hz. Low resolution
mass spectra (LRMS) were recorded on a Waters Micromass LCT
premier TOF spectrometer using electrospray ionization (ESI-MS).
High resolution mass spectra (HRMS) were recorded on a Bruker
MicroTOF ESI mass spectrometer. Thin layer chromatography
(TLC) was carried out using Merck aluminium backed sheets
coated with 60F254 silica gel. Visualization of the silica gel plates
was achieved using a UV lamp (kmax = 254 nm) and/or by dipping
the plate in ceric ammonium molybdate (CAM) stain followed by
heating.
(400 MHz, CDCl3) d ppm 5.34 (dd, J = 10.0, 3.3 Hz, 1H, H-3), 5.33–
5.25 (m, 2H, H-2, H-4), 4.86 (d, J = 1.0 Hz, 1H, H-1), 4.26 (dd,
J = 12.2, 5.5 Hz, 1H, H-6b), 4.12 (m, 2H, H-5, H-6a), 3.91 (td,
J = 11.2, 5.5 Hz, 1 H, H-1b ), 3.81 (td, J = 10.9, 5.3 Hz, 1H, H-1a ),
3.67 (t, J = 5.6 Hz, 2 H, H-20), 2.15, 2.09, 2.04, 1.99 (4 ꢂ s, 12H,
4 ꢂ COCH3); 13C NMR (100 MHz, CDCl3) d ppm 170.65, 170.06,
169.81, 169.73 (4 ꢂ COCH3), 97.79 (C-1), 69.41 (C-2), 68.82 (C-3),
68.90 (C-10), 68.60 (C-5), 66.00 (C-4), 62.39 (C-6), 42.35 (C-20),
20.64, 20.67, 20.70, 20.84 (4 ꢂ COCH3); HRMS (ESI): m/
z = 433.08624 [M+Na]+; calculated C16H23ClNaO10 (433.08720).
0
0
4.3.2. 2-Chloroethyl 2,3,4,6-tetra-O-acetyl-
a-D-mannopyranos
yl-(1?2)-3,4,6-tri-O-acetyl- -mannopyranoside (3a)
a-D
The synthesis was performed according to GP2 yielding the
monosaccharide 2a (330.1 mg, 0.804 mmol, 80%), the disaccharide
3a (44.2 mg, 63.2
Rf = 0.25 (60% EtOAc/petrol); [
lmol, 13%) as colourless solids. Data for 3a, TLC:
20
a]
+22.7 (c 1.90, CHCl3); 1H NMR
D
(400 MHz, CDCl3) d ppm 5.38 (dd, J = 10.0, 3.3 Hz, 1H, H-30), 5.31
(t, J = 9.9 Hz, 1H, H-4), 5.29–5.22 (m, 3H, H-3, H-20, H-40), 5.00 (d,
J = 1.3 Hz, 1H, H-1), 4.92 (d, J = 1.1 Hz, H-10), 4.25–4.09 (m, 5 H,
0
0
H-5, H-6a,b, H-6a ,b ), 4.07 (dd, J = 4.8, 1.3 Hz, 1H, H-2), 4.01 (ddd,
J = 8.7, 3.9, 2.3 Hz, 1H, H-5), 3.93 (td, J = 11.1, 5.5 Hz, 1H, H-1b00),
3.78 (td, J = 11.0, 5.4 Hz, 1H, H-1a00), 3.66 (t, J = 5.5 Hz, 2H, H-200),
2.13, 2.12, 2.07, 2.06, 2.03, 2.02, 1.99 (7 ꢂ s, 21H, 7 ꢂ COCH3); 13C
NMR (100 MHz, CDCl3) d ppm 169.53, 169.88, 169.85, 169.92,
170.41, 170.67, 170.91 (7 ꢂ COCH3), 99.05 (C-10), 98.55 (C-1),
76.59 (C-2), 70.14 (C-3), 69.69 (C-20), 69.14, 68.96 (C-5, C-50),
68.49 (C-100), 68.38 (C-30), 66.41, 66.11 (C-4, C-40), 62.17, 62.62
(C-6, C-60), 42.56 (C-200), 20.85, 20.74, 20.71, 20.66, 20.61
(7 ꢂ COCH3); HRMS (ESI): m/z = 721.16945 [M+Na]+; calculated
4.2. General procedures
4.2.1. General procedures for glycosylations of
monosaccharides (GP1)
The thiophenylmannoside 1 (440 mg, 1.00 mmol, 1.0 equiv) and
the corresponding alcohol (2.0 equiv) in CH2Cl2 (5 mL) were stirred
0
at 25 °C in the presence of 4 ÅA MS (500 mg) for 30 min. N-iodosuc-
cinimide (270 mg, 1.2 mmol, 1.2 equiv) and trifluoromethane sul-
fonic acid (30.0 mg, 17.7 mL, 200 mmol, 0.2 equiv) were slowly
added and stirring continued for 1 h. In situ acetylation of free
alcohols is achieved by addition of acetic anhydride (0.2–0.3 mL,
2.0–3.0 equiv). After 30 min the molecular sieves were filtered
using a pad of CeliteÒ and then washed with EtOAc. Filtrate was
then transferred into a separatory funnel and washed with ice-cold
10% Na2S2O5 solution (20 mL), phases separated and the water
layer reextracted with additional EtOAc (50 mL). The combined
organic layers were washed with ice-cold brine (40 mL), dried
(Na2SO4) and concentrated under vacuum. Column chromatogra-
phy (20 g silica, 3:1?2:1 petrol/EtOAc) gave the monosaccharides
as colourless materials.
C28H39ClNaO18 (721.17171).
4.3.3. 3-Chloropropyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyrano
side (2b)
The chloride 2b was prepared according to GP1 yielding the title
compound as colourless oil (415 mg, 0.977 mmol, 98%). TLC:
20
Rf = 0.49 (60% EtOAc/petrol); [
a]
+48.7 (c 1.65, CHCl3); 1H NMR
D
(400 MHz, CDCl3) d ppm 5.29 (dd, J = 9.9, 3.5 Hz, 1H, H-3), 5.27–
5.20 (m, 2H, H-2, H-4), 4.81 (d, J = 1.0 Hz, 1H, H-1), 4.26 (dd,
J = 12.2, 5.4 Hz, 1H, H-6b), 4.11 (dd, J = 12.4, 2.3 Hz, 1H, H-6a),
0
3.97 (m, 1H, H-1b ), 3.90 (ddd, J = 9.9, 7.3, 5.1 Hz, 1H, H-5), 3.70–
0
3.60 (m, 2H, H-30), 3.57 (td, J = 10.1, 5.6 Hz, 1H, H-1a ), 2.06–2.02
(m, 2H, H-20), 2.14, 2.09, 2.03, 1.98 (4 ꢂ s, 12H, 4 ꢂ COCH3); 13C
NMR (100 MHz, CDCl3) d ppm 170.65, 170.04, 169.91, 169.76
(4 ꢂ COCH3), 97.57 (C-1), 69.44 (C-2), 69.02 (C-3), 68.61 (C-5),
66.02 (C-4), 64.39 (C-10), 62.39 (C-6), 41.41 (C-30), 31.88 (C-20),
20.84, 20.69, 20.66 (4 ꢂ COCH3); HRMS (ESI): m/z = 447.10169
[M+Na]+; calculated C17H25ClNaO10 (447.10285).
4.2.2. General procedure for glycosylation towards
mannobiosides (GP2)
The thiophenylmannoside 1 (440 mg, 1.00 mmol, 1.0 equiv) and
the corresponding alcohol (1.05 equiv) in CH2Cl2 (5 mL) were stir-
0
red at 25 °C in the presence of 4 ÅA MS (500 mg) for 30 min. After
cooling to ꢀ2 °C with an ice/NaCl bath N-iodosuccinimide
(270 mg, 1.2 mmol, 1.2 equiv) and trifluoromethanesulfonic acid
(30.0 mg, 17.7 mL, 200 mmol, 0.2 equiv) were slowly added and
stirring continued at this temperature for 1 h. The reaction mixture
was allowed to warm to 25 °C and then acetic anhydride
(0.2–0.3 mL, 2.0–3.0 equiv) added. Work-up was analogous to
GP1 and column chromatography was performed with a gradient
3:1 ? 1:1 petrol/EtOAc to yield the mono, di and trisaccharides
as colourless materials.
4.3.4. 3-Chloropropyl 2,3,4,6-tetra-O-acetyl-
a-D-mannopyranos
yl-(1?2)-3,4,6-tri-O-acetyl- -mannopyranoside (3b)
a-D
The mannobioside 3b was prepared following GP2 to result in a
colourless solid (246 mg, 0.345 mmol, 69%) along with the mono-
saccharide 2b (104 mg, 0.245 mmol, 25%). Data for 3b, TLC:
20
Rf = 0.35 (65% EtOAc/petrol); [
a
]
D
+32.5 (c 0.95, CHCl3); 1H NMR
(400 MHz, CDCl3) d ppm 5.40 (dd, J = 10.0, 3.3 Hz, 1H, H-30), 5.32
(t, J = 9.9 Hz, 1H, H-4), 5.30–5.22 (m, 3H, H-3, H-20, H-40), 4.95 (d,
J = 1.0 Hz, 1H, H-1), 4.92 (d, J = 1.3 Hz, 1 H, H-10), 4.07–4.27 (m,
0
0
5H, H-5, H-6a,b, H-6a ,b ), 4.02 (m, 1H, H-2), 3.97–3.86 (m, 2H, H-
5, H-1b00), 3.65 (t, J = 6.1 Hz, 2H, H-300), 3.58 (td, J = 9.9, 5.7 Hz, 2H,
H-1a00), 2.15, 2.13, 2.08, 2.04, 2.00 (7 ꢂ s, 21H, 7 ꢂ COCH3), 2.05
(m, 2H, H-200); 13C NMR (100 MHz, CDCl3) d ppm 170.98, 170.56,
169.81, 169.74, 169.43 (7 ꢂ COCH3), 99.15 (C-10), 98.31 (C-1),
76.96 (C-2), 70.24 (C-3), 69.73 (C-20), 69.16, 68.70 (C-5, C-50),
68.33 (C-30), 66.37, 66.09 (C-4, C-40), 64.39 (C-100), 62.56, 62.14
(C-6, C-60), 41.42 (C-300), 31.92 (C-200), 20.86, 20.72, 20.71, 20.66,
4.3. Synthesis and characterization
4.3.1. 2-Chloroethyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyrano-
side (2a)
The chloride was prepared according to GP1 giving the title (2a)
compound as colourless solid (332 mg, 0.864 mmol, 87%). TLC:
20
Rf = 0.47 (60% EtOAc/petrol); [
a]
+44.5 (c 0.65, CHCl3); 1H NMR
D
Please cite this article in press as: Schuster, H. J.; et al. Carbohydr. Res. (2014), http://dx.doi.org/10.1016/j.carres.2014.06.021

6
H. J. Schuster et al. / Carbohydrate Research xxx (2014) xxx–xxx
20.63 (7 ꢂ COCH3),. HRMS (ESI): m/z = 735.18477 [M+Na]+; calcu-
66.25 (C-400, C-40, C-4), 62.51, 62.25, 62.11 (C-600, C-60, C-6), 44.87
(C-5000), 32.15 (C-4000), 29.58 (C-2000), 23.44 (C-3000), 20.88, 20.71,
20.63 (10 ꢂ COCH3); HRMS (ESI): m/z = 1051.29976 [M+Na]+;
calculated C43H61ClNaO26 (1051.30318).
lated C29H41ClNaO18 (735.18736).
4.3.5. 5-Chloropentyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranosi
de (2c)
The synthesis was performed according to GP1 yielding the
4.3.8. 5-(Benzyloxycarbonylamino)pentyl 2,3,4,6-tetra-O-acetyl-
monosaccharide 2c (438 mg, 0.968 mmol, 97%) as colourless oil.
a
-
D
-mannopyranoside (2d) & 5-(benzyloxycarbonylamino)
pentyl 2,3,4,6-tetra-O-acetyl- -mannopyranosyl-(1?2)-3,4,6-
tri-O-acetyl- -mannopyranoside (3d)
+ 41.5 (c 1.20, CHCl3); 1H
a-D
20
TLC: Rf = 0.55 (60% EtOAc/petrol); [
a
]
D
NMR (400 MHz, CDCl3) d ppm 5.33 (dd, J = 10.0, 3.3 Hz, 1H, H-3),
5.26 (t, J = 9.9 Hz, 1H, H-4), 5.22 (dd, J = 3.2, 1.6 Hz, 1H, H-2), 4.79
(d, J = 1.2 Hz, 1H, H-1), 4.27 (dd, J = 12.2, 5.2 Hz, 1H, H-6b), 4.09
(dd, J = 12.2, 2.1 Hz, 1H, H-6a), 3.97 (ddd, J = 7.3, 5.1, 2.0 Hz, 1H,
a-D
The mannobioside was prepared following GP2 to give two col-
ourless syrups of the corresponding monosaccharide 2d (130 mg,
0.229 mmol, 23%) along with mannobioside 3d (277 mg,
0
H-5), 3.69 (td, J = 9.7, 6.8 Hz, 1H, H-1b ), 3.54 (t, J = 6.6 Hz, 2H,
0.324 mmol, 65%). Data for 2d, TLC: Rf = 0.43 (50% EtOAc/Petrol);
H-50), 3.45 (td, J = 9.7, 6.3 Hz, 1 H, H-1a ), 2.14, 2.09, 2.03, 1.98
[a
]
+32.2 (c 1.05, CHCl3); 1H NMR (400 MHz, CDCl3) d ppm
20
0
D
(4 ꢂ s, 12H, 4 ꢂ COCH3), 1.80 (td, J = 13.9, 6.8 Hz, 2H, H-40), 1.62
7.35–7.25 (m, 5H, H-Ph), 5.34 (dd, J = 10.0, 3.3 Hz, 1H, H-3), 5.27
(t, J = 9.9 Hz, 1H, H-4), 5.23 (dd, J = 3.3, 1.7 Hz, 1H, H-2), 5.10 (s,
2H, CH2Ph), 4.86 (sbr, 1H, NH), 4.80 (d, J = 1.3 Hz, 1H, H-1), 4.29
(dd, J = 12.2, 5.3 Hz, 1H, H-6b), 4.12 (m, 1H, H-6a), 3.98 (ddd,
J = 9.4, 5.2, 2.3 Hz, 1H, H-5), 3.69 (td, J = 9.5, 6.3 Hz, 1H, H-1b ),
3.45 (td, J = 9.5, 6.3 Hz, 1H, H-1a ), 3.21 (dd, J = 9.2, 6.5 Hz, 2H, H-
(qd, J = 13.6, 7.2, 6.8 Hz, 2H, H-20), 1.51 (m, 2H, H-30); 13C NMR
(100 MHz, CDCl3)
d
ppm 170.65, 170.11, 169.93, 169.77
(4 ꢂ COCH3), 97.54 (C-1), 69.62 (C-2), 69.06 (C-3), 68.43 (C-5),
68.10 (C-10), 66.20 (C-4), 62.50 (C-6), 44.74 (C-50), 32.19 (C-40),
28.51 (C-20), 23.43(C-30), 20.87, 20.71, 20.67 (4 ꢂ COCH3); HRMS
(ESI): m/z = 475.13304 [M+Na]+; calculated C19H29ClNaO10
(475.13415).
0
0
50), 2.16, 2.10, 2.04, 1.99 (4s, 12H, 4 ꢂ COCH3), 1.70–1.48 (m, 4H,
H-20, H-40), 1.40 (m, 2H, H-30); 13C NMR (50 MHz, CDCl3) d ppm
170.64, 170.02, 169.91, 169.73 (4 ꢂ COCH3), 156.42 (NHCO),
136.51, 128.44, 128.07 (C-Ph), 97.49 (C-1), 69.67 (C-2), 69.06
(C-3), 68.31 (C-5), 68.22 (C-10), 66.51 (CH2Ph), 66.27 (C-4), 62.54
(C-6), 40.83 (C-50), 29.71 (C-40), 28.86 (C-20), 23.31(C-30), 20.86,
20.75, 20.69 (4 ꢂ COCH3); HRMS (ESI) m/z 590.21761 [M+Na]+; cal-
4.3.6. 5-Chloropentyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranos
yl-(1?2)-3,4,6-tri-O-acetyl- -mannopyranoside (3c)
a
-D
The mannobioside was prepared following GP2 to give two col-
ourless syrups of the mannobioside 3c (259 mg, 0.350 mmol, 70%)
along with the corresponding monosaccharide 2c (90 mg,
culated C27H37NNaO12 590.22135.
20
0.2 mmol, 20%). Data for 3c, TLC: Rf = 0.30 (50% EtOAc/petrol);
Data for 3d, TLC: Rf = 0.25 (50% EtOAc/petrol); [
a]
+24.1 (c
D
20
[a
]
D
+30.8 (c 1.60, CHCl3); 1H NMR (400 MHz, CDCl3) d ppm
1.90, CHCl3); 1H NMR (400 MHz, CDCl3) d ppm 7.36–7.27 (m, 5H,
H-Ph), 5.39 (dd, J = 10.0, 3.3 Hz, 1H, H-30), 5.34–5.20 (m, 4H, H-3,
H-4, H-20, H-40), 5.07 (sbr, 2H, CH2Ph), 4.90 (sbr, 3H, H-1, H-10,
5.39 (dd, J = 10.0, 3.3 Hz, 1H, H-30), 5.26 (t, J = 9.8 Hz, 1H, H-4),
5.22–5.28 (m, 3H, H-3, H-20, H-40), 4.91 (sbr, 2H, H-1, H-10), 4.06–
NH), 4.22–3.98 (m, 6H, H-2, H-50, H-6a,b, H-6a ,b ), 3.89 (dd, J = 5.0,
3.6 Hz, 1H, H-5), 3.67 (td, J = 9.3, 6.5 Hz, 1H, H-1b00), 3.41 (td,
J = 8.9, 6.3 Hz, 1H, H-1a00), 3.18 (t, J = 12.1, 6.4 Hz, 2H, H-500), 2.13,
2.11, 2.06, 2.02, 2.01, 1.99 (6 ꢂ s, 21H, 7 ꢂ COCH3), 1.61 (td,
J = 13.0, 6.4 Hz, 2H, H-400), 1.52 (td, J = 14.4, 7.3 Hz, 2 H, H-200),
1.37 (m, 2H, H-300); 13C NMR (100 MHz, CDCl3) d ppm 170.91,
170.44, 169.85, 169.78, 169.45 (7 ꢂ COCH3), 156.42 (NHCO),
136.51, 128.45, 128.05 (5 ꢂ C-Ph), 99.09 (C-10), 98.16 (C-1), 77.09
(C-2), 70.24 (C-3), 69.69 (C-20), 69.05 (C-50), 68.43 (C-5), 68.33
(C-30), 68.16 (C-100), 66.33 (C-4, C-40), 66.21 (CH2Ph), 62.46, 62.20
(C-6, C-60), 40.82 (C-500), 29.52 (C-400), 28.88 (C-200), 23.35 (C-300),
20.80, 20.68, 20.61 (7 ꢂ COCH3); HRMS (ESI): m/z = 878.30198
[M+Na]+; calculated C39H53NNaO20 (878.30586).
0
0
0
0
4.25 (m, 5H, H-5, H-6a,b, H-6a ,b ), 4.00 (dd, J = 2.4, 1.9 Hz, 1H, H-
2), 3.89 (ddd, J = 9.2, 3.9, 2.4 Hz, 1H, H-5), 3.69 (td, J = 9.5, 6.5 Hz,
1H, H-1b00), 3.53 (t, J = 6.6 Hz, 2H, H-500), 3.44 (td, J = 9.8, 6.4 Hz,
1H, H-1a00), 2.13, 2.12, 2.06, 2.02, 2.01, 1.99 (6 ꢂ s, 21H, 7 ꢂ COCH3),
1.78 (m, 2H, H-400), 1.62 (qd, J = 13.1, 6.5 Hz, 2H, H-200), 1.51 (m, 2H,
H-300); 13C NMR (100 MHz, CDCl3) d ppm 170.86, 170.43, 169.81,
169.73, 169.45 (7 ꢂ COCH3), 99.11 (C-10), 98.23 (C-1), 77.06 (C-2),
70.26 (C-3), 69.71 (C-20), 69.07 (C-50), 68.50 (C-5), 68.33 (C-30),
68.07 (C-100), 66.18, 66.34 (C-4, C-40), 62.19, 62.50 (C-6, C-60),
44.70 (C-500), 32.15 (C-400), 28.58 (C-200), 23.44 (C-300), 20.82, 20.69,
20.62 (7 ꢂ COCH3); HRMS (ESI): m/z = 763.21603 [M+Na]+;
calculated C31H45ClNaO18 (763.21866).
4.3.7. 5-Chloropentyl 2,3,4,6-tetra-O-acetyl-
yl-(1?2)-3,4,6-tri-O-acetyl- -mannopyranosyl-(1?2)-3,4,6-
tri-O-acetyl- -mannopyranoside (4c)
The mannobioside was prepared following GP2 (0.8 equiv of 5-
chloropentanol) to give two colourless syrups of the mannobioside
3c (189 mg, 0.254 mmol, 51%) along with the corresponding man-
a-D-mannopyranos
a
-D
4.3.9. 5-(tert-Butoxycarbonylamino)pentyl 2,3,4,6-tetra-O-
a-
D
acetyl-
amino)pentyl 2,3,4,6-tetra-O-acetyl-
(1?2)-3,4,6-tri-O-acetyl- -mannopyranoside (3e)
a
-D
-mannopyranoside (2e) & 5-(tert-butoxycarbonyl
a-D
-mannopyranosyl-
a-D
The mannobioside was prepared following GP2 to give two col-
ourless syrups of the corresponding monosaccharide 2e (53 mg,
0.100 mmol, 10%) along with mannobioside 3e (307 mg,
nose trisaccharide 4c (62 mg, 60 lmol, 20%). Data for 4c, TLC:
Rf = 0.18 (50% EtOAc/petrol); [
a]
+28.8 (c 0.80, CHCl3); 1H NMR
20
D
(400 MHz, CDCl3): d ppm 5.40 (dd, J = 9.8, 3.3 Hz, 1H, H-300),
5.34–5.25 (m, 6H, H-3, H-30, H-200, H-4, H-40, H-400), 5.11 (d, J = 1.3
Hz, 1H, H-100), 4.95 (sbr, 2H, H-1, H-10), 4.23 (dd, J = 12.0, 4.3 Hz,
0.374 mmol, 75%). Data for 2e, TLC: Rf = 0.38 (50% EtOAc/Petrol);
20
[a]
+38.3 (c 1.20, CHCl3); 1H NMR (400 MHz, CDCl3) d ppm
D
5.31–5.23 (m, 2H, H-2, H-4), 4.80 (d, J = 1.1 Hz, 1H, H-1), 4.58
(sbr, 1H, NH), 4.28 (dd, J = 12.2, 5.2 Hz, 1H, H-6b), 4.14 (m, 1H, H-
6a), 3.97 (ddd, J = 9.3, 5.2, 2.1 Hz, 1H, H-5), 3.68 (td, J = 9.7,
0
0
00
0
00
0
2H, H-6a , H-6a ), 4.20–4.10 (m, 7H, H-2 , H-5 , H-5 , H-6a,b, H-6b ,
00
H-6b ), 4.02 (sbr, 1H, H-2), 3.92 (sbr, 1H, H-5), 3.72 (td, J = 9.6,
6.6 Hz, 1H, H-1a000), 3.55 (t, J = 6.6 Hz, 2H, H-5000), 3.45 (td, J = 9.6,
6.3 Hz, 1H, H-1b000), 2.15, 2.13, 2.12, 2.09, 2.07, 2.06, 2.04, 2.03,
2.00 (9s, 30 H, 10 ꢂ COCH3), 1.85–1.78 (m, 2H, H-2000), 1.68–1.60
(m, 2H, H-4000), 1.55–1.46 (m, 2H, H-3000); 13C NMR (100 MHz, CDCl3)
d ppm 170.91, 170.75, 170.16, 170.05, 169.81, 169.56, 169.45
(10 ꢂ COCH3), 99.81 (C-100), 99.40 (C-10), 98.23 (C-1), 77.30 (C-2),
76.71 (C-500), 70.46 (C-3), 69.71 (C-20), 69.63 (C-200), 69.41 (C-300),
69.28 (C-50), 68.60 (C-5), 68.43 (C-30), 68.11 (C-1000), 66.48, 66.34,
6.3 Hz, 1H, H-1b ), 3.42 (td, J = 9.5, 6.3 Hz, 1H, H-1a ), 3.11 (t,
J = 6.8, 2H, H2-50), 2.15, 2.11, 2.03, 1.99 (4s, 12H, 4 ꢂ COCH3), 1.55
(m, 2H, H-20), 1.48 (q, J = 7.6 Hz, 2H, H-40), 1.42 (sbr, 9H, C(CH3)3),
1.41–1.33 (m, 2H, H-30); 13C NMR (100 MHz, CDCl3) d ppm
170.52, 170.18, 169.88, 169.55 (4 ꢂ COCH3), 156.22 (NHCO),
97.64 (C-1), 79.09 (C(CH3)3), 69.72 (C-2), 69.61 (C-3), 68.40 (C-5),
68.22 (C-10), 66.24 (C-4), 62.54 (C-6), 40.46 (C-50), 32.16 (C-20),
29.79 (C-40), 28.41 (C(CH3)3), 23.00 (C-30), 20.86, 20.75, 20.69
0
0
Please cite this article in press as: Schuster, H. J.; et al. Carbohydr. Res. (2014), http://dx.doi.org/10.1016/j.carres.2014.06.021

H. J. Schuster et al. / Carbohydrate Research xxx (2014) xxx–xxx
7
(4 ꢂ COCH3); HRMS (ESI) m/z 556.23212 [M+Na]+; calculated
4.23 (dd, J = 12.3, 4.5 Hz, 2H, H-6a , H-6a ), 4.19–4.10 (m, 6H, H-5 ,
0
0
00
0
00
C24H39NNaO12 556.23700.
H-500, H-6a,b, H-6b , H-6b ), 4.01 (sbr, 1H, H-2), 3.91 (ddd, J = 9.3,
4.5, 2.2 Hz, 1H, H-5), 3.72 (td, J = 9.6, 6.6 Hz, 1H, H-1a000), 3.45 (td,
J = 9.6, 6.3 Hz, 1H, H-1b000), 3.30 (t, J = 6.8 Hz, 2H, H-5000), 2.15, 2.13,
2.12, 2.08, 2.06, 2.05, 2.03, 2.00 (8 ꢂ s, 30H, 10 ꢂ COCH3),
1.68–1.58 (m, 4H, H-2000, H-4000), 1.46–1.42 (m, 2H, H-3000); 13C
NMR (100 MHz, CDCl3) d ppm 170.89, 170.75, 170.44, 170.11,
170.07, 169.74, 169.58, 169.32 (10 ꢂ COCH3), 99.83 (C-100), 99.45
(C-10), 98.32 (C-1), 77.30 (C-2), 76.81 (C-500), 70.46 (C-3), 69.91
(C-20), 69.63 (C-200), 69.43 (C-300), 69.23 (C-50), 68.60 (C-5), 68.43
(C-30), 68.11 (C-1000), 66.45, 66.36, 66.21 (C-400, C-40, C-4), 62.50,
62.28, 62.15 (C-600, C-60, C-6), 51.20 (C-5000), 28.99 (C-4000), 28.58
(C-2000), 23.44 (C-3000), 20.88, 20.71, 20.63 (10 ꢂ COCH3); HRMS
(ESI): m/z = 1058.34035 [M+Na]+; calculated C43H61N3NaO26
(1035.34355).
20
Data for 3e, TLC: Rf = 0.20 (1:1 = EtOAc/petrol); [
a
]
D
+26.9 (c
1.65, CHCl3); 1H NMR (400 MHz, CDCl3): d = 5.37 (dd, J = 10.0,
3.4 Hz, 1H, H-30), 5.33–5.19 (m, 3 H, H-3, H-4, H-20, H-40), 4.92
(sbr, 3H, H-1, H-10, NH), 4.22–3.98 (m, 6H, H-2, H-5, H-6a,b, H-6a ,b ),
3.88 (dd, J = 5.1, 3.6 Hz, 1H, H-5), 3.68 (td, J = 9.5, 6.3 Hz, 1H, H-1b00),
3.42 (td, J = 9.6, 6.3 Hz, 1H, H-1a00), 3.11 (t, J = 6.8, 2H, H2-500), 2.12,
2.10, 2.06, 2.02, 2.01, 1.98 (6 ꢂ s, 21H, 7 ꢂ COCH3), 1.55 (m, 2H,
H-200), 1.47 (q, J = 7.5 Hz, 2H, H-400), 1.42 (sbr, 9H, C(CH3)3), 1.37
(m, 2H, H-300); 13C NMR (100 MHz, CDCl3): d ppm 170.88, 170.42,
169.91, 169.75, 169.43 (7 ꢂ COCH3), 156.30 (NHCO), 99.10 (C-10),
98.22 (C-1), 79.19 (C(CH3)3), 77.09 (C-2), 70.24 (C-3), 69.74
(C-20), 69.03 (C-50), 68.44 (C-5), 68.35 (C-30), 68.19 (C-100), 66.32,
66.21 (C-4, C-40), 62.45, 62.21 (C-6, C-60), 40.50 (C-500), 32.16
(C-200), 29.82 (C-400), 28.36 (C(CH3)3), 22,89 (C-300), 20.80, 20.68,
20.61 (7 ꢂ COCH3); HRMS (ESI): m/z = 844.31846 [M+Na]+; Calcu-
lated C36H55NNaO20 (844.32151).
0
0
References
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4.3.10. 5-(Azido)pentyl 2,3,4,6-tetra-O-acetyl-
side (2f), 5-(azido)pentyl 2,3,4,6-tetra-O-acetyl-
nosyl-(1?2)-3,4,6-tetra-O-acetyl- -mannopyranoside (3f) &
5-(azido)pentyl 2,3,4,6-tetra-O-acetyl- -mannopyranosyl-
(1?2)-3,4,6-tri-O-acetyl- -mannopyranosyl-(1?2)-3,4,6-tri-
O-acetyl- -mannopyranoside (4f)
The corresponding azido-mannosides were prepared following
GP2 to give three colourless syrups of the monosaccharide 2f (69
mg, 0.15 mmol, 15%), mannobioside 3f (152 mg, 0.203 mmol,
41%) along with the corresponding mannose trisaccharide 4f
a
-
a
D
-mannopyrano
-D
-mannopyra
a-D
a-D
a
-D
a
-D
8. Pratt, M. R.; Bertozzi, C. R. J. Am. Chem. Soc. 2003, 6149.
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(51 mg, 50
lmol, 17%). Data for 2f, TLC: Rf = 0.52 (50 % EtOAc/Pet-
rol); [a]
20 +38.7 (c 1.10, CHCl3); 1H NMR (400 MHz, CDCl3) d ppm
D
5.48 (d, J = 2.5 Hz, 1H, H-1), 5.31 (dd, J = 10.4, 9.1 Hz, 1H, H-4), 5.15
(dd, J = 9.9, 3.9 Hz, 1H, H-3), 4.60 (dd, J = 3.9, 2.6 Hz, 1H, H-2), 4.24
(dd, J = 12.1, 4.9 Hz, 1H, H-6a), 4.15 (dd, J = 12.1, 2.6 Hz, 1H, H-6b),
3.69 (ddd, J = 9.4, 4.9, 2.6 Hz, 1H, H-5), 3.56–3.44 (m, 2 H, H-10),
3.27 (t, J = 6.8 Hz, 1H, H-50), 2.13, 2.08, 2.06 (3 ꢂ s, 4 ꢂ COCH3),
1.66–1.54 (m, 4H, H-20, H-40), 1.49–1.38 (m, 2H, H-30); 13C NMR
(100 MHz, CDCl3)
d
ppm 170.65, 170.01, 169.84, 169.68
(4 ꢂ COCH3), 97.31 (C-1), 76.35 (C-4), 71.31 (C-2), 70.64 (C-5),
70.52 (C-3), 65.45 (C-6), 62.52 (C-10), 51.34 (C-50), 28.57 (C-20),
24.68 (C-40), 23.35 (C-30), 20.83, 20.72, 20.64 (4 ꢂ COCH3); HRMS
(ESI) m/z = 482.17189 [M+Na]+; calculated C19H29N3NaO10
482.17506.
20
Data for 3f, TLC: Rf = 0.42 (50% EtOAc/Petrol); [
a
]
D
+28.9 (c
2.20, CHCl3); 1H NMR (400 MHz, CDCl3) d ppm 5.41 (dd, J = 10.0,
3.3 Hz, 1H, H-30), 5.34 (t, J = 9.6 Hz, 1H, H-4), 5.32–5.25 (m, 3H,
H-3, H-20, H-40), 4.93 (sbr, 2H, H-1, H-10), 4.25(dd, J = 10.8, 4.8 Hz,
2H, H-60a,b), 4.19–4.14 (m, 2H, H-6a,b), 4.11 (dd, J = 7.0, 2.5 Hz,
1H, H-50), 4.03 (t, J = 2.3 Hz, 1H, H-2), 3.91 (ddd, J = 9.3, 3.8,
2.2 Hz, 1H, H-5), 3.73 (td, J = 9.6, 6.3 Hz, 1H, H-1a00), 3.45 (td,
J = 9.0, 6.3 Hz, 1H, H-1b00), 3.30 (t, J = 6.8 Hz, 2H, H-500), 2.16, 2.15,
2.09, 2.05, 2.04, 2.02 (6s, 21H, 7 ꢂ COCH3), 1.68–1.60 (m, 2H,
H-200, H-400), 1.51–1.42 (m, 2H, H-300); 13C NMR (100 MHz, CDCl3)
d ppm 170.48, 169.92, 169.71, 169.54, 169.46 (7 ꢂ COCH3), 99.21
(C-10), 98.23 (C-1), 77.26 (C-2), 70.36 (C-3), 69.81 (C-20), 69.17
(C-50), 68.59 (C-5), 68.33 (C-30), 68.07 (C-100), 66.48, 66.34 (C-4,
C-40), 62.59, 62.25 (C-6, C-60), 51.25 (C-500), 28.96 (C-200), 28.58
(C-400), 23.44 (C-300), 20.92, 20.74, 20.62 (7 ꢂ COCH3); HRMS (ESI):
27. Flory, P. J. Principles of Polymer Chemistry; Cornell University Press, 1953.
28. Nukada, T.; Berces, A.; Whitfield, D. M. J. Org. Chem. 1999, 64, 9030–9045.
29. Fukase, K.; Kinoshita, I.; Kanoh, T.; Nakai, Y.; Hasuoka, A.; Kusumoto, S.
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30. Zhu, Y.; Kong, F. Synlett 2000, 1783–1787.
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35. Doores, K. J.; Fulton, Z.; Hong, V.; Patel, M. K.; Scanlan, C. N.; Wormald, M. R.;
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36. Haq, S.; Whelan, W. J. J. Chem. Soc., Perkin Trans. 1 1956, 4542–4549.
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m/z = 770.25639 [M+Na]+; calculated C31H45N3NaO18 (770.25903).
20
39. Matwiejuk, M.; Thiem, J. Chem. Commun. 2011, 8379–8381.
40. Li, L.; Franckowiak, E. A.; Xu, Y.; McClain, E.; Du, W. J. Polym. Sci. A 2013, 51,
3693–3699.
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419.
Data for 4f, TLC: Rf = 0.21 (50% EtOAc/Petrol); [
a
]
+27.2 (c
D
1.15, CHCl3); 1H NMR (400 MHz, CDCl3) d ppm 5.39 (dd, J = 9.8,
3.3 Hz, 1H, H-3 ), 5.34–5.24 (m, 7H, H-3, H-3 , H-2 , H-2, H-4,
00
0
00
´
H-40, H-400), 5.10 (d, J = 1.5 Hz, 1H, H-100), 4.94 (sbr, 2H, H-1, H-10),
Please cite this article in press as: Schuster, H. J.; et al. Carbohydr. Res. (2014), http://dx.doi.org/10.1016/j.carres.2014.06.021