Neoglycopeptides through direct functionalization of cysteine

Article abstract of DOI:10.1016/j.tetlet.2010.10.021

Neoglycopeptides are readily prepared by direct functionalization of cysteine-containing peptides followed by click triazole formation between the resulting propargylated peptides and protected or free (2-azido)-ethyl gluco-, manno,- and galactopyranosides.

Full text of DOI:10.1016/j.tetlet.2010.10.021

Tetrahedron Letters 52 (2011) 17–20
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Neoglycopeptides through direct functionalization of cysteine
⇑
Christine Vala, Françoise Chrétien, Eva Balentova, Sandrine Lamandé-Langle, Yves Chapleur
UMR 7565 Nancy Université, CNRS Groupe S.U.C.R.E.S, BP 239, F-54506 Nancy Vandoeuvre, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Neoglycopeptides are readily prepared by direct functionalization of cysteine-containing peptides fol-
lowed by click triazole formation between the resulting propargylated peptides and protected or free
Received 23 August 2010
Revised 4 October 2010
Accepted 5 October 2010
Available online 12 October 2010
(2-azido)-ethyl gluco-, manno,- and galactopyranosides.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Neoglycopeptide
Chemical ligation
Cysteine
Azido sugars
1
. Introduction
Post-translational protein glycosylation is an important biolog-
Dondoni7 to connect 1-thiosugars with cysteine-containing pep-
tides. This prompts us to disclose part of our own results along this
line.
ical process which plays a tremendous role in the conformation
and/or biological activity of the protein. Mimicking this type of
enzymatic reaction in a flask using chemical manipulation is still
The synthetic blueprint for connecting a peptide and a sugar is
depicted in Figure 1. The first step is the selective S-propargylation
of the peptide. The second step involves a copper catalyzed Huis-
gen reaction, one of the so-called ‘click chemistry’ reactions, the
efficiency of which, is now well established as a fast and traceless
1
a challenge. The search for general, efficient, and without side-
product chemical reactions to graft two biomolecules has been in-
tense in the last decade. This culminated with the discovery of the
so-called chemical ligation processes, such as native chemical liga-
8
–10
ligation process.
tion, Staudinger ligation,3 ‘click’ Huisgen reaction etc. Most of
these methods require modifications of the biomolecules to link.
In connection with a program of labeling glycopolypeptides and
2
4
H N
2
COOH
H
2
N
COOH
H
1
8
glycoproteins using F labeled sugars, we needed a fast sugar–
peptide ligation process. We reasoned that biologically significant
peptides or proteins often contain a cysteine residue not embedded
Peptide
SH
Peptide
S
cysteine
alkylation
in a disulfide bond. We planned to take advantage of the presence
of the cysteine thiol reactivity.5 The high nucleophilicity of the
OR
O
thiol function of this unique amino-acid can be exploited to pre-
pare S-alkylated derivatives. Ideally, this operation should be car-
Cu(I)
6
RO
O
ried out on
a free peptide and would provide a single
N3
functionalized peptide with an anchoring point allowing the
connection of a properly derivatized sugar. For example, the intro-
duction of a propargyl group on cysteine would allow its subse-
quent use in click triazole formation. To the best of our
knowledge, this possibility of exploiting S-propargyl-cysteine
derivatives for connection to a sugar has not been used until
recently. An elegant solution has recently been proposed by
H N
2
COOH
Peptide
S
OR
O
RO
O
N
N
N
⇑
Corresponding author. Tel.: +33 383 684 773; fax: +33 383 684 780.
E-mail address: yves.chapleur@srsmc.uhp-nancy.fr (Y. Chapleur).
Figure 1. Synthetic strategy for neoglycopeptides construction.
0
040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.10.021

1
8
C. Vala et al. / Tetrahedron Letters 52 (2011) 17–20
OR
derivative 7 in 55% yield. The latter was in turn deprotected by suc-
RO
RO
RO
RO
RO
RO
OR
cessive basic hydrolysis and acidic treatment to provide the known
O
O
O
RO
6
b
N3
free amino-acid 8 in 66% yield.
RO
O
O
OR
OR
A direct method of thiol alkylation on the free peptide was
investigated. To this end glutathione was chosen as a model of free
tripeptide. Glutathione (9) was treated in aqueous basic solution
O
N3
N3
1
2
R = OAc (65%)
R = H
3 R = OAc (65%)
4 R = H
5 R = OAc (60%)
6 R = H
(
2
0.4 N Ba(OH) ) followed by the addition of 1 equiv of freshly dis-
tilled propargyl bromide at room temperature. S-alkylation took
place in 15 h and the S-propargyl-glutathione derivative 10 was
obtained in 81% yield. Proton NMR spectrum of the crude com-
Figure 2. Structures of azido sugar derivatives.
13
pound showed that an almost pure compound was formed bearing
a single propargyl group. Only one signal corresponding to the
propargylic proton was observed at 2.60 ppm. The chemical shifts
observed for the methylene group of the propargyl at 3.29 ppm in
proton NMR and at 18.9 ppm in carbon NMR established the for-
mation of a S-propargyl appendage. Mass spectrum confirmed
the structure (Fig. 3).
S
O
SR
HOOC
N
COOH
R1
O
R2
N
H
N
H
H
NH2
O
O
1
2
9 R = H (Glutathione)
10 R = CH -CCH
7
8
R = BOC, R = Me
Click chemistry was then explored with the three protected
sugars 1, 3, and 5 and the three S-propargyl derivatives 7, 8, and
1
2
R = R = H
2
1
0. The reaction was performed in a 1:1 tert-butyl alcohol–water
Figure 3. Structure of S-propargyl-cysteine derivatives.
mixture using copper(II) acetate as the catalyst in the presence of
1
4
sodium ascorbate as the reducing agent. The results of these cyc-
loadditions are summarized on Table 1. As seen from this Table, the
reactions proceed under very mild conditions giving high yields of
2
. Results
In this model study, we investigated the coupling of 2-azido
1
5,16
the expected 1,2,3-triazoles as the only products
(Fig. 4). Inter-
estingly the reaction medium which became immediately light
green on the addition of copper acetate to the mixture of the al-
kyne and the azide component turned blue within 1–2 h at which
time the reaction was completed as seen from sugar consumption
by TLC.
To test the efficiency of the ligation reaction between water sol-
uble compounds, the click cycloaddition of the sugars 2, 4, and 6
with the tripeptide model glutathione 10 was investigated. In this
case, water was used as the solvent. The reactions proceed equally
well in short time. Treatment consisted of the removal of copper
salts with a chelating resin and gel filtration. Compounds 20–22
were obtained in good yields.
ethyl glycosides of different anomeric configurations. Three pyr-
anosides derivatives of gluco, manno, and galacto configuration
were chosen as the sugar components. Compounds 1, 3, and 5 were
easily prepared by boron trifluoride–etherate catalyzed glycosyla-
tion of the peracetylated sugars with bromoethanol, and subse-
quent bromine substitution by azide carried out in hot DMF. The
11
12
three compounds of b-gluco configuration (1),
and b-galacto (5)
a
-manno (3),
were obtained in 65%, 65%, and 60% yield,
respectively. They were quantitatively deprotected to compounds
1
0k
2
, 4, and 6, respectively, in basic medium (Fig. 2).
On the other hand, several cysteine-containing peptide models
were prepared by S-alkylation under different conditions. Boc-
OMe-cysteine was reacted with propargyl bromide in DMF in the
presence of cesium carbonate6 providing the protected cysteine
Finally, we explored the click ligation of a biologically signifi-
cant peptide, that is, the adhesion peptide Arg-Gly-Asp-Cys
(RGDC). Glycosylation of this peptide and its analogs has been
c
Table 1
Click ligation of azido-carbohydrate and S-propargyl amino-acids and peptides
O
Sugar
S
Cu(OAc)2
O
N
N
Sugar
+
R1
O
R2
S
N
H
N
R2
Na ascorbate
solvent
N3
O
R1
O
N
H
O
Entry
Azido component
Alkyne component
Product
Time (h)
Yield (%)
a
1
2
3
4
5
6
7
8
9
0
1
2
3
4
1
1
1
3
3
3
5
5
5
2
4
6
6
7
8
10
7
8
10
7
11
12
17
13
14
18
15
16
19
20
21
22
25
26
2
73
70
83
90
75
85
73
62
60
66
62
55
52
97
a
2
a
2
a
2
a
2
a
2
a
2
a
8
1
a
10
10
10
10
24
24
1
b
1
1
1
1
1
1
b
1
b
1
b
1
b
27
1
a
The reaction was conducted in a 1:1 tert-butanol–water mixture at room temperature in the presence of 10 mol % of Cu(OAc)
2
–H
2
O and 20 mol % of sodium ascorbate.
b
The reaction was conducted in water at room temperature in the presence of 10 mol % of Cu(OAc) –H O and 20 mol % of sodium ascorbate.
2 2

C. Vala et al. / Tetrahedron Letters 52 (2011) 17–20
19
N
N
N
explored and proved useful to target tumor cells and for imaging of
1
7
OAc
O
S
tumor angiogenesis. We chose to use two free carbohydrates, the
galactoside 6 and the 6-fluoro-6-deoxy glucoside 27. Commercially
available RGDC (23) was first propargylated as above by treatment
with propargyl bromide in water in the presence of a base for 1 h. A
cleaner compound was obtained when using ammonia as a base.7
NMR of the crude 24 showed almost one species in up to 85% pur-
ity. Only one signal corresponding to the propargylic proton was
observed at 2.63 ppm. The crude compound 24 was then reacted
with the appropriate azido compound in water. Although the reac-
tion was difficult to monitor it appeared from color changing that
the reaction was completed within 1–2 h. Copper ions’ removal
and gel filtration gave the two cycloadducts 25 and 26 in 52%
AcO
AcO
R1
O
O
R2
N
H
OAc
O
1
1
1 R1 = BOC, R2 = Me
2 R = R = H
1
2
AcO
AcO
OAc
O
N
N
N
S
AcO
R1
O
O
R2
N
H
1
8
O
and 67% yield, respectively (Fig. 5 and Table 1).
3 R1 = BOC, R2 = Me
4 R = R = H
From these results it appears that S-propargyl-cysteine deriva-
tives including highly functional tri and tetrapeptides are easily
available in a highly regiospecific manner by the treatment of free
peptides with propargyl bromide in basic medium. This simple
derivatization can be performed in the presence of carboxylic, ami-
no, and guanidino groups. 2-Azido ethyl glycosides react efficiently
with these alkynylated peptides in a click Huisgen reaction, what-
1
1
1
2
N N
N
AcO OAc
O
S
AcO
O
R1
O
R2
N
H
OAc
ever the sugar configurations (a-gluco, b-manno and a-galacto)
O
and the anomeric configuration. The reaction proceeds well in
water in short times and high yields and tolerates the presence
of a fluorine atom on the sugar.
1
1
5 R1 = BOC, R2 = Me
6 R1 = R2 = H
In conclusion, the facile propargylation of cysteine residues and
the excellent reactivity of the resulting S-propargyl ether with azi-
do ethyl glycosides provide an easy and fast ligation method of
sugars with cysteine-containing peptides. We are currently explor-
ing the use of this method on more complex biologically significant
peptides with the aim of constructing labeled glycopeptides from
labeled sugars.
N
N
N
S
O
R
O
H
N
HOOC
COOH
N
H
NH2
Acknowledgments
17 R = tetra-0-acetyl-β-D-glucopyranosyl
1
1
2
8 R = tetra-0-acetyl-α-D-mannopyranosyl
9 R = tetra-0-acetyl-β-D-galactopyranosyl
0 R = β-D-glucopyranosyl
We thank the European Commission for a fellowship to C.V.
Project N°516.984) the Région Lorraine and Université Henri Poin-
caré Nancy 1 for a postdoctoral fellowship to E.B., and Professor A.
Luxen and Drs. J. Aerts and C. Lemaire (Université de Liège, Bel-
gium) for helpful discussions. We are indebted to B. Fernette and
F. Dupire for recording NMR and mass spectra, respectively.
(
2
2
1 R = α-D-mannopyranosyl
2 R = β-D-galactopyranosyl
Figure 4. Structure of glutathione–sugar adducts.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2010.10.021.
SR
NH
O
H
N
O
References and notes
H N
N
H
N
H
N
COOH
2
H
NH2
O
N
1. Bertozzi, C. R.; Kiessling, L. L. Science 2001, 291, 2357–2364; Davis, B. G. Chem.
Rev. 2002, 102, 579–602; Nicotra, F.; Cipolla, L.; Peri, F.; Ferla, B. L.; Redaelli, C.
In Chemoselective Neoglycosylation Advances in Carbohydrate Chemistry and
Biochemistry; Academic Press: New York, 2007; Vol. 61. pp 353–398; Specker,
D.; Wittmann, V. Synthesis and Application of Glycopeptide and Glycoprotein
Mimetics Topics in Current Chemistry 2007, 267, 65–107.
COOH
2
2
3 R = H (RGDC)
4 R = CH -CCH
2
N
2. Dawson, P. E.; Muir, T. W.; Clark-Lewis, I.; Kent, S. B. H. Science 1994, 266, 776.
HO
HO
OH
O
N
3.
(a) Saxon, E.; Bertozzi, C. R. Science 2000, 287, 2007–2010; (b) Saxon, E.;
Armstrong, J. I.; Bertozzi, C. R. Org. Lett. 2000, 2, 2141–2143; (c) Nilsson, B. L.;
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Wong, C. ChemBioChem 2006, 7, 429–432.
2
2
5 R =
6 R =
O
HO
N
F
N
N
4.
(a) Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, B. K. K. Angew. Chem.,
Int. Ed. 2002, 41, 2596–2599; (b) Tornøe, C. W.; Christensen, C.; Meldal, M. J.
Org. Chem. 2002, 67, 3057–3064; For a review see: (c) Meldal, M.; Tornøe, C. W.
Chem. Rev. 2008, 108, 2952–3015.
O
HO
HO
O
HO
F
N3
5. For direct cysteine modification on protein surface see for example: Bernardes,
G. J. L.; Chalker, J. M.; Errey, J. C.; Davis, B. G. J. Am. Chem. Soc. 2008, 130, 5052–
5053.
6. For the S-alkylation of cysteine see: (a) du Vigneaud, V.; Loring, H. S.; Craft, H.
A. J. Biol. Chem. 1934, 105, 481–488; (b) Marrone, L.; Siemann, S.; Beecroft, M.;
Viswanatha, T. Bioorg. Chem. 1996, 24, 401–416; (c) Struthers, H.; Spingler, B.;
O
HO
HO
2
7 R =
O
HO
Figure 5. Structure of RGDC–sugar adducts.

2
0
C. Vala et al. / Tetrahedron Letters 52 (2011) 17–20
2
5
O); 1H NMR (D
O, 400 MHz): d 2.19 (m,
2 2
Mindt, T. L.; Schibli, R. Chem. Eur. J. 2008, 14, 6173–6183; (d) Kalai, T.; Hubbell,
W. L.; Hideg, K. Synthesis 2009, 1336–1340.
Lo Conte, M.; Pacifico, S.; Chambery, A.; Marra, A.; Dondoni, A. J. Org. Chem.
white solid, ½
aꢀ
ꢁ20.4 (c 0.4, H
D
2H), 2.55 (m, 2H), 2.88 (dd, 1H, J = 8 Hz, J = 14 Hz), 3.08 (dd, 1H, J = 5 Hz,
J = 14 Hz), 3.27(dd, 1H, J = 8.5 Hz), 3.36–3.55 (m, 3H), 3.69 (dd, 1H, J = 6 Hz,
J = 13 Hz), 3.75–3.95 (m, 6H), 4.15 (m, 1H), 4.33 (m, 2H), 4.45 (d, 1H, J = 8 Hz,
7
8
.
.
2
010, 75, 4644–4647.
For reviews on the use of click cycloaddition in carbohydrate chemistry see: (a)
Dedola, S.; Nepogodiev, S. A.; Field, R. A. Org. Biomol. Chem. 2007, 5, 1006–1017;
H-1), 4.56 (dd, 1H, J = 4.8 Hz, J = 9 Hz), 4.72 (dd, 1H, J = 5 Hz, H
1H, C@CH); 13C NMR (D
O, 100 MHz): d 25.6 (CH ), 26.5 (CH ), 31.7 (CH
(CH ), 43.7 (CH Gly), 50.7 (CH ), 53.1 (CH Cys), 54.4 (CH Glu), 61.0 (CH
68.4 (CH ), 69.9 (CH-4), 73.3 (CH-5), 75.9 (CH-2), 76.2 (CH-3), 102.7 (CH
anomer), 125.1 (CH triazole), 145.1 (C@C), 172.2 (CO), 174.3 (CO), 175.2 (CO),
a
Glu), 8.08 (s,
), 33.1
-6),
2
2
2
2
(
b) Wilkinson, B. L.; Bornaghi, L. F.; Houston, T. A.; Poulsen, S.-A. Drug Des. Res.
2
2
2
2
Perspect. 2007, 57–102; (c) Santoyo-Gonzalez, F.; Hernandez-Mateo, F. Top.
Heterocycl. Chem. 2007, 7, 133–177; Amblard, F.; Cho, J. H.; Schinazi, R. F. Chem.
Rev. 2009, 109, 4207–4220.
2
+
176.6 (CO); MS (HR-ESI) calcd for C21
found: 639.1672. S-[[1-[2-[(b- -Mannopyranosyl)oxy]ethyl]-1H-1,2,3-triazol-4-
yl]methyl]-
-glutathione (21): white solid, ½
400 MHz): d 2.13 (m, 2H, Hb Glu), 2.50 (m, 2H, H
3.05 (m, 2H), 3.59 (dd, 1H, J = 9.5 Hz, J = 9.5 Hz), 3.61–4.0 (m, H), 4.10 (m, 1H),
4.54 (dd, 1H, J = 5 Hz, J = 9 Hz, H
Cys), 4.67 (m, 2H), 8.03 (s, 1H, C@CH); 13
NMR (D O, 100 MHz): d 25.6 (CH ), 27.1 (CH ), 31.8 (CH ), 33.1 (CH ), 43.7 (CH
Gly), 50.5 (CH ), 53.1 (CH Cys), 54.6 (CH Glu), 61.0 (CH -6), 65.8 (CH
H
33
N
6
2
Na O
12S [MꢁH+2Na] 639.1673,
9
.
For the use of click cycloaddition between carbohydrate and amino-acids see:
D
2
5
O); 1H NMR (D
c Glu), 2.85 (m, 1H, Hb Cys),
(
2
a) dos Ajos, J. V.; Sinou, D.; de Melo, S. J.; Srivastava, R. M. Synthesis 2007,
647–2652; (b) Hotha, S.; Kashyap, S. J. Org. Chem. 2006, 71, 852; (c) Groothuys,
L
aꢀ
ꢁ3.5 (c 0.4, H O,
2
2
D
S.; Kuijpers, B. H. M.; Quaedflieg, P. J. L. M.; Roelen, H. C. P. F.; Wiertz, R. W.;
Blaauw, R. H.; van Delft, F. L.; Rutjes, F. P. J. T. Synthesis 2006, 3146–3152; (d)
Arosio, D.; Bertoli, M.; Manzoni, L.; Scolastico, C. Tetrahedron Lett. 2006, 47,
a
C
2
2
2
2
2
2
3
7
2
(
697–3700; (e) Wan, Q.; Chen, J.; Chen, G.; Danishefsky, S. J. J. Org. Chem. 2006,
1, 8244–8249; (f) Dondoni, A.; Giovannini, P. P.; Massi, A. Org. Lett. 2004, 6,
929–2932; (g) Lin, H.; Walsh, C. T. J. Am. Chem. Soc. 2004, 126, 13998–14003;
h) Kuijpers, B. H. M.; Groothuys, S.; Keereweer, A. B. R.; Quaedflieg, P. J. L. M.;
Blaauw, R. H.; van Delft, F. L.; Rutjes, F. P. J. T. Org. Lett. 2004, 6, 3123–3126.
2
2
2
), 66.7 (C-
4), 70.2 (C-5), 70.7 (C-2), 73.1 (C-3), 99.9 (CH anomer), 125.0 (CH triazole),
145.3 (C@C), 172.2 (CO), 175.3 (CO), 175.4 (CO), 176.6 (CO); MS (HR-ESI) calcd
ꢁ
for
C
21
H
33
N
6
O
12
S
[MꢁH]
593.1883, found: 593.1905. S-[[1-[2-[(b-
-glutathione (22):
O, 400 MHz): d 2.13 (m,
D-
Galactopyranosyl)oxy]ethyl]-1H-1,2,3-triazol-4-yl]methyl]-
L
2
5
O); 1H NMR (D
1
0. For recent references on glycoconjugate constructions using click cycloaddition
see: Zhang, X.; Yang, X.; Zhang, S. Synth. Commun. 2009, 39, 830–844; (b)
Haddleton, D. M.; Geng, J.; Mantovani, G.; Lindqvist, J. Polym. Prepr. 2008, 49,
white solid, ½
aꢀ
ꢁ14.2 (c 0.6, H
2
2
D
2H), 2.50 (m, 2H), 2.84 (dd, 1H, J = 8 Hz, J = 14 Hz), 3.05 (dd, 1H, J = 5 Hz,
J = 14 Hz), 3.48 (dd, 1H, J = 8 Hz, J = 9 Hz), 3.60–3.8 (m, 8H), 3.90 (m, 3H), 4.11
(m, 1H), 4.28 (m, 1H), 4.35 (d, 1H, J = 8 Hz, H-1), 4.51 (dd, 1H, J = 4.8 Hz,
6
02–603; (c) Yoon, S.; Hwang, S. H.; Ko, W. B. J. Nanosci. Nanotechnol. 2008, 8,
3
136–3141; (d) Chabre, Y. M.; Contino-Pepin, C.; Placide, V.; Shiao, T. C.; Roy, R.
J = 9 Hz), 4.72 (dd, 1H, J = 5 Hz), 8.05 (s, 1H, C@CH); 13C NMR (D
2
O, 100 MHz): d
Gly), 50.7 (CH ), 53.1
), 68.9 (CH), 70.9 (CH), 73.0
2
), 103.4 (CH anomer), 125.2 (CH), 145.1 (C@C), 172.2 (CO), 175.0
J. Org. Chem. 2008, 73, 5602–5605; (e) Ziegler, T.; Hermann, C. Tetrahedron Lett.
008, 49, 2166–2169; (f) Vecchi, A.; Melai, B.; Marra, A.; Chiappe, C.; Dondoni,
25.6 (CH
(CH Cys), 54.6 (CH Glu), 61.3 (CH
(CH), 75.5 (CH
2
), 26.9 (CH
2
), 31.8 (CH
2
), 33.1 (CH
2
), 43.7 (CH
2
2
2
2
-6), 68.4 (CH
2
A. J. Org. Chem. 2008, 73, 6437–6440; (g) Marra, A.; Vecchi, A.; Chiappe, C.;
Melai, B.; Dondoni, A. J. Org. Chem. 2008, 73, 2458–2461; (h) Dondoni, A.;
Marra, A. J. Org. Chem. 2006, 71, 7546–7557; (i) Perez-Balderas, F.; Ortega-
Munoz, M.; Morales-Sanfrutos, J.; Hernandez-Mateo, F.; Calvo-Flores, F. G.;
Calvo-Asin, J. A.; Isac-Garcia, J.; Santoyo-Gonzalez, F. Org. Lett. 2003, 5, 1951–
2ꢁ
(CO), 175.3 (CO), 176.6 (CO); MS (HR-ESI) calcd for C21
296.0905, found: 296.0920.
H
32
6
N O
12S [Mꢁ2H]
17. (a) Owen, R. M.; Carlson, C. B.; Xu, J.; Mowery, P.; Fasella, E.; Kiessling, L. L.
ChemBioChem 2007, 8, 68–82; (b) Schottelius, M.; Laufer, B.; Kessler, H.;
Wester, H.-J. Acc. Chem. Res. 2009, 42, 969–980; (c) Kuijpers, B. H. M.;
Groothuys, S.; Soede, A. C.; Laverman, P.; Boerman, O. C.; van Delft, F. L.; Rutjes,
F. P. J. T. Bioconjugate Chem. 2007, 18, 1847–1854; For a review see (d) Haubner,
R.; Wester, H. J. Curr. Pharm. Des. 2004, 10, 1439–1455.
1
954; (j) Fazio, F.; Wong, C.-H. Tetrahedron Lett. 2003, 44, 9083–9085; (k) Fazio,
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4397–14402.
1
1
1
1. Mackie, D. M.; Maradufu, A.; Perlin, A. S. Carbohydr. Res. 1986, 150, 23.
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Trans. 1 2001, 823–831.
18. Selected data of neoglycopeptides prepared from RGDC: Arg-Gly-Asp-Cys-S-[[1-[2-
[b-
D
25
D
-galactopyranosyl)oxy]ethyl]-1H-1,2,3-triazol-4-yl]methyl] (25): white solid,
2
5
O); 1H NMR (D
Glu),
O); 1H NMR (D
1
3. Selected data for 10: white solid, ½
a
ꢀ
ꢁ22.9 (c 1.5, H
2
2
O,
½
a
ꢀ
ꢁ14.8 (c 0.4, H
2 2
O, 400 MHz): d 1.64 (m, 2H), 1.73 (m, 2H),
D
4
00 MHz): d 2.07 (dd, 2H, J = 7.5 Hz, J = 15.0 Hz, Hb Glu), 2.45 (m, 2H, H-
c
2.61 (dd, 1H, J = 8 Hz, J = 16 Hz), 2.74 (dd, 1H, J = 4 Hz, J = 16 Hz), 2.86 (dd, 1H,
J = 5 Hz, J = 7 Hz), 2.98 (dd, 1H, J = 4.5 Hz, J = 14 Hz), 3.18–3.29 (m, 3H), 3.48
(dd, 1H, J = 8.5 Hz, J = 8.5 Hz), 3.56–3.80 (m, 2H), 3.84–3.98 (m, 5 H), 4.06–4.15
2
3
H-
2
5
.60 (dd, 1H, J = 2.5 Hz, H-alkyne), 2.92 (dd, 1H, J = 9.0, J = 14.5 Hz, H-b Cys),
0
.18 (dd, 1H, J = 5.0 Hz, H-b Cys), 3.29 (m, 2H, H-
c
Cys), 3.70 (m, 3H, H-
O, 100 MHz): d 18.9 (C-
Glu), 32.7 (C-b Cys), 43.4 (C- Gly), 52.8 (C-
a Glu,
1
3
13
a
Gly), 4.65 (dd, 1H, H-
a
Cys); C NMR (D
2
c
Cys),
Cys),
(m, 3H), 4.26–4.38 (m, 4H), 4.64–4.70 (m, 2H), 8.04 (s, 1H, C@CH); C NMR
6.2 (C-b Glu), 31.4 (C-
4.1 (C-
c
a
a
(D
41.1 (CH
68.3 (CH
2
O, 100 MHz): d 24.3 (CH
2
), 25.6 (CH
), 50.7 (CH ), 51.8 (CH), 54.2 (CH), 54.7 (CH), 61.3 (CH
), 68.9 (CH), 70.9 (CH), 73.0 (CH), 75.5 (CH), 103.4 (CH anomer), 125.2
2
), 30.9 (CH
2
), 33.7 (CH
2
), 38.6 (CH
2
),
a
Glu), 72.5 (CH alkyne), 80.3 (C alkyne), 171.8 (CO), 173.9 (CO), 174.9
2
), 42.7 (CH
2
2
2
-6),
+
(
CO), 176.2 (CO); MS (ESI) 368.2 [M+Na] .
2
1
4. General procedure for S-propargyl peptides and free sugars adduct formation: To a
solution of crude S-propargyl derivative (0.2 mmol), of the azido sugar
(CH), 145.2 (C@C), 157.1 (C@NH), 171.4 (CO), 172.9 (CO), 176.7 (CO), 178.0
(CO), 178.3 (CO); MS (HR-ESI) calcd for C26
10NaO13S [M+Na]+ 759.2708,
found: 759.2703. Arg-Gly-Asp-Cys-S-[[1-[2-[6-deoxy-6-fluoro-b-
glucopyranosyl)oxy]ethyl]-1H-1,2,3-triazol-4-yl]methyl] (26): white solid, ½
O); 1H NMR (D
O, 400 MHz): d 1.7 (m, 2H), 1.96 (m, 2H), 2.61
(dd, 1H, J = 8 Hz, J = 16 Hz), 2.74 (dd, 1H, J = 4 Hz, J = 16 Hz), 2.86 (dd, 1H,
J = 5 Hz, J = 7 Hz), 2.98 (dd, 1H, J = 4.5 Hz, J = 14 Hz), 3.18–3.29 (m, 3H), 3.43–
3.60 (m, 3H), 3.86 (s, 2H), 3.97 (d, 1H, J = 10 Hz), 4.06–4.28 (m, 3H), 4.24–4.38
(m, 3H), 4.44 (d, 1H, J = 5 Hz), 4.6–4.74 (m, 3H), 8.01 (s, 1H, C@CH); 13C NMR
44
H N
(
0.2 mmol) and sodium ascorbate (8 mg, 0.04 mmol) in water (4 ml) was
D-
25
added, at room temperature a solution of copper(II) acetate (4 mg, 0.02 mmol)
in water (0.5 ml). The solution turned immediately pale green. The reaction
was stopped when the intense blue color reappeared. Chelex resin (500 mg)
was then added to the blue solution and the suspension was stirred until the
solution became colorless. The resin was filtered off and the resulting solution
was freeze-dried. Purification was achieved by LH20 gel filtration. Elution with
water provided pure triazole.
aꢀ
D
ꢁ25.1 (c 0.3, H
2
2
(D
40.7 (CH
73.2 (CH
(CH), 145.3 (C), 157.1 (C@N), 170.5 (CO), 171.1 (CO), 172.9 (CO), 176.7 (CO),
2
O, 100 MHz): d 23.7 (CH
), 42.8 (CH ), 50.7 (CH
), 74.6 (CH), 75.7 (CH), 81.4 (CH), 83.0 (CH), 102.9 (CH anomer), 125.2
2
), 25.6 (CH
2
), 28.3 (CH
2 2 2
), 33.7 (CH ), 38.5 (CH ),
1
5. It must be noted that the 1,4 triazole is the major product but is often
contaminated by less than 10% of another yet unknown compound which is
not 1,5 triazole as seen from proton and carbon NMR spectra. The structure of
the latter was also established on the basis of carbon NMR (see Ref. 10h).
2
2
2
), 52.0 (CH
2
), 53.2 (CH), 54.6 (CH), 68.5 (CH),
2
178.2 (CO); 19F NMR (D
(HR-ESI) calcd for C26
O, 235 MHz): d ꢁ235 (ddd, J = 46 Hz, J = 24 Hz); MS
2
1
6. Selected data of neoglycopeptides prepared from glutathione: S-[[1-[2-[b-
D-
H
42FN10
O
12S [MꢁH]ꢁ 737.2688, found: 737.2710.
glucopyranosyl)oxy]ethyl]-1H-1,2,3-triazol-4-yl]methyl]- -glutathione (20):
L