R. M. J. Liskamp and H.-J. Gabius, ChemBioChem, 2001, 2, 822;
J. A. F. Joosten, N. T. H. Tholen, F. Ait El Maate, A. J. Brouwer,
G. W. van Esse, D. T. S. Rijkers, R. M. J. Liskamp and R. J. Pieters,
Eur. J. Org Chem., 2005, 3182.
3 (a) G. R. Newkome, C. N. Moorefield and F. V o¨ gtle, Dendrimers and
Dendrons: Concepts, Syntheses, Applications, Wiley, New York, 2001;
active fragment, connected to an v-aminohexanoic acid spacer)
and the cyclo RGD azido peptide 14 (an a integrin binding
) were coupled to alkynes 2
and 3. The divalent and tetravalent peptides 26, 28, 30 and 27, 29,
1, respectively (Fig. 2) were obtained after purification by HPLC
V 3
b
16,17
RGD peptide for tumor targeting
3
(b) J. M. J. Fr e´ chet, Proc. Natl. Acad. Sci. USA, 2002, 99, 4782.
in yields ranging from 14 to 84%. These peptides were identified by
MALDI-TOF analysis. Most challenging was the coupling of 4th
generation dendrimer (16 end-groups) 5 with cyclo RGD azido
peptide 14 in order to obtain a hexadecavalent peptide dendrimer.
HPLC analysis after work-up showed that the starting materials
were consumed. However, so far we have been unable to
characterize this construct by MALDI-TOF mass spectrometry.
By SDS-PAGE bands were visible corresponding to a molecular
weight ranging between 53000–65000 Da, corresponding to an
aggregate in a tetra- or pentamer.
4
G. T. Hermanson, Bioconjugate Techniques, Academic Press Limited,
London, UK, 1996; A. Garman, Non-radioactive Labelling: A Practical
Approach, Academic Press Limited, London, UK, 1997. For recent
examples of dendrimer modification using chemical ligation and/or
sulfhydryl groups see: I. Van Baal, H. Malda, S. A. W. Reulen,
T. M. Hackeng, M. Merkx and E. W. Meijer, Abstracts of Papers,
229th ACS National Meeting, San Diego, CA, United States,
March 13–17, 2005 (2005); A. Herrmann, G. Mihov,
G. W. M. Vandermeulen, H.-A. Klok and K. M u¨ llen, Tetrahedron,
2
003, 59, 3925; G. Mihov, D. Grebel-Koehler, A. L u¨ bbert,
G. W. M. VanderMeulen, A. Herrmann, H-A. Klok and K. M u¨ llen,
Bioconjugate Chem., 2005, 16, 283; I. Van Baal, H. Malda,
S. A. Synowsky, J. L. T. van Dongen, T. M. Hackeng, M. Merkx
and E. W. Meijer, Angew. Chem., Int. Ed., 2005, 44, 5052.
R. Huisgen, R. Knorr, L. Mobius and G. Szeimies, Chem. Ber., 1965,
98, 4014.
In conclusion, we have developed an efficient microwave-
assisted Huisgen 1,3-dipolar cycloaddition reaction for the
synthesis of di-, tetra-, octa- and hexadecavalent dendrimeric
peptides. Not only small peptide-based azides but also unprotected
biologically relevant larger - even cyclic - azido peptides are
efficiently converted into the corresponding multiple cycloaddition
products. These multivalent dendrimeric peptides may be useful
in the preparation of synthetic vaccines or for example in the
diagnosis and treatment of infections, where by multivalency the
biological activity can be enhanced significantly. In addition, this
methodology may provide access to the rapid synthesis of
highly functionalized dendrimers as possible protein mimics. The
synthesis and biological evaluation of multivalent dendrimeric
peptides including protein mimics is under current investigation in
our laboratory.§
5
6 C. W. Tornøe, C. Christensen and M. Meldal, J. Org. Chem., 2002, 67,
3057.
7
8
V. V. Rostovtsev, L. G. Green, V. V. Fokin and K. B. Sharpless,
Angew. Chem. Int. Ed., 2002, 41, 2596.
For recent reviews and applications see: R. Breinbauer and M. K o¨ hn,
ChemBioChem, 2003, 4, 1147; Q. Wang, R. Chan, R. Hilgraf,
V. V. Fokin, K. B. Sharpless and M. G. Finn, J. Am. Chem. Soc.,
2003, 125, 3192.
9
S. J. E. Mulders, A. J. Brouwer, P. G. J. van der Meer and
R. M. J. Liskamp, Tetrahedron Lett., 1997, 38, 631; S. J. E. Mulders,
A. J. Brouwer and R. M. J. Liskamp, Tetrahedron Lett., 1997, 38, 3085;
A. J. Brouwer, S. J. E. Mulders and R. M. J. Liskamp, Eur. J. Org.
Chem., 2001, 1903; A. J. Brouwer and R. M. J. Liskamp, Eur. J. Org.
Chem., 2005, 487.
10 H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew. Chem. Int. Ed.,
2001, 40, 2004; B. Helms, J. L. Mynar, C. J. Hawker and J. M. J. Fr ´e chet,
J. Am. Chem. Soc., 2004, 126, 15020; P. Wu, A. K. Feldman,
A. K. Nugent, C. J. Hawker, A. Scheel, B. Voit, J. Pyun, J. M. J. Frechet,
K. B. Sharpless and V. V. Fokin, Angew. Chem. Int. Ed., 2004, 43, 2938.
Notes and references
{
General procedure as illustrated for 16: Alkyne 3 (57 mg, 84 mmol,
equiv) and azide 6 (70 mg, 545 mmol, 1.6 equiv per arm) were dissolved in
1
THF/H
followed by CuSO
11 K. A. Savin, M. Robertson, D. Gernert, S. Green, E. J. Hembre and
J. Bishop, Mol. Diversity, 2003, 7, 171; P. Appukkuttan, W. Dehaen,
V. V. Fokin and E. Van der Eycken, Org. Lett., 2004, 6, 4223.
12 Azide 6 was prepared according to: S. G. Alvarez and M. T. Alvarez,
Synthesis, 1997, 413. Azides 7–10, 13 and 14 were synthesized according
to: J. T. Lundquist, IV and J. C. Pelletier, Org. Lett., 2001, 3, 781. azido
peptides 11 and 12 were synthesized according to: D. T. S. Rijkers,
H. H. R. van Vugt, H. J. F. Jacobs and R. M. J. Liskamp, Tetrahedron
Lett., 2002, 43, 3657.
13 For a recent review concerning peptide-based dendrimers: L. Crespo,
G. Sanclimens, M. Pons, E. Giralt, M. Royo and F. Albericio, Chem.
Rev., 2005, 105, 1663. Peptide-based dendrimers are also reviewed in
reference 3a.
2
O (2 mL, 1/1) and Na-ascorbate (8 mg, 40 mmol, 50 mol%)
)?5H O (1 mg, 4 mmol, 5 mol%) were added. The
4
2
reaction mixture was placed in the microwave reactor (Biotage) and
irradiated at 100 uC during 5 min. The precipitate was filtered off, washed
with ice-cold MeOH and dried in a desiccator. Compound 16 was obtained
1
as a white solid in 91% yield. R
NMR (300 MHz, DMSO-d
.81 (s, 3H), 4.17 (q, 8H, J 5 7.14 Hz), 4.21 (m, 4H), 5.21 (s, 8H), 5.42 (s,
H), 6.82 (m, 1H), 6.91 (m, 2H), 7.09 (m, 2H), 7.15 (m, 4H), 8.24 (s, 4H),
f
(CHCl
3
/MeOH/AcOH 95/20/3): 0.68; H-
6
): d 1.21 (t, 12H, J 5 7.14 Hz), 3.59 (m, 4H),
3
8
13
8.63 (t, 2H); C-NMR (75 MHz, DMSO-d
6
): d 14.2, 40.5, 50.6, 52.5, 61.5,
61.7, 66.6, 104.5, 106.6, 107.8, 126.3, 131.8, 136.5, 142.7, 159.2, 159.9, 166.1,
+
1
1
67.4; MALDI-TOF: calcd for C54
62
H N
14
O
18: 1194.437, found: [M + H]
195.597, [M + Na] 1217.578; elemental analysis calcd for C54
C 54.27%, H 5.23%, N 16.41%, found: C 54.16%, H 5.17%, N 16.22%.
Patent pending.
+
H N
62 14
O
18
:
14 Tesser’s base is a mixture of dioxane, methanol and aq. NaOH, see:
G. I. Tesser and I. C. Balvert-Geers, Int. J. Peptide Protein Res., 1975, 7,
295.
§
15 M. Zasloff, Proc. Natl. Acad. Sci. USA, 1987, 84, 5449.
1
2
M. Mammen, S.-K. Choi and G. M. Whitesides, Angew. Chem. Int. Ed.,
998, 37, 2754.
R. Autar, A. S. Khan, M. Schad, J. Hacker, R. M. J. Liskamp and
R. J. Pieters, ChemBioChem, 2003, 4, 1317; J. A. F. Joosten,
V. Loimaranta, C. C. M. Appeldoorn, S. Haataja, F. Ait El Maate,
R. M. J. Liskamp, J. Finne and R. J. Pieters, J. Med. Chem., 2004, 47,
6499; D. Arosio, I. Vrasidas, P. Valentini, R. M. J. Liskamp, R. J. Pieters
and A. Bernardi, Org. Biomol. Chem., 2004, 2, 2113; S. Andr e´ ,
R. J. Pieters, I. Vrasidas, H. Kaltner, I. Kuwabara, F.-T. Liu,
16 R. Haubner, R. Gratias, B. Diefenbach, S. L. Goodman, A. Jonczyk
and H. Kessler, J. Am. Chem. Soc., 1996, 118, 7461.
1
17 R. Haubner, H.-J. Wester, F. Burkhart, R. Senekowitsch-Schmidtke,
W. Weber, S. L. Goodman, H. Kessler and M. Schwaiger, J. Nucl.
Med., 2001, 42, 326; M. L. Janssen, W. J. Oyen, I. Dijkgraaf,
L. F. Massuger, C. Frielink, D. S. Edwards, M. Rajopadhye,
H. Boonstra, F. H. Corstens and O. C. Boerman, Cancer Res., 2002,
62, 6146; G. Thurmshirn, U. Hersel, S. L. Goodman and H. Kessler,
Chem. Eur. J., 2003, 9, 2717.
This journal is ß The Royal Society of Chemistry 2005
Chem. Commun., 2005, 4581–4583 | 4583