Efficient synthesis of phosphorus-containing dendrimers capped with isosteric functions of amino-bismethylene phosphonic acids

Article abstract of DOI:10.1016/j.tetlet.2009.02.127

An efficient synthetic strategy to synthesize phosphorus-containing dendrimers capped with isosteric acid functions derived from tyramine is described. The method is demonstrated on a first generation dendrimer that can be easily capped with 12 amino(bism

Full text of DOI:10.1016/j.tetlet.2009.02.127

Tetrahedron Letters 50 (2009) 2078–2082
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Efficient synthesis of phosphorus-containing dendrimers capped
with isosteric functions of amino-bismethylene phosphonic acids
c
d
d
Olivier Rolland a,b, Cédric-Olivier Turrin a,b, , Gérard Bacquet , Remy Poupot , Mary Poupot ,
*
Anne-Marie Caminade a,b, , Jean-Pierre Majoral
a,b,
*
*
a CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, F-31077 Toulouse, France
b Université de Toulouse, UPS, INPT, LCC, F-31077 Toulouse, France
c Rhodia, Centre de Recherches d’Aubervilliers 52 rue de la Haie Coq, F-93308 Aubervilliers Cedex, France
d INSERM 563, Centre de Physiopathologie de Toulouse-Purpan, Hôpital Purpan, BP 3048, F-31024, Toulouse Cedex 03, France
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient synthetic strategy to synthesize phosphorus-containing dendrimers capped with isosteric
acid functions derived from tyramine is described. The method is demonstrated on a first generation den-
drimer that can be easily capped with 12 amino(bismethylene) sulfonic acids and amino(bismethylene)
carboxylic acids that are strict analogs of the corresponding amino(bismethylene) phosphonic acids.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 15 January 2009
Revised 11 February 2009
Accepted 16 February 2009
Available online 21 February 2009
Keywords:
Dendrimers
Phosphonate
Sulfonate
Carboxylate
Polyanions
Dendrimers1 have generated a tremendous interest for many
applications ranging from materials science to biomedical applica-
tions. These macromolecules exhibit a high density of surface func-
tions that can be easily tuned according to the field of application.
Charged dendrimers are generally water-soluble compounds use-
ful for biomedical applications,2 and polyanionic dendrimers have
proven to be less toxic than polycationic ones.3 In this regard, sev-
eral routes have been described to synthesize various dendrimeric
scaffolds capped with carboxylic acid functions,4 and to a lesser ex-
tent to synthesize dendrimers capped with sulfonic acid5 or phos-
phonic acid functions.6 We have recently developed a versatile
approach to build PPH (PolyPhosphorHydrazone) dendrimers
equipped with a wide variety of phosphonate and phosphonic acid
functions located on their outer-shell6 and even at their focal
point.7 Some of these new highly phosphorylated PPH dendrimers
allow the dramatic promotion of (NK) Natural Killer cells8 as well
as the activation of monocytes9 from healthy human peripheral
blood mononuclear cells in cultures. NK cells and monocytes are
two subpopulations of the immune system strongly involved in
the first steps of the immune response, and the triggering of their
activity is of great interest for cell-based therapies, immunothera-
pies, or anti-inflammatory purposes.10 Among the series of com-
pounds that were assayed, dendrimer 1, a first-generation PPH
dendrimer with a cyclo(triphosphazene) core and 12 tyramine-
based amino(bismethylene) phosphonic acid surface functions on
its outer shell, was identified as a lead compound (Fig. 1). In order
to conduct a relevant structure–activity relationship study, we
were particularly interested in the replacement of phosphonic acid
groups located at the periphery of the lead compound 1 by strictly
analogous functional groups. In fact, phosphonic acids belong to
non-classical isosteric family of carboxylate functional groups as
well as sulfonamide, tetrazole, and sulfonate moieties do.11 Within
this category, we elicited functional groups having the primary
location of the negative charge on oxygen atom (carboxylic, phos-
phonic, and sulfonic acids), and not on nitrogen atom (tetrazole
PO3HNa
S
P
N
[N=P]3
O
O
PO3HNa
N
N
* Correspondingauthors.Tel.:+33(0)561333134;fax:+33(0)561553003(C.-O.T.);
tel.: +33 (0)561 333 125; fax: +33 (0)561 553 003 (A.-M.C.); tel.: +33 (0)561 333 123;
fax: +33 (0)561 553 003 (J.-P.M.).
2
6
1
E-mail addresses: turrin@lcc-toulouse.fr (C.-O. Turrin), caminade@lcc-toulouse.fr
(A.-M. Caminade), majoral@lcc-toulouse.fr (J.-P. Majoral).
Figure 1. Lead compound 1.
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.02.127

O. Rolland et al. / Tetrahedron Letters 50 (2009) 2078–2082
2079
and sulfonamide). The synthesis of carboxylated analog 6 is in-
spired from the strategy applied to access dendrimer 1,8 and in-
volves the grafting of a protected carboxylic acid-based phenol 3
115.3 ppm, shifts at 121.2 ppm once the phenol grafted. Unreacted
phenol 3 is readily removed by dissolving 5 in the minimum
amount of THF and precipitating it with pentane. Typical deprotec-
tion of tert-butyl esters into the corresponding carboxylic acids is
achieved by treatment with a 25% solution of trifluoroacetic acid
(TFA) in dichloromethane for 90 min. However, after three cycles
the deprotection was still uncomplete. Raising the temperature
or increasing the TFA concentration led to partial decomposition
of the dendrimeric skeleton, as indicated by the appearance of
several peaks in the 60–65 ppm region on 31P NMR spectra. Never-
theless, complete deprotection could be achieved after eight cycles
under the initial smooth conditions. Full deprotection of tert-butyl
esters was assessed by the disappearance of the tert-butyl signals
corresponding to the methyl protons at 1.45 ppm in 1H NMR spec-
troscopy and to the primary and quaternary carbons at, respec-
on a thiophosphoryl dichloride terminated PPH dendrimer12
4
(Scheme 1). Phenol 3 is obtained upon N-dialkylation of tyramine
by tert-butyl bromoacetate in the presence of sodium bicarbonate
as a base.
The reaction proceeds smoothly at room temperature in DMF to
afford 3 in 80% yield after column chromatography. The character-
istic N–CH2–CO methylene group is unambiguously identified as a
singlet at 3.51 ppm in 1H NMR spectroscopy and at 56.1 ppm in 13
C
NMR spectroscopy. This phenol is then grafted on the dendrimeric
scaffold 4 by nucleophilic substitution of the 12 chlorine atoms in
the presence of cesium carbonate in THF. The course of the reaction
is followed by 31P NMR spectroscopy in which two singlets are
observed at 8.3 ppm ([P@N]3 core phosphorus atoms) and
63.1 ppm (P@S thiophosphorus). The unreacted phenol 3 is easily
differentiated from the grafted one on 1H NMR spectra which
allows the distinction of the signals corresponding to the free phe-
nol. In fact, signals corresponding to tert-butyl and ortho aromatic
protons shift, respectively, from 1.49 ppm (free) to 1.45 ppm
(grafted), and from 6.77 ppm (free) to 7.02 ppm (grafted). 13C
NMR spectroscopy provides also an excellent probe to detect free
phenol whose carbon at the ortho position, initially resonating at
O
O
O
NH
N
OH
O
O
O
O
G1
G1
OH
OH
Figure 2. Possible zwitterionic conformation of 6.
CO2tBu
CO2tBu
NH2
N
N
a
HO
HO
2
3
CO2tBu
S
P
S
P O
N
b
Cl
Cl
[N=P]3
O
[N=P]3
O
CO2tBu
N
N
N
6
4
5
2
6
c
HO2C
HO2C CO2H
N
CO2H
N
CO2H
HO2C
HO2C
N
CO2H
N
O
O
O
S
O
N P
P S
CO2H
CO2H
N
N
N
HO2C
HO2C
N
N
O
O
O
S
N N
O
O
O
N
P
P
P
O
P
N
P
N
O
N N
S
N
CO2H
CO2H
O
O
HO2C
N
HO2C
N
S
O
N
N
O
P N
O
S
P
6
O
N
CO2H
CO2H
HO2C
N
HO2C
N
N
HO2C CO2H HO2C
CO2H
Scheme 1. Synthesis of the G1 carboxylate analog 6. Reagents and conditions: (a) BrCH2CO2tBu, Na2CO3, 0 °C; (b) 3, Cs2CO3; (c) TFA 25% in CH2Cl2 (repeat).

2080
O. Rolland et al. / Tetrahedron Letters 50 (2009) 2078–2082
tively, 28.3 and 81.0 ppm in 13C NMR. It was also confirmed in FT-
IR by the replacement of strong C@O stretching band of tert-butyl
esters at 1736 cmꢀ1 by a strong one corresponding to carboxylic
acid at 1722 cmꢀ1. Noteworthy, no trifluoroacetate ammonium
salts were formed at the dendrimer surface during the deprotec-
tion step, as demonstrated by the lack of corresponding signals
in 19F and 13C NMR and FT-IR spectroscopies. This unexpected re-
sult may be due to the formation of a zwitterionic form between
the tertiary amine and terminal carboxylic acids at the surface
(Fig. 2). In fact, FT-IR monitors two bands at 1679 and
1408 cmꢀ1, which might correspond to asymmetric and symmetric
stretching vibrations of a carboxylate anion in alpha position of an
amine.13 Further analysis of the 31P NMR spectrum of 6 shows that
the PPH scaffold is not affected under the tert-butyl esters removal
conditions, the cyclotriphosphazene and the P@S phosphorus res-
onating at 8.3 ppm (s) and 63.0 ppm (s), respectively (see Fig. 3).
Contrary to previous preparations of amino(bismethylene)
phosphonic and amino(bismethylene) carboxylic acid-terminated
dendrimers, we could not use the methodology involving the graft-
ing of a phenol carrying protected sulfonic acid moieties on dendri-
mers and their subsequent deprotection. Actually, to the best of
our knowledge, protection and deprotection of sulfonic acids are
very tedious to achieve, with corresponding reactions that are
not quantitative and generally incompatible with the PPH dendritic
structure.14 Therefore, we designed another pathway to prepare
the G1 sulfonated analog 10, involving the formation of amin-
obis(methylenesulfonate) directly at the surface of a G1 dendrimer
bearing primary amine groups. Actually, a routine procedure to
prepare aminobis(methylenesulfonate) involves a primary amine,
formaldehyde, and sodium bisulfite.15 This reaction is analogous
to the Kabachnik–Fields reaction16 involved in the synthesis of
the tyramine-based amino-bismethylene phosphonate to produce
dendrimer 10 (Scheme 2). The G1 dendrimer bearing primary
1
1
4
4
S
N
C
C
C
1
C
0
1
0
O
[N=P]3
P O
N N
3
3
2
2
C
1
C
C
C
1
0
0
2
6
Figure 3. Numbering scheme for NMR assignments (see Refs. 18–23).
S
S
NH
O
a
Cl
[N=P]3
O
P
[N=P]3
O
P O
O
Cl
N
N
N
N
6
8
4
2
6
b
S
NH3
CF3COO
O
[N=P]3
P O
N N
9
2
6
c
NaO3S
SO3Na
NaO3S SO3Na
N
N
SO3Na
N
NaO3S
NaO3S
SO3Na
N
O
O
S
O
O
N P
P S
SO3Na
N
N
N
NaO3S
NaO3S
N
SO3Na
N
O
O
O
S
N N
O
O
O
N
P
P
P
O
P
P
N
O
N N
S
N
N
SO3Na
SO3Na
O
O
NaO3S
NaO3S
N
10
N
S
N
N
O
N
P
S P
O
O
O
N
SO3Na
NaO3S
NaO3S
N
SO3Na
N
N
NaO3S SO Na
NaO3S
SO3Na
3
Scheme 2. Synthesis of the G1 sulfonate analog 10. Reagents and conditions: (a) Boc-tyramine 7, Cs2CO3; (b) TFA 25% in CH2Cl2; (c) Et3N, Na2S2O5, aqueous H2CO, 65–75 °C.

O. Rolland et al. / Tetrahedron Letters 50 (2009) 2078–2082
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6. Poupot, M.; Griffe, L.; Marchand, P.; Maraval, A.; Rolland, O.; Martinet, L.;
L’Faqihi-Olive, F. E.; Turrin, C.-O.; Caminade, A.-M.; Fournié, J.-J.; Majoral, J.-P.;
Poupot, R. FASEB J. 2006, 2339–2351.
7. Sebastián, R.-M.; Griffe, L.; Turrin, C.-O.; Donnadieu, B.; Caminade, A.-M.;
Majoral, J.-P. Eur. J. Inorg. Chem. 2004, 2459–2466.
8. Griffe, L.; Poupot, M.; Marchand, P.; Maraval, A.; Turrin, C.-O.; Rolland, O.;
Métivier, P.; Bacquet, G.; Fournié, J.-J.; Caminade, A.-M.; Poupot, R.; Majoral, J.-
P. Angew. Chem., Int. Ed. 2007, 46, 2523–2526.
amine groups 9 is synthesized by the grafting of Boc-protected
tyramine17 7 onto the surface of the PPH scaffold 3 in THF with ce-
sium carbonate as a base. Excess of free phenol is detected in 1H
NMR spectroscopy by a singlet corresponding to Boc groups at
1.45 ppm for the free phenol 7 in addition to the one at 1.42 ppm
resulting from the grafting of phenol.
The resulting dendrimer 8 exhibits a simple 31P NMR spectrum
with two singlets at 8.5 ppm and 62.8 ppm corresponding to the
[P@N]3 core and the P@S phosphorus atoms, respectively, after col-
umn chromatography. Deprotection of Boc-protected amine
groups is done with a methodology similar to one employed for
tert-butyl ester moieties, but in this case, full deprotection is
achieved after two cycles of the TFA/DCM procedure. Dendrimer
9 is isolated quantitatively as trifluoroacetate salts, whose fluorine
atoms resonate as a singlet at 0.63 ppm (19F NMR spectroscopy).
Complete removal of Boc moieties is followed by the disappear-
ance of corresponding signals in both 1H and 13C NMR spectrosco-
pies. Again, the PPH skeleton of 9 shows a typical 31P NMR
spectrum with two singlets at 9 ppm and 62.9 ppm.
9. Rolland, O.; Griffe, L.; Poupot, M.; Maraval, A.; Ouali, A.; Coppel, Y.; Fournié, J.-
J.; Bacquet, G.; Turrin, C.-O.; Caminade, A.-M.; Majoral, J.-P.; Poupot, R. Chem.
Eur. J. 2008, 14, 4836–4850.
10. Fruchon, S.; Poupot, M.; Martinet, L.; Turrin, C. O.; Majoral, J. P.; Fournié, J. J.;
Caminade, A. M.; Poupot, R. J. Leukocyte Biol. 2009, 85, 553–562.
11. Patani, G. A.; LaVoie, E. J. Chem. Rev. 1996, 96, 3147–3176.
12. Majoral, J.-P.; Caminade, A.-M. Chem. Rev. 1999, 99, 845–880.
13. Hesse, M.; Meier, H.; Zeeh, B. Spectroscopic Methods in Organic Chemistry;
Thieme: New York, 1997.
14. Roberts, J. C.; Gao, H.; Gopalsamy, A.; Kongsjahju, A.; Patch, R. J. Tetrahedron
Lett. 1997, 38, 355–358. and references cited therein.
15. Lacoste, R. G.; Martell, A. E. J. Am. Chem. Soc. 1955, 77, 5512–5515.
16. Cherkasov, R. A.; Galkin, V. I. Russ. Chem. Rev. 1998, 67, 857–882.
17. Ghirmai, S.; Mume, E.; Lundqvist, H.; Tolmachev, V.; Sjöberg, S. J. Labelled
Compd. Radiopharm. 2005, 48, 855–871.
18. Compound 3: To a solution of tert-butyl bromoacetate (0.481 mL, 3.280 mmol)
and sodium bicarbonate (306 mg, 3.644 mmol) in DMF (2 mL) was added, at
0 °C, dropwise (5 min) a solution of tyramine (200 mg, 1.458 mmol) in DMF
(3 mL). The mixture was stirred at rt for 12 h, filtered on celite, and evaporated.
The residue was purified by column chromatography (dichloromethane/
Dendrimer 9 is then treated with triethylamine to remove tri-
fluoroacetate ammonium salts, to produce in situ a dendrimer
bearing 12 primary amine groups at the periphery. This compound
is scarcely soluble in water or in organic solvents; it is then imme-
diately reacted with sodium hydroxymethylsulfonate at 75 °C. The
latter is generated by addition of sodium bisulfite to a solution of
aqueous formaldehyde at 65 °C. The expected dendrimer 10 is
obtained after three hours of reaction. The residue, which precipi-
tates upon the addition of isopropanol in the reaction mixture, is
then dissolved in the minimum amount of water and re-precipi-
tated with isopropanol to remove trifluoroacetate triethylammo-
nium salts (disappearance of corresponding signal in 19F NMR
spectroscopy). Stability of the dendritic structure is observed in
31P NMR with two peaks at 9.5 ppm (phosphorus atoms of the
core) and 64.4 ppm (phosphorus atoms of the divergent points).
Full dialkylation of amine groups is verified in 1H NMR by compar-
ing the integrations; the 8:1 ratio between the integrations of
N–CH2–S methylene group (singlet, 4.40 ppm) and hydrazone
groups (singlet, 8.09 ppm) fits to a fully disubstituted dendrimer.
The presence of sodium sulfonate moieties is also observed in
FT-IR spectroscopy with two strong S@O stretching bands at
methanol, 99.5:0.5) to give
3 as a
viscous oil (80%). 1H NMR (CDCl3,
250.1 MHz): 1.49 (s, 18H, CH3), 2.74 (AA0 part of an AA0BB0 syst., m, 2H, CH2–
CH2–N), 2.94 (BB0 part of an AA0BB0 syst., m, 2H, CH2–CH2–N), 3.51 (s, 4H, N–
CH2–CO), 5.77 (br s, 1H, OH), 6.77 (BB0 part of an AA0BB0 syst., m, 2H, Co–H),
7.06 (AA0 part of an AA0BB0 syst., m, 2H, Cm–H0); 13C{1H} NMR (acetone-d6,
500.3 MHz): 28.2 (s, CH3), 33.9 (s, CH2–CH2–N), 56.1 (s, N–CH2–CO), 56.5 (s,
CH2–CH2–N), 81.2 (s, C(CH3)3), 115.3 (s, Co), 129.8 (s, Cm), 131.7 (s, Cp), 154.2 (s,
Ci), 170.9 (s, CO2) ppm.
19. Compound 5: To a solution of 4 (194 mg, 0.106 mmol) in THF (6 mL) were
added phenol
3 (500 mg, 1.368 mmol) and cesium carbonate (892 mg,
2.736 mmol) and the mixture was stirred at rt for 12 h. The reaction mixture
was centrifuged, filtered, and evaporated. The residue was dissolved in THF and
precipitated by addition of pentane to give 5 as a sticky solid (90%). 31P{1H}
NMR (CDCl3, 121.5 MHz): 8.3 (s, N3P3), 63.1 (s, P@S); 1H NMR (CDCl3,
300.1 MHz): 1.45 (s, 216H, CH3), 2.74 (AA0 part of an AA0BB0 syst., m, 24H,
CH2–CH2–N), 2.92 (BB0 part of an AA0BB0 syst., m, 24H, CH2–CH23–N), 3.24 (d,
3JHP = 10.1 Hz, 18H, N–CH3), 3.45 (s, 48H, N–CH2–CO), 7.02 (d, JHH = 8.5 Hz,
12H, C20–H), 7.10 (m, 48H, C21–H, C13–H), 7.61 (br s, 12H, C30–H), 7.64 (s, 6H,
CH@N); 13C{1H} NMR (CDCl3, 62.9 MHz): 28.2 (s, CH3), 34.0 (d, 2JCP = 8.5 Hz, N–
CH3), 34.2 (s, CH2–CH2–N), 56.0 (br s, N–CH2–CO, CH2–CH2–N), 81.0 (s,
C(CH3)3), 121.2 (broad d, JCP = 4.6 Hz, C21, C02), 128.3 (s, C03), 129.8 (s, C13),
3
4
4
132.2 (s, C0), 137.2 (s, C1), 138.8 (m, CH@N), 148.9 (d, JCP = 7.2 Hz, C11), 151.2
2
(m, Ci), 170.6 (s, CO2) ppm.
20. Compound 6: A solution of 25% of TFA in dichloromethane (5 mL) was dropped
on 5 (100 mg, 0.017 mmol), and the reaction mixture was stirred at rt for 1.5 h
and evaporated to dryness. This sequence was repeated eight times and the
residue was suspended into ethyl acetate and evaporated to dryness three
1198 (asymmetrical) and 1037 (symmetrical) cmꢀ1
.
We have developed a versatile dendrimer derivatization strat-
egy to obtain aminobismethylene carboxylate18–20 and aminobism-
ethylene sulfonate21–23-terminated dendrimers that are isosteric to
the corresponding aminobismethylene phosphonate-terminated
one. The strategy based on the modification of tyramine is rather
quick, with fair to excellent yields, free of tedious purification step,
and applicable to other amine terminated dendrimers. Current
investigation is under progress to assay the biological properties
of these isosteric compounds toward NK cells and monocytes.
times to give
6 as a
white solid (yield = 90%). 31P{1H} NMR (DMSO-d6,
81.0 MHz): 8.3 (s, N3P3), 63.0 (s, P@S); 1H NMR (DMSO-d6, 500.3 MHz): 2.74
(AA0 part of an AA0BB0 syst., m, 24H, CH2–CH2–N), 2.98 (BB0 part of an AA0BB0
3
syst., m, 24H, CH2–CH2–N), 3.26 (d, JHP = 12.4 Hz, 18H, N–CH3), 3.60 (s, 48H,
N–CH2–CO), 7.05 (broad d, JHH = 8.3 Hz, 36H, C20–H, C12–H), 7.18 (d,
3
3JHH = 8.3 Hz, 24H, C13–H), 7.62 (d, JHH = 8.6 Hz, 12H, C30–H), 7.81 (s, 6H,
3
CH@N); 13C{1H} NMR (DMSO-d6, 500.3 MHz): 32.5 (s, CH2–CH2–N), 33.2 (d,
2JCP = 11.3 Hz, N–CH3), 55.3 (s, N–CH2–CO), 56.4 (s, CH2–CH2–N), 121.2 (d,
3JCP = 4.6 Hz, C12), 121.3 (s, C20), 128.6 (s, C03), 130.3 (s, C13), 132.7 (s, C04), 136.9 (s,
4
C1), 140.2 (d, JCP = 13.8 Hz CH@N), 149.1 (d, JCP = 7.1 Hz, C11), 151.1 (br s, Ci),
3
2
171.6 (s, CO2) ppm.
21. Compound 8: To a solution of 4 (1.50 g, 0.824 mmol) in THF (7 mL) were added
Boc-protected tyramine (2.57 g, 10.84 mmol) and cesium carbonate (7.06 g,
21.66 mmol) and the mixture was stirred at rt for 12 h. The reaction mixture
was centrifuged, filtered, and evaporated. The residue was purified by column
chromatography (silica gel, hexane/ethyl acetate, 2:1–0:1) to give 8 as a white
solid (75%). 31P-{1H} NMR (CDCl3, 121.5 MHz): 8.5 (s, N3P3), 62.8 (s, P@S); 1H
Acknowledgments
Rhodia and the INCa (Institut National du Cancer, Contract # PL
06-87) are acknowledged for financial support.
3
NMR (CDCl3, 300.1 MHz): 1.42 (s, 108H, CH3), 2.71 (t, JHH = 6.9 Hz, 24H, CH2–
CH2–N), 3.27 (m, 42H, CH3–N, CH2–CH2–N), 4.66 (br s, 12H, NH), 6.99 (d,
3JHH = 8.4 Hz, 12H, C02–H), 7.08 (m, 48H, C12–H, C13–H), 7.62 (m, 18H, C30–H,
References and notes
2
CH@N); 13C{1H} NMR (CDCl3, 62.9 MHz): 28.4 (s, CH3), 33.0 (d, JCP = 11.9 Hz,
1. Vögtle, F.; Richardt, G.; Werner, N. Dendritische Moleküle; Teubner: Wiesbaden,
2007.
2. Majoral, J.-P.; Caminade, A.-M.; Sebastian, R.-M.; Magro, G.; Loup, C.; Turrin, C.-
O.; Laurent, R. Polym. Mater. Sci. Eng. 2001, 84, 166–168.
CH3–N), 35.6 (s, CH2–CH2–N), 41.7 (s, CH2–CH2–N), 79.2 (s, C(CH3)3), 121.4 (d,
2JCP = 4.2 Hz, C20 and C12), 128.3 (s, C03), 129.8 (s, C31), 132.2 (s, C04), 136.3 (s, C41),
138.6 (d, JCP = 13.9 Hz, CH@N), 149.1 (d, JCP = 6.4 Hz, C11), 151.2 (br s, C01),
155.8 (s, CO2) ppm.
3
2
3. Boas, U.; Christensen, J. B.; Heegaard, P. M. H. Dendrimers in Medicine and
Biotechnology; The Royal Society of Chemistry: Cambridge, 2006.
4. Blanzat, M.; Turrin, C.-O.; Aubertin, A.-M.; Vidal, C.; Caminade, A.-M.; Majoral,
J.-P.; Rico-Lattes, I.; Lattes, A. ChemBioChem 2005, 6, 2207–2213.
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22. Compound 9: A solution of 25% of TFA in dichloromethane (5 mL) was dropped
on 8 (400 mg, 0.094 mmol), and the reaction mixture was stirred at rt for 1.5 h
and evaporated to dryness. This sequence was repeated twice. The residue was
diluted into methanol and then evaporated to dryness three times to give 9 as a
pale yellow solid (95%). 31P–{1H} NMR (CD3OD, 121.5 MHz): 9.0 (s, N3P3), 62.9
(s, P@S); 1H NMR (CD3OD, 300.1 MHz): 2.90 (m, 24H, CH2–CH2–N), 3.11 (m,

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O. Rolland et al. / Tetrahedron Letters 50 (2009) 2078–2082
3
3
24H, CH2–CH2–N), 3.28 (d, JHP = 10.5 Hz, 18H, CH3–N), 6.94 (d, JHH = 8.4 Hz,
12H, C20–H), 7.19 (m, 48H, C21–H, C13–H), 7.63 (d, 3JHH = 8.4 Hz, 12H, C30–H), 7.77
subsequently added and the mixture was allowed to stir at 75 °C for 3 h. It was
then cooled at rt and addition of isopropanol made the product precipitate. The
precipitate was filtered off and dissolved in the minimum amount of water and
precipitated again by addition of isopropanol. This procedure was repeated
three times to give 10 as a white powder (90%). 31P–{1H} NMR (D2O/CD3CN 7:1,
121.5 MHz): 9.5 (s, N3P3), 64.4 (s, P@S); 1H NMR (D2O/CD3CN 7:1, 250.1 MHz):
3.13 (m, 24H, CH2–CH2–N), 3.54 (m, 42H, CH2–CH2–N, CH3–N), 4.40 (s, 48H, N–
CH2-S), 7.21 (m, 12H, C20–H), 7.35 (m, 24H, C12–H), 7.51 (m, 24H, C31–H), 7.88 (m,
12H, C30–H), 8.09 (br s, 6H, CH@N); 13C{1H} NMR (DMSO, 62.9 MHz): 30.8 (s,
(s, 6H, CH@N); 13C{1H} NMR (CD3OD, 75.5 MHz): 32.2 (d, JCP = 11.8 Hz, CH3–
2
1
N), 32.4 (s, CH2–CH2–N), 40.3 (s, CH2–CH2–N), 116.9 (q, JCF = 293.9 Hz, CF3),
121.1 (s, C20), 121.4 (d, 2JCP = 4.6 Hz, C12), 128.1 (s, C30), 129.7 (s, C13), 132.6 (s, C40),
134.0 (s, C1), 139.3 (d, JCP = 14.4 Hz, CH@N), 149.7 (d, JCP = 6.9 Hz, C11), 151.1
4
3
2
(s, C10), 161.6 (d, JCF = 34.1 Hz, CO2); 19F{1H} (CD3OD, 188.3 MHz): 0.63 (s,
2
CF3) ppm.
23. Compound 10: To a solution of sodium bisulfite (218 mg, 1.144 mmol) in water
(5 mL) was added a 37% solution of formaldehyde (0.162 mL, 2.179 mmol), the
resulting mixture was stirred at 65 °C for 30 min. A solution of 9 (200 mg,
0.045 mmol) and triethylamine (0.084 mL, 0.599 mmol) in ethanol (5 mL) was
2
CH2–CH2–N), 32.5 (d, JCP = 11.9 Hz, CH3–N), 48.6 (s, CH2–CH2–N), 60.7 (s, N–
CH2–S), 121.0 (s, C20), 121.5 (s, C12), 128.8 (s, C30), 130.5 (s, C13), 132.6 (s, C40),
135.1 (s, C41), 140.5 (m, CH@N), 149.3 (s, C11), 150.9 (s, C10) ppm.