The use of solid phase synthesis for the preparation of monoadducts of fullerene C60

Article abstract of DOI:10.1007/s11172-012-0119-1

The method of solid phase synthesis was proposed for the preparation of monoadducts of fullerene C₆₀ using 3′H-cyclopropa[1,9](C ₆₀-I _h )[5,6]fullerene-3′-carboxylic acid as an example.

Full text of DOI:10.1007/s11172-012-0119-1

Russian Chemical Bulletin, International Edition, Vol. 61, No. 4, pp. 853—857, April, 2012
853
The use of solid phase synthesis for the preparation
of monoadducts of fullerene C60
D. N. Nikolaev,a Yu. S. Klimenicheva,a P. B. Davidovich,b and L. B. Piotrovskiia
аResearch Institute of Experimental Medicine, NorthꢀWestern Branch of the Russian Academy of Medical Sciences,
12 ul. Akad. Pavlova, 197376 Saint Petersburg, Russian Federation.
Fax: +7 (812) 234 9489. Eꢀmail: pp225@yandex.ru
bSaint Petersburg State Institute of Technology (Technical University),
26 Moskovsky prosp., 190013 Saint Petersburg, Russian Federation.
Fax: +7 (812) 712 7791
The method of solid phase synthesis was proposed for the preparation of monoadducts of
fullerene C60 using 3´Hꢀcyclopropa[1,9](C60ꢀIh)[5,6]fullereneꢀ3´ꢀcarboxylic acid as an example.
Key words: fullerene С60, cyclopropanation, solid phase synthesis.
Scheme 1
A unique framework structure of fullerenes and propꢀ
erties of their molecules have attracted attention of bioloꢀ
gists long ago. Therefore, there were many attempts to
modify various molecules by the residue of fullerene С60.
The examples are the modification of nucleic acids,1 the
synthesis of alamecithin analogs modified by fullerene resꢀ
idues at the C or N ends,2 the synthesis of peptideꢀconꢀ
taining fullerenoporphyrin dyads,3 the synthesis of amꢀ
phiphilic polymers,4 etc.5
A molecule of fullerene С60 is highly hydrophobic:
for unsubstituted fullerene С60 the octanol—water disꢀ
tribution coefficient (logPoct) is 6.67.6 That is why
the introduction of the fullerene residue results in a sharp
increase in the lipophilicity of the modified moleꢀ
cule, which can change its activity.7 For instance, it
was shown8 that the introduction of the fullerene reꢀ
sidue into a peptide molecule enhances its biological
activity.
R = But; n = 1—3
The examples presented above demonstrate that the
introduction of the fullerene residue into biologically imꢀ
portant molecules can impart new properties to these molꢀ
ecules. However, monoadducts of fullerene С60 are preferꢀ
able for similar modifications.9
One of such adducts is 3´Hꢀcyclopropa[1,9](C60ꢀIh)ꢀ
[5,6]fullereneꢀ3´ꢀcarboxylic acid (1). The synthesis of
compound 1 by the cyclopropanation of fullerene by tertꢀ
butylꢀ2ꢀ(dimethylꢀ4ꢀsulfanylidene)acetate (2) (R = But)
followed by the hydrolysis of the obtained tertꢀbutyl
3´Hꢀcyclopropa[1,9](C60ꢀIh)[5,6]fullereneꢀ3´ꢀcarboxylꢀ
ate (3)9,10 is known (Scheme 1).
alkyl radical in the ester group of sulfonium ylide 2. Thereꢀ
fore, in some cases, column chromatography needs reꢀ
peated two times to separate the monoadduct from a mixꢀ
ture of polyadducts.
The formation of polyadducts can be prevented if the
reaction of fullerene С60 is carried out with the reactant
immobilized on the solid phase, i.e., under the conditions
where a molecule of fullerene С60 can interact only with
one reactant molecule.
The addition of the residue of fullerene С60 to polyꢀ
mers has earlier been described.4,13 The modification of
the silica gel surface by fullerenopyrrolidine with the purꢀ
pose of obtaining new stationary phases for HPLC is also
known.14 However, only the synthesis of fullereneꢀconꢀ
taining polymers or sorbents are considered in all examꢀ
ples listed above.
However, this reaction, as the predominant majority
of other reactions involving fullerene С60, affords a mixꢀ
ture of substances.11 We have earlier12 shown that the yield
of monoadduct 3 (n = 1) depends on the nature of the
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 0850—0854, April, 2012.
1066ꢀ5285/12/6104ꢀ0853 © 2012 Springer Science+Business Media, Inc.

854
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
Nikolaev et al.
Table 1. Synthesis of bromoacetate resin 5
We propose the reaction of fullerene С60 with sulfonꢀ
ium ylide immobilized on the solid phase followed by the
elimination of the formed monoadduct, viz., 3´Hꢀcycloꢀ
propa[1,9](C60ꢀIh)[5,6]fullereneꢀ3´ꢀcarboxylic acid; i.e.,
the synthesis of the monoadduct of fullerene С60 on the
solid phase.
Entry Weight
of resin
Capacity
of resin 4 BrCH2COOH
/mmol g–1
Amount of
t/h
Сs(5)
/mmol g–1
4/g
/mmol
1
2
3
4
2
2
2
2
1.44
1.44
1.44
1.44
2.88
2.88
4.32
5.76
2
4
2
2
0.72
0.70
0.82
1.04
Results and Discussion
Earlier,9,10 when studying the influence of the nature
of the alkyl substituent in sulfonium ylide 2 (R = Et, But,
Bn, CHPh2) on the yield of compound 1 in the syntheses
by the known methods, we showed that benzhydryl ester 3
(n = 1) is easily hydrolyzed to acid 1 in a weakly acidic
medium.12 Therefore, we chose 2ꢀchlorotrityl chloride resꢀ
in 4 as a solid phase. Adduct 1 was synthesized on the solid
phase in five stages (Scheme 2).
The presence in the IR spectrum of the absorption
band of the carbonyl group at 1737 cm–1 confirms that
resin 5 contains the bromoacetate residue. The number of
bromoacetate groups in resin 5 (degree of substitution
Сs(5)) was determined by the amount of covalently bound
bromine (see Experimental). The maximum value of Сs(5)
was 1.04 mmol g–1 in a fourfold excess of bromoacetic
acid over the initial capacity of resin 4 (Table 1).
Resin 5 was treated for a long time with a solution of
dimethyl sulfide in toluene to convert the bromoacetate
group to the 2ꢀ(bromodimethylꢀ4ꢀsulfanyl)acetate group
(Table 2). The reaction course was monitored by deterꢀ
mining the amount of ionic bromine. The maximum conꢀ
version of resin 5 to resin 6 was ~60% (see Table 2). The
IR spectrum of resin 6 contains the absorption band of the
carbonyl group at 1730 cm–1, indicating that the ester
bond between the resin and 2ꢀ(bromodimethylꢀ4ꢀsulfꢀ
anyl)acetate residue is retained. The treatment of resin 6
with a solution of triethylamine in chloroform gives
2ꢀ(dimethylꢀ4ꢀsulfanylidene)acetate resin 7. The reacꢀ
tion occurs with an almost quantitative yield (Table 3).
Resin 7 gains an intensive yellow color. The IR spectrum
Note. Here and in Tables 2—4, t is the synthesis time and Сs is
the degree of substitution.
4
Table 2. Synthesis of 2ꢀ(bromodimethylꢀ ꢀsulfanyl)ꢀ
acetate resin 6
Entry t/days
Сs(5)
Сs(6)
Conversion
5  6 (%)
mmol g–1
1
2
3
4
12
24
36
60
1.04
1.04
1.04
1.04
0.26
0.52
0.63
0.64
25
50
61
62
of resin 7 exhibits the absorption band of the carbonyl
group at 1745 cm–1, indicating that the ester bond beꢀ
tween the resin and acyl residue containing the sulfonium
ylide group is retained.
Aromatic hydrocarbons are not usually used in solid
phase synthesis as solvents. However, the solubility of
fullerene С60 in them is several orders of magnitude higher
than in the solvents widely used for this purpose (dichloroꢀ
methane, THF, and DMF).15 Therefore, fullerene С60
was cyclopropanated by resin 7 in oꢀdichlorobenzene
(oꢀDCB). In the cyclopropanation of С60, 3% of 2ꢀ(diꢀ
methylꢀ4ꢀsulfanylidene)acetate groups immobilized on
the resin are involved, and this amount is independent of
the reaction temperature, amount of the loaded fullerene,
and synthesis time (Table 4). Resin 8 turns brown after the
Scheme 2

Solid phase synthesis of C60 monoadducts
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
855
4
Table 3. Synthesis of 2ꢀ(dimethylꢀ ꢀsulfanylidene)acetate resin 7
Entry
Weight
of resin 6/g
Сs(6)
/mmol g–1
t/h
Amount
Сs(7)
Conversion
6  7
of Et3N•HBr /mmol g–1
/mmol
(%)
1
2
0.5
0.5
0.64
0.64
2
4
0.31
0.32
0.62
0.64
097
100
Table 4. Cyclopropanation of fullerene С60 on resin 7
Entry
Weight
Сs(7)
Amount of С60
T/C
t
Reacted С60
of resin 7/g /mmol g–1
/days
mg
%*
%*
%**
1
2
3
4
0.5
0.5
0.5
0.5
0.63
0.63
0.63
0.63
11
11
23
5
5
10
30
60
30
30
2
2
4
4
3
3
3
3
56
57
29
03
227
100
* Of the number of ylide groups in resin 7.
** In percent of the loaded amount. The weight of reacted fullerene С60 was calculated by the difference
between the weights of loaded and washed off fullerene С60. The weight of washed off fullerene С60 was
determined by UV spectroscopy at the wavelength 334 nm.
reaction. In the IR spectrum, the intensity of the band of
the carbonyl group at 1740—1745 cm–1 decreases strongꢀ
ly, indicating that the most part of the 2ꢀ(dimethylꢀ4ꢀ
sulfanylidene)acetate groups disappeared.
avoiding of column chromatography at the stage of isolaꢀ
tion of the final product. The yield of the final product
when using the solid phase method of synthesis is compaꢀ
rable to that for the synthesis in solution (44%).10
Acid 1 was isolated by the treatment of resin 8 with
a 5% solution of trifluoroacetic acid (TFA) in an oꢀDCB—
dioxane—dichloromethane (6 : 1 : 1) mixture at ambient
temperature. The mass spectrum of compound 1 exhibits
a peak with m/z 778.01 (molecular weight of 1 is 778.64).
The UV spectrum of a solution of 1 in oꢀDCB contains an
intense absorption band at 327 nm, a narrow lowꢀintensity
band at 427 nm, and a broad lowꢀintensity band at 493 nm,
which is characteristic of 6,6ꢀadducts of monomethanoꢀ
fullerenes.16 The IR spectrum contains an intense narrow
vibration band of the fullerene core at 526 cm–1, a series
of narrow lowꢀintensity bands at 550—1000 cm–1, a narꢀ
row intense band at 1116 cm–1, which corresponds to
bending vibrations of the С—Н group of the cyclopropane
Thus, the principal possibility of the synthesis of
monoadducts of fullerene С60 by solid phase synthesis was
shown for the first time. However, the methods needs furꢀ
ther optimization, in particular, the use of other solid phases.
Experimental
UV spectra were recorded on a Beckman Coulter DU 800
Spectrophotometer instrument (USA) at 300—800 nm in oꢀDCB.
IR spectra were measured on an FSMꢀ1201 spectrophotometer
(Russia) at 400—5000 cm–1 in КBr pellets. Mass spectra were
obtained on a MALDIꢀTOF Voyager DE, AB instrument (USA)
(ꢀCHCA).
Commercial fullerene С60 (NeoTech Products, St. Petersꢀ
burg) and 2ꢀchlorotrityl chloride resin (2,ꢀdichlorobenzhydrꢀ
yl—polystyrene, Sigma—Aldrich, 100—200 mesh, 1% divinylꢀ
benzene, 1—1.5 mmoles of Cl g–1) were used. The following
commercial reagents were used: acetic, bromoacetic, and triꢀ
fluoroacetic acids; dichloromethane; methanol; chloroform; isoꢀ
propyl alcohol; and dimethyl sulfide. Toluene, dioxane, triꢀ
ethylamine, pyridine, and oꢀDCB were purified by standard
methods.19
2ꢀChlorotrityl chloride resin 4. The resin for the synthesis
was prepared and activated using a known method.20 The actiꢀ
vated resin was stored in a vacuum desiccator over phosphorus
pentaoxide and KOH.
Determination of the capacity of 2ꢀchlorotrityl chloride resin 4.
A roundꢀbottom 10ꢀmL flask equipped with a reflux condenser
was loaded with resin 4 (100 mg, exact weight), pyridine (3 mL),
fragment,17 a band of the carbonyl group at 1710 cm–1
,
and a broad intense band of the hydroxyl group at
3200—3640 cm–1. The yield of 3´Hꢀcyclopropa[1,9]ꢀ
(C60ꢀIh)[5,6]fullereneꢀ3´ꢀcarboxylic acid (1) is 44% based
on reacted С60. The spectral characteristics coincide with
those for acid 1 synthesized in solution.18
The absence of peaks with the mass higher than 780 in
the mass spectrum of compound 1 indicates the absence
of admixtures of polyadducts and confirms the possibility
of selective synthesis of monoadducts of fullerene С60 on
the solid phase. Advantages of the proposed method are in
the simplification of the procedure of treatment of the
reaction mixture at each stage of the synthesis, including

856
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
Nikolaev et al.
and glacial acetic acid (0.5 mL). The mixture was heated for 4 h
at 100 С. The reaction mixture was cooled to ambient temperaꢀ
ture and transferred to a 50ꢀmL volumetric flask filled with 25 mL
of 30% acetic acid and brought to mark with distilled water. The
amount of active chlorine was determined by a known method.21
resin turned intensely yellow. The resin was washed with chloroꢀ
form (3×3 mL) and diethyl ether (1×5 mL) and dried in a vacuꢀ
um desiccator over Р2О5/KOH. The amount of Et3N•HBr was
determined by a known method.21 The results are presented in
Table 3. IR (KBr), /cm–1: 1745 (CO).
The capacity after activation was 1.44 mmol g–1
.
Cyclopropanation of fullerene С60 by resin 7. A weighed samꢀ
Bromoacetate resin 5. The reaction vessel was loaded with
2 g of resin 4 (Сs = 1.44 mmol g–1) and 8 mL of methylene
chloride. The mixture was stirred for 10 min in a rocker for the
solid phase synthesis of peptides to provide swelling of the resin.
The resin was filtered off, and a solution of bromoacetic acid and
triethylamine (1.5 equiv. over bromoacetic acid) in methylene
chloride (10 mL) was added (see Table 1). The mixture was
again stirred on the rocker for peptide solid phase synthesis. The
resin was filtered off, washed with methylene chloride (3×10 mL),
a methylene chloride—methanol—triethylamine (16 : 3 : 1) mixꢀ
ture (3×15 mL), and methylene chloride (3×10 mL), and dried
in a vacuum desiccator over Р2О5/KOH for 4 days. IR (KBr),
/cm–1: 1737 (CO).
ple of fullerene С60 was dissolved in 3 mL of oꢀDCB in a flask.
After fullerene was dissolved, 0.5 g of resin 7 (Сs = 0.63 mmol g–1
)
was loaded. The reaction mixture was kept for 2 days. The color
of the resin changed from bright yellow to redꢀbrown. The resin
was filtered off on the Schott filter, washed with oꢀDCB (5×3 mL)
and diethyl ether (7×3 mL), and dried for 2 days in a vacuum
desiccator over Р2О5/KOH. IR (KBr), /cm–1: 1740—1745
(CO). The combined filtrate were evaporated in vacuo, the resiꢀ
due was dissolved in toluene, and the amount of unreacted
fullerene was determined spectrophotometrically. The results
are presented in Table 4.
3´HꢀCyclopropa[1,9](C60ꢀIh)[5,6]fullereneꢀ3´ꢀcarboxylic
acid (1). The reaction vessel was loaded with 0.5 g of resin 8 and
3 mL of oꢀDCB. The mixture was stirred for 10 min in a rocker
for peptide solid phase synthesis to provide swelling of the resin.
The resin was filtered off, and a solution of trifluoroacetic acid
(0.2 mL) in a mixture of 3 mL of oꢀDCB, 0.5 mL of dioxane, and
0.5 mL of dichloromethane was added. The reaction mixture
was kept for 3 h. The resin was filtered off and washed with
oꢀDCB (2×3 mL). The color of the resin remained unchanged
after washings. The combined filtrates were evaporated in vacuo.
The residue in the flask was washed by decantation (with
methanol and hexane) and dried in a vacuum desiccator over
Р2О5/KOH. Compound 1 was obtained in a yield of 3 mg (44%
based on fullerene entered the cyclopropanation reaction) as
a brown solid. UV (oꢀDCB), max/nm (): 327 (31 900), 427 (760).
IR (KBr), /cm–1: 526 (fullerene core); 1116 (CH); 1710 (CO);
3200—3640 (OH). MS, m/z: 778.01. C62H2O2. Calculated:
M = 778.64.
Determination of the degree of substitution of resin 5. A roundꢀ
bottom 10ꢀmL flask equipped with a reflux condenser was loadꢀ
ed with a 100 mg of resin 5 (exact weight) and 3 mL of pyridine.
The mixture was heated for 3 h at 100 С. The reaction mixture
was cooled to ambient temperature, transferred into a 50ꢀmL
volumetric flask filled with 25 mL of 30% acetic acid, and brought
to a mark with distilled water. The amount of bromine was deꢀ
termined by a known method.21 The results are presented in
Table 1.
4
2ꢀ(Bromodimethylꢀ ꢀsulfanyl)acetate resin 6. A reaction vesꢀ
sel was loaded with 0.5 g of resin 5 (Сs = 1.04 mmol g–1) and
5 mL of toluene. The mixture was stirred for 10 min in a rocker
for peptide solid phase synthesis for swelling of the resin. The
resin was filtered off, and a solution of dimethyl sulfide (0.8 mL,
0.52 mmol) in toluene (4 mL) was added. The resin was kept at
ambient temperature. The storage duration and the yields are
presented in Table 2. The obtained product was filtered off on
the Schott filter, washed with toluene (3×5 mL) and diethyl
ether (3×10 mL), and dried for 2 days in a vacuum desiccator
over Р2О5/KOH. IR (KBr), /cm–1: 1730 (CO).
References
Determination of the degree of substitution of resin 6. A reacꢀ
tion vessel was loaded with 100 mg of resin 6 (exact weight) and
3 mL of chloroform. The mixture was stirred for 10 min in
a rocker for peptide solid phase synthesis to provide swelling of the
resin. The resin was filtered off, and a solution of triethylamine
(0.5 mL, 0.0036 mol) in chloroform (2 mL) was added. The resin
was stirred for 4 h in a rocker for peptide solid phase synthesis,
filtered off, and washed with chloroform (2×2 mL), isopropyl
alcohol (1×2 mL), methanol (1×2 mL), and water (1×2 mL).
The collected filtrates were evaporated in vacuo. The residue of
triethylamine hydrobromide in the flask was dissolved in 25 mL
of 30% acetic acid, transferred to a 50ꢀmL volumetric flask, and
brought to a mark with distilled water. The amount of ionic
bromine was determined by a known method.21 The results are
presented in Table 2.
1. T. Da Ros, G. Spalluto, M. Prato, Croat. Chem. Acta, 2001,
74, 743.
2. G. Jung, T. Redemann, K. Kroll, S. Meder, A. Hirsch,
G. Boheim, J. Pept. Sci., 2003, 9, 784.
3. A. Polese, S. Mondini, A. Bianco, C. Toniolo, G. Scorrano,
D. M. Guldi, M. Maggini, J. Am. Chem. Soc., 1999,
121, 3446.
4. Y.ꢀP. Sun, G. E. Lawson, W. Huang, A. D. Wright, D. K.
Moton, Macromolecules, 1999, 32, 8747.
5. L. B. Piotrovskii, O. I. Kiselev, Fullereny v biologii [Fullerenes
in Biology], Rostok, St. Petersburg, 2006, 336 pp. (in Russian).
6. C. T. Jafvert, P. P. Kulkarni, Env. Sci. Technol., 2008,
42, 5945.
7. A. Bagno, S. Claeson, M. Maggini, M. I. Martini, M. Prato,
G. Scorrano, Chem. Eur. J., 2002, 8, 1016.
8. P. Sofou, Y. Elemes, E. PanouꢀPomonis, A. Stavrakoudis,
V. Tsikaris, C. Sakarellos, M. SakarellosꢀDaitsiotis, M. Magꢀ
gini, F. Formaggio, C. Toniolo, Tetrahedron, 2004, 60, 2823.
9. H. Ito, T. Tada, M. Sudo, Y. Ishida, T. Hino, K. Saigo, Org.
Lett., 2003, 5, 2643.
4
2ꢀ(Dimethylꢀ ꢀsulfanylidene)acetate resin 7. The reaction
flask was loaded with 0.5 g of resin 6 (Сs = 0.64 mmol g–1) and
3 mL of chloroform. The mixture was stirred for 10 min in
a rocker for peptide solid phase synthesis to provide swelling of
the resin. The resin was filtered off, and triethylamine (1 mL,
0.007 mol) in chloroform (3 mL) was added. The mixture was
stirred for 2 h in a rocker for peptide solid phase synthesis. The
10. T. Tada, Y. Ishida, K. Saigo, J. Org. Chem., 2006, 71, 1633.
11. A. Hirsch, Top. Curr. Chem., 1999, 199, 1.

Solid phase synthesis of C60 monoadducts
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
857
12. D. N. Nikolaev, P. B. Davidovich, Med. Akad. Zh. [Mediciꢀ
nal Academical Journal], 2010, 10, 169 (in Russian).
13. A. W. Jensen, C. Daniels, J. Org. Chem., 2003, 68, 207.
14. A. Bianco, T. Da Ros, M. Prato, C. Toniolo, J. Pept. Sci.,
2001, 7, 208.
15. K. N. Semenov, N. A. Charykov, V. A. Keskinov, A. K.
Piartman, A. A. Blokhin, A. A. Kopyrin, J. Chem. Eng. Data,
2010, 55, 13.
ganic Molecules"] (Ivanovo, April 20—22, 2011), Ivanovo,
2011, 69 (in Russian).
18. D. N. Nikolaev, P. B. Davidovich, L. B. Piotrovskiy, Book of
Abstrs Int. Conf. "Advanced Carbon Nanostructures" (St. Peꢀ
tersburg, July 4—8, 2011), St. Petersburg, 2011, 279.
19. L. Tietze, T. Eicher, Reaktionen und Synthesen im organischꢀ
chemischen Praktikum und Forschungslaboratorium, Georg
Thieme Verlag Stuttgart, New York, 1991.
16. L. Isaacs, A. Wehwig, F. Diederiсh, Helv. Chim. Acta, 1993,
76, 1231.
20. W. C. Chan, P. D. White, in Fmoc Solid Phase Peptide Synꢀ
thesis. A Practical Approach, Eds W. C. Chan, P. D. White,
Oxford University Press, New York, 2008, p. 50.
21. J. Stewart, J. Young, Solid Phase Peptide Synthesis, W. H.
Freeman and Co., San Francisco, 1969.
17. P. B. Davidovich, D. N. Nikolaev, L. B. Piotrovskii, N. S.
Panina, Tez. dokl. V shkolyꢀseminara molodykh uchenykh
"Kvantovoꢀkhimicheskie raschety: struktura i reaktsionnaya
sposobnost´ organicheskikh i neorganicheskikh molekul" [Abstrs
V School—Seminar of Young Scientists "Quantum Chemical
Calculations: Structure and Reactivity and Organic and Inorꢀ
Received November 16, 2011;
in revised form January 26, 2012