Synthesis of Pyrrolidine Ring-Fused Fullerene Multicarboxylates by Photoreaction

Article abstract of DOI:10.1021/jo971990i

Aminopolycarboxylic esters react with C₆₀ under photolysis to produce fullerene multicarboxylates. Irradiation of tetramethyl ethylenediaminetetraacetate (EDTA) with C₆₀ yields the EDTA-containing fullerene monoadduct C₆₀(MeOOCCH)₂NCH₂CH₂N(CH ₂COOMe)₂. In addition, several other C₆₀ monoadducts are also isolated and characterized, including compounds due to EDTA fragmentation. Similar results are observed with pentamethyldimethylenetriaminepentaacetate (DTPA). When partially methylated nitrilotriacetic acid is irradiated with C₆₀, decarboxylation occurs and organodihydrofullerene derivatives such as C₆₀(H)(CH₂N(CH₂COOMe)₂) are formed. Radical mechanisms are proposed for both types of photoreactions. The fullerene derivatives are characterized by their spectroscopic data. Photoreactions of C₆₀ with other analogous molecules also support the conclusions.

Full text of DOI:10.1021/jo971990i

4
240
J . Org. Chem. 1998, 63, 4240-4247
Syn th esis of P yr r olid in e Rin g-F u sed F u ller en e Mu ltica r boxyla tes
by P h otor ea ction
,
†
†
†
†
†
†
Liangbing Gan,* J ianfeng J iang, Wen Zhang, Yang Su, Yaru Shi, Chunhui Huang,
‡
‡
§
J inqi Pan, Mujian L u¨ , and Yi Wu
State Key Laboratory of Rare Earth Material Chemistry and Applications, Peking University,
Beijing 100871, China, Center of Instrumental Analysis, Department of Chemistry, Peking University,
Beijing 100871, China, and Beijing Institute of Microchemistry, Beijing 100091, China
Received October 29, 1997
Aminopolycarboxylic esters react with C60 under photolysis to produce fullerene multicarboxylates.
Irradiation of tetramethyl ethylenediaminetetraacetate (EDTA) with C60 yields the EDTA-containing
fullerene monoadduct C60(MeOOCCH) NCH CH N(CH COOMe) . In addition, several other C60
2 2 2 2 2
monoadducts are also isolated and characterized, including compounds due to EDTA fragmentation.
Similar results are observed with pentamethyldimethylenetriaminepentaacetate (DTPA). When
partially methylated nitrilotriacetic acid is irradiated with C60, decarboxylation occurs and
2 2 2
organodihydrofullerene derivatives such as C60(H)(CH N(CH COOMe) ) are formed. Radical
mechanisms are proposed for both types of photoreactions. The fullerene derivatives are
characterized by their spectroscopic data. Photoreactions of C60 with other analogous molecules
also support the conclusions.
Derivatization of C60 has played a key role in the
pyrrolidine ring-fused fullerenes.11 Even though multi-
steps of C-N bond-breaking and formation processes are
involved, the photoreaction gave isomerically pure
monoadduct very efficiently (80% yield in less than 30
min).
1
biological studies of fullerenes. The introduction of a
suitable pendant group not only improves the solubility
of the fullerene but also provides a handle to anchor C60
to a specific target for drug delivery and/or photostudy.2
During the past a few years, water-soluble fullerene
derivatives have been reported as HIV protease inhibitors
and DNA-cleavage reagents.3,4 Bioactive lipophilic
fullerene steroids have also been prepared that showed
inhibition of radiolabeled estradiol binding to the cytosolic
5
estrogen receptor. Several other steroidal fullerenes
have also been reported.6 Despite the wide variety of
biological activities reported, much work remains to be
done to develop practicable applications for fullerenes.
We have begun to investigate the photoreaction sys-
tematically and extended the reaction to aminopolycar-
boxylates. Aminopolycarboxylic acids such as EDTA and
DTPA are among the best known complexones or poly-
dentate ligands.12 They have been widely used in both
fundamental research and practical applications. Their
lanthanide complexes are potential immunoassay agents.
The Gd complex of DTPA is the first commercial MRI
contrast reagent. The attachment of such ligands to C60
should open the scope for their potential applications.
Here, we report the preparation of EDTA- and DTPA-
containing fullerenes. Most of our previous work involves
the use of amino acid esters. We have now found
serendipitously that amino acids may be decarboxylated
and add to C60 to form dihydrofullerenes.13
Fullerene amino acids are of great importance as
bioactive reagents. Several methods have been developed
We have recently reported that
glycine esters add directly to C60 under photolysis to form
for their preparation.7
-10
*
To whom correspondence should be addressed. E-mail: gan@
chemms.chem.pku.edu.cn. Fax: 86-10-6275-1708.
†
State Key Laboratory of Rare Earth Material Chemistry and
Applications.
‡
Department of Chemistry.
Beijing Institute of Microchemistry.
§
(
1) J ensen, A. W.; Wilson, S. R.; Schuster D. I. Bioorg. Med. Chem.
996, 4, 767.
2) An, Y. Z.; Chen, C. H. B.; Anderson, J . L.; Sigman, D. S.; Foote,
C. S.; Rubin, Y. Tetrahedron 1996, 52, 5179.
3) (a) Friedman, S. H.; DeCamp, D. L.; Sijbesma, R. P.; Srdanov,
1
(
(
G.; Wudl, F.; Kenyon, G. L. J . Am. Chem. Soc. 1993, 115, 6506. (b)
Sijbesma, R. P.; Srdanov, G.; Wudl, F.; Castoro, J . A.; Wilkins, C.;
Friedman, S. H.; DeCamp, D. L.; Kenyon, G. J . Am. Chem. Soc. 1993,
1
15, 6510.
4) Tokuyama, H.; Yamago, S.; Nakamura, E.; Shiraka, T.; Sugiura
Y. J . Am. Chem. Soc. 1993, 115, 7918.
5) Wilson, S. R.; Lu, Q.; Cao, J .; Zhao, H.; Wu, Y.; Schuster, D. I.
Proc. Electrochem. Soc. 1995, 95-10, 1179.
6) (a) Ganapathi, P. S.; Rubin, Y.; Friedman, S. H.; Kenyon, G. L.
(
(8) Prato, M.; Bianco, A.; Maggini, M.; Scorrano, G.; Toniolo, C.;
Wudl, F. J . Org. Chem. 1993, 58, 5578.
(9) Skiebe, A.; Hirsch, A. J . Chem. Soc., Chem. Commun. 1994, 335.
(10) Isaacs, L.; Wehrsig, A.; Diederich, F. Helv. Chim. Acta 1993,
76, 1231. Isaacs, L.; Diederich, F. Ibid. 1993, 76, 2454.
(
(
J . Org. Chem. 1995, 60, 2954. (b) Hummelen, J . C.; Knight, B. W.;
LePeq, F.; Wudl, F.; Yao, J .; Wilkins, C. L. J . Org. Chem. 1995, 60,
(11) Gan, L. B.; Zhou D. J .; Luo, C. P.; Tan, H. S.; Huang, C. H.;
Lu, M. J .; Pan, J . Q.; Wu, Y. J . Org. Chem. 1996, 61, 1954.
(12) (a) Wilkinson, G.; Gillard, R.; McCleverty, J . A. Comprehensive
Inorganic Chemistry; Pergmon Press: New York, 1987; Chapter 20.3
(by G. Anderegg). (b) Diamandis, E. P. Clin. Chem. 1991, 37, 1486.
5
32.
(7) An, Y. Z.; Anderson, L. J .; Rubin, Y. J . Org. Chem. 1993, 58,
4
799.
S0022-3263(97)01990-7 CCC: $15.00 © 1998 American Chemical Society
Published on Web 06/02/1998

Synthesis of Fullerene Multicarboxylates by Photoreaction
J . Org. Chem., Vol. 63, No. 13, 1998 4241
Syn th esis of Mon o- a n d Dica r boxylic F u ller en e
Der iva tives
Sch em e 1. Mech a n ism of P yr r olid in e Rin g-fu sed
F u ller en e F or m a tion
Treatment of L-alanine ester with bromoacetic methyl
ester results in the formation of R-methyliminodiacetic
ester. Photolysis of the iminodiacetic ester with C60
produced compound 2 in high yields. Pure R-alanine
ester reacts very slowly with C60. Introduction of the
second acetic group to L-alanine improves the photolysis
significantly in both the yield of the isomerically pure
product and the rate of the reaction.
lidine ring; the other is the unsymmetric product 4. In
the reaction, only the unsymmetric product 4 was iso-
lated. So the methyl group on the N instead of the second
methylene group loses the other H atom.
To confirm its structure, compound 4 was also prepared
by the 1,3-dipole thermal addition method, i.e., refluxing
a mixture of formaldehyde, iminodiacetic methyl ester,
The net result of the reaction is the loss of two
2
hydrogen atoms from the CH and CH carbons, respec-
tively. Unlike the glycine reaction,11 there is no C-N
bond-breaking process involved here. Isolation of the
mixed ester derivative 2 strongly supports this conclu-
sion. If there were C-N bond breaking and -formating
processes, some other products such as the dimethyl ester
anolog of 2 would be produced since the reaction was
carried out in a mixture of methanol and toluene.
and C60
.
To form compound 2, the initial key step is probably
the formation of the R-carbon-centered radical (Scheme
1
). The R-carbon-centered radical may be formed by
direct H atom transfer. C60 is well-known to generate
singlet O
acid. The presence of a small amount of O
1
4
2
,
which may abstract the H from the amino
has been
2
proven to accelerate the photoreaction. Alternatively, the
radical may also be formed by electron transfer, followed
by proton loss. C60 could act as the electron acceptor.
The radical then adds to the electron-deficient C60. The
cyclization and the formation of the other C-C bond
could follow the same procedure. Pathways similar to
Scheme 1 can also explain the formation of compounds
Like the primary and secondary aminocarboxylic acids,
tertiary aminocarboxylic acids also react under the same
conditions. Sarcosine was first treated with methyl
iodide to give the N,N-dimethylglycine ester. Photolysis
of this glycine-derived tertiary aminocarboxylic acid gave
3
and 4.
According to the above-proposed mechanism, the chiral-
ity due to the asymmetric carbon of L-alanine part would
2
be changed because of the formation of an sp carbon
3
as the only isolated product. The net result of the
radical. To confirm the chirality change, we measured
the CD spectra of the starting materials and the product.
There is no apparent band in the CD spectra of product
reaction is also a loss of two H atoms, reminiscent of the
above iminodiacetic acid reaction. Compound 3 can also
be prepared by the 1,3-dipole thermal addition.11 Thus,
2
.
A comparison of the spectra indicates that the
heating a mixture of sarcosine and formaldehyde with
1
chirality has indeed been changed.
C
60 gives a compound with the same H NMR and FTIR
It is well-known that the R-centered radical is the most
stable for amino acids.15 The combined action of electron-
donating amino group and the electron-withdrawing
carboxyl group helps to stabilize the radical. Such a
spectra as those of 3.
“
push-pull”-stabilized radical has been extensively stud-
16
ied. Free-radical amino acid reaction is one of the major
synthesis methods for amino acid and derivatives.
1
5
In a separate study, we found that â-alanine ethyl ester
does not react with C60 under exactly the same photo-
conditions. This supports the idea that the above R-car-
bon-centered radical is the reactive species and the
R-carbon is the reactive center. If the amino group were
In an extension of the iminodiacetic reaction, the
iminodiacetic methyl ester was treated with methyl
iodide to yield the N-methylnitrilodiacetic ester with two
acetic groups attached to the same nitrogen atom. Ac-
cording to the previous results, two products may be
expected: one is the symmetric pyrrolidine with the two
ester groups attached at the 2,5-positions of the pyrro-
the reactive site, â-alanine should also add to C60
.
(14) (a) Tokuyama, H.; Yamago, S.; Nakamura, E.; Shiraki, T.;
Sugiura, Y. J . Am. Chem. Soc. 1993, 115, 7918. (b) Orfanopoulos, M.;
Kambourakis, S. Tetrohedron Lett. 1994, 35, 1945.
(15) Easton, C. J . Chem. Rev. 1997, 97, 53.
(16) Katritzky, A. R.; Soti, F. J . Chem. Soc., Perkin Trans. 1 1974,
1427.
(
13) A communication of the decarboxylation work has been pub-
lished. Zhang, W.; Su, Y.; Gan, L.; J iang, J .; Huang, C. Chem. Lett.
997, 10, 1007.
1

4
242 J . Org. Chem., Vol. 63, No. 13, 1998
Gan et al.
Because of the presence of the two carbon units between
the amino and the carbonyl groups in the â-alanine, there
is no “push-pull” stabilization effect as in the R-amino
acids. Radiolysis results show that amino acids such as
â-alanine and ꢀ-aminocaproic do not undergo deamina-
tion, whereas deamination of R-amino acids through
radical mechanism is well documented.17
Recently, Sun and co-workers reported that triethyl-
amine adds to C60 to form a pyrrolidine ring-fused product
under photolysis.18 Cheng and co-workers later found
that irradiation of trimethylamine with C60 also yields a
pyrrolidine product.19 For both the two reactions, a two-
step photoinduced electron-transfer-proton loss mech-
anism was proposed.
Syn th esis of EDTA a n d DTP A Con ta in in g C60
Der iva tives
reaction solution. The enhanced thermal stability of 6
over 5 may be due to steric reasons. In compound 6, the
bigger substituent group is further away from the C60
sphere.
The above results have demonstrated that both sec-
ondary and tertiary aminocarboxylates can add to C60
under photolysis. To explore the photoreaction further,
we tried the reaction with the methyl ester of EDTA.
EDTA forms stable complexes with almost all metal
cations. Such aminoacetic group-containing organic
1
2
ligands have been named complexones. Formation of
a C60-EDTA derivative introduces C60 into the complex-
one family.
DTPA is another well-known aminopolycarboxylic acid.
It has one more carboxyl group than EDTA. Similar to
the EDTA reaction, there are several bands eluted from
the silica gel column. Three of them are due to the
degradation of DTPA, namely compounds 1, 4 and 7.
Both 1 and 4 are also produced in the EDTA reaction.
Compound 7 is very similar to the EDTA product 6 but
has one less ester group. The substituents on compounds
4 and 7 are just the two fragments of a CH -CH bond
Photolysis of the EDTA tetramethyl ester with C60
produced four products, namely compounds 1, 4, 5 and
. The first two were eluted on the silica gel column with
6
toluene. Both of them have been prepared previously
using other starting materials. The purity of the EDTA
2
2
1
ester was checked by H NMR. There is no noticeable
cleavage in a DTPA molecule. The same type of CH -
2
impurity. To form the symmetric dicarboxylic compound
CH bond cleavage of a EDTA molecule gives two frag-
2
1
, the nitrogen ethylene bond N-CH
in the EDTA molecule; to form the unsymmetric dicar-
boxylic compound 4, the ethylene CH -CH bond must
2
CH
2
must be broken
ments with the same structure, both of which result in
compound 4.
2
2
be broken. The percentage of these two products in-
creases along with the length of the irradiation.
Both compounds 5 and 6 are what we intended. They
contain an entire EDTA substituent. The formation of
5
is analogous to the earlier reaction of N-methylnitrilo-
diacetic ester. The ethylene carbon instead of the second
methylene carbon next to the carboxyl group is added to
C
60. Compound 6 is symmetric. Here, two methylene
From the result of the EDTA reaction, three DTPA-
containing products are possible, 8a -c, depending on
which two carbons are added to C60. Analogous to the
EDTA products 5 and 6, at least one of the CH groups
on the pyrrolidine ring is next to a carboxylic ester group
in these three DTPA-containing isomers. The yield of
8a appears to be the highest and is the only one
characterized among them. Compound 8a is both the
kinetic and the thermodynamic product. Unlike the
EDTA derivative 5, it does not rearrange to the sterically
favored isomer 8c. The rearrangement here would
require the cleavage of two C-C bonds and the C60 sphere
to shift a relatively long distance. The two CH groups
on the two pyrrolidine rings between 8a and 8b are
essentially the same. They only slightly differ in the
sterical hindrance. The observed preference for 8a over
carbons on the same N atom are attached to the 1,2-
positions of C60. Between compound 5 and 6, 5 appears
to be the kinetic product, whereas 6 is the thermody-
namic product. If the product mixture is chromato-
graphed right after the photolysis, the relative yield of 5
is higher than that of 6. On the other hand, if the
reaction solution is kept at room temperature overnight
after the irradiation, the same purification procedure
gives 6 in much higher percentage than that of 5. This
indicates that 5 could slowly rearrange into 6 in the
(
(
17) Garrison, W. M. Chem. Rev. 1987, 87, 381.
18) Lawson, G. E.; Kitaygorodskiy, A.; Ma, B.; Bunker, C. E.; Sun,
Y. P. J . Chem. Soc., Chem. Commun. 1995, 2225.
19) Liou, K. F.; Cheng, C. H. J . Chem. Soc., Chem. Commun. 1996,
423.
(
1

Synthesis of Fullerene Multicarboxylates by Photoreaction
J . Org. Chem., Vol. 63, No. 13, 1998 4243
F igu r e 1. 13C NMR spectrum of 6.
8
b may be due to the slightly stronger electron-donating
2
are the two CH groups of the same acetic group, but the
ability of the center N atom. Thus, a stronger push-
pull stabilization effect is present for the R-carbon-
centered radical formed from the center acetic group.
2
two H atoms on each of these two CH are nonequivalent.
In the 1H NMR spectrum, it is evident that a small
amount of the stereoisomer is also present. The major
1
stereoisomer may have the transconfiguration. The H
NMR spectrum of 6 also shows just one major stereoi-
somer. The CH
exhibits complex multiplets due to germinal coupling and
coupling to the adjacent CH group. This indicates that
2
group attached to the pyrrolidine
2
the pyrrolidine probably has a trans geometry. The
coupling of the two methylene protons attached to the
pyrrolidine should be much simpler in a cis configuration.
Such magnetic difference between the cis and transiso-
mers has been successfully used to assign the configu-
ration of heterocyclic bases.20 In such a photoinduced
radical addition reaction, the sterically favored transi-
1
3
somer is expected and has been further proven by
NMR spectra.
C
In the 13C NMR spectrum of 5, there are a total of 10
3
sp signals in the range 49-76 ppm, corresponding to the
eight types of EDTA ester carbons and the two fullerene
carbons at the junction. The carbonyl carbons are in a
1:1:2 intensity ratio at 171.83, 171.42, and 171.14 ppm.
Sp ectr oscop ic Da ta of th e EDTA a n d DTP A C60
Der iva tives
2
For the fullerene sp carbons, 58 signals are observed in
The compounds were characterized by their spectro-
the 136-156 ppm range, some of which are overlapped.
1
13
scopic data, in particular their H and C NMR spectra.
All compounds clearly showed bands at around 430 nm
on the UV-vis spectra. This band is characteristic of
addition at the [6,6] junction. The FDMS showed clearly
the molecular ion signal for compounds 5-8.
The 13C NMR spectrum of the symmetric compound 6
(Figure 1) showed fewer signals. There is a total of 30
well-resolved fullerene carbon signals, including the two
at the junction. This clearly indicates the above-
mentioned trans configuration, which has a C
For the cis isomer there should be a total of 32 fullerene
signals due to the C symmetry.
2
symmetry.
1
In the H NMR spectrum of 5, the methine proton next
to the carboxylic group appears as a singlet. The other
methine proton on the pyrrolidine ring shows a doublet
s
The 13C NMR spectrum of 8a shows three signals in a
of doublets due to coupling to the adjacent CH
The two H atoms of this CH are nonequivalent and
appear at 4.20 and 3.53 ppm, respectively, as two doublet
of doublets. The other CH group attached to the
2
group.
2
:2:1 intensity ratio both for the carboxyl carbons and
2
for the methoxy carbons (confirmed by DEPT spectrum).
This rules out the structure 8b, for which there should
2
pyrrolidine also shows germinal coupling. The two
methoxy groups distant from the C60 are equivalent, so
(20) Hill, R. K.; Chan, T. H. Tetrahedron 1965, 21, 2015.

4
244 J . Org. Chem., Vol. 63, No. 13, 1998
Gan et al.
Sch em e 2. Mech a m ism of Dih yd r ofu ller en e
be four methoxy signals. Structure 8c is ruled out by
the number of signals in the fullerene region. There
F or m a tion
should be 30 fullerene signals for 8c due to its C
2
symmetry, but 58 signals in the 130-150 ppm region are
observed with a few overlapped. The signals show a
pattern very similar to that of 5, in agreement with the
similarity between 5 and 8a .
P r ep a r a tion of Or ga n od ih yd r ofu ller en es by
Deca r boxyla tion
The decarboxylation reaction is a case of serendipity.
The initial purpose was to investigate the reactivity of
nitrilotriacetic ester with C60. Nitrilotriacetic acid has
three acetic groups attached to the same N atom. All
the previous aminocarboxylic acids have only up to two
acetic groups attached to the same N atom. In an
attempt to prepare the nitrilotriacetic methyl ester,
nitrilotriacetic acid ester was refluxed in methanol under
HCl atmosphere. The crude mixture was used directly
without further purification except the pH of the solution
was adjusted to around 8.5 by addition of sodium carbon-
ate. Its photoreaction with C60 was repeated several
times. Each time some compound 1 could be isolated. It
appears that 1 is probably the most stable product in this
system. Several reactions give it as a degradation
byproduct, such as those of EDTA and DTPA.
roacetic methyl ester in methanol at pH 9. The resulting
mixture was then irradiated with C60. Indeed, compound
9
was isolated as the major product. Another side
product isolated here is again compound 1. To test the
assumption of the presence of bisesterified product,
iminodiacetic methyl ester was refluxed with bromoacetic
acid in methanol at pH 9. The resulting mixture yielded
compound 10 when irradiated with C60
.
The reaction between iminodiacetic acid and chloro-
acetic methyl ester was repeated under different condi-
tions. If the reaction was stopped after refluxing for 4
h, irradiation of the mixture with C60 gave just 9 and 1.
When the refluxing was continued for 12 h, irradiation
of the mixture with C60 gave a third product, 10. There
are two carbonyl ester groups in compound 10. So in the
slightly basic methanol solution, the acetic acid groups
could be esterified by refluxing, and some nitrilotriacetic
monoester was converted to the bisester.
Two other products were also isolated from the above
reaction, namely compounds 9 and 10. There are two
structures possible for compound 9. Structure 9A is the
bis-[6,6] closed adduct, reminiscent of the 1,2,3,4-tet-
2
1b
rahydrofullerene C60
H
4
.
Structre 9B is the bis-[6,5]
closed C60 adduct. Wilson et al. reported a similar
tetrahydro fullerene adduct in the irradiation of 1,3-
2
1a
diones with C60
.
Both 9A and 9B have a pyrrolidine
To further verify the decarboxylation of nitrilotriacetic
acid, we prepared the following acetic acid derivatives
and investigated their photoreaction with C60. As ex-
pected, decarboxylation takes place, and products 11 and
ring and two H atoms on the same six-membered ring.
The NMR data could not distinguish them since they both
have a C
formation is that some monoesterified product
MeOOCCH N(CH COOH) is present in the crude mix-
ture of the esterification reaction. To form compound 10,
some bisesterified product (MeOOCCH NCH COOH is
s
symmetry. A plausible explanation for its
1
2 were isolated.
2
2
2
2
)
2
2
probably present. It has been shown that acids are easier
to decarboxylate than the corresponding ester. In the
1
,3-dipole addition reactions of sarcosine with C60, CO
2
is lost, whereas in the reaction of sarcosine esters with
C
60, the ester group remains on the pyrrolidine.22
A possible path way is shown in Scheme 2. Similar to
the ester reaction pathway, the first step is the electron
transfer and proton loss. Under the conditions employed
2
here, these steps are easily initiated. The CO loss from
carboxyl radicals is well-known.23 The so-formed ami-
nomethyl radical then adds to C60. The final step is the
abstraction of hydrogen from the environment. The
alkylation of electron-deficient molecules by decarboxy-
lation via photoinduced electron transfer is also well-
(21) (a) J ensen, A. W.; Khong, A.; Saunders: M.; Wilson, S. T.;
Schuster, D. I. J . Am. Chem. Soc. 1997, 119, 7303. (b) Henserson, C.
C.; Rohlfing C. M.; Assink, R. A.; Cahill, P. A. Angew. Chem., Int. Ed.
Engl. 1994, 33, 786.
(
22) (a) Maggini, M.; Scorrano, G.; Prato, M. J . Am. Chem. Soc. 1993,
15, 9798. (b) Maggini, M.; Scorrano, G.; Bianco, A.; Toniolo, C.;
Sijbesma, R. P.; Wudl, F.; Prato, M. J . Chem. Soc., Chem. Commun.
994, 305.
23) Okada, K.; Okubo, K.; Oda, M. J . Photochem. Photobiol. A:
Chem., 1991, 57, 265
1
1
To test the assumption of the presence of monoesteri-
fied product, iminodiacetic acid was refluxed with chlo-
(

Synthesis of Fullerene Multicarboxylates by Photoreaction
J . Org. Chem., Vol. 63, No. 13, 1998 4245
Ta ble 1. F u ller en yl P r oton Ch em ica l Sh ifts of Selected
Dih yd r ofu ller en es w ith th e Gen er a l F or m u la r C60(H)R
known.24 These reactions usually give many byproducts,
and the yields of alkyldihydro derivatives are less than
2
0%.
Photolysis of the methyl ester of the piperidineacetic
acid still follows the previous pattern, yielding the
pyrrolidine ring-fused derivative 13.
F igu r e 2. 1H NMR spectrum of 9.
Ch a r a cter iza tion of Or ga n od ih yd r ofu ller en es
All the NMR data were obtained using a mixture of
CS
compound 9, for which an additional sample was pre-
pared using o-dichlorobenzene-d as the solvent. All the
H NMR spectra showed a clear fullerenyl proton. Table
2 3
and CDCl in a 10:1 ratio as the solvent except for
4
1
1
shows a comparison of the chemical shifts between
several dihydrofullerenes in the literature and the de-
rivatives prepared here. It has been well demonstrated
that the chemical shift of the fullerenyl proton depends
on the steric size of the adjacent group. The increased
size of the adjacent group causes downfield shift. For
example, the chemical shift changes from 6.04 to 6.67
ppm on going from C60(H)Me to C60(H)-t-Bu.26 Our
compounds also support this trend. Among compounds
F igu r e 3. 13C NMR spectrum of 10.
addition. The two protons on each methylene group of
the pyrrolidine ring are nonequivalent. They appear at
4.07 and 4.49 ppm as two doublets with a germinal
coupling constant of 9.2 Hz. The CH next to the ester
2
group appears as a singlet, reflecting the mirror plane
bisecting the pyrrolidine ring.
The 13C NMR spectrum confirms the proposed struc-
ture. The spectrum of 10 (Figure 3) shows a distinct
signal at 57.36 ppm for the fullerenyl C-H. The assign-
ment was carried out by performing a DEPT spectrum.
Unlike the spectrum of 6, there are 32 well-resolved
fullerene carbon signals, reflecting the C symmetry. The
s
four fullerene carbons located on the mirror plane are
with half-intensity compared to others. Compounds 11
1
1, 12, and 10, the steric hindrance of the R group
increases from the six-membered ring to the noncyclic
iminodiacetic group. In correspondence with this order,
the chemical shifts of the fullerenyl proton also increase
from 6.9 to 7.1 ppm. Between the two sterically compa-
rable compounds 11 and 12, the chemical shifts are
virtually the same.
Compound 9 exhibits fullerenyl proton at 6.03 ppm
(
Figure 2). This chemical shift is only slightly greater
than that of the dihydrofullerene and close to that of C60
H)Me with the smallest R group methyl. This strongly
suggests that the structure of 9 is different from the 1,2-
and 12, also with C
pattern on the 13C NMR spectra. The solubility of 9 is
smaller. The signals from saturated CS and CDCl were
not intense enough to assign all the signals. When the
solvent was changed to o-dichlorobenzene-d , all the
signals appeared as expected. The DEPT spectrum
located the CH , CH, and two CH signals at 51.25, 56.28,
3.79, and 72.05 ppm, respectively. The carbonyl ester
carbons appear at 169.13 ppm. In the 140-151 ppm
s
symmetry, show an almost identical
-
(
2
3
4
(24) (a) Brimage, D. R. G.; Davidson, R. S. J . Chem. Soc., Perkin
Trans. 1 1973, 496. (b) Libman, J . J . Am. Chem. Soc. 1975, 97, 4139.
3
2
(
(
25) Henderson, C. C.; Cahill, P. A. Science 1993, 259, 1885.
26) Hirsch, A.; Grosser, T.; Skiebe, A.; Soi Antonio. Chem. Ber.
5
1
993, 126, 1061.

4
246 J . Org. Chem., Vol. 63, No. 13, 1998
Gan et al.
region, there are 30 signals corresponding to the remain-
ing 56 fullerene sp carbons.
+ 1). UV-vis (CHCl
3
): 258, 313, 428 nm. Anal. Calcd for
C H NO : C, 89.96; H, 1.44; N, 1.54. Found: C, 89.28; H,
68 13 4
2
1
.22; N, 1.23.
Com p ou n d 4 was prepared using the same procedure as
Su m m a r y
that for compound 2. The yield is about 60% on the basis of
1
converted C60 (about 20% could be recovered). H NMR (400
Photolysis of aminopolycarboxylates with C60 has been
shown to be an effective method for the preparation of
isomerically pure fullerene derivatives. Both aminocar-
boxylic acids and aminocarboxylic esters are reactive
toward C60 under the photochemical conditions. For the
acids, decarboxylation occurs and organodihydrofullerenes
are formed; for the esters, pyrrolidine ring-fused fullerenes
are the major products. All the reactions involve radical
formation. Unlike the primary amino acid esters that
undergo complicated bond-breaking and -forming pro-
cesses, amino acid esters with secondary and tertiary
amino groups can add to C60 by simply losing two H
atoms. Compared to the well-known 1,3-dipole addition
method for the preparation of pyrrolidine ring-fused
fullerenes, the photoreaction reported here avoids the use
of aldehydes or ketones and is specially suited for the
fullerene-containing complexones such as the EDTA C60
derivative.
MHz, CS
H), 3.90 (s, 3H), 3.86 (s, 3H). C NMR (100.6 MHz, CS
CDCl ) δ: 169.24 (COOCH ), 168.60 (COOCH ), 154.28 (2C),
153.46, 152.58, 151.83, 150.43, 147.01, 146.90, 146.13, 146.04,
145.94 (3C), 145.70 (4C), 145.44, 145.42, 145.32, 145.25, 145.18
2 3
/CDCl ) δ: 5.60 (s, 1H), 4.77-5.06 (q, 2H), 4.22 (q,
13
2
2
/
3
3
3
(2C), 145.10 (2C), 145.07, 144.90 (3C), 144.34, 144.13 (2C),
1
1
1
6
1
44.05, 142.72 (3C), 142.35, 142.31 (3C), 141.86 (3C), 141.75,
41.70, 141.59, 141.49 (2C), 141.46, 141.43, 139.99, 139.94,
39.38, 139.26, 137.47, 136.12, 135.90, 135.39, 73.80, 72.19,
8.66, 64.22, 51.56, 51.19, 50.48. FT-IR: 527, 1173, 1188,
-1
+
202, 1431, 1738, 1751 cm . FDMS m/z: 895 (M + 1), 837
+
(M - Me). UV-vis (CHCl ): 256, 310, 430 nm. Anal. Calcd
for C67
3
11 4
H O N: C, 90.03; H, 1.24; N, 1.57. Found: C, 89.60;
H, 0.95; N, 1.30.
P h otolysis of EDTA Tetr a m eth yl Ester w ith C60. To a
C
60 (60 mg, 0.08 mmol) solution in 250 mL of toluene was
added 0.7 g (2.0 mmol) of EDTA tetramethyl ester in 10 mL
of methanol. The mixture was irradiated until the color
changed from purple to slightly reddish (about 30 min). The
solvent was removed by a rotavapor. The residue was chro-
matographed on silica gel. Toluene first eluted 10 mg of
unreacted C60 and then compound 4 (6 mg, 0.0067 mmol) in
Exp er im en ta l Section
1
0% yield based on converted C60. The third band was
Gen er a l Meth od s. Reagents were all reagent-grade com-
mercials. C60 includes traces of solvents. EDTA tetramethyl
ester was prepared according to the literature.28 DTPA
pentamethyl ester was prepared in a similar way. All the
reactions were carried out under atmosphere without any
special caution to exclude air. All the photochemical reactions
were carried out similarly. Various household light bulbs can
be used as the light source. In this experiment, an overhead
project light bulb (250 W) was used for most of the reactions,
which was cooled by a water jacket and emerged into the
reaction container.
Com p ou n d 2. L-alanine ethyl ester and bromoacetic meth-
yl ester in 1:1.4 ratio were mixed in methanol. The pH of the
solution was adjusted with sodium carbonate to around 8.5.
The solution was refluxed for 8 h and then filtered. During
the refluxing, sodium carbonate was added occasionally to
maintain the pH at 8.5. Enough of the methanol filtrate (about
compound 1 (6 mg, 0.0067 mmol), also in 10% yield on the
basis of converted C60. At this stage, the eluting solvent was
changed to toluene/ethyl acetate 4:1. Compounds 5 and 6 were
eluted as two well- separated bands. The yields of 5 and 6
were about the same at 25% on the basis of converted C60 (19
mg, 0.017 mmol).
Com p ou n d 5. 1H NMR (400 MHz, CS
/CDCl ) δ: 5.82 (s,
2 3
1H), 5.60 (q, 1H), 5.04 (d, 1H), 4.20 (q, 1H), 4.18 (d, 1H), 3.89
(s, 3H), 3.87 (s, 3H), 3.85 (d, 2H), 3.75 (d, 2H), 3.71 (s, 6H),
3.53 (q, 1H). 13C NMR (100.6 MHz, CS
/CDCl
), 171.14 (2C, 2COOCH
55.06, 153.89, 152.40, 150.91, 147.37, 147.36, 147.31, 146.64,
) δ: 171.83 (1C,
2
3
COOCH
3
), 171.42 (1C, COOCH
3
3
),
1
1
1
46.61, 146.45, 146.37, 146.35 (2C), 146.26, 146.19, 146.17,
46.15, 146.09, 146.05, 145.99, 145.72, 145.52 (2C), 145.45
(
1
(
2C), 145.38, 145.36, 145.34, 145.33, 145.28, 145.24 (2C),
45.22, 143.15, 143.02, 142.74, 142.66 (2C), 142.64, 142.24
2C), 142.13 (3C), 142.04, 142.01, 141.88, 141.84, 141.72,
1
1
5
1
2
41.67, 140.25, 139.88, 139.67, 139.34, 137.01, 136.99, 136.38,
36.01, 75.12, 73.12, 71.75, 66.84, 56.82, 54.68 (2C), 52.00,
1.95, 51.64 (2C), 49.94. FT-IR: 527, 1017, 1174, 1203, 1351,
3
0 mL) was added to a C60 (60 mg) toluene (200 mL) solution
so that the ratio between C60 and the ester is about 1:100. To
make the solution homogeneous, some toluene should be added
if the C60 was precipitated by methanol; some methanol should
be added if the solution separated into two layers. The
resulting solution was irradiated until the color changed from
purple to reddish (about 30 min). Solvent was removed in a
vacuum and the residue chromatographed over a silica gel
column using toluene as eluent. Toluene first eluted unreacted
-
1
+
433, 1740 cm
56, 311, 431 nm.
Com p ou n d 6. 1H NMR (400 MHz, CS
H), 3.90 (d, 2H), 3.81 (s, 6H), 3.78 (d, 2H), 3.70 (s, 6H), 3.47-
.
FDMS m/z 1066 (M ). UV-vis (CHCl
3
):
2
3
/CDCl ) δ: 6.07 (s,
2
3
1
3
.50 (m, 2H), 3.18-3.32 (m, 2H). C NMR (100.6 MHz, CS
) δ: 170.97 (2C, 2COOCH ), 170.28 (2C, 2COOCH
53.83, 151.12, 147.42, 146.42, 146.38, 146.10 (6C), 145.79,
2
/
3
),
CDCl
3
3
1
1
1
C
60 (10 mg) and then compound 2 as well separated bands.
The yield is about 50% on the basis of converted C60. Crystal-
line solid was obtained upon slow evaporation of a CS
45.64 (4C), 145.52, 145.34, 145.30, 144.60, 144.56, 143.12,
42.77, 142.71, 142.27, 142.20, 142.07, 141.95, 141.88, 141.78,
2
/
1
140.06, 139.70, 137.02, 136.40 (all represent 2C except indi-
petroleum ether solution. H NMR (400 MHz, CS
2
/CDCl
3
) δ:
3
3
cated), 73.71 (2C, CHCOOCH ), 71.46 (2C, sp C60), 54.59 (2C,
5
3
.69 (s, 1H), 4.42 (m, 1H), 4.25 (m, 1H), 3.88 (s, 3H), 2.40 (s,
1
3
2CH COOCH ), 51.79 (2C, 2COOCH ), 51.56 (1C, CH CH ),
H), 1.25 (t, 3H). C NMR (100.6 MHz, CS
2
/CDCl
3
) δ: 171.34
2
3
3
2
2
5
1.18 (2C, 2COOCH
3
), 46.35 (1C, CH
2
CH
2
). DEPT spectrum
(
COO), 169.56 (COO), 153.01, 151.65, 150.94, 150.19, 147.11,
located the H containing carbons. FT-IR: 527, 1015, 1100,
1
1
1
1
1
1
1
7
47.09, 146.35, 146.33, 146.31, 146.27, 146.25, 146.00, 145.98,
45.95, 145.75, 145.73, 145.65, 145.61, 145.39, 145.37, 145.36,
45.33, 145.31, 145.24, 145.22, 145.18, 144.87, 144.36, 144.34,
44.26, 144.24, 143.16, 143.11, 143.08, 142.74, 142.71, 142.69,
42.37, 142.33, 142.28, 142.19, 142.10, 142.04, 142.01, 141.76,
41.74, 141.71, 141.57, 139.80, 139.79, 139.75, 139.15, 136.34,
36.32, 136.25, 136.23, 136.07, 136.04, 77.06, 76.83, 80.88,
2.53, 62.62, 52.95, 25.33, 14.11. FDMS m/z: 893 (M+ - 15
-
1
1
1
175, 1204, 1247, 1346, 1433, 1664, 1747 cm . FDMS m/z:
+
066 (M ). UV-vis (CHCl
‚3H O: C, 79.00; H, 2.47; N, 2.56. Found: C,
9.28; H, 2.52; N, 2.50.
P h otolysis of DTP A tetr a m eth yl ester w ith C60 was
3
): 256, 312, 429 nm. Anal. Calcd
for C74
7
H
22
O
8
N
2
2
carried out using the same procedure as that for the EDTA
analogue. Recovery of C60 was ∼10%. The yields of com-
pounds 7 and 8 are around 5% and 10% on the basis of
converted C60
.
(
27) Anderson, H. L.; Faust, R.; Rubin, Y.; Diederich, F. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1366.
28) Alner, D. J .; Claret, P. A.; Osborne, A. G. J . Appl. Chem.
Biotechnol. 1972, 22, 126.
Com p ou n d 7. 1H NMR (400 MHz, CS
2
3
/CDCl ) δ: 5.18 (d,
(
1H), 5.12 (s, 1H), 4.31 (d, 1H), 3.77 (s, 3H), 3.76 (s, 4H), 3.61
(s, 6H), 3.44 (m, 1H), 3.30 (m, 1H), 3.22 (m, 1H), 3.09 (m, 1H).

Synthesis of Fullerene Multicarboxylates by Photoreaction
J . Org. Chem., Vol. 63, No. 13, 1998 4247
Anal. Calcd for C67 N: C, 89.83; H, 1.46; N, 1.56.
13C NMR (100.6 MHz, CS
/CDCl
) δ: 76.70 (1C, CHCOOCH
COOCH ), 51.58 (1C,
), 50.50
),
2
3
3
13 4
H O
6
-
(
4.92 (1C, CH N), 54.52 (2C, 2CH
CH -), 51.30 (1C, COOCH ), 50.74 (2C, 2COOCH
1C, -CH -). DEPT spectrum located the H containing
2
2
3
Found: C, 90.20; H, 1.30; N, 1.38.
2
3
3
Com p ou n d 11. Piperidinoacetic acid (715 mg, 5.0 mmol)
in 50 mL of methanol (pH around 8.5) was added to a solution
of C60 (72 mg, 0.10 mmol) in toluene (200 mL). The resulting
mixture was irradiated under stirring for 10 min. The solvent
was removed. Isolation by flash column chromatography on
silica gel using toluene as eluent afforded 25 mg of unreacted
2
+
carbons. FDMS m/z: 1008 (M + 1).
1
Com p ou n d 8a . H NMR (400 MHz, CS
2
/CDCl
3
) δ: 5.78
(s, 1H), 5.53 (t, 1H), 4.83 (b, 1H), 4.74 (b, 1H), 4.00 (m, 2H),
3
6
.84 (s, 3H), 3.79 (m, 4H), 3.75 (m, 4H), 3.72 (s, 6H), 3.66 (s,
1
3
H), 3.31 (m, 2H). C NMR (100.6 MHz, CS
2
/CDCl
3
) δ: 171.48
(2C, 2COOCH
3
), 171.23 (1C, COOCH ), 170.93 (2C, 2COOCH
3
3
),
C60 and compound 11 (37 mg, in 70% yield based on converted
1
1
1
1
55.60, 153.79, 152.47, 151.31, 147.25, 147.18, 146.99, 146.73,
46.30 (2C), 146.27, 146.22, 146.19, 146.07, 145.99 (2C),
45.93, 145.62, 145.50, 145.41, 145.35 (2C), 145.28, 145.24
C ). H NMR (400 MHz, CDCl /CS ) δ: 1.71 (m, 2H), 1.93
(
6
0
3
2
13
m, 4H), 3.23 (m, 4H), 4.33 (s, 2H), 6.95 (s, 1H). C NMR
100.6 MHz, CDCl /CS ) δ: 155.53, 154.66, 147.41 (1C), 147.33,
47.28 (1C), 146.85, 146.43, 146.26, 146.21, 145.88, 145.55,
45.46, 145.44, 144.78, 144.63, 143.35, 143.16 (4C), 142.66,
42.65, 142.44, 142.14, 142.08, 141.95, 141.75, 141.72, 140.40,
(
3
2
(3C), 145.12, 144.60, 144.57, 144.46, 144.27, 143.09, 142.97,
1
1
1
1
1
42.69, 142.64 (2C), 142.59, 142.24, 142.18, 142.16, 142.12,
42.06, 142.00, 141.93, 141.85 (2C), 141.79, 141.69, 141.67
(
1
sp
2
2C), 140.19, 139.65, 139.62, 139.12, 136.84, 136.56, 136.12,
3
140.22, 136.30, 135.99, 72.59, 67.36, 58.37, 57.04 (2C), 30.29,
27.39, 24.97. FT-IR: 512, 527, 574, 1114, 1161, 1182, 1427,
35.72, 74.80 (1C, CHCOOCH
3
), 73.74 (1C, sp C60), 72.15 (1C,
60), 68.41 (1C, -CH-), 55.95 (1C, -CH -), 55.13 (2C,
COOCH ), 54.47 (2C, 2CH COOCH ), 53.39 (1C,
-), 51.42 (1C, COOCH ), 51.38 (2C, 2COOCH ), 51.28
), 46.83 (1C, -CH -). DEPT spectrum located
3
C
2
-
1
1
437, 1462, 1511 cm . UV-vis (CHCl ): 258, 324, 431 nm.
3
CH
2
3
2
3
-
CH
2
3
3
Anal. Calcd for C60H[CH N(CH ]0.5H O: C, 95.87; H, 2.02;
2
2
)
5
2
(2C, 2COOCH
3
2
N, 1.67. Found: C, 95.64; H, 1.70; N, 1.69.
the H containing carbons. FT-IR: 527, 1015, 1170, 1203, 1265,
350, 1402, 1433, 1711, 1739 cm- . FDMS m/z: 1082 (M ).
UV-vis (CHCl ): 255, 310, 431 nm. Anal. Calcd for
O: C, 77.12; H, 2.88; N, 3.43. Found: C,
1
+
Com p ou n d 12 was prepared using the same procedure as
that for compound 11. The yield is about 60% on the basis of
1
3
1
converted C60 (about 10% could be recovered). H NMR (400
C
7
79
H
31
O
10
N
3
‚2.5H
2
3 2
MHz, CDCl /CS ) δ: 3.28 (t, 4H), 3.99 (t, 4H), 4.38 (s, 2H),
7.32; H, 2.96; N, 3.4.
1
3
6
.97 (s, 1H).
3 2
C NMR (100.6 MHz, CDCl /CS ) δ: 155.04,
P r ep a r a tion of Com p ou n d s 9 a n d 10. To an iminodi-
1
54.36, 147.48, 147.32, 147.23, 146.28, 146.49, 146.47, 146.32,
acetic acid solution (5.32 g, 40 mmol) in 250 mL of methanol
were added 8.48 g (80 mmol) of anhydrous sodium carbonate
and 8.68 g (80 mmol) methyl chloroacetate. The mixture was
stirred at room temperature for 12 h and then refluxed for
another 12 h. The pH of the solution was adjusted with
sodium carbonate to 8.5 and then filtered. One-eighth of the
filtrate was taken and diluted with methanol to 50 mL. This
solution containing about 5 mmol of nitrilotriacetate was added
to a C60 (72 mg, 0.1 mmol) solution in 250 mL of toluene. To
make the solution homogeneous, more methanol was added
146.27, 145.85, 145.63, 145.51, 145.50, 145.48, 144.82, 144.61,
143.38, 142.72, 142.69, 142.41, 142.17, 142.08, 141.88, 141.80,
141.76, 140.49, 140.28, 136.17, 136.09, 72.21 (CH
2
), 67.46
3
(2CH ), 66.85 (sp C), 58.26 (CH), 55.98 (2CH ). DEPT
2
2
spectrum located the H containing carbons. FDMS m/z: 822
+
(
M ). UV-vis (CHCl
3
): 258, 327, 434 nm.
Com p ou n d 13 was prepared using the same procedure as
that for 2. The yield is about 70% on the basis of converted
1
(about 30-50 mL). The reaction flask was fitted with a
C60 (about 10% could be recovered). H NMR (400 MHz,
condenser. The mixture was irradiated for 2.5 h with two 150
W high-pressure fluorescent bulbs (the same as the bulbs on
the street in Beijing). During the photolysis, the solution
began to reflux after 1 h. The solution was treated with water
twice (20 mL each time) to separate some water-soluble
components. The organic solvents were evaporated. The
residue was chromotographed on silica gel using toluene as
eluent. Unreacted C60 (40 mg, 0.055 mmol) and compounds 9
CDCl
3
/CS
2
) δ: 1.75 (m, 1H), 2.01 (m, 3H), 2.25 (m, 1H), 2.67
(m, 1H), 3.01 (m, 1H), 3.54 (m, 1H), 3.88 (s, 3H), 5.07 (q, 1H),
13
5
.48 (s, 1H).
3 2
C NMR (100.6 MHz, CDCl /CS ) δ: 170.01,
(COOMe), 155.51, 154.11, 154.04, 150.44, 147.38, 147.26,
1
1
1
1
46.76, 146.66, 146.35 (2C), 146.32, 146.30, 146.20, 146.09,
46.08, 145.99 (2C), 145.71, 145.55, 145.54, 145.53, 145.42,
45.34 (2C), 145.31, 145.28, 145.15, 144.74, 144.65, 144.55,
44.34, 144.20, 143.13, 143.11 (2C), 143.05, 142.74, 142.70
(15 mg, 0.018 mmol), 10 (6.7 mg, 0.007 mmol), and 1 (6 mg,
0
.007 mmol) were eluted as well-separated bands.
Com p ou n d 9. 1H NMR (400 MH
, CDCl /CS ) δ: 3.80 (s,
H), 3.84 (s, 3H), 4.04 (d, 2H), 4.47 (d, 2H), 6.03 (s, 2H).
, o-C Cl /CS ) δ: 169.13 (COOMe), 150.36,
50.28 (1C), 149.51, 149.30, 149.18 (1C), 149.16, 148.72,
(2C), 142.60, 142.36, 142.24, 142.23, 142.21, 142.10, 142.08,
142.06, 141.95, 141.84 (2C), 141.77, 141.72, 140.31, 140.20,
139.95, 139.66, 137.90, 136.48, 136.34, 76.17, 74.35, 71.48,
Z
3
2
1
3
2
C
+
NMR (100.6 MH
Z
6
D
4
2
2
69.23, 51.21, 48.76, 31.57, 26.25, 24.91. FDMS m/z: 875 (M ).
1
1
1
1
UV-vis (CHCl
3
): 256, 309, 430 nm. Anal. Calcd for
48.23, 146.99, 146.57, 146.42, 145.65, 145.18, 145.12, 144.79,
44.63, 144.39, 144.18, 144.14, 143.73, 143.00, 142.85 (4C),
42.70(1C), 142.37, 142.30 (1C), 141.78, 141.22, 136.24, 135.19
C [CH(CH ) NCHCOOCH ]: C, 92.81; H, 1.25; N, 1.33.
6
0
2
4
3
Found: C, 93.25; H, 1.50; N, 1.60.
(all represent 2C except indicated), 72.05 (2CH
2
), 61.74 (sp3
). DEPT spectrum
2
C), 56.28 (2CH), 53.79 (CH
2
), 51.25 (CH
3
Ack n ow led gm en t. We thank the Natural Science
Foundation of China (29471004), the Climbing
ProgramsA Fundamental Research Program of China
and FEYUTSEDU for Financial Support. We also
thank the reviewers for reading the manuscript care-
fully and providing excellent suggestions.
located the H-containing cabons. FT-IR: 522, 530, 558, 567,
5
1
81, 1020, 1125, 1165, 1187, 1201, 1266, 1420, 1429, 1462,
-1
+
748 cm . FDMS (m/z, relative intensity): 837 (M , 100), 720
(C
60, 18). UV-vis (CHCl
Com p ou n d 10. H NMR (400 MHz, CDCl
3
): 257, 433 nm.
1
3
3
/CS
2
) δ: 3.76
1
(
s, 6H), 4.15 (s, 4H), 4.72 (s, 2H), 7.11 (s, 1H). C NMR (100.6
/CS ) δ: 170.16 (2COOMe), 154.36, 154.19, 147.07
1C), 146.95, 146.88 (1C), 146.44, 146.12, 146.04, 145.91,
MHz, CDCl
(
3
2
1
1
1
2
45.86, 145.50, 145.28, 145.11, 145.07, 145.05, 144.46, 144.18,
42.96, 142.31, 142.27, 142.07, 141.81, 141.68, 141.42, 141.40,
41.36, 140.08, 139.84, 135.92, 135.63 (all signals represent
Su p p or tin g In for m a tion Ava ila ble: Characterization
data and 1H and C NMR and FDMS data for 5, 6, 8-10,
and 12 (26 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
13
C except indicated). 68.13 (CH), 67.10, 57.35 (CH
), 51.17 (CH ). DEPT spectrum located the H containing
carbons. FT-IR: 527, 574, 998, 1012, 1144, 1169, 1203, 1261,
2
), 56.09
(CH
3
2
-1
+
1
384, 1411, 1429, 1742 cm . FDMS m/z: 895 (M + 1). UV-
vis (CHCl ): 257 (with shoulder centered at 328), 434 nm.
3
J O971990I