Use of ferrocene scaffolds as pendant groups in hairpin-type pyrrole-imidazole polyamide molecules showing sequence-selective binding to DNA duplexes

Article abstract of DOI:10.1021/jo051247n

The synthesis and properties of new conjugate molecules, Fc-PIA, composed of ferrocene (Fc) and pyrrole-imidazole polyamides (PIA) are reported. As a PIA sequence, we chose Im-Py-Im/Py-Im-Py considering its future application to the SNPs detection of gene

Full text of DOI:10.1021/jo051247n

Use of Ferrocene Scaffolds as Pendant Groups in Hairpin-Type
Pyrrole-Imidazole Polyamide Molecules Showing
Sequence-Selective Binding to DNA Duplexes
Kohji Seio, Masahiro Mizuta, Takeshi Terada, and Mitsuo Sekine*
Frontier Collaborative Research Center and Department of Life Science, Tokyo Institute of Technology,
Japan Science and Technology Agency (JST), 4259 Midori-ku, Nagatsuta-cho, Yokohama, Japan
msekine@bio.titech.ac.jp
Received June 17, 2005
The synthesis and properties of new conjugate molecules, Fc-PIA, composed of ferrocene (Fc) and
pyrrole-imidazole polyamides (PIA) are reported. As a PIA sequence, we chose Im-Py-Im/Py-Im-Py
considering its future application to the SNPs detection of genes having a GCG/CGC sequence.
Two types of Fc-containing linkers, i.e., ferrocene-1,1′-dicarboxamide and ferrocenecarboxamide,
were designed, and several Fc-PIPA molecules having these linkers were synthesized. Titration
studies by use of circular dichroism revealed that the carboxamide-type Fc-PIA could bind to the
7
-1
target DNA with an association constant of 10 M . In contrast, ferrocene dicarboxamide-type
compounds have slightly weaker affinity for the target DNA. However, the affinity could be recovered
by replacing one of the pyrrole residues with â-alanine. We carried out the CV measurement and
observed quasi-irreversible oxidation of the ferrocene moieties in the Fc-PIA compounds. These
properties of Fc-PIA indicate the potential usefulness of these molecules in electrochemical detection
of genes.
4
5
6
Introduction
molecules, nucleobases, dinucleotides, and amino ac-
7
ids. The molecular recognition ability of these molecules
Ferrocene is an organometallic compound in which an
iron atom is flanked by two cyclopentadienyl (Cp) rings.
The unique structural and conformational properties of
together with the electrochemical properties of the fer-
rocene moiety has enabled the development of electro-
chemical molecular sensors. However, the development
of DNA binding molecules utilizing the unique properties
of ferrocene has so far not been reported.
In this paper, the development of new DNA binding
molecules utilizing the structural and conformational
1
ferrocene, an atomic ball bearing character , are char-
acterized by the parallel alignment of the two Cp rings
and the free rotation of the rings around the axis
penetrating their centers. Because of such unique prop-
erties that cannot be obtained by use of simple organic
molecules, ferrocene derivatives have been used as scaf-
folds to design new molecules that recognize various
kinds of substances such as cation,2 anion, organic
(
2) (a) Beer, P. D.; Sikanyika, H.; Slawin, A. M. Z.; David, J.
Polyhedron 1989, 8, 879-886. (b) Chen, Z.; Pilgrim, A. J.; Beer, P. D.
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3
2
369. Ion, A.; Moutet, J.-C.; Saint-Aman, E.; Royal, G.; Gautier-
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1366.
1
0.1021/jo051247n CCC: $30.25 © 2005 American Chemical Society
Published on Web 11/08/2005
J. Org. Chem. 2005, 70, 10311-10322
10311

Seio et al.
SCHEME 1. Ferrocene-Containing Minor Groove Binders Synthesized in this Study
properties of ferrocene is reported. Our design concept
is based on the fact that the distance between the two
Cp rings of ferrocene, ca. 3.3 Å, is close to the distance
to the DNA minor groove as stacked dimers.11 Therefore,
PIA must be aromatic compounds of prime interest to
design new ferrocene molecules having DNA binding
ability. Compounds 1a-c and 2 were designed by inser-
tion of a ferrocene-1,1′-dicarboxamide moiety as part of
the linker, and 3 was designed to clarify the properties
of the pendant ferrocenylcarbonyl group on the amino
group of the linker. In both types of compounds, strong
affinity for DNA was expected because of the similarity
8
between two aromatic rings stacked with each other. In
addition, it is well-known that the minor groove of DNA
can accommodate stacked aromatic rings, as established
by the structural studies of natural or synthetic molecules
that recognize the minor groove.9 Therefore, it was
expected that ferrocene derivatives could be a new type
of DNA binding molecules if appropriately designed
aromatic rings were attached to the Cp rings.
For this purpose we designed hybrid molecules (Fc-
PIA; 1a, 1b, 1c, 2, and 3 in Scheme 1) combining
ferrocene (Fc) and pyrrole-imidazole amides (PIA).10 PIA
derivatives are well recognized as molecules that can bind
12
in the whole structure between Fc-PIA and hairpin PIA.
In addition to such DNA binding properties, the
electrochemical properties of ferrocene can be utilized in
1
3
the electrochemical detection of DNA hybridization.
There have been reported a number of strategies to detect
DNA hybridization electrochemically. In most systems
the target DNAs are hybridized to probe DNAs attached
to an electrode, and the hybridization is detected by the
(
3) (a) Beer, P. D.; Graydon, A. R.; Johnson, A. O. M.; Smith, D. K.
Inorg. Chem. 1997, 36, 2112-2118. (b) Buda, M.; Ion, A.; Moutet, J.-
C.; Saint-Aman, E.; Ziessel, R. J. Electroanal. Chem. 1999, 469, 132-
14
electric current from electrochemical dyes covalently or
noncovalently15 attached to the target-probe duplexes.
1
38. (c) Reynes, O.; Maillard, F.; Moutet, J.-C.; Royal, G.; Saint-Aman,
E.; Stanciu, G.; Dutasta, J.-P.; Gosse, I.; Mulatier, J.-C. J. Organomet.
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Chem. Rev. 2003, 240, 167-189. (e) Pratt, M. D.; Beer, P. D. Polyhedron
The dyes used in the latter strategy included inter-
15a-d
15e,f
calators,
minor groove binder,
and other com-
2
003, 22, 649-653. (f) Kuo, L.-J.; Liao, J.-H.; Chen, C.-T.; Huang, C.-
pounds that interact with DNA through electrostatic
interactions.1
5g,h
Among them, duplex-specific ligands
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1
10312 J. Org. Chem., Vol. 70, No. 25, 2005

Ferrocene-Pyrolle-imidazole Polyamide Conjugates
groups. For example, duplex-specific threading-inter-
1
5a-c
calators
and an electrochemically active minor groove
15e,f
binder, Heochst 33258, were reported.
Because our Fc-PIAs are expected to bind to duplex
DNA more tightly than single-stranded DNA, they could
be new duplex-specific electrochemical dyes. Keeping
such future applications in mind, the synthesis, DNA
binding properties, and electrochemical properties of the
Fc-PIA compounds are reported in this article.
Results and Discussion
Selection of Target Sequence. In this study, we
chose a CGC/GCG triplet as the target sequence. Re-
cently, it has been proposed that the CGC to CTC
mutation in the promoter region of MxA gene could
influence the response to interferon therapy for patients
infected by the hepatitis C virus.16 Therefore, rapid and
accurate detection of the G/T SNP in the CXC sequence
must be clinically important in the diagnosis of HCV
infected patients.
Unfortunately, it is well-known that hairpin PIA binds
to the CGC sequence with rather low affinity.17 Therefore,
the compounds targeting CGC sequences must be de-
signed carefully to maintain the DNA binding affinity.
In this study, we used a DNA 11 mer, GACTGCG-
TAGG, as a model target in place of the GC-rich MxA
promoter sequence and designed compounds 1a, 1b, 1c,
FIGURE 1. Comparison of the molecular structure and the
size of a stacked dimer of a PIA (left) and ferrocene (right).
rings in parallel-stacking geometry. Because PIA can
bind to the DNA minor groove as a stacked dimer, it is
expected that the ferrocene moiety of Fc-PIA can fit the
minor groove when they bind to the DNA duplex in a
conformation similar to that of the conventional PIA
dimers.
The idea is illustrated graphically by computer graph-
ics, as shown in Figure 1. The structure of a PIA dimer
19
extracted from a PIA-DNA complex (PDB 408D) and a
ferrocene residue extracted from the complex of a fer-
rocene dicarboxylic acid derivative and an antibody (PDB
20
1
A3L) was used. As shown in Figure 1, it is indicated
that the thickness of the ferrocene and the stacked PIA
dimer is almost identical so that they can bind to the
minor groove together. This molecular model indicates
that Fc-PIA could bind to the minor groove without
severe structural distortion. Moreover, because the Cp
rings can rotate almost freely, the important hydrogen
bonds between the nucleobases and the PIA moiety could
be maintained even if some structural perturbation exits.
On the basis of these structural considerations, we tried
to synthesize 1a-c, 2, and 3.
2
, and 3. Particularly, compound 2 was designed to
increase the affinity of PIA for the GCG sequence by
introduction of a â-alanine residue in place of a pyrrole
1
8
residue.
Can Ferrocene Moiety Fit the Minor Groove of
DNA? Because ferrocene is a hydrophobic compound, the
ferrocene moiety of Fc-PIAs 1a-c, 2, and 3 should be
buried in the minor groove to avoid exposure to the bulk
water on binding to the target DNA duplex. A number
of molecular structures of ferrocene derivatives have been
well characterized, and the typical distance between the
two Cp rings has been proved to be approximately 3.3
Synthesis of Pyrrole-Imidazole Polyamides 10,
6, and 21. The synthesis of the upper-half pyrrole-
1
imidazole triamide (Im-Py-Im in Scheme 1) was per-
formed by use of pyrrole and imidazole building blocks
8
Å, which is close to the typical distance of two aromatic
2
1
22
21
22
4
,
5, 8, and 11 (Scheme 2). The nitro group of 4
(
14) (a) Kertesz, V.; Whittemore, N. A.; Inamati, G. B.; Manoharan,
was converted to an amino group by hydrogenolysis, and
the amino derivative was coupled with 5 to give 6 in
M.; Cook, P. D.; Baker, D. C.; Chambers, J. Q. Electroanalysis 2000,
23
1
2, 889-894. (b) Brazill, S. A.; Kim, P. H.; Kuhr, W. G. Anal. Chem.
001, 73, 4882-4890. (c) Ihara, T.; Maruo, Y.; Takenaka, S.; Takagi,
2
78% yield. The hydrolysis of 6 followed by coupling with
the 3-aminoimidazole derivative 8 gave the trimer 9.
Compound 9 thus obtained was hydrolyzed to give
compound 10.
Next, we synthesized the lower-half pyrrole-imidazole
triamide (Py-Im-Py in Scheme 1), as shown in Scheme
3. The pyrrole derivative 11 was condensed with N,N-
dimethyl-1,3-propanediamine to give 12. The hydro-
genolysis of 12 followed by reaction with the 1-(trichlo-
roacetyl)imidazole derivative 13 gave the dimer 14.
Finally, the hydrogenolysis of 14 and the successive
M. Nucleic Acids Res. 1996, 24, 4273-7280. (d) Yu, C. J.; Wan, Y.;
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002, 56, 829-835. (c) Yamashita, K.; Takagi, M.; Kondo, H.; Tak-
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1
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J. Org. Chem, Vol. 70, No. 25, 2005 10313

Seio et al.
SCHEME 2
FIGURE 2. Anodic currents of CV profiles of Fc-PIA 1a and
3
in DMF.
ethyl ester of 19 was hydrolyzed, and the resulting
carboxylic acid was converted to the pentafluorophenyl
ester 20 in 96% yield from 19.
Synthesis of Fc-PIAs 1a-c. The ferrocene-1,1′-di-
carboxylamide linkers 24a-c were synthesized, as shown
in Scheme 5. The monoester 2124 was condensed with the
protected ethylenediamine and propylenediamine deriva-
tives to give 22a and 22b, respectively. The methyl esters
of 22a and 22b were hydrolyzed and then condensed with
the ethyl esters of glycine or â-alanine to give compounds
2
3a, 23b, and 23c, which could be converted to the
ferrocene-dicarboxamide linkers 24a, 24b, and 24c.
The synthesis of Fc-PIAs 1a, 1b, 1c, and 2 was
performed according to Scheme 6. Pyrrole-imidazole
polyamide 15, which was synthesized as described in
Scheme 3, was converted to the amino derivative 16 by
hydrogenolysis. The amine thus obtained was coupled
with ferrocene-1,1′-decarboxamide linkers 24a, 24b, and
SCHEME 3
2
4c to give the ferrocene-polyamide derivatives 25a, 25b,
and 25c, respectively. The t-Boc groups of 24a-c were
removed by acid treatment to give the amino derivatives
2
6a, 26b, and 26c, which were further condensed with
pyrrole-imidazole polyamide 10 to give the desired prod-
ucts 1a, 1b, and 1c. Similarly, Fc-PIA 2 was synthesized
by the condensation of 20 with 26a.
Synthesis of PIA-Ferrocene Hybrid 3. Fc-PIA 3
was synthesized as shown in Scheme 7. The triamide 15
was subjected to hydrogenolysis followed by condensation
with the commercially available diaminocarboxylic acid
derivative 27. During the reaction, partial cleavage of the
fmoc group occurred probably due to the intramolecular
attack by the dimethylaminopropyl group. Therefore, we
isolated the product as 28 after the complete removal of
the fmoc group by treatment with piperidine. The amino
group of 28 was condensed with the triamide 10 to give
the hairpin PIA 29. Then, the t-Boc group of 29 was
removed by treatment with 20% TFA, and the released
amino group was coupled with ferrocene carboxylic acid
derivative to give the desired product 3.
Electrochemical Properties of Fc-PIAs. The elec-
trochemical properties of Fc-PIA 1a, 1b, 1c, 2, and 3 were
examined by use of cyclic voltammetry (CV). Shown in
Figure 2 are the CV profiles of the Fc-PIA 1a and 3
measured in DMF. In these cases, the electrochemical
reactions were quasi-irreversible, giving rather large
anodic currents of ferrocene and PIA. In contrast, the
cathodic currents were much smaller than the corre-
sponding anodic currents and are not shown in Figure
condensation with 11 gave the trimer 15, which could
be further converted to the amino derivative 16 by
hydrogenolysis before the next reaction.
To synthesize an Fc-PIA derivative containing a â-ala-
nine residue 2, the triamide 20 was synthesized, as
shown in Scheme 4. The pyrrole derivative 1721 was
converted to the amino derivative by hydrogenolysis, and
the following condensation with â-N-t-Boc-alanine gave
the diamide 18. After removal of the t-Boc group of 18,
the amino group was condensed with compound 5 to give
the triamide 19 in 63% yield from 18. Successively, the
2
.
(
24) Barisic, L. R.; Vladimir, K. V. Croat. Chem. Acta 2002, 75, 199-
210.
10314 J. Org. Chem., Vol. 70, No. 25, 2005

Ferrocene-Pyrolle-imidazole Polyamide Conjugates
SCHEME 4
SCHEME 5
The anodic peak currents of the ferrocene moieties in
a and 3 were observed at around 0.38 and 0.24 V,
1
respectively. The positions of the anodic peaks shifted to
higher potentials than that of ferrocene (0.08 V) because
of the presence of the electron-withdrawing carbonyl
groups on the cyclopentadienyl rings. In the case of 1b,
1
c, and 2, the electrochemical behavior was similar to
that of 1a (data not shown). These results indicated that
the electrochemical properties of the Fc-PIAs were domi-
nated by the number of the carbonyl groups directly
attached to the ferrocene moieties.
FIGURE 3. Titration of DNA1 (5 µM) by (a) 1a (0-1.8 equiv),
b) 3 (0-1.6 equiv), and (c) 2 (0-2.0 equiv).
(
Binding of Ferrocene-PIAs (1a-c, 2, and 3) to
Cognate DNA Duplexes. The binding of Fc-PIAs to
DNA duplexes was studied by use of circular dichroism
(GACTGCGTAGG/CTGACGCATCC) and DNA2 (GACT-
GAGTAGG/CTGACTCATCC) were prepared to study the
DNA binding affinity of the Fc-PIAs and their difference
(
CD) spectroscopy. Two DNA duplexes named DNA1
J. Org. Chem, Vol. 70, No. 25, 2005 10315

Seio et al.
SCHEME 6
SCHEME 7
of 1a to a solution of DNA1 showed dose-dependent
increase of the Cotton effect in this range. The positive
Cotton effect increases until the ratio of the cognate
double strand DNA duplex (cog-dsDNA):1a reaches 1:1.8.
Addition of 1a beyond 1:1.8 stoichiometry did not lead
to further increase of the peak intensity. Similarly, both
Fc-PIAs 2 and 3 gave similar titration profiles showing
saturation at 1:1.4 stoichiometry. In all these cases,
single-binding modes are indicated by the presence of
isosbestic points before the saturation is reached.
Next, we carried out the same CD titration experi-
ments of the binding of 1b and 1c to DNA1 (data not
shown). In both cases, the titration was saturated at 1:3.4
stoichiometry of DNA and ligands. These results indi-
cated that 1b and 1c have affinities for the DNA duplex
lower than that of 1a.
To compare the affinity of 1a-c and 3 for the DNA
duplex more quantitatively, the binding constants were
estimated by fitting the theoretical titration curve and
the experimental curves plotting the maximum Cotton
effect vs concentration of the Fc-PIAs. The results are
shown in Table 1. Compounds 3 and 2 gave the largest
7
-1
and the second largest binding constants of ca. 10 (M ),
respectively. In both cases, the least-squares fit associ-
ated with correlation factors (R) of >0.989 supported the
validity of the assumption of the formation of 1:1 com-
plexes of the DNA target and Fc-PIA compounds 2 and
3
. In contrast, compound 1a, which is a derivative of 2
having a pyrrole residue in place of the â-alanine residue,
showed slightly weaker affinity compared with 2. This
observation clearly suggested that introduction of the
â-alanine residue can improve the affinity of Fc-PIAs for
the GC-rich sequence as described in the case of the
original PIAs that were developed by Dervan P. et al.
On the other hand, the same curve fitting and correlation
analyses revealed that the titration by 1b and 1c gave a
in sequence selectivity between the cognate GCG/CGC
and noncognate GAG/CTC sequences.
Initially, the binding properties of Fc-PIAs 1a, 2, and
were studied to clarify the influence of the linker
3
structures and the insertion of â-alanine on their DNA-
binding properties. Shown in Figure 3 are the CD-
titration profiles of DNA duplexes DNA1. It is well-
known that the binding of minor groove binders to DNA
duplexes can be monitored by the positive Cotton effect
at around 300-330 nm.25 As shown in Figure 3a, addition
6
much smaller binding constant of ca. 1 × 10 probably
because the linker length of these compounds was not
optimal for the DNA binding.
Binding of Ferrocene-PIA Hybrids (1a, 2, and 3)
to Noncognate DNA Duplex. On the basis of the above-
mentioned binding properties of 1a, 2, and 3 to the
cognate sequence, we examined the binding of Fc-PIAs
(25) (a) Pilch, D. S.; Poklar, N.; Baird, E. E.; Dervan, P. B.;
Breslauer, K. J. Biochemistry 1999, 38, 2143-2151. (b) Pilch, D. S.;
Poklar, N.; Gelfand, C. A.; Law, S. M.; Beslauer, K. J.; Baird, E. E.
Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 8306-8311.
1
a, 2, and 3 to the DNA duplex DNA2 having a
noncognate sequence. The results are shown in Figure
10316 J. Org. Chem., Vol. 70, No. 25, 2005

Ferrocene-Pyrolle-imidazole Polyamide Conjugates
TABLE 1. Binding Constants (K, M-1) of Fc-PIA and Cognate DNA1
1a
1b
1c
2
3
6
6
6
7
7
(7.4 ( 1.1) × 10
(1.3 ( 0.2) × 10
(1.5 ( 0.2) × 10
(1.4 ( 0.6) × 10
(2.3 ( 0.8) × 10
Similarly, 2 showed only a small increase of the Cotton
effect at around 330 nm before the 1:2.0 stoichiometry
was reached. However, in this case, the further addition
of 3 increased the Cotton effect almost linearly to the
ligand concentration even after 10 equiv of 3 had been
added.
From these observations, it is suggested that all of the
Fc-PIAs 1a, 2, and 3 bind more strongly to the cognate
DNA1 than to the noncognate DNA2. In addition, it was
also suggested 1a and 3 and/or 2 bind to the noncognate
DNA2 in several binding modes at the higher concentra-
tions.
Conclusion
There have been numerous studies on the use of
ferrocene scaffolds to design molecules that recognize
other chemical substances. We reported the synthesis and
properties of new conjugate molecules (Fc-PIA), 1a-c,
2
, and 3, having ferrocene and pyrrole-imidazole poly-
amides (PIA). To our best knowledge, it is the first
example of the development of DNA minor groove binders
by use of the structural properties of ferrocene, i.e., the
parallel alignment of the two Cp rings displaced by ca.
3
.3 Å and the free rotation of the rings around the axis
penetrating them. In addition, we also synthesized 3 to
clarify the compatibility between the conventional hair-
pin PIA and the ferrocene moiety. As expected from the
comparison between the minor groove width and the
molecular size of ferrocene, the insertion of a ferrocene
moiety did not interfere with the binding of the minor
groove binder to target DNA duplex. Therefore, it must
be possible to design new minor groove binders by the
combination of various heteroaromatic compounds, other
than pyrrole-imidazole amides, and ferrocene-type scaf-
folds.
FIGURE 4. Titration of DNA2 (5 µM) by (a) 1a (0, 1, 2, 3,
and 6 equiv), (b) 3 (0, 0.4, 0.8, and 2 equiv), and (c) 2 (0, 2, 4,
6, and 10 equiv).
The affinity of the Fc-PIA for the target DNA contain-
ing a CGC/GCG site depends on the linker structure that
linked the ferrocene to PIA moieties. The CD titration
studies revealed that 3 having a ferrocene carboxamide
showed the strongest binding to the target DNA. Al-
though the affinity of ferrocene-1,1′-dicarboxamide com-
pounds 1a-c was slightly lower, the affinity could be
recovered by replacement of the pyrrole moiety by a
â-alanine moiety as in the case of 1a and 2. Because the
insertion of the â-alanine moiety was proved to be
effective to improve the affinity of the original pyrrole-
imidazole polyamide for GC-rich sequences, these obser-
vations suggest that the Fc-PIAs synthesized in this
study recognize DNA in a similar way as do the original
hairpin pyrrole-imidazole polyamides. It should be noted
that similar CD titration experiments revealed that these
Fc-PIA also had sequence selectivity in the binding to
DNA duplexes.
4
. Titration of DNA2 with Fc-PIA 1a showed increase of
the positive Cotton effect at 315 nm until the stoichiom-
etry of DNA2:1a approached 1:6.0. It should be noted
that the magnitude of the induced CD signals was much
smaller than that observed in the combination of DNA1
and 1a. The requirement of the high DNA to drug ratio
for the saturation of the titration suggested the lower
affinity of 1a for the noncognate sequence.
Unfortunately, the quantitative binding constants of
a to the noncognate DNA2 could not be determined
1
because the peaks started to decrease on the addition of
higher amounts of 1a beyond 6 equiv. This phenomenon
indicated the involvement of several binding modes
having lower affinity at the higher concentration
of 1a.
On the other hand, compound 3 showed only small
changes even after 1:2.0 stoichiometry had been reached.
This small change in the spectra indicates the weak
binding of 3 to the noncognate DNA2. As in the case of
The electrochemical properties of the ferrocene moiety
in the Fc-PIA were also studied by cyclic voltammetry
(CV). The CV studies in N,N-dimethylformamide re-
vealed the irreversible oxidation of the ferrocene moiety
at around 0.38 and 0.24 V for 1a and 3, respectively.
1
a, the addition of higher amounts of 3 beyond 2.0 equiv
led to decrease of the signals at around 330 nm to give a
negative peak in this range.
J. Org. Chem, Vol. 70, No. 25, 2005 10317

Seio et al.
These strong DNA binding, sequence selectivity and
electrochemical properties of Fc-PIA must be useful for
the electrochemical detection of DNAs. Particularly, the
ferrocene amide-type compound 3 should be a prototype
of such a ligand because of its high affinity for duplex
DNAs, low affinity for noncognate DNAs, and lower redox
potential. The development of an electrochemical gene
detection system by use of Fc-PIA is under way and will
be reported elsewhere.
The reaction mixture was warmed to room temperature, and
stirring was continued for 1 h. The solvent was removed in
vacuo, and the residual solid was recrystallized from ethanol
1
to give compound 12 (19.6 g, 84%): HNMR (DMSO-d
6
) δ 1.6
(
2Η, t, J ) 7.1 Hz), 2.1 (6H, s), 2.2 (2H, t, J ) 7.1 Hz), 3.2 (2H,
q, J ) 7.1 Hz), 3.9 (3H, s), 7.9 (1H, s), 8.1 (1H, s), 8.4 (1H, t,
13
J ) 5.5 Hz); CNMR (DMSO-d
6
) δ 27.2, 37.2, 37.5, 45.4, 56.9,
+
107.3, 126.7, 127.9, 133.9, 159.9. MS m/z calcd for C H N O
11
19
4
3
+
255.14572, found 255.13045 [M + H] .
1-Methyl-4-(1-methyl-4-nitroimidazole-2-carboxamido)-
-(3-dimethyl(aminopropyl)aminocarbonyl)pyrrole (14).
2
Compound 12 (2.8 g, 10.9 mmol) was dissolved in ethanol (44
mL), and to this solution was added 10% Pd/C (545 mg). A
balloon of hydrogen gas was attached, and the suspension was
stirred under hydrogen atmosphere for 4 h at ambient tem-
perature. The catalysts were removed by filtration, and the
solvent was removed under reduced pressure. The residue was
dissolved in DMF (10 mL) and concentrated to half of its
original volume under reduced pressure to remove methanol
completely. A solution of compound 13 (3.0 g, 10.9 mmol) in
DMF (10 mL) was added with stirred at 0 °C. The temperature
was allowed to rise to ambient temperature. The solvent was
removed in vacuo. The resultant crystalline solid was collected
Experimental Section
1
-Methyl-4-(1-methylimidazole-2-carboxamido)pyrrole-
2
-carboxylic Acid (7). Compound 6 (8.8 g, 34 mmol) was
dissolved in ethanol (230 mL). To this solution was added 0.6
M aqueous NaOH (168 mL, 101 mmol), and the resulting
solution was stirred at 70 °C for 1 h. The solution was cooled
to ambient temperature and adjusted to pH 3.0 by addition of
3
M aqueous HCl. The resulting white precipitates were
1
collected by filtration to give 7 (8.1 g, 97%): H NMR (DMSO-
6
d
) δ 3.82 (3H, s), 3.97 (3H, s), 6.97 (1H, d, J ) 2.0 Hz), 7.03
(
1H, s), 7.38 (1H, s), 7.47 (1H, d, J ) 2.0 Hz), 10.48 (1H, s),
1
3
and washed with 2-propanol to give compound 14 (3.68 g,
1
2.19 (1H, s); C NMR (DMSO-d
20.7, 122.1, 126.6, 127.2, 138.8, 156.3, 162.1. Anal. Calcd for
: C, 53.22; H, 4.89; N, 22.57. Found: C, 52.45; H,
.72; N, 22.34.
-Ethoxycarbonyl-1-methyl-4-{4-(1-methylimidazole-
-carboxamido)-1-methypyrrole-2-carboxamido)imida-
6
) δ 35.3, 36.4, 109.1, 119.9,
1
9
0%): H NMR (DMSO-d
6
) δ 1.6 (2Η,t, J ) 7.1 Hz), 2.1 (6H,
1
s), 2.2 (2H, t, J ) 7.1 Hz), 3.2 (2H, m), 3.8 (3H, s), 4.0 (3H, s),
C
11
H
12
N
O
4 3
7
5
3
1
3
.0 (1H, d, J ) 1.7 Hz), 7.3 (1H, d, J ) 1.7 Hz), 8.1 (1H, t, J )
4
13
6
.5 Hz), 8.6 (1H, s), 10.8 (1H, s); C NMR (DMSO-d ) δ 27.2,
2
6.2, 36.7, 37.4, 39.2, 45.4, 57.4, 104.5, 118.6, 121.1, 123.6,
2
+
26.8, 138.1, 144.5, 154.8, 161.2. MS m/z calcd for C16
24 7 4
H N O
zole (9). 10% Pd/C (1.2 g) was added to a solution of
+
78.18898, found 378.18801 [M + H] .
2-ethoxycarbonyl-1-methyl-4-nitroimidazole (4.7 g, 23.6 mmol)
in methanol (94 mL). The suspension was stirred for 4 h under
hydrogen atmosphere where a balloon filled with hydrogen gas
was attached to a reaction vessel. The catalysts were removed
by filtration, and the solvent was removed under reduced
pressure. The residual methanol was removed by coevapora-
tion with DMF, and the residue was finally dissolved in DMF
1-Methyl-4-{1-methyl-4-(1-methyl-4-nitropyrole-2-car-
boxamido)imidazole-2-carboxamido}-2-(3-dimethyl(ami-
nopropyl)aminocarbonyl)pyrrole (15). Compound 14 (3.6
g, 9.6 mmol) was dissolved in methanol (38 mL), and to this
solution was added 10% Pd/C (481 mg). A balloon of hydrogen
gas was attached, and the suspension was stirred under
hydrogen atmosphere for 4 h at ambient temperature. The
catalysts were removed by filtration, and the solvent was
removed under reduced pressure. The residue was dissolved
in DMF (10 mL) and concentrated to half of its original volume
under reduced pressure to remove methanol completely. A
solution of compound 11 (2.6 g, 9.6 mmol) in DMF (10 mL)
was added with stirring at 0 °C. The temperature was allowed
to rise to ambient temperature. The solvent was removed in
vacuo. The resultant crystalline solid was collected and washed
(
10 mL). To this solution were added 7 (5.9 g, 24 mmol), N-(3-
dimethylaminopropyl)-N′-ethylcarbodiimide (9.1 g, 47 mmol),
and 4-dimethylaminopyridine (290 mg, 2.4 mmol). The result-
ing solution was stirred at ambient temperature for 10 h.
Chloroform/ethyl acetate (15 mL/100 mL) was added to the
reaction mixture, and the white powder was collected by
filtration and washed with ethyl acetate to give 9 (5.9 g,
1
6
3
7
7
3%): H NMR(DMSO-d
6
) δ 1.28-1.30 (3H, t, J ) 7.1 Hz),
.85 (3H, s), 3.93 (3H, s), 3.98 (3H, s), 4.25-4.29 (2H, dd, J )
.1 Hz), 7.03 (1H, d, J ) 0.7 Hz), 7.22 (1H, d, J ) 2.0 Hz),
.38 (1H, s), 7.38(1H, s), 7.66 (1H, s), 10.35 (1H, s), 10.74 (1H,
1
with 2-propanol to give compound 15 (3.5 g, 74%): H NMR
6
(DMSO-d ) δ 1.58-1.62 (2H, t, J ) 6.9 Hz), 2.1 (6H, s), 2.23-
1
3
s); C NMR (DMSO-d
6
) δ 14.3, 35.3, 35.7, 36.5, 60.8, 106.4,
2.25 (2H, t, J ) 6.9 Hz), 3.17-3.21 (2H, m), 3.81 (3H, s), 3.97
(3H, s), 3.98 (3H, s), 6.89 (1H, d, J ) 1.7 Hz), 7.23 (1H, d, J )
1.5 Hz), 7.58 (1H, s), 7.76 (1H, d, J ) 2.0 Hz), 8.11-8.14 (1H,
1
1
15.6, 119.8, 121.6, 122.2, 126.5, 127.2, 131.0, 138.0, 139.0,
56.3, 158.7, 158.9. Anal. Calcd for C18
12 4 3 2
H N O ‚H O: C, 53.22;
1
3
H,4.89; N,22.57. Found: C, 50.88; H,4.88; N,23.13.
t, J ) 5.4 Hz), 8.21 (1H, s), 9.97 (1H, s), 10.82 (1H, s);
C
NMR (DMSO-d
6
) δ 27.3, 35.2, 36.3, 37.4, 37.9, 45.4, 57.4, 104.1,
Sodium 1-Methyl-4-{4-(1-methylimidazole-2-carboxa-
mido)-1-methypyrrole-2-carboxamido}imidazole-2-car-
boxylate (10). To a solution of compound 9 (3.0 g, 7.5 mmol)
in methanol (38 mL) was added 0.2 M aqueous sodium
hydroxide (38 mL, 7.6 mmol). The resulting solution was
stirred for 1 h at 50 °C. The solution was cooled to ambient
temperature and then acidified to pH 2.0 by addition of 1 M
aqueous HCl. The product was separated by addition of
1
1
08.8, 115.2, 118.1, 121.3, 123.6, 125.6, 128.9, 134.1, 134.7,
+
35.7, 155.9, 157.7, 161.2. MS m/z calcd for C22
30 9 5
H N O
+
500.23699, found 500.23755 [M + H] .
2-Ethoxycarbonyl-1-methyl-4-{3-(tert-butoxycarbonyl-
amino)propanamido}pyrrole (18). Compound 17 (546 mg,
2.7 mmol) was dissolved in methanol (11 mL), and to this
solution was added 10% Pd/C (137 mg). A balloon of hydrogen
gas was attached, and the suspension was stirred under
hydrogen atmosphere for 1.5 h at ambient temperature. The
catalysts were removed by filtration, and the solvent was
removed under reduced pressure. The residue was dissolved
in CH Cl and N-(tert-butoxycarbonyl)-â-alanine (518 mg, 2.7
2
-propanol. The resulting white precipitates were colleted by
filtration and washed with 2-propanol to give 10 (2.9 g, 94%):
1
H NMR (DMSO-d
6
) δ 3.86 (3H, s), 3.92 (3H, s), 4.01 (3H, s),
7
.23 (1H, s), 7.25 (1H, s), 7.40 (1H, s), 7.52 (1H, s), 7.61 (1H,
1
3
s), 10.70 (1H, s), 10.71 (1H, s); C NMR (DMSO-d
6
) δ 25.6,
2
2
3
1
3
5.7, 36.5, 106.2, 115.3, 119.9, 121.3, 122.4, 125.1, 126.6, 131.9,
37.3, 138.1, 154.7, 158.8, 160.1. MS m/z calcd for C16
mmol), 1-(3-dimethylaminopropyl)-3-etylcarbodiimide hydro-
chloride (578 mg, 3.0 mmol), and 1-hydoxybenzotriazol (407
mg, 3.0 mmol) were added. The mixture was stirred at ambient
temperature for 2 h. The mixture was extracted with ethyl
+
H N O
18 7 4
+
72.14203, found 394.11781 [M + Na] .
2
-(3-Dimethylaminopropyl)aminocarbonyl-1-methyl-
4
-nitropyrrole (12). A solution of 3-dimethylaminopropyl-
acetate (50 mL), washed with water (50 mL), dried over Na
SO , and concentrated under reduced pressure. The residue
was chromatographed on a column of silica gel (11 g, hexane-
2
-
amine(12.6 g, 101 mmol) in THF (10 mL) was added dropwise
to a stirred solution of compound 11 (25 g, 92 mmol) at 0 °C.
4
10318 J. Org. Chem., Vol. 70, No. 25, 2005

Ferrocene-Pyrolle-imidazole Polyamide Conjugates
chloroform, 100: 20, v/v) to give 18 (510 mg, 56%): 1H NMR
diamine in 88% yield: 1H NMR (DMSO-d
) δ 1.38 (9H, s),
6
(
DMSO-d
6
) δ 1.27-1.30 (t, J ) 7.2 Hz), 1.36 (9H, s), 2.40-
1.57-1.63 (2H, q, J ) 6.3 Hz), 2.97-3.01 (2H, q, J ) 6.3 Hz,
6.6 Hz), 3.14-3.18 (2H, q, J ) 6.3 Hz), 3.72 (3H, s), 4.37-4.44
2
.43 (2H, t, J ) 7.2 Hz), 0.3.16-3.20 (2H, m), 3.90 (3H, s),
.23-4.28 (2H, q, J ) 7.1 Hz), 6.78 (1H, m), 7.51 (1H, s), 10.6
4
(4H, m), 4.71-4.81 (4H, m), 6.81-6.83 (1H, t, J ) 5.6 Hz),
13
13
(
1H, s); C NMR (DMSO-d
6
) δ 14.3, 28.4, 35.6, 35.8, 36.7, 60.8,
7.77-7.80 (1H, t, J ) 5.6 Hz); C NMR (DMSO-d
6
) δ 28.3,
7
7.8, 115.1, 131.0, 137.6, 155.7, 158.7, 168.5. MS m/z calcd for
29.8, 36.5, 37.7, 51.5, 69.5, 70.9, 71.5, 72.0, 72.8, 77.5, 78.5,
155.7, 167.5, 170.3. MS m/z calcd for C21
+
+
+
C
15
H
24
N
4
NaO
-Ethoxycarbonyl-1-methyl-4-{3-(1-methyimidazole-2-
carboxamido)propanamido}pyrrole (19). Compound 18
510 mg, 1.5 mmol) was dissolved in 10% trifluoroacetic acid/
CH Cl (24 mL, 30 mmol), and the solution was stirred at
ambient temperature for 1 h. The solution was washed with
5
363.16444, found 363.30490 [M + Na] .
H
29FeN
2
O
5
: 445.14259,
+
found [M + H] 445.14270.
2
General Procedure for the Synthesis of Ferrocene
Derivatives 23a, 23b, and 23c. Synthesis of 23a. To a
solution of 22a (1.1 g, 2.55 mmol) in methanol (26 mL) was
added 0.5 M aqueous NaOH (26 mL, 2.55 mmol). The mixture
was stirred at 80 °C for 12 h and then cooled to ambient
temperature. The solution was acidified to pH 3.0 by addition
of citric acid, diluted with ethyl acetate (20 mL), and washed
with water (20 mL). The organic layer was collected and dried
over Na SO . The solvents were removed under reduced
(
2
2
2 4
water (15 mL), dried over Na SO , filtered, and concentrated
under reduced pressure. The residue was dissolved in DMF,
and ethyldiisopropylamine (128 µL, 0.75 mmol) and compound
5
(490 mg, 1.8 mmol) were added. The mixture was stirred at
ambient temperature for 2 h. The mixture was extracted with
chloroform (30 mL), washed with water (20 mL), dried over
2
4
pressure, and the residue was dissolved in CH Cl (22 mL).
2
2
Na
2 4
SO , and concentrated under reduced pressure. The residue
Ethyl 3-aminopropionate hydrochloride (354 mg, 2.31 mmol),
n-tributylamine (1.87 mL, 7.85 mmol), and 2-chloro-1-meth-
ylpyridinium iodide (710 mg, 2.77 mmol) were added to the
solution under argon atmosphere, and the resulting mixture
was stirred at ambient temperature for 2 h. The solution was
washed with water (50 mL), and the organic layer was dried
over Na SO . The salt was removed by filtration, and the
was precipitated from chloroform and diisopropyl ether to give
1
1
9 (475 mg, 91%): H NMR (DMSO-d
6
) δ 1.26-1.38 (2H, t,
J ) 7.1 Hz), 2.53-2.56 (2H, t, J ) 6.8 Hz), 3.45-3.49 (2H, m),
3
(
(
.89 (3H, s), 3.92 (3H, s), 4.22-4.26 (2H, m), 6.94 (1H, s), 7.31
13
1H, s), 7.53 (1H, s), 8.34 (1H, m), 10.7 (1H, s). C NMR
DMSO-d ) δ 14.5, 35.4, 35.7, 36.2, 36.4, 61.6, 115.3, 125.6,
27.9, 131.7, 137.2, 139.2, 139.3, 159.0, 159.7, 168.7. MS m/z
6
2
4
1
filtrate was concentrated under reduced pressure. The residue
was chromatographed on a column of silica gel (20 g, hexane/
+
+
calcd for C15
H
21
6
N O
4
349.16243, found 349.16073 [M + H] .
1
2-Pentafluorophenoxycarbonyl-1-methyl-4-{3-(1-meth-
chloroform, 50:50, v/v) to give 23a (741 mg, 56%): H NMR
yimidazole-2-carboxamido)propanamido}pyrrole (20).
To a solution of compound 19 (65 mg, 0.19 mmol) in ethanol
3
(CDCl ) δ 1.18-1.21 (3H, t, J ) 7.1 Hz), 1.32 (9H, s), 2.59-
2.61 (2H, t, J ) 6.3 Hz), 3.32 (2H, m), 3.42-3.45 (2H, dd, J )
5.4 Hz), 3.57-3.60 (2H, dd, J ) 6.3 Hz), 4.07-4.12 (2H, dd,
J ) 7.1 Hz), 4.27 (3H, t, J ) 2.0 Hz), 4.29-4.30 (3H, t, J ) 1.8
Hz), 4.46 (4H, d, J ) 1.5 Hz), 5.89 (1H, m), 7.34-7.37 (1H, t,
(
1.9 mL) was added 0.4 M aqueous sodium hydroxide (1.4 mL,
0
.56 mmol). The resulting solution was stirred for 1 h at 50
°
C. The solution was cooled to ambient temperature and then
1
3
acidified to pH 2.0 by addition of 1 M aqueous HCl. The
product was separated by addition of 2-propanol, and the
resulting white precipitates were colleted by filtration and
washed with 2-propanol. The filtrate was concentrated in
vacuo. The residue was dissolved in DMF (1.3 mL). Pentafluo-
rophenyl trifluoromethyl acetate (68 µL, 0.39 mmol) and
pyridine (32 µL, 0.39 mmol) were added to the solution under
argon atmosphere, and the resulting mixture was stirred at
ambient temperature for 1 h. The solution was washed with
3
J ) 1.8 Hz), 7.55-7.57 (1H, t, J ) 1.8 Hz); C NMR (CDCl )
δ 14.0, 28.2, 33.9, 35.3, 40.2, 40.5, 60.4, 70.4, 70.5, 70.9, 71.0,
77.6, 78.0, 78.9, 156.5, 170.4, 170.5, 172.2. MS m/z calcd for
+
23
C H
34FeN
O
3 6
516.17970, found 516.23203.
Compounds 23b and 23c were prepared in 84% and 98%,
respectively, according to general procedure by use of 22a and
1
22b and appropriate amino acid esters. Data for 23b: H NMR
(500 MHz, DMSO) δ 1.16-1.19 (3H, t, J ) 7.1 Hz), 1.38 (9H,
s), 1.75-1.78 (2H, m, J ) 7.1 Hz), 2.35-2.38 (2H, m), 3.09-
3.11 (2H, m, J ) 5.9, 6.1 Hz), 3.18-3.23 (2H, q, J ) 5.9, 6.1,
6.6 Hz), 4.03-4.08 (2H, q, J ) 7.1 Hz), 4.29-4.31 (4H, m),
4.69-4.72 (4H, m), 6.90 (1H, t), 7.86-7.88 (1H, t, J ) 5.6 Hz),
0
.1 M aqueous HCl (10 mL × 3), 5% NaHCO
brine (10 mL). The organic layer was dried over Na
residue was concentrated under reduced pressure to give 20
3
(10 mL), and
2
SO . The
4
1
13
(
88 mg, 96%): H NMR (DMSO-d
.0 Hz), 3.49-3.53 (2H, m), 3.94 (3H, s), 3.98 (3H, s), 6.96 (1H,
d, J ) 1.0 Hz), 7.37 (1H, d, J ) 0.6 Hz), 8.37-8.39 (1H, t, J )
6
) δ 2.58-2.61 (2H, t, J )
7.90-7.92 (1H, t. J ) 5.6 Hz); C NMR (500 MHz, DMSO-d )
6
7
δ 14.1, 24.7, 24.7, 28.3, 30.8, 31.1, 38.2, 51.3, 59.8, 69.6, 69.6,
71.4, 71.5, 77.7, 77.8, 77.9, 155.8, 168.5, 168.7, 172.8, 173.3.
1
3
1
6
3
1
4
.0 Hz), 10.9 (1H, s). C NMR (DMSO-d
6
) δ 35.0, 35.1, 35.2,
Data for 23c: H NMR (500 MHz, DMSO) δ 1.18-1.21 (3H,
5.9, 118.3, 126.2, 127.2, 127.6, 138.8, 138.8, 154.0, 159.0,
t, J ) 7.1 Hz), 1.38 (9H, s), 1.59-1.62 (2H, m, J ) 7.1 Hz),
2.56-2.59 (2H, t, J ) 6.8 Hz), 2.97-3.01 (2H, q, J ) 6.6 Hz),
3.15-3.19 (2H, q, J ) 6.6, 6.8 Hz), 3.39-3.43 (2H, q, J ) 6.6,
7.1 Hz), 4.07-4.11 (2H q, J ) 7.1 Hz), 4.28-4.30 (4H, m),
4.69-4.70 (4H, m), 6.81-6.83 (1H, t), 7.82-7.85 (1H, t, J )
+
69.0. MS m/z calcd for C19
H
16
F
5 6
N O
4
487.11532, found
+
87.10453 [M + H] .
General Procedure for the Synthesis of Ferrocene
Derivatives 22a and 22b. To a solution of monoester 21 (1.0
g, 3.47 mmol) in 35 mL of CH Cl were added N-tert-
1
3
2
2
5.9 Hz), 7.96-7.98 (1H, t, J ) 5.8 Hz); C NMR (500 MHz,
butoxycarbonyl ethylenediamine (0.56 g, 3.47 mmol) and
n-tributylamine (2.0 mL, 8.3 mmol), followed by 2-chloro-1-
methylpyridinium iodide (1.1 g, 4.16 mmol). The organic layer
was washed successively with water (20 mL) and brine (20
6
DMSO-d ) δ 14.1, 28.3, 29.8, 34.0, 35.2, 36.5, 37.7, 60.0, 69.5,
71.5, 71.6, 77.5, 77.6, 78.0, 155.7, 168.4, 168.6, 171.5.
General Procedure for the Synthesis of Ferrocene
Derivatives 24a, 24b, and 24c. Synthesis of 24a. To a
solution of 23a (2.0 g, 3.9 mmol) in methanol (39 mL) was
added 0.1 M aqueous NaOH (41 mL, 4.1 mmol), and the
resulting solution was stirred at ambient temperature for 12
h. The solution was acidified to pH 3.0 by addition of 1 M
aqueous HCl and partitioned between chloroform (100 mL) and
water (100 mL). The organic layer was collected and dried over
2 4
mL) and dried over anhydrous Na SO . After filtration, the
filtrate was concentrated in vacuo. Chromatography of the
residue on a column of silica gel with hexane/chloroform (70:
3
0-65:45, v/v) gave 22a (1.3 g, 87% yield): 1H NMR (DMSO-
6
d
) δ 1.38 (9H, s), 3.07-3.11 (2H, q, J ) 6.1 Hz), 3.20-3.23
2H, q, J ) 6.1 Hz), 3.73 (3H, s), 4.37-4.44 (4H, m), 4.71-
.81 (4H, m), 6.84-6.86 (1H, t, J ) 5.4 Hz), 7.82-7.85 (1H, t,
(
4
2 4
Na SO . The solvents were removed under reduced pressure,
1
3
J ) 5.6 Hz); CNMR (DMSO-d
6
) δ 28.4, 39.1, 40.2, 51.7, 69.7,
and the residue was chromatographed on a column of silica
71.2, 71.6, 72.2, 73.0, 77.9, 78.4, 155.9, 167.9, 170.5. MS m/z
gel (22 g, chloroform/methanol, 100:2, v/v) to give 24a (1.84 g,
+
+
calcd for C20
H27FeN O
2 5
431.12694, found 431.12623 [M + H] .
1
9
6
7%): H NMR (DMSO-d ) δ 1.37 (9H, s), 2.49-2.53 (2H, m),
Compound 22b was synthesized according to the general
procedure described above by use of N-tert-butoxycarbonyl-
propylenediamine in place of N-tert-butoxycarbonyl-ethylene-
3.07-3.10 (2H,dd, J ) 6.1 Hz), 3.19-3.22 (2H, dd, J ) 6.1
Hz), 3.36-3.40 (2H, dd, J ) 6.3 Hz), 4.28-4.29 (4H, t,, J )
1.7 Hz), 4.69-4.71 (4H, m), 6.91-6.94 (1H, t, J ) 5.6 Hz),
J. Org. Chem, Vol. 70, No. 25, 2005 10319

Seio et al.
7
1
7
.83-7.86 (1H, t, J ) 5.7 Hz), 7.93-7.95 (1H, t, J ) 5.4 Hz),
5.6 Hz), 9.95 (1H, s), 9.97 (1H, s), 10.23 (1H, s); 13C NMR (500
13
2.25 (1H, s); C NMR (DMSO-d
6
) δ 28.5, 34.3, 35.5, 38.8, 69.8,
6
MHz, DMSO-d ) δ 27.1, 28.2, 29.8, 34.8, 35.8, 36.0, 36.3, 36.5,
1.7, 71.8, 72.2, 77.8, 77.8, 77.9, 79.4, 155.9, 168.7, 168.8, 173.3.
37.2, 37.7, 45.2, 57.2, 69.5, 71.5, 71.6, 77.5, 77.8, 77.9, 103.9,
104.6, 109.3, 114.7, 117.8, 119.1, 121.2, 121.8, 122.1, 123.4,
+
3 6
MS m/z calcd for C22H30FeN O 488.14840, found 488.22584.
134.2, 136.0, 155.6, 155.7, 158.7, 161.0, 167.9, 168.4, 168.4.
Compounds 24b and 24c were prepared according to general
procedure by use of 23b and 23c, respectively. Data for 24b:
General Procedure for the Synthesis of Ferrocene
Derivatives 26a, 26b, and 26c. Synthesis of 26a. Com-
pound 25a (1.5 g, 1.6 mmol) was dissolved in 10% trifluoro-
1
H NMR (500 MHz, DMSO-d
6
) δ 1.38 (9H, s), 1.72-1.77 (2H,
m, J ) 7.1, 7.3 Hz), 2.28-2.31 (2H, t, J ) 7.3 Hz), 3.08-3.11
(
2H, q, J ) 6.3 Hz), 3.18-3.24 (4H, m, J ) 6.3 Hz), 4.29-4.30
acetic acid/CH
2 2
Cl (25 mL, 32 mmol), and the solution was
(
4H, s), 4.69-4.72 (4H, m), 6.91-6.93 (1H, t, J ) 5.6 Hz), 7.87-
stirred at ambient temperature for 5 h. The mixture was
13
7
.92 (2H, m, J ) 5.6, 5.8 Hz), 12.1 (1H, s); C NMR (500 MHz,
2 4
washed with water (50 mL), dried over Na SO , filtered, and
DMSO) δ 25.4, 29.0, 31.9, 39.0, 70.2, 70.3, 72.1, 72.2, 78.3, 78.5,
concentrated under reduced pressure. The residue was chro-
1
7
8.6,156.4, 169.1, 169.3, 175.0. Data for 24c: H NMR (500
MHz, DMSO-d ) δ 1.38 (9H, s), 1.59-1.63 (2H, m, J ) 6.8 Hz),
.97-3.01 (2H, m, J ) 6.6 Hz), 3.15-3.19 (2H, q, J ) 6.6, 6.8
matographed on a column of silica gel (30 g, chloroform/
1
6
methanol, 100:3, v/v) to give 26a (1.0 g, 78%): H NMR (CDCl
3
)
2
δ1.66-1.71 (2H, m), 2.20 (6H, s), 2.35-2.38 (2H, t, J ) 6.4
Hz), 2.74 (2H, s), 2.97 (2H, m), 3.39-3.40 (2H, m), 3.47 (2H,
m), 3.69 (2H, s), 3.84 (3H, s), 3.87 (3H, s), 3.97 (3H, s), 4.27
(2H, s), 4.31 (2H, s), 4.58-4.60 (4H, d, J ) 7.3 Hz), 6.70 (1H,
s), 6.90 (1H, s), 7.20 (1H, s), 7.23 (1H, s), 7.38 (1H, s), 7.45-
7.46 (1H, m), 7.76 (2H, m), 7.83 (1H, m), 9.07 (1H, br), 9.21
Hz), 3.36-3.40 (2H, m, J ) 6.8 Hz), 4.28-4.29 (4H, t), 4.70-
4
.72 (4H, m), 6.81-6.83 (1H, t, J ) 5.6 Hz), 7.81-7.83 (1H, t,
13
J ) 5.9 Hz), 7.92-7.94 (1H, t, J ) 5.4 Hz), 12.2 (1H, s);
C
6
NMR (500 MHz, DMSO-d ) δ 28.3, 29.8, 34.1, 35.3, 36.5, 37.7,
6
9.5, 69.5, 71.5, 71.6, 77.5, 77.7, 78.0, 155.6, 168.4, 168.4, 168.5,
73.0, 173.1.
1
3
1
3
(1H, br), 9.88(1H, s); C NMR(CDCl ) δ 26.2, 35.4, 36.3, 36.5,
3
7
1
6.6, 38.9, 41.2, 42.1, 45.3, 58.4, 70.3, 70.4, 71.0, 71.2, 77.3,
General Procedure for the Synthesis of Ferrocene
7.5, 78.1, 103.2, 104.5, 114.0, 118.4, 120.0, 120.8, 121.7, 122.3,
Derivatives 25a, 25b, and 25c. Synthesis of 25a. To a
solution of 15 (1.6 g, 3.3 mmol) in methanol (13 mL) was added
23.8, 133.9, 136.1, 156.0, 158.6, 161.7, 169.4, 170.4, 170.6.
+
MS m/z calcd forC39H51FeN12O
6
839.34039, found 839.33831.
1
0% Pd/C (164 mg). A balloon of hydrogen gas was attached,
and the suspension was stirred under hydrogen atmosphere
for 4 h. The catalysts were removed by filtration, and the
filtrate was concentrated under reduced pressure. The residue
Compounds 26b and 26c were synthesized according to
general procedure by use of 25b and 25c, respectively. Data
1
for 26b: H NMR (500 MHz, DMSO-d
6
) δ 1.58-1.64 (2H, m,
was dissolved in CH
1.6 g, 3.3 mmol), N,N′-dicyclohexylcarbodiimide (744 mg, 3.6
mmol), and 1-hydroxybenzotriazole (488 mg, 3.6 mmol). After
h, the white precipitates were removed by filtration. The
filtrate was washed with water (50 mL), dried over Na SO
2
Cl
2
, and to this solution was added 24a
J ) 7.1 Hz), 1.80-1.85 (2H, m), 2.14 (6H, s), 2.23-2.27 (2H, t,
J ) 7.1 Hz), 2.31-2.36 (2H, m, J ) 7.1 Hz), 2.69-2.72 (2H, t,
J ) 6.6 Hz), 3.17-3.23 (6H, m), 3.81 (3H, s), 3.84 (3H, s), 3.97
(3H, s), 4.29-4.33 (4H, m), 4.70-4.73 (4H, m), 6.88 (1H, s),
6.93 (1H, s), 7.22 (1H, s), 7.29 (1H, m), 7.53 (1H, s), 7.86-7.88
(1H, t, J ) 5.6 Hz), 7.92-7.97 (2H, m), 8.10-8.12 (1H, t, J )
(
1
2
4
,
filtered, and concentrated under reduced pressure. The residue
was chromatographed on a column of silica gel (32 g, chloroform/
methanol.conc NH
1
3
5.6 Hz), 9.90-9.91 (1H, d), 9.97 (1H, s); C NMR (500 MHz,
DMSO-d ) δ 27.1, 33.2, 34.9, 36.0, 36.2, 37.2, 45.2, 57.2, 69.6,
3
aq, 100:7:0.2, v/v/v) to give 25a (2.5 g,
6
1
8
2%): H NMR(DMSO-d ) δ 1.37 (9H, s), 1.70-1.73 (2H, t,
6
69.7, 71.3, 71.5, 77.9, 78.1, 78.1, 103.9, 104.6, 114.7, 114.7,
117.8, 119.1, 121.2, 121.8, 122.2, 123.4, 134.2, 136.1, 136.1,
J ) 7.1 Hz), 2.42 (6H, s), 2.55-2.61 (4H, m), 3.09-3.47 (16H,
m), 3.80 (3H, s), 3.83 (3H, s), 3.95 (3H, s), 4.28-4.29 (4H, m),
155.7, 158.7, 161.0, 167.3, 168.4, 168.4, 168.5, 168.6, 169.3.
1
4
1
7
.71-4.73 (4H, m), 6.92 (1H, d, J ) 1.5 Hz), 6.94 (1H, d, J )
.7 Hz), 7.21 (1H, d, J ) 1.7 Hz), 7.29 (1H, d, J ) 1.5 Hz),
.51 (1H, s), 7.88-7.91 (1H, t, J ) 5.5 Hz), 8.00-8.01 (1H, t,
Data for 26c: H NMR (500 MHz, DMSO-d
6
) δ 1.59-1.62 (4H,
m), 2.14 (6H, s), 2.23-2.26 (2H, t, J ) 7.1 Hz), 2.57-2.59 (2H,
t), 3.19-3.20 (2H, m), 3.24-3.25 (2H, m), 3.45-3.47 (2H, m),
3.80 (3H, s), 3.84 (3H, s), 3.97 (3H, s), 4.29 (4H, s), 4.71 (4H,
d), 6.89 (1H, d, J ) 1.5 Hz), 6.94 (1H, s), 7.22 (1H, s), 7.30
(1H, s), 7.53 (1H, s), 7.93-7.95 (1H, t, J ) 5.4 Hz), 7.99-8.10
J ) 5.5 Hz), 8.14-8.16 (1H, t, J ) 5.4 Hz), 8.31 (1H, s), 9.95
1
3
(
6
1H, s), 10.23 (1H, s); C NMR(DMSO-d ) δ 26.1, 28.4, 35.0,
3
7
1
6.0, 36.0, 36.2, 36.4, 36.6, 43.9, 56.2, 69.8, 71.7, 77.8, 77.9,
13
9.3, 104.3, 104.8, 114.9, 118.1, 119.3, 121.4, 122.0, 122.3,
(2H, m, J ) 5.1 Hz), 9.99-10.02 (1H, m, J ) 5.1 Hz); C NMR
(500 MHz, DMSO-d ) δ 27.1, 32.6, 34.9, 35.9, 36.0, 36.3, 36.5,
37.2, 45.2, 57.2, 69.5, 69.5, 71.4, 71.5, 77.8, 78.1, 79.2, 103.9,
23.3, 134.3, 136.2, 155.9, 158.8, 161.4, 168.1, 168.7, 168.8.
6
+
MS m/z calcd for C44
H
59FeN12
O
8
939.39282, found 939.2523.
1
1
04.6, 114.7, 117.8, 119.1, 121.2, 121.8, 122.1, 123.4, 134.2,
36.1, 155.7, 158.7, 161.0, 167.9, 168.4, 168.5, 168.5.
Polyamide (28). Compound 15 (806 mg, 1.6 mmol) was
Compounds 25b and 25c were synthesized according to the
general procedure by use of 24b and 24c, respectively. Data
1
for 25b: H NMR (500 MHz, DMSO-d
6
) δ 1.38 (9H, s), 1.59-
1
(
7
3
(
1
.63 (2H, m, J ) 7.1 Hz), 1.81-1.84 (2H, m, J ) 7.3 Hz), 2.14
dissolved in methanol (6.5 mL), and to this solution was added
10% Pd/C (81 mg). A balloon of hydrogen gas was attached,
and the suspension was stirred under hydrogen atmosphere
for 4 h at ambient temperature. The catalysts were removed
by filtration, and the solvent was removed under reduced
6H, s), 2.23-2.26 (2H, t, J ) 7.1 Hz), 2.31-2.34 (2H, m, J )
.3 Hz), 3.09-3.12 (2H, m, J ) 5.9 Hz), 3.17-3.25 (6H, m),
.80 (3H, s), 3.84 (3H, s), 3.97 (3H, s), 4.32 (4H, s), 4.70-4.73
4H, m), 6.89-6.93 (3H, m, J ) 1.7, 1.9 Hz), 7.22 (1H, d, J )
.7 Hz), 7.28 (1H, d, J ) 1.7 Hz), 7.53 (1H, s), 7.89-7.94 (2H,
2 2
pressure. The residue was dissolved in CH Cl , and the
m, J ) 5.6, 5.9 Hz), 8.09-8.11 (1H, t, J ) 5.6 Hz), 9.88 (1H,
protected γ-butyric acid 27 (710 mg, 1.6 mmol), N,N′-dicyclo-
hexyl carbodiimide (332 mg, 1.6 mmol) ,and 1-hydroxybenzo-
triazole (218 mg, 1.6 mmol) were added. The mixture was
stirred at ambient temperature for 1 h. The precipitation was
removed by filtration, and to the filtrate was added 5%
piperidine/DMF (28 mL, 16 mmol). After 30 min, the solution
1
3
s), 9.95 (1H, s), 10.22 (1H, s); C NMR (500 MHz, DMSO-d
6
)
δ 25.7, 27.1, 28.2, 33.2, 34.9, 36.0, 36.2, 37.2, 38.6, 45.2, 57.2,
6
1
1
9.6, 69.6, 71.4, 77.7, 77.8, 78.0, 79.2, 103.9, 104.6,114.7, 117.8,
19.1, 121.2, 121.8, 122.2, 123.4, 134.2, 136.1, 155.7, 158.7,
1
61.0, 168.4, 168.7, 169.3. Data for 25c: H NMR (500 MHz,
DMSO-d
6
) δ 1.38 (9H, s), 1.58-1.64 (4H, m, J ) 6.8, 7,1 Hz),
2 4
was washed with water (100 mL), dried over Na SO , and
concentrated under reduced pressure. The residue was chro-
matographed on a column of silica gel (16 g, chloroform/
methanol/conc NH
42%): HNMR (CDCl ) δ 1.44 (9H, s), 1.71-1.76 (2H, t, J )
6.3 Hz), 1.91-1.98 (2H, t, J ) 6.3 Hz), 2.26 (6H, s), 2.41-2.44
(2H, t, J ) 6.3 Hz), 2.90-2.95 (2H, m), 3.44-3.47 (2H, dd,
J ) 5.7 Hz), 3.83 (3H, s), 3.91 (3H, s), 4.01 (3H, s), 4.52 (1H,
s), 6.46 (1H, s), 6.63 (1H, s), 6.67 (1H, s), 7.15 (1H, s), 7.26
2
.14 (6H, s), 2.23-2.26 (2H, t, J ) 7.1 Hz), 2.56-2.58 (2H, t,
J ) 7.1 Hz), 2.98-3.02 (2H, m, J ) 6.3, 6.6 Hz), 3.16-3.21
4H, m, J ) 6.3, 6.6 Hz), 3.43-3.47 (2H, m, J ) 6.6, 6.8 Hz),
.80 (3H, s), 3.84 (3H, s), 3.97 (3H, s), 4.28-4.29 (4H, m), 4.71-
.73 (4H, m) 6.81-6.83 (1H, t, J ) 5.6 Hz), 6.89 (1H, d, J )
.0 Hz), 6.93 (1H, d, J ) 2 0.0 Hz), 7.22 (1H, d, J ) 1.7 Hz),
.30 (1H, d, J ) 1.7 Hz), 7.52 (1H, s), 7.83-7.85 (1H, t, J )
.9 Hz), 7.96-7.97 (1H, t, J ) 5.6 Hz), 8.08-8.11 (1H, t, J )
(
3
aq,100:10:1, v/v/v) to give 28 (453 mg,
3
1
3
4
2
7
5
10320 J. Org. Chem., Vol. 70, No. 25, 2005

Ferrocene-Pyrolle-imidazole Polyamide Conjugates
(
1H, s), 7.37 (1H, s), 7.77 (1H, s), 8.24 (1H, s), 9.10 (1H, s),
3.23 (4H, m), 3.44-3.50 (4H, m), 3.80 (3H, s), 3.83 (3H, s), 3.85
(3H, s), 3.94 (3H, s), 3.96 (3H, s), 3.99 (3H, s), 4.29-4.32 (4H,
d), 4.74 (4H, s), 6.90 (1H, s), 6.93 (1H, s), 7.04 (1H, s), 7.16
(1H, s), 7.22 (1H, s), 7.28 (1H, s), 739 (1H, m), 7.50 (1H, s),
7.53 (1H, s), 7.91-7.93 (1H, t, J ) 5.0 Hz), 8.04 (1H, t), 8.11-
8.12 (1H, t, J ) 5.1 Hz), 8.14-8.16 (1H, t, J ) 5.3 Hz), 9.89
13
9
3
1
1
6
.64 (1H, s); C NMR (DMSO-d ) δ 27.1, 28.2, 34.9, 35.7, 36.0,
6.2, 37.2, 38.4, 45.2, 57.2, 78.0, 79.2, 104.0, 114.7, 115.7, 117.8,
19.2, 121.2, 121.8, 121.9, 123.4, 134.2, 136.1, 155.4, 155.8,
+
58.7, 161.1, 169.7. MS m/z calcd for C31
H N O
48 11 6
670.37890,
found 670.33883.
(
1H, s), 9.98 (1H, s), 10.23 (1H, s), 10.24 (1H, s), 10.38 (1H, s);
Polyamide (29). To a solution of compound 10 (304 mg,
.77 mmol) were added ethyldiisopopylamine (239 µL, 1.4
1
3
C NMR (500 MHz, DMSO-d
6
) δ 26.4, 27.8, 33.9, 35.6, 35.7,
0
3
5.8, 35.8, 36.8, 36.9, 37.0, 37.9 39.3, 39.5, 45.9, 57.9, 63.5,
mmol) and O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluro-
nium hexafluorophosphate (533 mg, 1.4 mmol), and the
mixture was stirred at ambient temperature for 30 min. To
70.3, 70.3, 72.2, 72.3, 78.4, 78.8, 104.6,105.3, 106.6, 115.1,
115.4, 118.5, 119.8, 120.2, 121.9, 122.2, 122.5, 122.9, 124.1,
127.1, 127.7, 134.6, 134.9, 136.8, 139.4, 156.4, 156.8, 159.4,
this mixture was added 28 (470 mg, 0.70 mmol) in CH
mL), and the mixture was stirred for an additional 1 h. The
solution was washed with water (10 mL), dried over Na SO
2 2
Cl (7
1
159.4, 159.7, 161.8, 169.1, 169.5, 170.1. Data for 1c: H NMR
4
,
6
(500 MHz, DMSO-d ) δ 1.58-1.63 (2H, m, J ) 7.1 Hz), 1.72-
2
filtered, and concentrated under reduced pressure. The residue
was chromatographed on a column of silica gel (10 g, chloroform/
1.75 (2H, m, J ) 6.7 Hz), 2.13 (6H, s), 2.22-2.25 (2H, t, J )
7.1 Hz), 2.56-2.58 (2H, t, J ) 7.0 Hz), 3.17-3.21 (2H, q, J )
6.1, 6.6 Hz), 3.22-3.26 (2H, q, J ) 6.1, 6.6 Hz), 3.44-3.48 (2H,
q, J ) 6.1, 6.8 Hz), 3.80 (3H, s), 3.83 (3H, s), 3.85 (3H, s), 3.94
(3H, s), 3.96 (3H, s), 3.99 (3H, s), 4.30-4.32 (4H, m), 4.72-
4.75 (4H, m), 6.89 (1H, d, J ) 2.0 Hz), 6.92 (1H, d, J ) 1.7
Hz), 7.03 (1H, d, J ) 1.7 Hz), 7.17 (1H, d, J ) 1.7 Hz), 7.21
(1H, d, J ) 1.7 Hz), 7.30 (1H, d, J ) 1.7 Hz), 7.39 (2H, d, J )
2.2 Hz), 7.50 (1H, s), 7.52 (1H, s), 7.93-7.95 (1H, t, J ) 5.9
Hz), 7.99-8.01 (1H, t, J ) 5.9 Hz), 8.09-8.12 (1H, t, J ) 5.6
Hz), 8.14-8.16 (1H, t, J ) 5.9 Hz), 9.97 (1H, s), 9.99 (1H, s),
methanol/triethylamine, 100:5:0.5, v/v/v) to give 29 (673 mg,
1
9
4%): H NMR (DMSO-d
6
) δ 1.34 (9H, s), 1.70-1.73 (2H, t,
J ) 7.1 Hz) 1.75-193 (2H, m), 2.41 (6H, s), 2.61 (2H, m), 3.19-
.22 (2H,dd, J ) 1.7 Hz), 3.27-3.37 (2H, m), 3.80 (3H, s), 3.83
3H, s), 3.85 (3H, s), 3.92 (3H, s), 3.96 (3H, s), 3.98 (3H, s),
.08-4.13 (1H, m) 6.94 (1H, d, J ) 1.5 Hz), 6.97 (1H, s), 7.02
3
(
4
(
1H, s), 7.16 (1H, d, J ) 1.5 Hz), 7.22 (1H, s), 7.26 (1H, d, J )
1
.2 Hz), 7.37 (1H, s), 7.38 (1H, d, J ) 1.5 Hz), 7.49 (1H, s),
.53 (1H, s), 7.97-7.80 (1H, t, J ) 5.5 Hz), 8.15-8.17 (1H, t,
7
1
3
J ) 5.5 Hz), 9.94 (1H, s), 9.99 (1H, s), 10.27 (1H, s), 10.34 (1H,
s), 10.36 (1H, s); C NMR(DMSO-d
10.24 (1H, s), 10.27 (1H, s), 10.38 (1H, s); C NMR (500 MHz,
DMSO-d ) δ 27.1, 29.7, 34.9, 34.9, 35.1, 35.8, 35.9, 36.0, 36.1,
1
3
6
) δ 26.1, 28.4, 32.2, 35.1,
6
3
7
1
1
1
1
5.3, 35.7, 36.3, 36.4, 36.5, 36.6, 38.4, 43.9, 52.6, 56.1, 78.4,
36.2, 36.3, 36.3, 37.2, 45.2, 57.2, 69.5, 71.6, 71.6, 77.8, 77.9,
103.9, 104.6, 105.9, 114.4, 114.7, 117.8, 119.2, 119.5, 121.2,
121.5, 121.8, 122.1, 122.2, 123.4, 126.4, 127.0, 134.0, 134.2,
9.4, 104.4, 105.0, 106.1, 114.5, 115.0, 118.2, 119.5, 119.7,
21.4, 121.7, 121.9, 122.1, 122.4, 123.3, 126.6, 127.2, 134.2,
34.4, 136.2, 136.2, 138.9, 155.6, 155.9, 156.3, 158.9, 158.9,
136.0, 136.0, 134.7,155.7, 156.1, 158.7, 158.8, 161.0, 167.9,
+
1
61.4, 169.4. MS m/z calcd for C47
H N O
63 18 9
1023.50254, found
168.5, 168. Data for 2: H NMR (DMSO-d
6
) δ 1.59-1.62 (2H,
023.49821.
t, J ) 7.0 Hz), 2.14 (6H, s), 2.23-2.25 (2H, t, J ) 7.0 Hz),
.55-2.60 (4H, m), 3.17-3.21 (2H, m), 3.35-3.37 (2H, m),
.42-3.50 (6H, m), 3.80 (3H, s), 3.83 (3H, s), 3.91 (3H, s), 3.93
3H, s), 3.96 (3H, s), 4.25-4.26 (2H, m), 4.29 (2H, m), 4.72-
.73 (2H, m), 4.74-4.75 (2H, m), 6.89 (1H, d, J ) 1.8 Hz), 6.93-
2
General Procedure for the Synthesis of Fc-PIAs 1a,
3
1
b, 1c, and 2 (3). Synthesis of 1a. To a solution of 10 (188
(
mg, 0.48 mmol) were added ethyldiisopopylamine (0.16 mL,
.95 mmol) and O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethy-
4
0
(
(
1H, d, J ) 1.7 Hz), 6.95 (1H, s), 7.21 (1H, d, J ) 1.7 Hz), 7.31
1H, d, J ) 1.6 Hz), 7.32 (1H, s), 7.41 (1H, s), 7.52 (1H, s),
luronium hexafluorophosphate (362 mg, 0.95 mmol), and the
mixture was stirred at ambient temperature for 30 min. To
7
.99-8.01 (2H, m), 8.10-8.12 (2H, m), 8.34 (1H, t, J ) 6.0
Hz), 9.95 (1H, s), 10.0 (1H, s), 10.2 (1H, s), 10.2 (1H, s), 10.3
1H, s).
Fc-PIA 3. Compound 30 (300 mg, 0.29 mmol) was dissolved
in 20% trifluoroacetic acid /CH Cl (1.2 mL, 2.9 mmol). After
this mixture was added 26a (400 mg, 0.48 mmol) in CH
4.8 mL), and the mixture was stirred for an additional 1 h.
The solution was washed with water (20 mL), dried over Na
2 2
Cl
(
(
2
-
4
SO , filtered, and concentrated under reduced pressure. The
residue was chromatographed on a column of silica gel (10 g,
2
2
chloroform/methanol/triethylamine, 100:5:0.5, v/v/v) to give 1a
1 h, the solution was washed with water (20 mL), dried over
Na SO , filtered, and concentrated under reduced pressure.
1
(
349 mg, 61%): H NMR (DMSO-d
6
) δ 1.59-1.65 (2H, m), 2.15
2
4
(
6H, s), 2.26-2.28 (2H, t, J ) 7.1 Hz), 2.56-2.59 (2H, t, J )
2 2
The residue was dissolved in CH Cl (2.9 mL), and to this
7
3
.0 Hz), 3.18-3.22 (2H, m), 3.37-3.50 (6H, m), 3.81(3H, s),
solution were added ethyldiisopropylamine (0.10 mL, 0.59
mmol), ferrocenecarboxylic acid (67 mg, 0.29 mmol), and
O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluo-
rophosphate (111 mg, 0.29 mmol). The solution was stirred at
ambient temperature for 10 h, then washed with water (20
mL), dried over Na SO , filtered, and concentrated under
.83 (3H, s), 3.85 (3H, s), 3.94 (3H, s), 3.97 (3H, s), 3.99 (3H,
s), 4.27-4.30 (4H, m), 4.73 (4H, s), 6.88 (1H, d, J ) 1.7 Hz),
6
.94 (1H, d, J ) 1.5 Hz), 7.02 (1H, s), 7.16 (1H, d, J ) 1.7 Hz),
.19 (1H, d, J ) 1.5 Hz), 7.26 (1H, d, J ) 1.7 Hz), 7.35-7.36
7
(
2H, m), 7.46 (1H, s), 7.49 (1H, s), 7.86-7,87 (1H, t, J ) 5.6
2
4
Hz), 7.91-7.93 (1H, t, J ) 5.5 Hz), 7.98-7.80 (1H, t, J ) 5.5
Hz), 8.05-8.08 (1H, t, J ) 5.7 Hz), 9.77 (1H, s), 9.88 (1H, s),
reduced pressure. The residue was chromatographed on a
column of silica gel (7 g, chloroform/methanol/triethylamine,
0.03 (1H, s), 10.06 1H, s), 10.19 (1H, s); 13C NMR (DMSO-d
)
1
1
6
100:5:0.5, v/v/v) to give 3 (204 mg, 61%): HNMR(DMSO-d6)
δ 27.2, 35.1, 35.1, 35.3, 36.0, 36.1, 36.2, 36.4, 36.5, 37.4,
δ 1.57-1.62 (2H, m), 2.12 (6H, s), 2.22-2.24 (2H, t, J ) 7.0
Hz), 3.16-3.20 (2H, m), 3.37-3.43 (2H, m), 3.80 (3H, s), 3.83
(3H, s), 3.85 (3H, s), 3.93 (3H, s), 3.96 (3H, s), 3.98 (3H, s),
4.22 (5H, s), 4.36-4.37 (2H, m), 4.85 (2H, m), 4.94 (2H, m),
6.86 (1H, d, J ) 1.7 Hz), 6.99 (1H, d, J ) 1.7 Hz), 7.02 (1H, d,
J ) 1.0 Hz), 7.17 (1H, d, J ) 1.7 Hz), 7.20(1H, d, J ) 1.7 Hz),
7.28 (1H, d, J ) 1.7 Hz), 7.37 (1H, s), 7.38 (1H, d, J ) 1.7 Hz),
7.49 (1H, s), 7.52 (1H, s), 7.86-7.87 (1H, d, J ) 1.7 Hz), 8.05-
8.10 (2H, m), 9.95 (1H, s), 10.04 (1H, s), 10.24 (1H, s), 10.25
3
1
1
1
1
1
8.8, 39.0, 45.3, 57.3, 69.8, 71.7, 71.8, 77.9, 78.0, 79.3, 104.1,
04.8, 106.1, 114.6, 114.9, 118.0, 119.4, 119.6, 121.4, 1221.7,
22.2, 122.3, 122.4, 123.5, 126.6, 127.2, 134.1, 134.4, 136.2,
38.9, 155.9, 156.3, 158.9, 158.9, 159.2, 161.2, 168.2, 168.6,
+
69.0. MS m/z calcd forC55
H
66FeN19
O
9
1192.46403, found
192.37089.
Compounds 1b and 1c were synthesized according to
general procedure by use of 26b and 26c, respectively.
Compound 2 was synthesized by the reaction of 26a (138 mg,
1
3
6
(1H, s), 10.27 (1H, s), 10.36 (1H, s); C NMR (DMSO-d ) δ
0
.17 mmol) and 20 (88 mg, 0.18 mmol) in the presence of
ethyldiisopropylamine (31 mL, 0.18 mmol) in CH Cl . The
product was purified according to the general procedure to give
27.2, 35.1, 35.1, 35.3, 36.0, 36.1, 36.2, 36.4, 36.5, 37.4, 38.8,
39.0, 45.3, 57.3, 69.8, 71.7, 71.8, 77.9, 78.0, 79.4, 104.1, 104.8,
106.1, 114.6, 114.9, 118.0, 119.4, 119.6, 121.4, 121.7, 122.0,
122.3, 122.4, 123.5, 126.6, 127.2, 134.1, 134.4, 136.2, 138.9,
2
2
1
2
(152 mg, 81%). Data for 1b: H NMR (500 MHz, DMSO-d
δ 1.59-1.63 (2H, m), 1.80-1.83 (2H, m), 2.14 (6H, s), 2.23-
.26 (2H, t, J ) 6.8 Hz), 2.31-2.34 (2H, t, J ) 7.2 Hz), 3.18-
6
)
155.9, 156.3, 158.9, 158.9, 159.2, 161.2, 168.2, 168.6, 169.0.
+
2
MS m/z calcd for C53H63FeN18O
8
1135.44257, found 1135.43889.
J. Org. Chem, Vol. 70, No. 25, 2005 10321

Seio et al.
CD Spectra. Solutions (1 mM) of Fc-PIA were prepared by
addition of 0.1 M HCl (8.8 µL) to a suspension of Fc-PIA (10
mg, 8.8µmol) in a buffer composed of 10 mM sodium cacodylate
Acknowledgment. This work was supported by
CREST of JST (Japan Science and Technology Agency)
and supported by The Sumitomo Foundation. We thank
Dr. Yoshio Ishimori and Dr. Jun Okada (Toshiba Co.
Ltd.) for fruitful discussion on the electrochemical
detection of DNA hybridization in this study.
(
pH6.9), 10 mM KCl, 10 mM MgCl
The titration was performed at 20 °C by incrementally adding
.5 µL aliquots of the Fc-PIA solution into a 1.5 mL solution
2 2
, and 5 mM CaCl (8.8 mL).
1
of 5 µM duplex (DNA1 or DNA2). The spectra were recorded
from 200 to 400 nm. The titration curves were drawn by
plotting the molar ellipticity at the wavelength that gave
maximum Cotton effects within a 300-350 nm range.
Cyclic Voltammetry in DMF. Fc-PIA (200 µL, 5 mM) was
dissolved in DMF (10 mL). The CV profiles were measured by
a general three-electrode system by use of a Pt electrode (6
mm) and platinum wire as working electrode and counter
Supporting Information Available: 1H and 13C NMR
spectra of all of the newly synthesized compounds and th
procedure and results of curve fitting of the CD titration. This
material is available free of charge via the Internet at
http://pubs.acs.org.
electrode, respectively. Ag/AgCl in CH
3
CN was used as a
reference.
JO051247N
10322 J. Org. Chem., Vol. 70, No. 25, 2005