Preparation of N-phenyl-substituted quinolinium derivatives labeled with tritium by chemonuclear synthesis

Article abstract of DOI:10.1007/s10593-009-0359-7

A chemonuclear method of synthesis is proposed for obtaining difficultly available phenyl-substituted derivatives of quinoline labeled with tritium. The ion-molecule reaction of free phenyl cations, generated on β-decay of tritium, with the nucleophilic c

Full text of DOI:10.1007/s10593-009-0359-7

Chemistry of Heterocyclic Compounds, Vol. 45, No. 7, 2009
PREPARATION OF N-PHENYL-SUBSTITUTED
QUINOLINIUM DERIVATIVES LABELED WITH
TRITIUM BY CHEMONUCLEAR SYNTHESIS
1
2
3
1
N. E. Shchepina *, V. V. Avrorin , G. A. Badun , G. A. Alexandrova ,
4
3
5
6
S. E. Ukhanov , V. M. Fedoseev , S. B. Lewis , and I. I. Boiko
A chemonuclear method of synthesis is proposed for obtaining difficultly available phenyl-substituted
derivatives of quinoline labeled with tritium. The ion-molecule reaction of free phenyl cations,
generated on β-decay of tritium, with the nucleophilic centers of heterocyclic compounds is the basis of
the synthesis. The onium derivatives synthesized possess significant inhibitory antimicrobial activity and
are promising for a detailed study of the reaction mechanisms and metabolic processes using
radioactive indicators.
Keywords: N-phenylquinolinium and quinaldinium salts, tritium, phenyl cations, six-membered
nitrogen heterocyclic compounds, chemonuclear synthesis.
Fragments of quinoline and isoquinoline are part of many alkaloids and enzymes. Together with natural
therapeutic preparations, such as quinine and papaverine, a large number of effective synthetic drugs has been
developed: chloroxine, cyprofloxacin, norfloxacin, etc. [1-3]. A large contribution to the development of
methods of synthesis and study of the biological activity of quinoline derivatives has been made by Soviet
scientists [4, 5]. It was established on biological monitoring that lipophilic derivatives of quaternary nitrogen,
and particularly quinolinium salts, display higher biological activity. In many cases N-phenyl compounds
surpass their aliphatic analogs. In spite of the large number of studies and the broad aspects of biological and
medicinal application (antiseptics, biocides, antimalarials, antitumor, antirecidive, and antipyretic preparations)
[
[
6-14], the search still goes on for new biologically active compounds in the area of quinoline derivatives
15-26].
_
*
______
To whom correspondence should be addressed, e-mail: neshchepina@mail.ru.
1
Natural Sciences Institute, Perm State University, Perm 614990, Russia.
2
3
4
5
6
Saint Petersburg State University, Saint Petersburg 199034, Russia; e-mail: radiochem@yandex.ru.
M. V. Lomonosov Moscow State University, Moscow 119991, Russia; e-mail: badun@radio.chem.msu.ru.
Perm State Technical University, Perm 614600, Russia.
James Madison University, Harrisonburg, VA, USA; e-mail: lewissb@jmu.edu.
Tekhnolog", Pereslavl-Zalessky 152025, Yaroslavl region, Russia; e-mail: technolog@slavich.ru.
"
_
_________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1008-1014, July, 2009. Original
article submitted February 26, 2008.
7
96 0009-3122/09/4507-0796©2009 Springer Science+Business Media, Inc.

At the present time isotopic, especially tritium, methods of labeling [27-29] are widely used for the
detailed study of the mechanism of action of drugs and the processes of their metabolism in the organism,
enabling very sensitive investigations of bioorganic molecules and pharma preparations. Regretably the
synthesis of complex biologically active subjects with a fixed tritium label is extremely complex and laborious.
There are no direct methods of phenylation of nitrogen in pyridine derivatives [30]. Only in the middle
of the twentieth century was a quaternary quinolinium salt obtained for the first time by cyclization of secondary
amines with various carbonyl-containing organic compounds by the Skraup or Döbner-Miller reactions [2,
3
1-35]. The precursors labeled with tritium for this reaction, diphenylamine, aniline, or nitrobenzene which
contain tritium in the benzene ring are commercially unavailable, and lead to the need for a multistage synthesis
of these compounds. The extreme complexity of traditional schemes of obtaining, and also the significant losses
of radioactivity as a result of dilution and hydrogen exchange in such multistage syntheses makes this route
difficult to carry out and extremely expensive.
More promising in the synthesis of heterocyclic compounds labeled with tritium is the chemonuclear
method, including the direct one-step phenylation of the nitrogen atom of the heterocycle with free phenyl
cations, generated on spontaneous β-decay of tritium in the composition of benzene labeled with tritium. The
source of the phenyl cations, benzene labeled with tritium, may be synthesized from molecular tritium by the
following reactions.
4
73 K
7
73 K
CuO
catalyst
T2
T2O
C2T2
C6T6
Li C
2
2
–
β
+
+
C6T6
[C T He]
6 5
C6T
5
+
He
Since a double label must be present in the benzene molecule to study the ion-molecule reactions of
phenyl cations generated by the chemonuclear method, we changed over from the more laborious synthesis of
multilabeled benzene to the more simple and convenient synthesis of double-labeled benzene, the source of
phenyl cations. The basis of the synthesis of doubly labeled benzene was the catalytic replacement of halogen
atoms by tritium in the p-dibromobenzene molecule [37].
5
% Pd/BaSO4
5°C
C H Br + T2
C H T
6 4 2
6
4
2
2
–
β
+
+
C H T
+
He
C H T
[C H THe]
6
4
6
4
2
6
4
This method of obtaining phenyl cations has a series of advantages:
1
2
3
4
) the obtained phenyl cations are "free", i.e. they have no counter ion;
) phenyl cations are fairly stable since they are formed in a matrix of helium atoms (solid phase);
) ion-molecule reactions proceed on the surface of stabilizing salt in the absence of solvent;
) reactions proceed under mild conditions, since β-decay processes do not depend on temperature,
pressure, etc.
A characteristic special feature of the phenyl cations is their subsequent ion-molecule reactions with the
nucleophiles being investigated. On interacting phenyl cations with quinoline an electrophilic addition reaction
occurs at the unshared electron pair at the nitrogen atom (formation of a quinolinium salt), and also an
electrophilic substitution at the benzene and heterocyclic rings.
7
97

AdE
–
X
–
X
N
N
+
+
C H T
6
4
C H T
6 4
1
+
C H T
6
4
+
N
C H T
6
4
SE
;
N
N
C H T
6
4
In the case of quinaldine the presence of the methyl group leads to an additional reaction center and, as a
result, to an additional reaction with the formation of benzyl derivatives of quinoline.
–
–
N
Me
X
+
N
Me
X
+
C H T
C H T
6
4
6
4
2
AdE
SE
+
C H T
6
4
+
N
Me
C H T
6
4
;
Me
;
N
N
N
CH C H T
2 6 4
TH C
4
6
Me
The ion-molecule reactions were carried out in sealed ampoules containing tritiated benzene (the source
of phenyl cations) and the substrates quinoline or quinaldine, which were applied onto crystals of the stabilizing
salt. Ampoules with the reaction mixture were stored for reaction products to accumulate in quantities sufficient
for their reliable determination (not less than 1 month). After the accumulation the ampoules were opened and
analysis of reaction products labeled with tritium was carried out. The distribution of radioactivity of reaction
products labeled with tritium is given in Fig. 1. The first peaks belong to quinolinium and quinaldinium salts.
The yield of derivatives of N-phenylquinolinium (1) was 21 ± 3%, and of N-phenylquinaldinium (2) 18 ± 3%.
The remaining peaks belong to products of electrophilic substitution. A significant conformity is observed (see
Fig. 1) in the chromatographic behavior of the obtained labeled reaction products in the case of quinoline and
2
-methylquinoline.
Benzoannelation on going from pyridine to quinoline is accompanied by a reduction in the basicity of
the latter by approximately 0.3 pKa [38]. On comparing the results of ion-molecule reactions we discovered a
significant reduction in the yield of products of addition at the aza group in the case of benzoquinolines (the
yield of N-phenylpyridinium derivatives was more than 60%) [39]. In the case of quinaldine the picture is
complicated even more by the presence of the methyl substituent in the heteroaromatic ring. Although it is
7
98

known that donor substituents increase the basicity of the pyridine nitrogen [2, 31, 33-35, 38], nevertheless for
-substituted pyridines, as also for 2-R-quinolines, a so-called anomalous electronic effect is observed [40, 41].
2
R
f
Fig. 1. Distribution of radioactivity of compounds labeled with tritium from
ion-molecule reactions with quinoline and quinaldine.
The nature of this phenomenon has not been finally clarified, but it indicates the predominance of an
inductive effect, the action of which at a distance of one bond from the aza group is extremely significant. In our
investigations, probably, a similar effect leads to a somewhat smaller reduction in the yield of
N-phenylquinaldinium derivative in comparison with the quinolinium.
Similarly to α- and γ-picoline, methylquinolines containing a methyl group in the positions ortho and
para to the heteroatom are capable of reacting as CH-reactive components. Regretably, in view of the absence of
commercially available compounds and the fact that syntheses of unlabeled phenyl-substituted quinolines are
extremely difficultly available, the precise assignment of all the peaks on the radiochromatogram is difficult at
the present time.
The antimicrobial action of the unlabeled carriers N-phenylquinolinium and N-phenylquinaldinium
perchlorates has been investigated.
The given compounds displayed an inhibitory action in relation to gram-positive and gram-negative
bacteria in the range 500.0 to 1000.0 µg/ml, and a bactericidal effect was noted at a concentration of 1000.0
µg/ml in relation to both types of microorganism.
Due to the application of a chemonuclear method a simple procedure has been developed for the
synthesis of difficultly available biologically active quinolinium and quinaldinium salts labeled with tritium. The
new compounds are of interest as radioactive indicators for studying the mechanism of action of biologically
active compounds which are potential drugs.
The presence of a radioactive label enables new data to be obtained on the mechanism of electrophilic
reactions in process.
EXPERIMENTAL
Reference samples and carriers, unlabeled N-phenylquinolinium and quinaldinium derivatives, were
o
synthesized according to known procedures [35, 42-44]. N-Phenylquinolinium perchlorate, mp 156-157 C (lit.
o
o
o
o
mp 155-156 C [42] and 157 C [43]), N-phenylquinaldinium perchlorate, mp 159-160 C (mp 159-160 C [35] and
1
o
60 C [44]).
7
99

Radiochromatography of the obtained tritiated compounds was effected on Reverse Phase C18 silica gel
Fluorescent Indicator) glass plates in acetonitrile. Portions about 0.5 cm in length of the adsorption layer of
(
chromatograms were removed into dioxan scintillator and their radioactivity measured with the aid of a liquid
scintillation Rack-beta (USA) counting apparatus.
Benzene Doubly-labeled with Tritium. A mixture of dibromobenzene (5 mg) and triethylamine
(
6.5 µliter) in hexane (0.5 ml) and gaseous tritium (5 Ci) was hydrogenated on 5% Pd/BaSO catalyst for 1 h at
4
room temperature, and a solution of benzene doubly labeled with tritium was obtained with a chemical purity of
not less than 99%. The volume specific activity of the obtained solution was 4 Ci/ml.
Synthesis of N-Phenylquinolinium Salts (1). Crystals of stabilizing salts (KBF , KClO , KI) were
4
4
introduced into a glass ampoule of capacity 0.5 ml, then quinoline (6.5 µliter, 0.055 mmol), and with cooling in
liquid nitrogen C H T (1 µliter, 0.011 mmol) were added. The ampoule was sealed and kept for 1-2 month for
6
4
2
accumulation of the products of chemonuclear synthesis. The ampoule was opened, the contents were
transferred to a special vial, benzene (0.5 ml) was added, and an acetone solution of the carrier (0.5 ml)
(
unlabeled N-phenylquinolinium salt, 1 mg/ml). Unreacted tritiated benzene was distilled off in vacuum.
Acetone (0.5 ml) was added to the dry residue and test samples (~5 µliter) were taken out for separation of the
labeled compounds by TLC.
Synthesis of N-Phenylquinaldinium derivatives (2). The chemonuclear synthesis of quinaldine
derivatives was carried out analogously. The ampoule contained tritiated benzene (1 µliter, 0.011mmol) and
quinaldine (7.4 µliter, 0.055 mmol).
Determination of Antimicrobial Activity. To carry out experiments initial dilutions of microbial
bodies were prepared according to the optical standard from the daily agar culture. The microbial load
5
corresponded to 2.5×10 microbial bodies in 1 ml. The microbial suspension was introduced into prepared
dilutions of preparations in nutrient medium. Results were recorded after 20 h and 7 day of thermostatting at
o
3
7 C. The antimicrobial bacteriostatic (MIC) and bactericidal (MBC) activity was estimated from the minimally
acting concentration. The maximum test concentration of new compounds was 1000 µg/ml.
The work was carried out with the support of the Russian Foundation for Fundamental Investigations
(
RFFI), grant No. 07-03-00881.
REFERENCES
1
.
A. F. Pozharskii, A. T. Soldatenkov, and A. R. Katritzky, Heterocycles in Life and Society, Wiley, New
York (1997).
th
2
3
4
5
.
.
.
.
J. A. Joule and K. Mills, Heterocyclic Chemistry, 4 Edition, Blackwell Science, (2000).
Chemistry of Organic Fluorine Compounds, II ACS Monograph 187, Washington DC (1995).
G. E. Pilyugin and B. M. Gutsulyak, Usp. Khim., 32, 167 (1963).
I. I. Sidorchuk, R. F. Stadniichuk, E. N. Tishchenko, and L. T. Bordyakovskaya, Khim.-Farm. Zh., 12,
7
8 (1978).
6
7
8
9
.
.
.
.
W. A. Cox, Appl. Microbiol., 13, 956 (1965).
B. K. Sinha, R. M. Philen, R. Sato, and R. L. Cysyk, J. Med. Chem., 20, 1528 (1977).
J. W. Bunting, K. R. Laderoute, and D. J. Norris, Can. J. Biochem., 58, 49 (1980).
S. M. Taylor, C. Stubley-Beedman, and J. G. P. Stell, Biochem. J., 220, 67 (1984).
C. Beedham, S. E. Bruce, D. I. Crithley, Y. Al-Tayib, and D. J. Rance, Eur. J. Drug Metab.
Pharmacokinet., 12, 307 (1987).
1
1
8
0.
1.
G. A. Atwell, B. C. Baguley, and W. A. Denny, J. Med. Chem., 32, 396 (1989).
00

1
2.
S. A. Rotenberg, S. Smiley, M. Ueffing, R. S. Krauss, L. B. Chen, and B. Weinstein, Cancer Res., 50,
77 (1990).
6
1
1
1
1
3.
4.
5.
6.
D. J. P. Critchley, D. J. Rance, and C. Beedham, Biophys. Res. Commun., 185, 54 (1992).
J. Stojan, V. Marcelb, and D. Fournierb, Chem.-Biol. Interactions, 119-120, 147 (1999).
M. Malik-Hal, R. Ganellin, D. Galanakis, and D. H. Jenkinson, Brit. J. Pharmacol., 129, 1431 (2000).
C. R. Joaquin, D. Galanakis, A. Piergentili, K. Bhandari, C. R. Ganellin, P. M. Dunn, and
D. H. Jenkinson, J. Med. Chem., 43, 420 (2000).
1
7.
C. Pina-Vaz, F. Sansonetty, A. G. Rodrigues, S. Costa-Oliveira, C. Tavares, and J. Martinez-de-
Oliveira, Clin. Microbiol. Infection, 7, 609 (2001).
1
1
8.
9.
S. Jayaraman, Y. Song, V. L. Shankar, and A. S. Verkman, J. Clin. Invest., 107, 317 (2001).
K. A. Marr, M. Koudadoust, M. Black, and S. A. Balajee, Clin. Diagnostic Lab. Immunol., 8, 1240
(
2001).
2
2
2
0.
1.
2.
O. Kogi, H.-B. Kim, and N. Kitamura, Analyst, 127, 967 (2002).
P. K. Mukherjee, J. Chandra, D. M. Kuhn, and M. A. Ghannoum, Infection Immunity, 71, 4333 (2003).
T. N. Bennett, M. Paguio, B. Gligorijevic, C. Seudieu, A. D. Kosar, E. Davidson, and P. D. Roepe,
Antimicrobial Agents Chemotherapy, 1807 (2004).
2
2
2
2
3.
4.
5.
6.
R. M. Abd El-Aala, and M. Younis, Bioorg. Chem., 32, 193 (2004).
M. Otarigi, Drug Metab. Pharmacokinet., 20, 309 (2005).
U.-C. Hipler, P. Elsner, and J. W. Fluhr, Curr. Probl. Dermatol., 33, 165 (2006).
C.-H. Lee, H. J. Kim, J.-H. Lee, H.-J. Cho, J. Kim, K. C. Chung, and S. Jung, J. Biol. Chem., 281, 3463
(
2006).
2
2
2
7.
8.
9.
M. Saljoughian, Synthesis, 1781 (2002).
G. V. Sidorov and N. F. Myasoedov, Usp. Khim., 13, 398 (1999).
V. P. Shevchenko, I. Yu. Nagaev, and N. F. Myasoedov, Lipophilic Compounds Labeled with Tritium
[in Russian], Nauka, Moscow (2003).
3
3
0.
1.
K. H. Pausacker, Austr. J. Chem., 11, 200 (1958).
V. I. Ivanskii, Chemistry of Heterocyclic Compounds [in Russian], Vyssh. Shkola, Moscow (1978),
p. 459.
3
3
3
3
3
3
2.
3.
4.
5.
6.
7.
C. Mortelmans and G. Van Binst, Tetrahedron, 34, 363 (1978).
T. L. Gilchrist, Heterocyclic Chemistry, 3 Edit. Longmans, Harlow (1997), 414 pp.
rd
A. R. Katritzky and A. F. Pozharski, Handbook of Heterocyclic Chemistry, Pergamon (2000).
G. T. Pilyugin and Z. Ya. Krainer, Dokl. Akad. Nauk, 81, 609 (1951).
V. D. Nefedov, E. N. Sinotova, M. V. Korsakov, and E. G. Alekseev, Radiokhimiya, 15, 635 (1973).
N. E. Shchepina, V. V. Avrorin, G. A. Badun, V. M. Fedoseev, S. E. Ukhanov, and S. B. Lewis,
Radiokhimiya, 49, 551 (2007).
3
3
8.
9.
A. F. Pozharskii, Theoretical Basis of the Chemistry of Heterocycles [in Russian], Khimiya, Moscow
(
1985).
V. D. Nefedov, M. A. Toropova, V. V. Avrorin, D. S. Gembitskii, S. B. Lewis, and B. Mettson,
Radiokhimiya, 41, 523 (1999).
4
4
4
4
4
0.
1.
2.
3.
4.
M. Charton, J. Am. Chem. Soc., 86, 2033 (1964).
M. Charton, J. Org. Chem., 30, 3341 (1965).
R. F. Stadniichuk, G. T. Pilugin, and O. E. Petrenko, Zh. Obshch. Khim., 40, 1834 (1970).
B. I. Ardashev and V. I. Minkin, Zh. Obshch. Khim., 29, 200 (1959).
M. I. Rogovik, I. N. Chernyak, Yu. S. Rozum, and G. T. Pilyugin, Zh. Obshch. Khim., 34, 3320 (1964).
8
01