Synthesis of (13C6-Ring-(U))-(±)-benzo(a) pyrene metabolites from (13C6-Ring-(U))benzene

Full text of DOI:10.1002/jlcr.1267

Journal of Labelled Compounds and Radiopharmaceuticals
J Label Compd Radiopharm 2007; 50: 551–553.
Published online in Wiley InterScience
JLCR
(www.interscience.wiley.com). DOI: 10.1002/jlcr.1267
Short Research Article
Synthesis of [13C6-Ring-(U)]-( ꢀ )-benzo[a]pyrene metabolites
from [13C6-Ring-(U)]benzeney
BRUCE N. DIEL*, MINGCHENG HAN, PANNA L. KOLE and DAVID B. BOAZ
Midwest Research Institute, 425 Volker Boulevard, Kansas City, MO 64110, USA
Received 31 August 2006; Revised 8 January 2007; Accepted 20 January 2007
Keywords: polycyclic aromatic hydrocarbons; PAHs; pyrene; benzo[a]pyrene; metabolites; dihydrodiols; diol epoxides; tetrols;
carbon-13; synthesis; mass labeling; stable isotope labeling; carcinogenesis; mutagenesis
Introduction
Results and discussion
Benzo[a]pyrene, B[a]P, is one of the most potent and
most prevalent environmental procarcinogens. The
B[a]P metabolites, e.g. the diols 2, diol-epoxides 3 and
tetrols 4, appear to be the ultimate carcinogenic
derivatives. To facilitate research in the mechanisms
of carcinogenesis/mutagenesis by such compounds,
stable isotope-labeled analogs are valuable aids for
mass spectrometric analysis. An efficient synthetic
route utilizing Suzuki-coupling chemistry provided
isotopomeric [13C6-1,2,3,3a,10a,10b]-pyrene 18, which
served as the central intermediate for subsequent
production of the 13C6-ring-labeled diols 2, diol-epox-
ides 3, and tetrols 4.
To our knowledge, there have been no previous reports
of a simple and efficient method to introduce a [13C6-
Ring-(U)] into pyrene 13, especially for the purpose of
producing
[
13C6-Ring-(U)]-labeled benzo[a]pyrenes
and/or any of the associated metabolites. In order to
obtain the target benzo[a]pyrene metabolites, we have
designed and successfully executed a new synthetic
route for this purpose. This new strategy is summar-
ized in Schemes 1 and 2.
[Ring-13C6 (U)]-benzene 1 was selected as the basic
building block and successfully incorporated into the
key intermediate 18, 9,10-dihydrobenzo[a]pyrene, via
[
13C6-1,2,3,3a,10a,10b]-pyrene 13, via a Suzuki-cou-
OH
total
36 steps
O
10
HO
HO
9
HO
HO
8
7
1
OH
OH
OH
( )-4a:9α, 10α, ( )-4b:9α, 10β
( )-4c:9β, 10α, ( )-4d:9β, 10β
( )-2a:7β, 8α
( )-2b:7β, 8β
( )-3a:9β, 10β
( )-3b:9α, 10α
pling reaction of the diformyl aryl bromide 9 and
phenylboronic acid 6.1,2 The diformyl biaryl 10 was
converted to the bis(2-methoxyvinyl) compound 11,
which upon acidic hydrolysis and ring closure provided
*Correspondence to: Bruce N. Diel, Midwest Research Institute,
Chemical Sciences, 425 Volker Boulevard, Kansas City, MO, 64110
USA. E-mail: bdiel@mriresearch.org
[
13C6-Ring-(U)]-pyrene 13. The pyrene core was subse-
quently elaborated to the isotopomeric [13C6-Ring-(U)]-
9,10-dihydrobenzo[a]pyrene 18 via standard Friedel–
Crafts methodology.3,4 The ( ꢀ )-trans-dihydrodiol 19
y
Proceedings of the Ninth International Symposium on the Synthesis
and Applications of Isotopically Labelled Compounds, Edinburgh,
16–20 July 2006.
Copyright # 2007 John Wiley & Sons, Ltd.

552 B. N. DIEL ET AL.
R
R
R
5
8
+
Br
R
R
13
7: R=CH3
8: R=CH2Br
9: R=CHO
1: R= H
5: R=Br
6: R=B(OH)2
10: R = CHO
1
2
3
4
6
7
~
11Z/11E: R = CH=CH OMe
12: R = CH2CHO
9
R
R
13
11
14,15
OH
RO
OR
1
R
R
O
18
20
16: R = R1 = O
( )-19 : 7β, 8α, R = Bz
( )-20 : 7β, 8β, R = H
( )-21 : 7β, 8β, R = Bz
14: R = R = O
15: R = R = H
10
12
17: R = H, R1 = OH
16
Reagents and conditions: (1) 1,3-Dibromo-5,5-dimethylhydantoin, CH2Cl2, F3CSO3H, 70%; (2) (i)
Mg, ether, (ii) B(OEt)3, ether, 100%; (3) NBS, AIBN, benzene, external 85W UV lamp, 92%; (4) 88%
formic acid, reflux, 99%; (5) Pd(PPh3)4, DME, H2O, Na2CO3, reflux, 90%; (6) (i) 6, MeOCH2P(Ph3),
ether, t-BuOK, (ii) 9, THF, 96%; (7) 6N HCl, H2O, acetone, 100%; (8) 10% F3CCOOH in CH2Cl2,
87%; (9) Succinic anhydride, nitrobenzene, AlCl3, 92%; (10) Zn−Hg, HCl, Chlorobenzene, xylene,
reflux, 100%; (11) (i) PCl5, benzene, (ii) SnCl4, 98%; (12) NaBH4, EtOH, 70%; (13) HOAc, conc.
HCl, reflux, 100%; (14) for 19, 89%: (i) AgOBz, I2, benzene, (ii) added 18, reflux; (15) for 20
Acetone, N-methyl-morpholine-N-oxide, H2O, OsO4, 49%; (16) Pyridine, benzoylchloride, 86%.
Scheme 1
and ( ꢀ )-cis-dihydrodiol 20, protected as their respec-
tive benzoates, were accessed by reaction of 18 with
either silver benzoate/iodine or osmium tetroxide
followed by benzoyl chloride, respectively .5,6
tetrols ( ꢀ )-4 is an especially challenging aspect of this
chemistry. Fortunately, the purification of these inter-
esting products was resolved by repeating the hydroxyl
acetylations and base hydrolyses, as well as via
recrystallization.
The double bond between C-9 and C-10 of ( ꢀ )-22 or
( ꢀ )-23 was introduced by the reaction of ( ꢀ )-19 or
( ꢀ )-21 with DDQ, followed by base hydrolysis to afford
the trans- and cis-dihydrodiols ( ꢀ )-2a or ( ꢀ )-2b,
respectively (Scheme 2). The ( ꢀ )-anti-3b, (9a,10a),
was synthesized directly from the dihydrodiol 2a by
oxidation with 3-chloroperoxybenzoic acid (MCPBA).
The corresponding ( ꢀ )-syn-3a was accessed via the
intermediate bromide ( ꢀ )-26, which was obtained via
the bromohydrin 26 with N-bromoacetamide in the
presence of catalytic conc. HCl(aq), and subsequent
elimination using ion-exchange resin (base form).
Tetrol ( ꢀ )-4b was prepared by the same procedure
described for preparing ( ꢀ )-20, with the addition of a
basic ester hydrolysis (step 22), acetylation using acetic
anhydride/pyridine (step 23), and subsequent acetate
hydrolysis (step 24), all for the purpose of facilitating
efficient purification of the desired tetrol. The remain-
ing three tetrols, ( ꢀ )-4c, ( ꢀ )-4d and ( ꢀ )-4a, were
prepared from diol epoxides ( ꢀ )-3a or ( ꢀ )-3b by acidic
or base peroxide ring opening.7 Purification of the
Conclusion
A
new facile and efficient synthetic method was
designed and developed for preparing benzo[a]pyrene
diols. By this synthetic strategy, eight metabolites, diol:
ðꢀÞ2a, ðꢀÞ2b, diol-epoxides: ðꢀÞ3a, ðꢀÞ3b, tetrols:
ðꢀÞ4a, ðꢀÞ4b, ðꢀÞ4c and ðꢀÞ4d were synthesized
successfully by 36 steps totally.
REFERENCES
1. Zippi EM. J Label Compd Radiopharm 2001; 44:
757.
2. Wu Y, Yang L, Zhang J, Wang M, Zhao L, Song M,
Gong J. ARKIVOC 2004; 9: 111.
3. (a) Fuson RF, Scott SL, Lindsey RV. J Am Chem Soc
1941; 63: 1679; (b) Bachmann WE, Carmack M,
Safir SR. J Am Chem Soc 1941; 63: 1682; (c) Fieser
LF, Novello FC. J Am Chem Soc 1940; 62: 1855.
Copyright # 2007 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2007; 50: 551–553
DOI: 10.1002.jlcr

SYNTHESIS OF [13C6-RING-(U)]-( ꢀ )-BENZO[A]PYRENE METABOLITES 553
28
29
OR1
17
18
O
R2O
30
27
( )-19
( )-21
R2O
RO
HO
OR2
OR
OH
( )-22:7β, 8α, R = Bz
( )-2a:7β, 8α, R = H
( )-23:7β, 8β, R = Bz
( )-2b:7β, 8β, R = H
( )-3a:9β, 10β
( )-27a:10α, ( )-27b:10β; 9α,
19
20
( )-3b:9α, 10α
31
32
R1 = Ac, R2 = H; 10α/10β = 15/85
( )-28a:10α, ( )-28b:10β; 9α, R1 = R2 = Ac
( )-4c:9α, 10β, R2 = R2 = H
25
26
( )-29:9β, 10α, R1 = Ac, R2 = H
21
( )-30:9β, 10α, R1 = R2 = Ac
34
33
( )-4d:9β, 10α, R1 = R2 = H
OR1
OH
( )-31a:9β, 10α, R1 = Ac, R2 = H, ( )-4b
( )-31b:9β, 10β, R1 = Ac, R2 =H, ( )-4a
( )-32a:10α, ( )-32b:10β;
R1O
R2O
Br
35
36
HO
OR2
OH
9β, R1 = R2 = Ac; α/β =20/80
( )-4a:9β, 10β, R1 = R2 = H
( )-24:R1 = H, R2 = Bz
( )-4b:R1 = R2 = H
( )-25:R1 = R2 = Ac
( )-26
22
24
23
Reagents and conditions: (17) for 22, DDQ, 1,4-dioxane, reflux, 93%; (18) for 23, DDQ, benzene,
reflux, 41%; (19) NaOMe, MeOH, reflux, 94%; (20) K2CO3, MeOH, THF, 75%; (21) OsO4, pyridine,
72%; (22) 10% NaOH, THF, 89%; (23) Ac2O, Py, 86%; (24) 10% NaOH, THF, 63%; (25) N-bromo-
acetamide, THF, H2O, conc. HCl aq, 94%; (26) for 3a, THF, Amberlite ®IRA-400 OH, 76%; (27) for 3b,
·
MCPBA, THF, 91%; (28) for 32, AcOH, H2O, 1,4-dioxane, 85%; (29) for 29 ,KOAc, dibenzo-18-crown-
6, acetonitrile, 89%; (30) for 31, AcOH, H2O, 1,4-dioxane; (31) Ac2O, pyridine, 99%; (32) 20% NaOH,
THF, 97%; (33) Ac2O, pyridine, 25%; (34) 10% NaOH, THF, 83%; (35) Ac2O, pyridine, 43% from 3a
through step 30; (36) 10% NaOH, THF, 43%.
Scheme 2
4. Klassen SE, Daub GH, VanderJagt DL. J Org Chem
1983; 48: 4361.
6. Fu PP, Harvey RG. Tetrahedron Lett 1977; 24:
2059.
5. Kumar S, Panna LK, Sehgal RK. J Org Chem 1989;
54: 5272.
7. Yagi H, Thakker DR, Hernandez O, Koreeda M,
Jerina DM. J Am Chem Soc 1977; 99: 1604.
Copyright # 2007 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2007; 50: 551–553
DOI: 10.1002.jlcr