18-iodooctadeca-(8Z,11Z)-dienoic acid as useful intermediate for the synthesis of special lipoxygenase substrates bearing bulky substituents at the ω-position

Article abstract of DOI:10.1016/S0040-4020(99)01032-7

18-Iodooctadeca-(8Z, 11Z)-dienoic acid (7) was synthesized in five steps starting from methyl 10-bromodec-7-ynoate (2) in an overall yield of 53%. The synthetic procedure involves Cu(I)-catalyzed cross-coupling of propargylic bromide 2 with 7-octyn-1-ol (3), followed by hydrogenation of the coupling product 4 to Z,Z-diene 5 on Lindlar's catalyst and subsequent substitution of the OH- group of 5 with iodine. Coupling of the resulting iodide 7 with low- order organic cuprates [t-Bu₂CuLi or (PhCH₂)₂CuMgCl] leads to 19,19- dimethyl-eicosa-(8Z, 11Z)-dienoic acid (1a) and 19-phenylnonadeca-(8Z, 11Z)- dienoic acid (1b), respectively. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(99)01032-7

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 553–556
18-Iodooctadeca-(8Z,11Z)-dienoic Acid as Useful Intermediate for
the Synthesis of Special Lipoxygenase Substrates Bearing Bulky
Substituents at the v-Position
a,b,*
a
a
b
Igor V. Ivanov,
Nataliya V. Groza, Stepan G. Romanov, Hartmut Kuhn
a
and Galina I. Myagkova
a
M.V. Lomonosov State Academy of Fine Chemical Technology, 117571 Moscow, Russian Federation
Institute of Biochemistry, University Clinics Charite, Humboldt University, D-10115, Berlin, Germany
b
Received 26 October 1999; accepted 25 November 1999
Abstract—18-Iodooctadeca-(8Z,11Z)-dienoic acid (7) was synthesized in five steps starting from methyl 10-bromodec-7-ynoate (2) in an
overall yield of 53%. The synthetic procedure involves Cu(I)-catalyzed cross-coupling of propargylic bromide 2 with 7-octyn-1-ol (3),
followed by hydrogenation of the coupling product 4 to Z,Z-diene 5 on Lindlar’s catalyst and subsequent substitution of the OH– group of 5
with iodine. Coupling of the resulting iodide 7 with low-order organic cuprates [t-Bu CuLi or (PhCH ) CuMgCl] leads to 19,19-dimethyl-
2 2 2
eicosa-(8Z,11Z)-dienoic acid (1a) and 19-phenylnonadeca-(8Z,11Z)-dienoic acid (1b), respectively. ᭧ 2000 Elsevier Science Ltd. All rights
reserved.
Lipoxygenases (LOXs) constitute a family of lipid peroxi-
dizing enzymes, which are involved in the biosynthesis of
inflammatory mediators, in cell differentiation and athero-
To find out whether steric constrains or alterations in the
hydrophobicity of the methyl terminus may be responsible
for this effect we synthesized two fatty acid derivatives
[19,19-dimethyleicosa-(8Z,11Z)-dienoic acid (1a) and
19-phenylnonadeca-(8Z,11Z)-dienoic acid (1b)] bearing
bulky residues at the methyl terminus of the fatty acid
chain. For this purpose we developed a flexible synthetic
procedure which allows the preparation of v-modified fatty
acids in the mg-scale. These compounds may further be
used to investigate the detailed mechanism of the LOX
reaction, in particular to answer the question of whether
or not there may be an inverse head to tail substrate orien-
tation.
1
genesis. These enzymes have been well characterized with
1
respect to their enzymatic and molecular biological proper-
2
ties. The crystal structures of three LOX isoforms have
3
recently been solved and the X-ray coordinates were used
4
to construct models for enzyme/substrate interaction. More
recently colonies of knockout mice have been bred in which
the genes coding several LOX isoforms were functionally
5
disrupted. Although there is a substantial body of experi-
6
mental data as to the biological relevance of LOX, the
chemistry of the lipoxygenase reaction is less well investi-
7
gated. Previous site directed mutagenesis studies8 and
experiments with synthetic arachidonic acid isomers indi-
cated that the methyl terminus of fatty acid substrates
appears to be important for substrate binding. Introduction
of a bulky group at the methyl end of the fatty acid
molecules may alter the substrate alignment at the active
site and thus, the reaction characteristics. In addition, a shift
in the position of the double bonds in either direction altered
the specificity of the oxygenase reaction and caused a
The synthesis of 1a and 1b was accomplished via the for-
mation of 18-iodooctadeca-(8Z,11Z)-dienoic acid (7) as
crucial intermediate (Scheme 1). The diacetylenic ester 4
was prepared (87%) by Cu(I)-catalyzed cross-coupling of
propargylic bromide 210 and 7-octyn-1-ol (3) followed by
purification of the reaction product using silica gel flash
chromatography (Et O/hexane 2:1, argon atmosphere).
2
The alcohol 3 was prepared by reduction of methyl
8
11
modification of the product pattern. We have recently
7-octinoate with LiBH in THF by a standard procedure.
4
synthesized a set of v-hydroxylated fatty acid isomers and
found them to be much less effective LOX substrates than9
naturally occurring polyunsaturated fatty acids (PUFA’s).
Stereospecific hydrogenation of the skipped-triple bonds of
4 with Lindlar’s catalyst and quinoline in benzene resulted
in crude 5 with 92% purity, as indicated by RP-HPLC. The
reaction product was purified by preparative RP-HPLC
resulting in pure 5 with an 84% yield. The hydroxy ester
Keywords: fatty acids; coupling reactions; Grignard reagents; copper and
compounds; eicosanoids.
5
was converted to the iodide 7 via intermediate formation
of the corresponding chloride 6. The complete substitution
*
Corresponding author. Address: Humboldt-Universitat, Institut fur
Biochemie, Hessische Strasse 3-4, D-10115, Berlin, Germany.
of chlorine to iodine which was controlled by RP-HPLC
0
040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(99)01032-7

5
54
I. V. Ivanov et al. / Tetrahedron 56 (2000) 553–556
Scheme 1. (a) 3, CuI, NaI, K
2
CO
3
, DMF, rt, 8 h; (b) H
2
3 4 2 2 2
/Lindlar’s catalyst, quinoline, benzene, 10ЊC; (c) Ph P, CCl , CH Cl , rt, 24 h; (d) LiOH, MeOH–H O,
2
rt, 8 h; (e) NaI, acetone, 65ЊC, 20 h; (f) CuI, t-BuLi, THF, HMPA, Ϫ78 to Ϫ50ЊC, (g) CuI, PhCh MgCl, THF, HMPA, Ϫ50ЊC.
took about 20 h. Finally, either the tertiary alkyl
t-Bu CuLi) or benzyl [(PhCH ) CuMgCl] organocuprates
were coupled to the iodide 7 affording the acids 1a and 1b
MeOH/CH CN/H O (47.5:47.5:5, by vol.) and a flow rate
3 2
(
of 1.2 mL/min were employed. Preparative purification
was carried out on a Lichrospher 100 RP18 column;
250×22:5 mm; 10 mm particle size (Knauer, Berlin,
Germany). For EIMS analysis a Shimadzu GC-MS
QP-2000 system was used with an ion source temperature
of 180ЊC and an electron energy of 70 eV. Column chroma-
tography was carried out on silica gel 60 from Merck
(Darmstadt, Germany), particle size ranging from 70–
230 mesh. For thin-layer chromatography we employed
precast silica gel 60 F254 sheets (Merck, Darmstadt,
Germany). THF was freshly distilled from sodium/benzo-
2
2 2
with a 79–82% yield. The low-order organocuprates were
prepared in THF/HMPA from t-BuLi and PhCH MgCl,
2
respectively. Formation of the organocuprate from the
corresponding Grignard reagent required 1.5 h (Ϫ50ЊC)
and preparation of t-Bu CuLi at Ϫ78ЊC took only about
2
3
5–45 min. Neither PhCu nor Ph CuLi have been alkylated
2
by the iodide 7 even at elevated temperatures and no
reaction has been observed with corresponding tosylate.
In conclusion, the synthesis of the key intermediate 7
provides an efficient and economic route for the preparation
of v-modified polyenoic fatty acids which can be used to
further investigate the detailed mechanism of the LOX
reaction, in particular the structural basis of enzyme/
substrate interaction.
phenone ketyl, and HMPA was dried over CaH . All
2
solvents and reagents used were of extra pure grade and
purchased from Merck or Aldrich (Germany). t-Butyl-
lithium (Merck) and benzylmagnesium chloride (Aldrich)
12
were preliminarily titrated as described by Watson. Prior
to use, all glassware and syringes were dried at 140ЊC over-
night and all reactions were carried out under atmosphere of
dry argon.
Experimental
General
Methyl 18-hydroxyoctadeca-8,11-diynoate (4). To a
suspension of previously dried salts CuI (1.460 g,
7
.66 mmol), NaI (1.149 g, 7.66 mmol) and K CO3
2
1
13
H NMR and C NMR spectra were recorded either on a
(0.793 g, 5.74 mmol) in DMF (10 mL) the bromide 2
(1.100 g, 4.21 mmol) and alcohol 3 (0.483 g, 3.83 mmol)
were added under argon atmosphere. After stirring for 8 h
Bruker MSL 200 or on a Bruker MSL 300 spectro-
photometer in CDCl3 as solvent. Chemical shifts are
referenced to tetramethylsilane as an internal standard for
at rt, the mixture was quenched with sat. aq NH
(100 mL) and extracted with Et
O ꢀ4×40 mL†: The
combined organic extracts were washed with sat. aq. NaCl
ꢀ2×70 mL†; dried over Na SO and the solvent was evapo-
rated under reduced pressure. The residue was purified by
silica gel flash chromatography (Et O/hexane 2:1) to afford
Cl
4
1
H NMR or to the deuterium lock signal of CDCl
2
3
13
(
d Cˆ77.24 ppm). IR spectra were recorded on Shimadzu
IR-435. RP-HPLC analysis was carried out on a Shimadzu
2
4
LC-10Avp liquid chromatograph connected to SPD-
1
0Advp UV detector. Fatty acid analysis was performed
2
Ϫ1
on a Nucleosil C18-column; 150×4 mm; 5 mm particle
4 (1.021 g, 87%) as a colorless oil. IR (neat)/cm : 3600–
3200 (OH), 2170 (CxC), 1740 (CyO). H NMR (200 MHz,
1
size (Macherey–Nagel, D u¨ ren, Germany). A solvent system
of MeOH/H O/AcOH (85:15:0.1, by vol.) and a flow rate of
CDCl
18-CH
7.0 Hz, 2-CH
3
) d: 3.65 (s, 3H, OCH
), 3.22 (m, 2H, 10-CH
), 2.14 (m, 4H, 7-CH
3
), 3.62 (t, 2H, Jˆ6.4 Hz,
), 2.36 (t, 2H, Jˆ
and 12-CH ), 1.3–1.6
2
1
mL/min were used for all compounds except for the final
synthesis of product 1. For this product a solvent system of
2
2
2
2
2

I. V. Ivanov et al. / Tetrahedron 56 (2000) 553–556
555
(
m, 16H). Anal. calcd for C H O : C, 74.46; H, 9.87.
to yield 7 as a colorless oil, which was analyzed to be Ͼ98%
1
9
30
3
Found C, 74.21; H, 9.59.
pure by RP-HPLC; yield: 556 mg (90%). TLC: R ˆ0.34
f
1
(
Et O/hexane 1:1). RP-HPLC: RTˆ4.31 min. H NMR
2
Methyl 18-hydroxyoctadeca-(5Z,8Z)-dienoate (5). Dry
benzene (30 mL) was added to a 250-mL Erlenmeyer
flask with Lindlar’s catalyst (1.12 g). The mixture was satu-
(200 MHz, CDCl ) d: 5.28–5.38 (m, 4H, CHyCH), 3.17
3
(t, 2H, Jˆ6.8 Hz, 18-CH ), 2.74 (m, 2H, 10-CH ), 2.33 (t,
2
2
2H, Jˆ7.1 Hz, 2-CH ), 2.04 (m, 4H, 7-CH and 13-CH ),
2
2
2
rated with H at rt and cooled to 10ЊC. Then a solution of 4
1.80 (m, 2H, 16-CH ), 1.61 (m, 4H, 3-CH and 17-CH ),
2
2
2
2
13
(
(
0.81 g, 2.64 mmol) in benzene (30 mL) and quinoline
1.1 mL) were added under a stream of Ar. After the Ar
1.25–1.45 (m, 10H). C NMR (75 MHz, CDCl ) d:
3
177.90, 130.16, 130.05, 128.43, 128.32, 33.76, 30.60, 29.60
was exchanged with H , the reaction mixture was stirred
for 1 h at 10ЊC, then filtered, washed with 2 M HCl
(3C), 29.16, 29.09, 28.35, 27.36 (2C), 25.89, 24.86, 7.04.
2
ϩ
ϩ
EIMS m/z (%): 406 (1.39) [M ], 388 (0.1) [M ϪH O],
2
ϩ
ꢀ
2×30 mL† and the solvent was evaporated. The crude resi-
278 (2.01) [M ϪIϩ1]. Anal. calcd for C H O I: C,
18
31
2
due was purified by preparative RP-HPLC (solvent system
53.20; H, 7.69. Found C, 53.47; H, 7.41.
MeOH/H O, 9:1) to yield 0.69 g (84%) pure 5. RP-HPLC
2
1
RTˆ4.57 min. H NMR (200 MHz, CDCl ) d: 5.28–5.38
19,19-Dimethyleicosa-(8Z,11Z)-dienoic acid (1a). To a
suspension of CuI (234 mg, 1.23 mmol) in THF (7 mL)
and HMPA (2 mL), which was cooled to Ϫ78ЊC, t-BuLi
(1.68 mL, 2.45 mmol) was added with a syringe. After the
mixture was stirred for 45 min at Ϫ75ЊC, a solution of acid 7
(154 mg, 0.37 mmol) in THF (2 mL) was added. The resul-
ting mixture was warmed to Ϫ50ЊC and stirred for 1 h. Then
3
(
m, 4H, CHyCH), 3.65 (s, 3H, OCH ), 3.62 (t, 2H,
3
Jˆ6.4 Hz, 18-CH ), 2.75 (m, 2H, 10-CH ), 2.35 (t, 2H,
2
2
Jˆ7.0 Hz, 2-CH ), 2.08 (m, 4H, 7-CH and 13-CH ), 1.63
2
2
2
1
3
(m, 4H, 3-CH and 17-CH ), 1.25–1.45 (m, 12H). C NMR
2 2
(
1
75 MHz, CDCl ) d: 174.75, 130.16, 129.83, 128.27,
27.89, 62.79, 51.54, 34.09, 32.77, 29.64, 29.46, 29.09
3
(
3C), 27.18 (2C), 25.67 (2C), 24.94. EIMS: m/z (%) 310
the reaction was quenched with sat. aq. NH Cl, acidified
with HCl (1 M) to pH 5.0 and the organic products were
4
ϩ
ϩ
(0.05) [M ], 278 (2.16) [M ϪCH OH]. Anal. calcd for
3
C H O : C, 73.50; H, 11.04. Found C, 73.79; H, 11.30.
extracted with Et O ꢀ2×60 mL†. The combined etheric
19
34
3
2
extracts were washed with sat. aq. NaCl, dried over
Na SO and then concentrated under vacuum. Filtration
18-Chlorooctadeca-(8Z,11Z)-dienoic acid (6). To a solu-
2
4
tion of alcohol 5 (600 mg, 1.93 mmol) in CCl (5 mL), a
through silica gel (Et O/hexane 1:1) and further preparative
4
2
solution of PPh (709 mg, 2.71 mmol) in CH Cl (6 mL)
HPLC (MeOH/CH CN/H O 47.5:47.5:5) gave 102 mg
3
2
2
3
2
1
was added at rt. After the reaction mixture was stirred for
(82%) of pure 1a. RP-HPLC: RTˆ3.38 min. H NMR
24 h, the solvent was removed under reduced pressure and
(200 MHz, CDCl ) d: 5.26–5.36 (m, 4H, CHyCH), 2.74
3
the residue was filtrated over silica gel (hexane/Et O, 1:1)
(m, 2H, 10-CH ), 2.33 (t, 2H, Jˆ7.3 Hz, 2-CH ), 2.04 (m,
2
2
2
affording 614 mg of a colorless oil as a product. The latter
was reconstituted in methanol (60 mL) and added to an
aqueous solution of LiO H (1.8 M, 15 mL) under Ar. The
mixture was stirred at rt for 8 h. After the reaction was
completed, methanol was removed by evaporation, the pH
was adjusted carefully to 5.0 using diluted HCl (1 M) and
4H, 7-CH and 13-CH ), 1.61 (m, 2H, 3-CH ), 1.25–1.45
2
2
2
13
(m, 14H), 0.85 (s, 9H). C NMR (75 MHz, CDCl ) d:
3
178.60, 130.26, 129.92, 128.24, 127.93, 44.32, 33.80,
30.51, 29.70, 29.42 (6C), 28.98, 28.89, 27.27, 27.14,
ϩ
25.65, 24.66, 24.53. EIMS m/z (%): 336 (3.76) [M ], 321
ϩ
ϩ
t
(1.5) [M ϪCH ], 280 (1.89) [M Ϫ Bu]. Anal. calcd for
3
the lipophilic compounds were extracted with Et O
C H O : C, 78.51; H, 11.98. Found C, 78.79; H,
12.09.
2
22 40
2
ꢀ
3×40 mL†. The combined organic extracts were dried
over Na SO , concentrated under reduced pressure and the
2
4
product was purified by silica gel chromatography (hexane/
19-Phenylnonadeca-(8Z,11Z)-dienoic acid (1b). To a
suspension of CuI (179 mg, 0.94 mmol) in THF (5 mL)
and HMPA (2 mL), which was cooled to Ϫ50ЊC, a solution
Et O, 1:2) yielding pure 6 (492 mg, 81%). TLC: R ˆ0.35
2
f
(
hexane/Et O, 1:1, with 1% AcOH). RP-HPLC:
2
RTˆ3.42 min. IR (neat) n: 3030, 1670 (CHyCH), 1705
of PhCH MgCl (1.88 mL, 1.88 mmol) was added with a
2
Ϫ1
1
(
CyO), 720, 640 (C–Cl) cm . H NMR (200 MHz,
syringe. After the mixture was stirred for 1.5 h at Ϫ50ЊC,
a solution of acid 7 (118 mg, 0.29 mmol) in THF (2 mL)
was added. The resulting mixture was stirred for 1 h. Then
CDCl ) d: 5.28–5.38 (m, 4H, CHyCH), 3.51 (t, 2H,
3
Jˆ6.8 Hz, 18-CH ), 2.75 (m, 2H, 10-CH ), 2.34 (t, 2H,
2
2
Jˆ7.1 Hz, 2-CH ), 2.05 (m, 4H, 7-CH and 13-CH ),
the reaction was quenched with sat. aq. NH Cl, acidified
2
2
2
4
1
1
1
.61–1.80 (m, 6H, 3-CH , 16-CH and 17-CH ), 1.25–
with HCl (1 M) to pH 5.0 and the organic products were
2
2
2
1
3
.45 (m, 10H). C NMR (75 MHz, CDCl ) d: 180.70,
extracted with Et O ꢀ2×50 mL†. The combined ethereal
3
2
30.24, 129.94, 128.44, 128.07, 45.33, 34.27, 32.77, 29.61
extracts were washed with sat. aq. NaCl, dried over
Na SO and then concentrated under vacuum. Filtration
(
2C), 29.09 (2C), 28.68, 27.29 (3C), 25.78, 24.79. EIMS m/z
%): 314 (M ). Anal. calcd for C H O Cl: C, 68.65; H,
2
4
ϩ
(
through silica gel (Et O/hexane 1:1) and further preparative
1
8
31
2
2
9
.92. Found C, 68.80; H, 10.04.
HPLC (MeOH/CH CN/H O 47.5:47.5:5) gave 85 mg (79%)
3
2
1
of pure 1b. RP-HPLC: RTˆ2.67 min. H NMR (200 MHz,
19-Iodooctadeca-(8Z,11Z)-dienoic acid (7). A mixture of
CDCl ) d: 7.10–7.25 (m, 5H, Ph), 5.27–5.37 (m, 4H,
3
acid 6 (480 mg, 1.52 mmol) and NaI (686 mg, 4.56 mmol)
in dry acetone (6 mL) was stirred at 65ЊC for 20 h. After the
acetone was evaporated, the residue was reconstituted in
CHyCH), 2.76 (m, 2H, 10-CH ), 2.60 (t, 2H, Jˆ8.1 Hz,
2
19-CH ), 2.34 (t, 2H, Jˆ7.3 Hz, 2-CH ), 2.03 (m, 4H,
2
2
7-CH and 13-CH ), 1.60 (m, 4H, 3-CH and 18-CH ),
2
2
2
2
13
Et O (60 mL). The resulting mixture was washed with
2
1.20-1.40 (m, 14H). C NMR (75 MHz, CDCl ) d: 180.48,
3
H O ꢀ2×50 mL† and the organic layer was dried over
143.14, 130.57, 130.24, 129.94, 128.55, 128.33, 125.90,
125.64, 36.22, 34.27, 31.77, 29.86, 29.64 (4C), 29.17
(2C), 27.44 (2C), 25.86, 24.87. EIMS m/z (%): 370 (12)
2
Na SO . After evaporation under reduced pressure, the
2
4
crude residue was purified on silica gel (hexane/Et O, 1:1)
2

5
56
I. V. Ivanov et al. / Tetrahedron 56 (2000) 553–556
ϩ
ϩ
ϩ
[
M ], 352 (0.9) [M ϪH O], 279 (2.0) [M ϪCH Ph]. Anal.
4. (a) Prigge, S. T.; Boyington, J. C.; Gaffney, B. J.; Amzel, L. M.
Proteins 1996 24, 275. (b) Browner, M.; Gillmor, S. A.; Fletterick,
R. Nat. Struct. Biol. 1998, 5, 179. (c) Prigge, S. T.; Gaffney, B. J.;
Amzel, L. M. Nat. Struct. Biol. 1998, 5, 178.
2
2
calcd for C H O : C, 81.03; H, 10.33. Found C, 79.80; H,
0.54.
2
5
38
2
1
5
. (a) Chen, X. S.; Sheller, J. R.; Johnson, E. N.; Funk, C. D.
Acknowledgements
Nature 1994, 372, 179. (b) Sun, D.; Funk, C. D. J. Biol. Chem.
1
996, 271, 240.
This work was supported by the Deutsche Forschungs-
gemeinschaft (Ku 961/2-3) and by the European Comm-
ission (BMTH4-98-3191). The authors wish to thank the
Deutsche Akademische Austauschdienst (DAAD) for
providing an HPLC system to I. I. at the Lomonosov State
Academy of Fine Chemical Technology.
6
. K u¨ hn, H. Prostaglandins, Leukotrienes and other Eicosanoids;
Marks, F., Ed.; Wiley-VCH: Heidelberg, 1999.
7
3
. Sloane, D. L.; Leung, R.; Craik, C. S.; Sigal, E. Nature 1990,
54, 149. (b) Borngr a¨ ber, S.; Kuban, R. J.; Anton, M.; K u¨ hn, H.
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