Design, synthesis and antimycobacterial activities of 1-methyl-2-alkenyl- 4(1H)-quinolones

Article abstract of DOI:10.1016/j.bmc.2010.10.060

A series of 23 new 1-methyl-2-alkenyl-4(1H)quinolones have been synthesized and evaluated in vitro for their antimycobacterial activities against fast growing species of mycobacteria, such as Mycobacterium fortuitum, M. smegmatis and M. phlei. The compounds displayed good to excellent inhibition of the growth of the mycobacterial test strains with improved antimycobacterial activity compared to the hit compound, evocarpine. The most active compounds, which possessed chain length of 11-13 carbons at position-2 displayed potent inhibitory effects with an MIC value of 1.0 mg/L. In a human diploid embryonic lung cell line, MRC-5 cytotoxicity assay, the alkaloids showed weak to moderate cytotoxic activity. Biological evaluation of these evocarpine analogues on the less pathogenic fast growing strains of mycobacteria showed an interesting antimycobacterial profile and provided significant insight into the structure-activity relationships.

Full text of DOI:10.1016/j.bmc.2010.10.060

Bioorganic & Medicinal Chemistry 19 (2011) 567–579
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Design, synthesis and antimycobacterial activities
of 1-methyl-2-alkenyl-4(1H)-quinolones
Abraham A. Wube a, Antje Hüfner b, Christina Thomaschitz a, Martina Blunder a, Manfred Kollroser c,
Rudolf Bauer a, Franz Bucar a,
⇑
a Institute of Pharmaceutical Sciences, Department of Pharmacognosy, University of Graz, Universitätsplatz 4/1, 8010 Graz, Austria
b Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, University of Graz, Universitätsplatz 1, 8010 Graz, Austria
c Institute of Forensic Medicine, Medical University of Graz, Universitätsplatz 4/2, 8010 Graz, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 10 May 2010
Revised 30 September 2010
Accepted 29 October 2010
Available online 3 November 2010
A series of 23 new 1-methyl-2-alkenyl-4(1H)quinolones have been synthesized and evaluated in vitro for
their antimycobacterial activities against fast growing species of mycobacteria, such as Mycobacterium
fortuitum, M. smegmatis and M. phlei. The compounds displayed good to excellent inhibition of the growth
of the mycobacterial test strains with improved antimycobacterial activity compared to the hit com-
pound, evocarpine. The most active compounds, which possessed chain length of 11–13 carbons at posi-
tion-2 displayed potent inhibitory effects with an MIC value of 1.0 mg/L. In a human diploid embryonic
lung cell line, MRC-5 cytotoxicity assay, the alkaloids showed weak to moderate cytotoxic activity.
Biological evaluation of these evocarpine analogues on the less pathogenic fast growing strains of
mycobacteria showed an interesting antimycobacterial profile and provided significant insight into the
structure–activity relationships.
Keywords:
1-Methyl-2-alkenyl-4(1H)-quinolone
Antimycobacterial
Tuberculosis
SAR
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
fluorine at position-6, a piperazine with and without fluorine at
position-7 and an alkyl at position-1. Non-fluorinated quinolones,
Tuberculosis (TB) is one of the most common infectious dis-
eases. According to the World Health Organization (WHO), 196
countries reported 2.6 million new smear-positive TB cases in
2008, of which 1.78 million people died from TB.1 Despite a contin-
ues effort made by researchers to fight the disease, resistance to
the current antituberculosis drugs posed a serious threat to the
treatment and management of the disease. By the end of 2008,
55 countries and territories had reported at least one case of exten-
sively drug resistant tuberculosis (XDR-TB).2 These statistical data
show that TB remains a major global health problem.
In the last decade several new classes of tuberculosis chemo-
therapeutic agents have been introduced to the market. Of these,
quinolones and fluoroquinolones constitute a class of compounds
which are highly effective in the treatment of many types of infec-
tious diseases caused by bacteria, including tuberculosis. Since the
introduction of ciprofloxacin in the late 1980s, the fluoroquino-
lones constitute a major class of antibacterial chemotherapeutic
agents, which have a broad spectrum of activity against bacteria,
mycobacteria, parasites and other microorganisms. Various struc-
ture-biological activity reports indicated that successful antibacte-
rial quinolones are characterized by a carboxyl group at position-3,
however, have shown good in vitro antibacterial activities match-
ing those of their fluorinated counterparts.3
Medicinal plants have long been used as sources of potential
new drugs. Our previous research which has been focused on iso-
lation of antimycobacterial agents from traditional medicinal
plants collected from various parts of the world enabled us to
identify potential antimycobacterial compounds for further inves-
tigations.4,5 Of the various compounds studied, 1-methyl-2-alkyl-
4(1H)-quinolones isolated from the fruits of the Chinese medicinal
plant Euodia rutaecarpa Hook f. & Thomson (Rutaceae) displayed
promising antimycobacterial activity. Results of our in vitro assay
revealed that evocarpine tested against fast growing strains of
mycobacteria, such as Mycobacterium fortuitum, M. smegmatis and
M. phlei displayed superior activity compared to the standard drugs
ethambutol and isoniazid.5 Furthermore, tested against CCRF-CEM
leukaemia cells, evocarpine showed slight toxicity at the highest
test concentration of 30 l
M.6 Consequently, we have identified
evocarpine as a hit compound for the development of further
derivatives with improved antimycobacterial activity. The fact that
evocarpine is a potent antimycobacterial natural product suggests
that the aliphatic side chain at position-2 is a key structural feature
to inhibit the growth of mycobacteria. Thus, we have synthesized a
variety of analogues exploring modifications of the aliphatic side
chain at position-2 with various degrees of unsaturation, chain
⇑
Corresponding author. Tel.: +43 316 380 5531; fax: +43 316 380 9860.
E-mail address: franz.bucar@uni-graz.at (F. Bucar).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.10.060

568
A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
lengths and double bond positions. Although, a wide variety of
quinolones having substituents at positions-3, -6 and -7 have been
synthesized and examined for their antibacterial effects, no at-
tempt has been made so far to assess the role of aliphatic substit-
uents at position-2 that could contribute to the antimycobacterial
activity. Herein, we disclose an approach directed towards the syn-
thesis of 1-methyl-2-alkenyl-4(1H)-quinolones as potential new
antimycobacterial agents.
the cheaply available x-lactones 1 and 2, respectively, by treating
with HBr and conc H2SO4. On the other hand, 10-bromodecanoic
acid (4d) was prepared by treatment of the diol 3 with HBr in tol-
uene followed by oxidation with chromic acid. Subsequent treat-
ment of the
x-bromoacids (4a, 4c and 4d) and the commercially
available 5-bromopentanoic acid (4b) and 11-bromoundecanoic
acid (4e) with triphenylphosphine gave phosphonium salts (5a–
e). Wittig condensation of various aldehydes with ylides derived
from the phosphonium salts 5a–e under the action of sodium hex-
amethyldisilylamide at room temperature afforded predominantly
the cis unsaturated carboxylic acids 6a–m. One major advantage of
the use of phosphonium salts of carboxylic acids 5a–e is that the
triphenylphosphine oxide co-product, which often complicates
product isolation and purification, can be easily removed upon
aqueous work-up. Wittig reaction is frequently used as important
synthetic means for preparation of alkenes, as it is possible to con-
trol the stereoselectivity of the carbon–carbon double bond.
Although Wittig reactions provide a mixture of geometrical iso-
mers, various studies revealed that Z stereoselectivity is maxi-
mized by polar solvents, low reaction temperature and exclusion
of lithium salt.7 The unsaturated methyl ketones 7a–o, the crucial
intermediates for the synthesis of our target alkaloids, were pre-
pared by treatment of unsaturated carboxylic acids with methyl
lithium in THF at 0 °C as previously reported.8 When unsaturated
methyl ketones 7a–‘o’ were treated with LDA at ꢀ78 °C followed
by N-methylisatoic anhydride (20), the intended 1-methyl-2-alke-
nyl-4(1H)-quinolones 8a–‘o’ were formed according to a literature
procedure.9 To examine the biological role of the double bond in
the aliphatic side chain, catalytic hydrogenation of the quinolones
was efficiently undertaken in the presence of 10% Pd/C to afford the
corresponding saturated quinolones 9a–c.
2. Results and discussion
2.1. Chemistry
The 4(1H)-quinolone alkaloids having a cis aliphatic side chain
at position-2 were prepared as shown in Scheme 1. The starting
x
-bromocarboxylic acids 4a and 4c were easily prepared from
HO-(CH2)10-OH
3
i
O
O
ii
O
ii
O
Br-(CH2)n-COOH
4a, n = 3 (61%)
4b, n = 4
4c, n = 5 (82%)
4d, n = 9 (73%)
4e, n =10
1
2
iii
As shown in Scheme 2, treatment of chloroacetone (10) with
PPh3 provided the phosphonium salt (11), which upon dehydro-
chlorination with NaOH afforded ylide 12. The resulting ylide 12
proved to be a versatile intermediate, making itself suitable for
condensation with varieties of saturated and unsaturated alde-
BrPPh3-(CH2)n-COOH
R'-CHO
+
-C H5, -C4H9, -C5H11
5
R' =
2
5a, n = 3 (92%)
-C6H13, -C8H17, -C9H19
-C10H21
5b, n = 4 (88%)
5c, n = 5 (94%)
5d, n = 9 (94%)
5e, n = 10 (91%)
iv
hydes. The acetaldehyde ylide 16, used for the synthesis of
a,b-
unsaturated aldehydes 17a–b was prepared from commercially
available chloroacetaldehyde (15) by refluxing with PPh3. In our
synthesis strategy, the key precursors 13a–c, which were em-
ployed to synthesize the quinolone alkaloids 14a–c, was obtained
by refluxing the ylide 12 with the corresponding aldehydes under
R'-CH=CH-(CH2)n-1-COOH
6
6h, n = 3, R' = -C6H13 (87%)
6i, n = 5, R' = -C6H13 (68%)
6j, n = 3, R' = -C9H19 (76%)
6k, n = 9, R' = -C8H17 (65%)
6l, n = 9, R' = -C9H19 (65%)
6m, n = 9, R' = -C10H21 (55%)
6n, n = 8, R' = -C8H17
6a, n = 4, R' = -C8H17 (84%)
6b, n = 10, R' = -C2H5 (68%)
6c, n = 5, R' = -C9H19 (74%)
6d, n = 5, R' = -C4H9 (85%)
6e, n = 3, R' = -C10H21 (87%)
6f, n = 3, R' = -C8H17 (82%)
6g, n = 5, R' = -C5H11 (83%)
argon. As an extension of this method we synthesized
a,b and c,d-
v
unsaturated ketones 18a–b from , b-unsaturated aldehydes 17a–
a
b by refluxing with ylide 12. In contrast to the Wittig condensation
described in Scheme 1, these reactions gave rather pure trans
unsaturated methyl ketones from which the desired quinolones
were obtained in moderate yield. Finally, the quinolone alkaloids
14a–c and 19a–b were prepared in a manner similar to that de-
scribed for compounds 8a–‘o’. The identity of the quinolone alka-
loids and their corresponding intermediates was confirmed by
analysis of 1D and 2D NMR spectroscopic, LC–ESI–MS and ESI-
HRMS data.
6o, n = 8, R' = -C8H15
O
N
O
+
O
R'-CH=CH-(CH2)n-1-C-CH3
O
7a-o (47-60%)
vi
CH3
20
O
N
O
2.2. Antimycobacterial and cytotoxicity testing
vii
(CH2)n-1-CH=CH-R'
The in vitro antimycobacterial activity of the synthesized com-
pounds was determined by the broth microtiter dilution method
against fast growing strains of mycobacteria and their minimum
inhibition concentrations (MICs) are presented in Table 1. All
tested compounds demonstrated good to excellent in vitro activity
against M. smegmatis. Compounds 8c (1-methyl-2-(50Z-pentadece-
nyl)-4(1H)-quinolone), 8e (1-methyl-2-(30Z-tetradecenyl)-4(1H)-
quinolone), 8i (1-methyl-2-(50Z-dodecenyl)-4(1H)-quinolone) and
14a (1-methyl-2-[(E)-10-undecenyl]-4(1H)-quinolone) displayed
potent in vitro activity showing an MIC value of 1.0 mg/L against
N
R
CH3
8a-o (34-45%)
CH3
9
9a, R = -C13H27 (95%) from 8a
9b, R = -C15H31 (93%) from 8c
9c, R = -C17H35 (91%) from 8n
Scheme 1. Reagents and conditions: (i) HBr, CrO3, H2SO4, acetone; (ii) HBr, H2SO4,
reflux, 5 h; (iii) PPh3, toluene, reflux, 48 h; (iv) NaN(SiMe2)3, THF; (v) CH3Li, THF,
0 °C; (vi) LDA, ꢀ78 °C; (vii) H2, EtOH, 10% Pd/C. The values of n and R0 for 7a–o and
8a–o are the same as their corresponding intermediate 6a–o.

A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
569
H
iii
Cl
Cl
O
O
10
15
i
H
R'-CHO
Ph3P
+
ClPh3P
R' = -C10H21 and -C11H23
O
O
16 (53%)
11 (88%)
iv
ii
Ph3P
R'-CH=CH-CHO
Ph3P
+
R'-CHO
+
O
O
17
R' = -C9H19
-C6H13
12 (96%)
12 (96%)
17a, R' = -C10H21 (42%)
17b, R' = -C11H23 (44%)
-C5H11
v
v
O
O
N
O
O
O
O
+
+
R'-CH=CH-CH=CH-C-CH3
18
R'-CH=CH-C-CH3
N
O
O
13
CH3
CH3
18a, R' = -C10H21 (64%)
18b, R' = -C11H23 (59%)
13a, R' = -C9H19 (59%)
13b, R' = -C6H13 (79%)
13c, R' = -C5H11 (82%)
20
20
vi
vi
O
O
R'
N
N
R'
CH3
CH3
14
19
14a, R' = -C9H19 (45%)
14b, R' = -C6H13 (42%)
14c, R' = -C5H11 (38%)
19a, R' = -C10H21 (38%)
19b, R' = -C11H23 (43%)
Scheme 2. Reagents and conditions: (i) PPh3, AcCN, reflux, 24 h; (ii) 1 N NaOH (PH 7–8); (iii) PPh3, CHCl3, 2 N NaOH; (iv) toluene, reflux, 15 h; (v) THF, reflux, 48 h; (vi) LDA,
THF, ꢀ78 °C.
M. smegmatis, which was more active than the standard antibiotic
drugs ethambutol and isoniazid, but less active than ciprofloxacin.
Compounds 8a, 8b, 8f, 8j and 8‘o’, on the other hand, showed
inhibitory effects comparable to the positive drugs. Except, 1-
methyl-2-heptadecyl-4(1H)-quinolone (9c) the remaining quino-
lone alkaloids showed moderate activity (MIC range 4–128 mg/L).
Some of the synthesized compounds, which displayed the greatest
activity against M. smegmatis and those having exceptional ali-
phatic group were further tested against M. fortuitum and M. phlei
and the MIC values are presented in Table 2.
From the results of our antimycobacterial investigation, impor-
tant structure–activity relationships are readily apparent. If we
examine the chain length–activity relationship, the alkaloids with
one carbon–carbon double bond in the aliphatic side chain at posi-
tion-2 exhibited a parabolic chain length–activity relationship. In a
number of compounds, antimycobacterial activity increases with
increasing chain length, and optimal activity was observed when
the side chain consisted of 14 carbons. A dramatic decrease in activ-
ity was noticed with further increase in the side chains length. For
instance, compounds 8n, 8k, 8‘l’ and 8m, which contain aliphatic
side chain with 17, 18, 19 and 20 carbons, respectively, inhibited
the growth of M. smegmatis with MIC values of 8, 16, 64 and
128 mg/L, respectively. A previous report by Haemers et al.10 re-
vealed the same structure activity relationship for ciprofloxacin
derivatives, where lipophilicity might play an important role in
the antimycobacterial activity. It is interesting to point out that
the alkaloids 9a–c with a saturated aliphatic side chain exhibited
a very low inhibitory effect on M. smegmatis (MIC values range from
64 to >128 mg/L) compared to their unsaturated analogues. This
implies that unsaturation of the aliphatic side chain is an essential
structural feature for the in vitro antimycobacterial activity. This is
further supported by recent findings which revealed that the ali-
phatic side chain, such as alkyl, alkenyl and alkynyl at position-5
of uracil significantly contributes to the antimycobacterial activity
of pyrimidine nucleosides on M. tuberculosis.11 To further explore
the effect of degree of unsaturation on the antimycobacterial prop-
erties, methyl ketones having two carbon–carbon double bonds
were synthesized and incorporated into the alkaloid. Compound
8‘o’, having two double bonds in the side chain displayed a four fold
inhibitory effect on M. smegmatis compared to compound 8n having
the same chain length but one double bond less. This suggests that
degree of unsaturation of the side chain seems to influence the
in vitro antimycobacterial activity of quinolone alkaloids. Further
studies are, of course, required to reinforce this assertion.

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A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
Table 1
In vitro biological activity of the synthesized compounds and positive controls
O
N
R
CH3
Compound
R
MICa
Metabolic Active Cells (%)b
30
(mg/L)
lM
100
lM
lM
8a
8b
8c
8d
8e
8f
8g
8h
8i
2
2
1
8
1
2
4
16
1
5.9
5.9
2.7
26.9
2.8
6.2
12.9
53.9
3.1
32.0 7.26
95.4 0.91
0.8 0.13
83.5 1.74
4.9 4.11
85.6 2.87
88.5 1.24
47.9 2.55
81.2 3.28
82.1 2.04
25.5 2.71
19.9 8.68
91.5 1.85
0.4 0.19
76.3 1.62
95.3 0.64
46.6 4.14
96.8 1.69
55.1 2.15
88.3 1.60
94.9 0.75
73.8 1.32
94.7 0.98
89.7 2.11
84.4 0.87
95.9 0.72
98.9 0.84
53.4 6.37
44.2 5.79
101.9 1.01
79.8 1.65
100 1.73
98.9 1.19
8j
2
5.9
8k
8‘l’
8m
8n
8‘o’
9a
9b
9c
16
64
128
8
39.1
151.3
292.9
20.3
5.1
187.7
346.9
322.4
3.2
2
0.4 0.33
64
128
>128
1
69.6 6.71
57.9 1.04
95.2 0.94
52.9 8.96
14a
14b
14c
19a
19b
Evocarpine
Ciprofloxcin
4
14.9
62.7
182.3
10.9
5.9
76.5 2.43
77.2 0.68
32.5 4.82
18.5 7.71
87.6 3.39
ND
96.8 1.94
86.2 1.82
73.8 1.47
50.7 2.23
94.0 0.58
16
64
4
2
0.125
Ethambutol
Isoniazid
2
2
ND
ND
Vinblastin at 0.12
l
M
ND
51.5 2.36
ND, not determined.
a
Minimum inhibition concentration against M. smegmatis (ATCC 19420).
Cytotoxicity against human diploid embryonic lung cell line MRC-5 compared to control cells (treated with 0.1% EtOH), 72 h incubation time, mean SEM, n = 6.
b
Table 2
only in the position of the double bond. The remarkable inhibitory
feature of compounds 14a–c may be due to the position of the dou-
ble bond being part of the conjugated system of the quinolone
alkaloid.
In vitro inhibitory activity data of selected compounds against M. fortuitum, M. phlei
and the positive control drugs
Compound
MIC (mg/L)
M. fortuitum (ATCC 6841)
M. phlei (ATCC 19249)
To examine the effect of additional unsaturation on the antimy-
cobacterial properties of quinolones with a double bond a,b to the
8d
8e
8‘o’
14a
8
1
4
1
2
2
8
1
8
1
8
1
4
2
4
4
quinolone ring, compounds 19a–b were synthesized and tested.
The results of our study revealed that, in contrast to compound
8‘o’, incorporation of further double bond did not enhance the
activity.
To compare the antimycobacterial activity with toxicity to
mammalian cells, the cytotoxic activity of the synthesized alka-
loids were evaluated against a human diploid embryonic lung cell
line, MRC-5, and the compounds displayed low to moderate toxic-
19b
Evocarpine
Ethambutol
Isoniazid
It is worth mentioning that compound 8‘o’, which was prepared
from commercially available linoleic acid showed eightfold anti-
mycobacterial potency against M. smegmatis and twofold potency
against M. fortuitum and M. phlei compared to its synthetic precur-
sor linoleic acid tested previously in our test method.12
In order to evaluate the influence of the double bond position
on the antimycobacterial properties, we introduced a double bond
at various positions of the side chain. Thus, the results of our bio-
logical study showed that the quinolone alkaloid 14a having a dou-
ity. At 30 lM test concentration and 72 h incubation time (which is
equal to incubation time of test compounds with mycobacteria),
the most active antimycobacterial compounds 8c, 8e, 8i and 14a
exhibited 46.6, 55.1, 94.7 and 98.9% metabolic active cells, respec-
tively, suggesting that the antimycobacterial efficacy of these com-
pounds did not arise from in vitro cytotoxicity (Table 1). Most
favourable concerning a selectivity towards antimycobacterial
activity were compounds 8b, 8f, 8i, 8j and 14a with monounsatu-
rated side chains of 11 – 13 carbons. Although no exact IC50 values
could be determined by the two concentrations tested it is obvious
that the selectivity index (IC50/MIC) of the above mentioned com-
pounds exceeds an SI of 20.
ble bond
a,b to the quinolone ring has a more pronounced
antimycobacterial potency compared to its corresponding ana-
logue, compound 8g, having the same chain length, but differing

A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
571
3.2.3. Synthesis of 10-bromodecanoic acid (4d)
3. Experimental
3.1. General
To a solution of 1,10-decandiol (3) (34.8 g, 0.2 mol, 1 equiv) in
toluene (400 mL) was added 48% HBr (22.6 mL, 0.2 mol, 1 equiv)
dropwise with stirring and refluxed at 180 °C using Dean–Stark
trap for 24 h. The mixture was cooled to room temperature and
washed with 6 N NaOH (150 mL), 10% HCl (150 mL), H2O (2 x
250 mL) and brine (200 mL). The organic layer was dried over
Na2SO4, concentrated and chromatographed on silica gel eluting
with cyclohexane/ethylacetate (4:1) to give 43.5 g (92%) of 10-bro-
mo-1-decanol as a colourless liquid. 1H NMR d 3.65 (t, J = 6.7 Hz,
2H, H-1), 3.43 (t, J = 7.0 Hz, 2H, H-10), 1.87 (m, 2H, H-9), 1.57 (m,
2H, H-2), 1.43 (m, 2H, H-3), 1.26–1.41 (m, 10H, H-4-8). 13C NMR
d 63.0 (C1), 34.1 (C10), 32.8, 32.6, 29.5, 29.4, 29.3, 28.6, 28.2, 25.6.
To a solution of 10-bromo-1-decanol (41 g, 0.17 mol, 1 equiv) in
130 mL of acetone at ꢀ5 °C was added slowly chromic acid solu-
tion prepared from CrO3 (25.7 g, 0.26 mol, 1.5 equiv), water
(25 mL) and conc H2SO4 (22.5 mL, 0.34 mol, 2 equiv) at 0 °C, then
stirred for 2 h and left over night at room temperature. The mixture
was extracted with diethyl ether (3 x 250 mL), washed with water
(250 mL) and brine (250 mL), dried over Na2SO4 and concentrated.
The residue was chromatographed on silica gel eluting with CH2Cl2
afforded 31.0 g of 10-bromodecanoic acid (4d) (73%) as a white so-
lid after recrystallization from petroleum ether. Mp 36–37 °C. 1H
NMR d 11.23 (bs, 1H, –OH), 3.41 (t, J = 7.0 Hz, 2H, H-10), 2.36 (t,
J = 7.6 Hz, 2H, H-2), 1.87 (m, 2H, H-9), 1.64 (m, 2H, H-3),
1.22–1.44 (m, 10H, H-4-8). 13C NMR d 180.2 (C1), 34.1 (C2), 34.0
(C10), 32.9, 29.1, 28.9, 28.6, 28.4, 28.2, 24.7.
All chemicals were purchased from Sigma–Aldrich, Germany.
THF was distilled from sodium. Melting points were determined
with KOFLER microscope and are uncorrected. IR spectra obtained
on a Perkin–Elmer 281 B spectrometer, were recorded in KBr un-
less and otherwise noted. 1H and 13C NMR spectra were recorded
on a Varian 400 MHz spectrometer (400 and 100 MHz, respec-
tively) using deuterated chloroform as solvent with TMS as inter-
nal standard. Mass spectra were obtained by LC–ESI–MS analysis
in positive mode on a Thermo Finnigan LCQ Deca XP Plus mass
spectrometer connected to a Surveyor LC-system (Thermo-Finni-
gan). Accurate mass determinations were performed using a LC/
FTMS system consisting of an Exactive Orbitrap mass spectrome-
ter, equipped with a heated ESI II source (ThermoFisher Scientific,
Inc., Bremen, Germany) and operated in ultra high resolution mode
(100.000) coupled to a U-HPLC system (Accela, ThermoFisher Sci-
entific, Inc., Bremen, Germany). Operating conditions for the ESI
source used in the positive ionization mode were: 3.5 kV spray
voltage, 325 °C capillary temperature, 300 °C heater temperature,
sheath gas flow rate 45 units and auxillary gas flow 10 units (units
refer to arbitrary values set by the Exactive software). Nitrogen
was used for sample nebulization. U-HPLC separations were per-
formed on a Hypersil Gold C18 (ThermoFisher Scientific, USA),
1.9
l
m, 2.1 ꢁ 50 mm i.d. HPLC column, operated at 30 °C. Each
10 min chromatographic run was carried out at a flow rate of
0.3 mL/min with a binary mobile phase consisting of acetonitrile
(A) and 0.1% formic acid (B) using a step gradient profile of 50%
A for 0.5 min, increase up to 100% A in 5 min, isocratic at 100%
for 0.5 min, down to 50% A in 0.1 min. After re-equilibration at
50% A for 3.9 min, the next sample was injected.
3.2.4. General procedure for the synthesis of phosphonium salts
(5)
A mixture of
x-bromocarboxylic acid (1 equiv) and triphenyl-
phosphine (1 equiv) in 300 mL of toluene was refluxed for 48 h un-
der argon. The mixture was allowed to cool at room temperature
and concentrated in vacuum. The residue was crystallized from
various solvents to give the corresponding phosphonium salt.
Precoated Si gel 60 F254 plates (Merck, Darmstadt) were used to
monitor the progress of the reactions and column fractions. Spots
were detected by UV/254 nm and spraying with molybdatophos-
phoric acid and subsequent heating. Compounds were purified
by column chromatography on Silica gel 60 (0.063–0.200 mm)
using cyclohexane/ethyl acetate mixtures as eluent. Strains of M.
fortuitum (ATCC 6841), M. smegmatis (ATCC 19420), M. phlei (ATCC
19249) were obtained from the American Type culture collection
or the Pasteur institute.
3.2.4.1. 3-(Carboxypropyl)triphenylphosphonium bromide (5a).
Starting from 4-bromobutanoic acid (4a) (35.0 g, 0.21 mol) and tri-
phenylphosphine (55.0 g, 0.21 mol). Compound 5a was formed as a
white solid (83.0 g, 92%) after crystallization from diethyl ether/
ethyl acetate mixture. Mp 242–244 °C.
3.2.4.2. 4-(Carboxybutyl)triphenylphosphonium bromide (5b).
Starting from commercially obtained 5-bromopentanoic acid (4b)
(18.1 g, 0.1 mol) and triphenylphosphine (26.2 g, 0.1 mol). Com-
pound 5b was formed as a white solid (39.0 g, 88%) after recrystal-
lization from THF. Mp 205–207 °C.
3.2. Synthesis
3.2.1. Synthesis of 4-bromobutanoic acid (4a)
4-Butyrolactone (1) (48.2 g, 0.56 mol, 1 equiv) was dissolved in
a mixture of 48% HBr solution (317 mL, 2.8 mol, 5 equiv) and conc
H2SO4 (76 mL, 1.4 mol, 2.5 equiv) and left at room temperature for
2 h. The mixture was refluxed for 5 h, cooled to room temperature
and poured to 1.5 L distilled water. The mixture was extracted with
diethyl ether, washed with brine, dried over Na2SO4 and concen-
trated. Distillation of the crude product under reduced pressure
(ꢂ7 mbar) gave 57.0 g (61%) of colourless oil (bp 110–113 °C). 1H
NMR d 11.05 (bs, 1H, –OH), 3.64 (t, J = 6.7 Hz, 2H, H-4), 2.55 (t,
J = 7.6 Hz, 2H, H-2), 2.34 (m, 2H, H-3). 13C NMR d 180.2 (C1), 34.1
(C2), 32.9 (C4), 26.7 (C3).
3.2.4.3. 5-(Carboxypentyl)triphenylphosphonium bromide (5c).
Starting from 6-bromohexanoic acid (4c) (48.75 g, 0.25 mol) and tri-
phenylphosphine (65.5 g, 0.25 mol). Compound 5c was obtained as
a white solid (107.0 g, 94%) after crystallization from ethyl acetate.
Mp 193–195 °C.
3.2.4.4. 9-(Carboxynonyl)triphenylphosphonium bromide (5d).
Starting from 10-bromodecanoic acid (4d) (30.0 g, 0.12 mol) and
triphenylphosphine (31.0 g, 0.12 mol). Compound 5d was obtained
as a pale yellow wax (58.0 g, 94%) and an attempt to recrystallize
this product was not successful.
3.2.2. Synthesis of 6-bromohexanoic acid (4c)
The synthesis was carried out as described above starting from 6-
caprolactone (2) (56.0 g, 0.49 mol, 1 equiv), 48% HBr solution
(276 mL, 2.5 mol, 5 equiv) and conc. H2SO4 (65 mL, 1.2 mol, 2.5
equiv). Compound 4c was obtained as a colourless solid (78.0 g,
82%). 1H NMR d 11.13 (bs, 1H, –OH), 3.60 (t, J = 6.7 Hz, 2H, H-6),
2.49 (t, J = 7.6 Hz, 2H, H-2), 2.03 (m, 2H, H-3), 1.44–1.61 (m, 4H, H-
4, 5). 13C NMR d 180.2 (C1), 34.1 (C2), 32.9 (C6), 28.6, 28.1, 24.7 (C4).
3.2.4.5. 10-(Carboxydecyl)triphenylphosphonium bromide(5e).
Starting from commercially obtained 11-bromoundecanoic acid (4e)
(10.5 g, 0.04 mol) and triphenylphosphine (10.4 g, 0.04 mol). Com-
pound 5e was obtained as a white solid (19.0 g, 91%) after crystalliza-
tion from ethyl acetate. Mp 103–105 °C.

572
A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
3.2.5. General procedure for the synthesis of unsaturated
carboxylic acids (6)
NMR d 11.45 (bs, 1H, –OH), 5.43 (m, 1H, H-5), 5.34 (m, 1H, H-4),
2.39 (t, J = 6.7 Hz, 2H, H-2), 2.37 (t, J = 6.7 Hz, 2H, H-3), 2.04 (q,
J = 6.7 Hz, 2H, H-6), 1.22–1.36 (m, 16H, H-7-14), 0.87 (t,
J = 6.7 Hz, 3H, H-15). 13C NMR d 179.8 (C1), 131.8 (C5), 126.9
(C4), 34.2 (C2), 31.9 (C12), 29.6, 29.6, 29.5, 29.4, 29.3, 29.3, 27.2
(C6), 22.9 (C3), 22.5 (C14), 14.1 (C15).
To a stirring suspension of phosphonium salts (5a–e) (1 equiv)
in THF (250 mL) was added slowly 40% solution of sodium
hexamethyldisilylamide (2 equiv) THF at room temperature in
argon and stirring continued for 2 h. Aldehyde (1 equiv) was dis-
solved in THF (25 mL) and introduced drop wise. The mixture
was stirred for further 3 h and then poured into 150 mL of water
to get a clear solution. The resulting solution was concentrated in
vacuum and the residue was extracted with diethyl ether (3 x
250 mL). The aqueous layer was acidified with 10% HCl and ex-
tracted with ether (3 x 200 mL). The organic layer obtained from
the aqueous extract was dried and concentrated to afford the cor-
responding unsaturated carboxylic acids (6a–m).
3.2.5.6. (Z)-4-Tridecenoic acid (6f). Starting from 3-(carboxy-
propyl)triphenylphosphonium bromide (5a) (15.0 g, 34.9 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (35.0 mL,
69.8 mmol), and nonanal (4.9 g, 34.9 mmol) in THF (25 mL). Com-
pound 6f was obtained as a light yellow oil (6.1 g, 82%). 1H NMR d
11.57 (bs, 1H, –OH), 5.43 (m, 1H, H-5), 5.34 (m, 1H, H-4), 2.40 (t,
J = 6.7 Hz, 2H, H-2), 2.37 (t, J = 6.7 Hz, 2H, H-3), 2.04 (q, J = 7.3 Hz,
2H, H-6), 1.22–1.37 (m, 12H, H-7-12), 0.87 (t, J = 6.7 Hz, 3H, H-
13). 13C NMR d 179.9 (C1), 131.8 (C5), 126.9 (C4), 34.2 (C2), 31.9
(C11), 29.6, 29.5, 29.5, 29.3, 27.2 (C6), 22.7 (C12), 22.5 (C3), 14.1
(C13).
3.2.5.1. (Z)-5-Tetradecenoic acid (6a). Starting from 4-(carbo-
xybutyl)triphenylphosphonium bromide (5b) (12.0 g, 27.1 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (27.1 mL,
54.2 mmol) and nonanal (3.9 g, 27.1 mmol) in THF (25 mL). Com-
pound 6a was obtained as pale yellow oil (5.2 g, 84%).1H NMR d
11.46 (bs, 1H, –OH), 5.21–5.44 (m, 2H, H-5, 6), 2.37 (t, J = 6.7 Hz,
2H, H-2), 2.02 (m, 4H, H-4, 7), 1.66 (quint, J = 7.3 Hz, 2H, H-3),
1.24–1.32 (m, 12H, H-8-13), 0.88 (t, J = 6.7 Hz, 3H, H-14). 13C
NMR d 180.2 (C1), 131.2 (C6), 128.1 (C5), 34.4 (C2), 31.9, 29.6,
29.5, 29.3, 29.1, 27.1 26.9, 24.2 (C3), 22.3 (C13), 14.0 (C14).
3.2.5.7. (Z)-6-Dodecenoic acid (6g). Starting from 5-(carboxy-
pentyl)triphenylphosphonium bromide (5c) (15.0 g, 32.8 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (32.8 mL,
65.6 mmol), and hexanal (6.5 g, 32.8 mmol) in THF (25 mL). Com-
pound 6g was obtained as a light yellow oil (5.4 g, 83%). 1H NMR
d
11.76 (bs, 1H, –OH), 5.28–5.40 (m, 2H, H-6, 7), 2.33 (t,
J = 6.7 Hz, 2H, H-2), 2.01 (m, 4H, H-5, 8), 1.64 (quint, J = 7.3 Hz,
2H, H-3), 1.40 (quint, J = 7.3 Hz, 2H, H-4), 1.23–1.36 (m, 6H, H-9-
11), 0.89 (t, J = 6.7 Hz, 3H, H-12). 13C NMR d 180.4 (C1), 130.4
(C7), 128.9 (C6), 33.9 (C2), 31.4, 29.3, 29.0, 27.1 (C8), 26.7 (C5),
24.2 (C3), 22.5 (C11), 13.9 (C12).
3.2.5.2. (Z)-11-Tetradecenoic acid (6b). Starting from 10-(carbo-
xydecyl)triphenylphosphonium bromide (5e) (15.0 g, 28.5 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (28.5 mL,
57 mmol) and propanal (1.7 g, 28.5 mmol) in THF (10 mL). Com-
pound 6b was obtained as light yellow oil (4.4 g, 68%).1H NMR d
11.56 (bs, 1H, –OH), 5.27–5.43 (m, 2H, H-11, 12), 2.34 (t,
J = 7.3 Hz, 2H, H-2), 2.02 (m, 4H, H-10, 13), 1.62 (m, 2H, H-3),
1.21–1.32 (m, 12H, H-4-9), 0.93 (t, J = 6.7 Hz, 3H, H-14). 13C NMR
d 180.7 (C1), 131.7 (C12), 129.1 (C11), 34.8 (C2), 29.9, 29.4, 29.3,
29.3, 29.3, 29.1, 27.1 (C10), 24.5 (C3), 20.6 (C13), 14.2 (C14).
3.2.5.8. (Z)-4-Undecenoic acid (6h). Starting from 3-(carboxy-
propyl)triphenylphosphonium bromide (5a) (15.0 g, 35.0 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (35.0 mL,
70 mmol) and heptanal (4.0 g, 35 mmol) in THF (25 mL). Com-
pound 6h was obtained as a light yellow oil (5.6 g, 87%). 1H NMR
d 11.72 (bs, 1H, –OH), 5.43 (m, 1H, H-5), 5.34 (m, 1H, H-4), 2.40
(t, J = 6.7 Hz, 2H, H-2), 2.36 (t, J = 6.7 Hz, 2H, H-3), 2.04 (q,
J = 6.7 Hz, 2H, H-6), 1.24–1.37 (m, 8H, H-7-10), 0.89 (t, J = 6.7 Hz,
3H, H-11). 13C NMR d 179.9 (C1), 131.8 (C5), 126.9 (C4), 34.2
(C2), 31.7 (C9), 29.5 (C8), 28.9 (C7), 27.2 (C6), 22.6 (C10), 22.5
(C3), 14.0 (C11).
3.2.5.3. (Z)-6-Hexadecenoic acid (6c). Starting from 5-(carb-
oxypentyl)triphenylphosphonium bromide (5c) (15.0 g, 32.8
mmol) in THF (250 mL), sodium hexamethyldisilylamide (32.8
mL, 65.6 mmol) and decanal (5.1 g, 32.8 mmol) in THF (25 mL).
Compound 6c was obtained as a light yellow oil (6.2 g, 74%).1H
NMR d 11.72 (bs, 1H, –OH), 5.27–5.40 (m, 2H, H-6, 7), 2.32 (t,
J = 6.7 Hz, 2H, H-2), 2.02 (m, 4H, H-5, 8), 1.64 (quint, J = 7.3 Hz,
2H, H-3), 1.41 (quint, J = 7.3 Hz, 2H, H-4), 1.21–1.37 (m, 14H, H-
9-15), 0.91 (t, J = 6.7 Hz, 3H, H-16). 13C NMR d 180.5 (C1), 130.4
(C7), 129.0 (C6), 33.9 (C2), 31.4, 29.6, 29.5, 29.3, 29.3, 29.2, 29.0,
27.1 (C8), 26.7 (C5), 24.2 (C3), 22.5 (C15), 13.9 (C16).
3.2.5.9. (Z)-6-Tridecenoic acid (6i). Starting from 5-(carboxy-
pentyl)triphenylphosphonium bromide (5c) (15.0 g, 32.8 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (32.8 mL,
65.6 mmol), and heptanal (3.7 g, 32.8 mmol) in THF (20 mL). Com-
pound 6i was obtained as a light yellow oil (4.7 g, 68%). 1H NMR d
11.73 (bs, 1H, –OH), 5.28–5.41 (m, 2H, H-6, 7), 2.32 (t, J = 6.7 Hz,
2H, H-2), 2.01 (m, 4H, H-5, 8), 1.64 (quint, J = 7.3 Hz, 2H, H-3),
1.41 (quint, J = 7.3 Hz, 2H, H-4), 1.22–1.35 (m, 8H, H-9-12), 0.89
(t, J = 6.7 Hz, 3H, H-13). 13C NMR d 180.4 (C1), 130.4 (C7), 129.0
(C6), 33.9 (C2), 31.4, 29.5, 29.3, 29.0, 27.1 (C8), 26.7 (C5), 24.2
(C3), 22.6 (C12), 14.0 (C13).
3.2.5.4. (Z)-6-Undecenoic acid (6d). Starting from 5-(carboxy-
pentyl)triphenylphosphonium bromide (5c) (15.0 g, 32.8 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (32.8 mL,
65.6 mmol) and pentanal (2.8 g, 32.8 mmol) in THF (15 mL). Com-
pound 6d was collected as a light yellow oil (5.1 g, 85%).1H NMR d
11.54 (bs, 1H, –OH), 5.29–5.43 (m, 2H, H-6, 7), 2.35 (t, J = 6.7 Hz,
2H, H-2), 2.02 (m, 4H, H-5, 8), 1.64 (quint, J = 7.3 Hz, 2H, H-3),
1.41 (quint, J = 7.3 Hz, 2H, H-4), 1.28–1.35 (m, 4H, H-9, 10), 0.88
(t, J = 6.7 Hz, 3H, H-11). 13C NMR d 180.4 (C1), 130.4 (C7), 128.9
(C6), 34.0 (C2), 31.9, 29.1, 26.9 (C8), 26.7 (C5), 24.4 (C3),
22.3(10), 13.9 (C11).
3.2.5.10. (Z)-4-Tetradecenoic acid (6j). Starting from 3-(carb-
oxypropyl)triphenylphosphonium bromide (5a) (7.0 g, 16.3 mmol)
in THF (150 mL), sodium hexamethyldisilylamide (16.3 mL,
32.6 mmol) and decanal (2.5 g, 16.3 mmol) in THF (15 mL). Com-
pound 6j was obtained as light yellow oil (2.8 g, 76%). 1H NMR d
11.55 (bs, 1H, –OH), 5.42 (m, 1H, H-5), 5.34 (m, 1H, H-4), 2.41 (t,
J = 6.7 Hz, 2H, H-2), 2.37 (t, J = 6.7 Hz, 2H, H-3), 2.04 (q, J = 7.3 Hz,
2H, H-6), 1.21–1.37 (m, 14H, H-7-13), 0.88 (t, J = 6.7 Hz, 3H, H-
14). 13C NMR d 179.8 (C1), 131.8 (C5), 126.9 (C4), 34.2 (C2), 31.8
(C12), 29.6, 29.5, 29.5, 29.3, 29.2, 27.2 (C6), 22.7 (C13), 22.5 (C3),
14.0 (C14).
3.2.5.5. (Z)-4-Pentadecenoic acid (6e). Starting from 3-(carb-
oxypropyl)triphenylphosphonium bromide (5a) (15.0 g, 34.9
mmol) in THF (250 mL), sodium hexamethyldisilylamide (35.0
mL, 69.8 mmol) and undecanal (5.9 g, 34.9 mmol) in THF (25 mL).
Compound 6e was obtained as a light yellow oil (7.3 g, 87%). 1H

A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
573
3.2.5.11. (Z)-10-Nonadecenoic acid (6k). Starting from 9-(car-
boxynonyl)triphenylphosphonium bromide (5d) (15.0 g, 29.2
mmol) in THF (250 mL), sodium hexamethyldisilylamide
(29.2 mL, 58.5 mmol) and nonanal (4.2 g, 29.2 mmol) in THF
(25 mL). Compound 6k was collected as a light yellow oil (5.6 g,
65%). 1H NMR d 10.60 (bs, 1H, –OH), 5.35–5.44 (m, 2H, H-10, 11),
2.35 (t, J = 7.3 Hz, 2H, H-2), 1.99 (m, 4H, H-9, 12), 1.65 (quint,
J = 7.3 Hz, 2H, H-3), 1.23–1.40 (m, 22H, H-3-7, 13–18), 0.90 (t,
J = 6.7 Hz, 3H, H-19). 13C NMR d 180.2 (C1), 130.4, 130.3, 34.2
(C2), 31.9 (C17), 29.6, 29.6, 29.5, 29.4, 29.3, 29.3, 29.2, 29.1, 29.0,
27.2 (C9), 27.2 (C12), 24.6 (C3), 22.6 (C18), 14.1 (C19).
3.2.6.3. (Z)-7-Heptadecen-2-one (7c). Starting from 6-hexadece-
noic acid (6c) (5.5 g, 21.6 mmol) in THF (25 mL) and methyl lith-
ium (33.8 mL, 54.1 mmol). Compound 7c was obtained as a
colourless oil (2.9 g, 53%). 1H NMR d 5.26–5.39 (m, 2H, H-7, 8),
2.40 (t, J = 7.6 Hz, 2H, H-3), 2.11 (s, 3H, H-1), 2.00 (m, 4H, H-6, 9),
1.57 (quint, J = 7.6 Hz, 2H, H-4), 1.22–1.36 (m, 16H, H-5, 10–16),
0.86 (t, J = 6.7 Hz, 3H, H-17). 13C NMR d 208.9 (C2), 130.4 (C8),
129.0 (C7), 43.6 (C3), 31.9 (C15), 29.9 (C1), 29.6, 29.5, 29.3, 29.3,
29.2, 29.2, 27.2 (C6), 26.9 (C9), 23.4 (C4), 22.6 (C16), 14.0 (C17).
3.2.6.4. (Z)-7-Dodecen-2-one (7d). Starting from 6-undecenoic
acid (6d) (5.0 g, 27.2 mmol) in THF (25 mL) and methyl lithium
(42.4 mL, 67.9 mmol). Compound 7d was formed as a colourless
oil (2.4 g, 48%). 1H NMR d 5.27–5.39 (m, 2H, H-7, 8), 2.41 (t,
J = 7.6 Hz, 2H, H-3), 2.12 (s, 3H, H-1), 2.01 (m, 4H, H-6, 9), 1.58
(quint, J = 7.6 Hz, 2H, H-4), 1.26–1.36 (m, 6H, H-5, 10, 11), 0.89
(t, J = 6.9 Hz, 3H, H-12). 13C NMR d 209.0 (C2), 130.3 (C8), 129.1
(C7), 43.6 (C3), 31.9 (C10), 29.8 (C1), 29.2 (C5), 26.9 (C6), 26.9
(C9), 23.4 (C4), 22.3 (C11), 13.9 (C12).
3.2.5.12. (Z)-10-Eicosenoic acid (6‘l’). Starting from 9-(carbo-
xynonyl)triphenylphosphonium bromide (5d) (15.0 g, 29.2 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (29.2 mL,
58.5 mmol) and decanal (4.6 g, 29.2 mmol) in THF (25 mL). Com-
pound 6‘l’ was collected as a light yellow oil (5.9 g, 65%). 1H
NMR d 10.59 (bs, 1H, –OH), 5.36–5.45 (m, 2H, H-10, 11), 2.35 (t,
J = 7.3 Hz, 2H, H-2), 1.99 (m, 4H, H-9, 12), 1.65 (quint, J = 7.3 Hz,
2H, H-3), 1.22–1.42 (m, 24H, H-3-7, 13–19), 0.90 (t, J = 6.7 Hz,
3H, H-20). 13C NMR d 180.3 (C1), 130.4, 130.3, 34.2 (C2), 31.8
(C18), 29.6, 29.6, 29.5, 29.5, 29.4, 29.3, 29.3, 29.2, 29.1, 29.0, 27.2
(C9), 27.2 (C12), 24.6 (C3), 22.6 (C19), 14.1 (C20).
3.2.6.5. (Z)-5-Hexadecen-2-one (7e). Starting from 4-penta-
decenoic acid (6e) (7.0 g, 29.2 mmol) in THF (30 mL) and methyl
lithium (45.6 mL, 73 mmol). Compound 7e was formed as a colour-
less oil (3.8 g, 55%). 1H NMR d 5.36 (m, 1H, H-6), 5.27 (m, 1H, H-5),
2.44 (t, J = 7.6 Hz, 2H, H-3), 2.28 (q, J = 7.6 Hz, 2H, H-4), 2.11 (s, 3H,
H-1), 2.00 (q, J = 6.7 Hz, 2H, H-7), 1.19–1.32 (m, 16H, H-8-15), 0.85
(t, J = 6.7 Hz, 3H, H-16). 13C NMR d 208.2 (C2), 131.2 (C6), 127.5
(C5), 43.5 (C3), 31.8 (C14), 29.8 (C1), 29.6, 29.6, 29.5, 29.4, 29.3,
27.1, 26.8, 22.6 (C15), 21.6 (C4), 14.0 (C16).
3.2.5.13. (Z)-10-Heneicosenoic acid (6m). Starting from 9-(car-
boxynonyl)triphenylphosphonium bromide (5d) (15.0 g, 29.2 mmol)
in THF (250 mL), sodium hexamethyldisilylamide (29.2 mL,
58.5 mmol) and undecanal (5 0 g, 29.2 mmol) in THF (25 mL).
Compound 6m was obtained as a light yellow oil (5.2 g, 55%). 1H
NMR d 10.63 (bs, 1H, –OH), 5.36–5.45 (m, 2H, H-10, 11), 2.35 (t,
J = 7.3 Hz, 2H, H-2), 1.99 (m, 4H, H-9, 12), 1.66 (quint, J = 7.3 Hz,
2H, H-3), 1.22–1.43 (m, 26H, H-3-7, 13–20), 0.90 (t, J = 6.7 Hz,
3H, H-21). 13C NMR d 180.2 (C1), 130.4, 130.3, 34.2 (C2), 31.8
(C19), 29.6, 29.6, 29.5, 29.5, 29.4, 29.3, 29.3, 29.2, 29.1, 29.1, 29.0,
27.2 (C9), 27.2 (C12), 24.6 (C3), 22.6 (C20), 14.1 (C21).
3.2.6.6. (Z)-5-Tetradecen-2-one (7f). Starting from 4-tridece-
noic acid (6f) (6.0 g, 28.3 mmol) in THF (30 mL) and methyl lithium
(44.3 mL, 70.8 mmol). Compound 7f was formed as a colourless oil
(3.4 g, 57%). 1H NMR d 5.35 (m, 1H, H-6), 5.26 (m, 1H, H-5), 2.43 (t,
J = 7.6 Hz, 2H,, H-3), 2.26 (q, J = 7.6 Hz, 2H, H-4), 2.10 (s, 3H, H-1),
1.98 (q, J = 6.7 Hz, 2H, H-7), 1.18–1.32 (m, 12H, H-8-13), 0.85 (t,
J = 6.7 Hz, 3H, H-14). 13C NMR d 208.2 (C2), 131.2 (C6), 127.5
(C5), 43.5 (C3), 31.8 (C12), 29.8 (C1), 29.6, 29.4, 29.2, 27.1, 26.9,
22.1 (C13), 21.6 (C4), 13.9 (C14).
3.2.6. General procedure for the synthesis of unsaturated
methyl ketones (7)
To a stirred solution of methyl lithium (2.5 equiv, 1.6 M in
ether) cooled at 0 °C in argon was added drop wise the correspond-
ing unsaturated acid (1 equiv) in THF (50 mL). After 3 h of stirring,
the mixture was poured onto ice and extracted with diethyl ether,
washed with Na2CO3 solution, dried and concentrated in vacuum.
The residue was purified by column chromatography eluting with
cyclohexane/ethyl acetate (95:5) to give the corresponding unsat-
urated methyl ketone (7a–‘o’).
3.2.6.7. (Z)-7-Tridecen-2-one (7g). Starting from 6-dodecenoic
acid (6g) (5.3 g, 26.8 mmol) in THF (25 mL) and methyl lithium
(41.8 mL, 66.9 mmol). Compound 7g was formed as a colourless
oil (2.8 g, 53%). 1H NMR d 5.29–5.41 (m, 2H, H-7, 8), 2.42 (t,
J = 7.6 Hz, 2H, H-3), 2.12 (s, 3H, H-1), 2.02 (m, 4H, H-6, 9), 1.58
(quint, J = 7.3 Hz, 2H, H-4), 1.22–1.38 (m, 8H, H-5, 10–12), 0.88
(t, J = 6.9 Hz, 3H, H-13). 13C NMR d 209.1 (C2), 130.5 (C8), 129.2
(C7), 43.6 (C3), 31.8 (C11), 29.7 (C1), 29.3, 29.2, 27.2 (C9), 26.9
(C6), 23.5 (C4), 22.6 (C12), 14.0 (C13).
3.2.6.1. (Z)-6-Pentadecen-2-one (7a). Starting from 5-tetra-
decenoic acid (6a) (5.0 g, 22.1 mmol) in THF (25 mL) and methyl
lithium (43.5 mL, 55.1 mmol). Compound 7a was obtained as a col-
ourless oil (2.8 g, 57%). 1H NMR d 5.38 (m, 1H, H-7), 5.32 (m, 1H, H-
6), 2.42 (t, J = 7.6 Hz, 2H, H-3), 2.12 (s, 3H, H-1), 2.01 (m, 4H, H-6,
7), 1.63 (quint, J = 7.6 Hz, 2H, H-4), 1.22–1.31 (m, 12H, H-9-14),
0.89 (t, J = 6.7 Hz, 3H, H-15).13C NMR d 208.9 (C2), 131.0 (C7),
128.5 (C6), 43.0 (C3), 31.8 (C13), 29.8 (C1), 29.7, 29.3, 29.3, 29.2,
27.2 (C8), 26.9 (C5), 23.7 (C4), 22.6 (C14), 14.0 (C15).
3.2.6.8. (Z)-5-Dodecen-2-one (7h). Starting from 4-undecenoic
acid (6h) (5.2 g, 28.3 mmol) in THF (25 mL) and methyl lithium
(44.2 mL, 70.7 mmol). Compound 7h was formed as a colourless
oil (2.7 g, 52%). 1H NMR d 5.38 (m, 1H, H-6), 5.29 (m, 1H, H-5),
2.45 (t, J = 7.6 Hz, 2H, H-3), 2.29 (q, J = 7.6 Hz, 2H, H-4), 2.10 (s,
3H, H-1), 2.10 (m, 2H, H-7), 1.21–1.32 (m, 8H, H-8-11), 0.88 (t,
J = 6.7 Hz, 3H, H-12). 13C NMR d 208.6 (C2), 131.4 (C6), 127.5
(C5), 43.6 (C3), 31.8 (C10), 29.8 (C1), 29.5, 29.3, 27.1 (C7), 22.6
(C11), 21.6 (C4), 14.0 (C12).
3.2.6.2. (Z)-12-Pentadecen-2-one (7b). Starting from 11-tetra-
decenoic acid (6b) (3.0 g, 13.3 mmol) in THF (20 mL) and methyl
lithium (20.7 mL, 33.2 mmol). Compound 7b was obtained as a col-
ourless oil (1.8 g, 60%). 1H NMR d 5.25–5.41 (m, 2H, H-12, 13), 2.39
(t, J = 7.3 Hz, 2H, H-3), 2.11 (s, 3H, H-1), 2.00 (m, 4H, H-11, 14), 1.55
(m, 2H, H-4), 1.23–1.34 (m, 12H, H-5-10), 0.94 (t, J = 7.5 Hz, 3H, H-
15). 13C NMR d 209.2 (C2), 131.5 (C13), 129.2 (C12), 43.7 (C3), 29.8
(C1), 29.7, 29.4, 29.3, 29.2, 29.1, 27.0 (C11), 26.9, 23.8 (C4), 20.4
(C14), 14.3 (C15).
3.2.6.9. (Z)-7-Tetradecen-2-one (7i). Starting from 6-tridece-
noic acid (6i) (4.0 g, 18.9 mmol) in THF (20 mL) and methyl lithium
(29.5 mL, 47.3 mmol). Compound 7i was obtained as a colourless
oil (1.9 g, 48%). 1H NMR d 5.28–5.41 (m, 2H, H-7, 8), 2.42 (t,
J = 7.6 Hz, 2H, H-3), 2.12 (s, 3H, H-1), 2.01 (m, 4H, H-6, 9), 1.58
(quint, J = 7.3 Hz, 2H, H-4), 1.22–1.38 (m, 10H, H-5, 10–13), 0.88

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A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
(t, J = 6.9 Hz, 3H, H-14). 13C NMR d 209.1 (C2), 130.4 (C8), 129.1
(C7), 43.6 (C3), 31.7 (C12), 29.7 (C1), 29.3, 29.2, 29.1, 27.2 (C9),
26.9 (C6), 23.5 (C4), 22.6 (C13), 14.1 (C14).
3.2.7. General procedure for the synthesis of 1-methyl-2-
alkenyl-4(1H)-quinolones (8)
To a stirred solution of LDA (1.8 M, in THF/heptane/ethylben-
zene, 1 equiv) unsaturated methyl ketone (1 equiv) (7) in THF
(20 mL) was added dropwise at ꢀ78 °C in argon. After stirring for
1 h, N-methyl isatoic anhydride (20) (0.75 equiv) in THF (10 mL)
was applied dropwise at ꢀ78 °C and stirring continued for
30 min. The reaction was quenched with saturated NH4Cl solution
and concentrated in vacuum. The resulting yellowish residue was
extracted with diethyl ether (3 x 150 mL), dried, concentrated
and purified by column chromatography eluting with cyclohex-
ane/ethyl acetate mixture of increasing polarity to give the corre-
sponding alkaloids (8a–‘o’).
3.2.6.10. (Z)-5-Pentadecen-2-one (7j). Starting from 4-tetra-
decenoic acid (6j) (2.5 g, 11.1 mmol) in THF (15 mL) and methyl
lithium (17.3 mL, 27.7 mmol). Compound 7j was formed as a col-
ourless oil (1.4 g, 56%). 1H NMR d 5.37 (m, 1H, H-6), 5.28 (m, 1H,
H-5), 2.45 (t, J = 7.6 Hz, 2H, H-3), 2.28 (q, J = 7.6 Hz, 2H, H-4),
2.12 (s, 3H, H-1), 2.10 (m, 2H, H-7), 1.21–1.35 (m, 14H, H-8-14),
0.86 (t, J = 6.7 Hz, 3H, H-15). 13C NMR d 208.4 (C2), 131.3 (C6),
127.5 (C5), 43.6 (C3), 31.9 (C13), 29.8 (C1), 29.6, 29.6, 29.5, 29.3,
29.1, 27.1 (C7), 22.6 (C14), 21.6 (C4), 14.0 (C15).
3.2.6.11. (Z)-11-Eicosen-2-one (7k). Starting from 10-nona-
decenoic acid (6k) (4.0 g, 13.5 mmol) in THF (20 mL) and methyl
lithium (21.1 mL, 33.8 mmol). Compound 7k was obtained as a col-
ourless oil (1.9 g, 48%). 1H NMR d 5.27–5.36 (m, 2H, H-11, 12), 2.38
(t, J = 7.6 Hz, 2H, H-3), 2.10 (s, 3H, H-1), 1.98 (m, 4H, H-10, 13), 1.54
(m, 2H, H-4), 1.20–1.32 (m, 22H, H-5-9, 14–19), 0.86 (t, J = 6.7 Hz,
3H, H-20). 13C NMR d 208.9 (C2), 129.8 (C12), 129.7 (C11), 43.7
(C3), 31.8 (C18), 29.7 (C1), 29.7, 29.6, 29.5, 29.4, 29.3, 29.3, 29.2,
29.2, 29.1, 27.1, 27.1, 23.8 (C4), 22.6 (C19), 14.0 (C20).
3.2.7.1. 1-Methyl-2-[(Z)-40-tridecenyl]-4(1H)-quinolone (8a).
Starting from 6-pentadecen-2-one (7a) (2.2 g, 9.8 mmol) in THF
(30 mL), LDA (5.4 mL, 9.8 mmol) and N-methyl isatoic anhydride
(1.3 g, 7.4 mmol) in THF (25 mL). Compound 8a was formed as a
light yellow solid (1.4 g, 42%).13 Mp 50–52 °C. IR (cmꢀ1): 3425,
2919, 2852, 1637, 1597, 1469, 777. 1H NMR CDCl3): d 8.36 (d,
J = 8.5 Hz, 1H, H-5), 7.58 (t, J = 7.6 Hz, 1H, H-7), 7.44 (d, J = 8.5 Hz,
1H, H-8), 7.29 (t, J = 7.6 Hz, 1H, H-6), 6.19 (s, 1H, H-3), 5.43 (m,
1H, H-50), 5.31 (m, 1H, H-40), 3.64 (s, 3H, N-CH3), 2.63 (t,
J = 7.6 Hz, 2H, H-10), 2.14 (m, 2H, H-30), 1.98 (m, 2H, H-60), 1.64
(quint, J = 7.3 Hz, 2H, H-20), 1.19–1.37 (m, 12H, H-70-120), 0.83 (t,
J = 6.7 Hz, 3H, H-130). 13C NMR d 177.6 (C4), 154.9 (C2), 141.7
(C8a), 132.0 (C7), 131.7 (C60), 127.6 (C50), 126.3 (C5), 126.1 (C4a),
123.3 (C6), 115.3 (C8), 110.6 (C3), 34.1 (C10), 34.0 (N-CH3), 31.7
(C110), 29.5, 29.4, 29.2, 29.1, 28.3 (C20), 27.2 (C60), 26.5 (C30), 22.5
(C120), 14.0 (C130). ESI-MS m/z (rel. int.): [M+H]+ 340 (100). ESI-
HRMS (+) found 340.26306 for C23H34NO [M+H]+, calcd 340.26349.
3.2.6.12. (Z)-11-Heneicosen-2-one (7‘l’). Starting from 10-ei-
cosenoic acid (6‘l’) (5.0 g, 16.1 mmol) in THF (25 mL) and methyl
lithium (25.2 mL, 40.3 mmol). Compound 7‘l’ was obtained as a
colourless oil (2.6 g, 52%). 1H NMR d 5.26–5.35 (m, 2H, H-11, 12),
2.38 (t, J = 7.6 Hz, 2H, H-3), 2.09 (s, 3H, H-1), 1.98 (m, 4H, H-10,
13), 1.53 (m, 2H, H-4), 1.20–1.34 (m, 24H, H-5-9, 14–20), 0.85 (t,
J = 6.7 Hz, 3H, H-21). 13C NMR d 208.9 (C2), 129.8 (C12), 129.7
(C11), 43.7 (C3), 31.8 (C19), 29.7 (C1), 29.7, 29.7, 29.5, 29.5, 29.3,
29.3, 29.3, 29.2, 29.2, 29.1, 27.1, 27.1, 23.8 (C4), 22.6 (C20), 14.0
(C21).
3.2.7.2. 1-Methyl-2-[((Z)-100-tridecenyl]-4(1H)-quinolone (8b).
Starting from 12-pentadecen-2-one (7b) (1.5 g, 6.7 mmol) in THF
(25 mL), LDA (3.7 mL, 6.7 mmol) and N-methyl isatoic anhydride
(0.89 g, 5.0 mmol) in THF (20 mL). Compound 8b was formed as
light yellow oil (0.94 g, 41%). IR (neat, cmꢀ1): 3425, 2926, 2853,
1628, 1598, 1467, 761. 1H NMR d 8.45 (dd, J = 1.6, 8.0 Hz, 1H, H-
5), 7.66 (dt, J = 1.6, 8.0 Hz, 1H, H-7), 7.51 (dd, J = 1.6, 7.5 Hz, 1H,
H-8), 7.38 (dt, J = 1.6, 8.0 Hz, 1H, H-6), 6.28 (s, 1H, H-3), 5.36 (m,
1H, H-110), 5.31 (m, 1H, H-100), 3.74 (s, 3H, N-CH3), 2.71 (t,
J = 8.0 Hz, 2H, H-10), 2.03 (m, 2H, H-120), 2.01 (m, 2H, H-90), 1.68
(quint, J = 7.4 Hz, 2H, H-20), 1.41 (m, 2H, H-30), 1.22–1.34 (m,
10H, H-40-80), 0.95 (t, J = 8.0 Hz, 3H, H-130). 13C NMR d 177.6 (C4),
154.9 (C2), 141.9 (C8a), 132.0 (C7), 131.5 (C110), 129.2 (C100),
126.6 (C5), 126.3 (C4a), 123.3 (C6), 115.3 (C8), 110.9 (C3), 34.7
(C10), 34.1 (N-CH3), 29.7, 29.4, 29.4, 29.3, 29.2 (C30), 29.1, 28.5
(C20), 27.0 (C90), 20.5 (C120), 14.3 (C130). ESI-MS m/z (rel. int.):
[M+H]+ 340 (100). ESI-HRMS (+) found 340.26297 for C23H34NO
[M+H]+, calcd 340.26349.
3.2.6.13. (Z)-11-Docosen-2-one (7m). Starting from 10-hene-
icosenic acid (6m) (4.5 g, 13.9 mmol) in THF (25 mL) and methyl
lithium (21.7 mL, 34.7 mmol). Compound 7m was formed as a col-
ourless oil (2.1 g, 47%). 1H NMR d 5.26–5.35 (m, 2H, H-11, 12), 2.38
(t, J = 7.6 Hz, 2H, H-3), 2.09 (s, 3H, H-1), 1.97 (m, 4H, H-10, 13), 1.53
(m, 2H, H-4), 1.21–1.33 (m, 26H, H-5-9, 14–21), 0.85 (t, J = 6.7 Hz,
3H, H-22). 13C NMR d 208.9 (C2), 129.8 (C12), 129.7 (C11), 43.7
(C3), 31.8 (C20), 29.7 (C1), 29.7, 29.6, 29.6, 29.5, 29.4, 29.3, 29.3,
29.2, 29.2, 29.1, 29.0, 27.1 (C11), 27.1 (C12), 23.8 (C4), 22.6
(C21), 14.0 (C22).
3.2.6.14. (Z)-10-Nonadecen-2-one (7n). Starting from commer-
cial oleic acid (5.0 g, 17.7 mmol) in THF (25 mL) and methyl lith-
ium (27.7 mL, 44.3 mmol). Compound 7n was formed as a light
yellow oil (2.7 g, 54%). 1H NMR d 5.26–5.35 (m, 2H, H-10, 11),
2.38 (t, J = 7.6 Hz, 2H, H-3), 2.10 (s, 3H, H-1), 1.98 (m, 4H, H-9,
12), 1.55 (m, 2H, H-4), 1.21–1.32 (m, 20H, H-5-8, 13–18), 0.87 (t,
J = 6.7 Hz, 3H, H-19). 13C NMR d 209.1 (C2), 130.0 (C11), 129.8
(C10), 43.8 (C3), 31.8 (C17), 29.8 (C1), 29.6, 29.5, 29.4, 29.3, 29.3,
29.2, 29.2, 29.1, 27.1, 27.0, 23.8 (C4), 22.6 (C18), 14.0 (C19).
3.2.7.3. 1-Methyl-2-[(Z)-50-pentadecenyl]-4(1H)-quinolone (8c).
Starting from 7-heptadecen-2-one (7c) (2.0 g, 7.9 mmol) in THF
(30 mL), LDA (4.4 mL, 7.9 mmol) and N-methyl isatoic anhydride
(1.06 g, 5.9 mmol) in THF (25 mL). Compound 8c was formed as a
light yellow oil (1.3 g, 45%). IR (neat, cmꢀ1): 3427, 2924, 2853,
1637, 1596, 1465, 775. 1H NMR d 8.46 (dd, J = 1.2, 8.0 Hz, 1H, H-
5), 7.68 (dt, J = 1.2, 7.8 Hz, 1H, H-7), 7.53 (dd, J = 1.2, 7.6 Hz, 1H,
H-8), 7.39 (t, J = 7.5 Hz, 1H, H-6), 6.34 (s, 1H, H-3), 5.40 (m, 1H,
H-60), 5.32 (m, 1H, H-50), 3.76 (s, 3H, N-CH3), 2.74 (t, J = 8.0 Hz,
2H, H-10), 2.09 (m, 2H, H-40), 2.01 (m, 2H, H-70), 1.70 (quint,
J = 7.3 Hz, 2H, H-20), 1.51 (m, 2H, H-30), 1.22–1.33 (m, 14H, H-80-
140), 0.87 (t, J = 7.0, 3H, H-150). 13C NMR d 177.7 (C4), 155.0 (C2),
141.8 (C8a), 132.1 (C7), 130.8 (C60), 128.5 (C50), 126.6 (C5), 126.2
(C4a), 123.4 (C6), 115.3 (C8), 110.9 (C3), 34.6 (C10), 34.2 (N-CH3),
31.8 (C130), 29.7, 29.5, 29.5, 29.3, 29.3, 29.2 (C30), 28.0 (C20), 27.2
3.2.6.15. (Z,Z)-Nonadeca-10,13-dien-2-one (7‘o’). Starting from
commercial linoleic acid (1.5 g, 5.3 mmol) in THF (10 mL) and
methyl lithium (8.4 mL, 13.4 mmol). Compound 7‘o’ was formed
as a light yellow oil (0.7 g, 47%). 1H NMR d 5.30–5.53 (m, 4H, H-
10, 11, 13, 14), 2.72 (t, J = 6.0 Hz, 2H, H-12), 2.42 (t, J = 7.3 Hz,
2H, H-3), 2.10 (s, 3H, H-1), 1.94–2.06 (m, 4H, H-9, 15), 1.53 (m,
2H, H-4), 1.22–1.36 (m, 14H, H-5-8, 16–18), 0.89 (t, J = 6.7 Hz,
3H, H-19).13C NMR d 209.1 (C2), 131.0 (C14), 130.2 (C10), 128.3
(C11), 128.1 (C13), 43.7 (C3), 32.3, 31.4, 30.5, 30.0, 29.5, 29.3,
29.3, 29.2, 29.0, 26.9, 23.7 (C4), 22.6 (C18), 14.0 (C19).

A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
575
(C70), 26.6 (C40), 22.6 (C140), 14.0 (C150). ESI-MS m/z (rel. int.):
[M+H]+ 368 (100). ESI-HRMS (+) found 368.29440 for C25H38NO
[M+H]+, calcd 368.29479.
(m, 1H, H-50), 3.68 (s, 3H, N-CH3), 2.65 (t, J = 7.6 Hz, 2H, H-10),
2.06 (m, 2H, H-40), 1.98 (m, 2H, H-70), 1.64 (quint, J = 7.3 Hz, 2H,
H-20), 1.46 (quint, J = 7.6 Hz, 2H, H-30), 1.21–1.33 (m, 6H, H-80-
100), 0.84 (t, J = 6.7 Hz, 3H, H-110). 13C NMR d 177.8 (C4), 154.8 (C2),
141.8 (C8a), 131.9 (C7), 130.8 (C60), 128.5 (C50), 126.4 (C5), 126.2
(C4a), 123.2 (C6), 115.3 (C8), 110.8 (C3), 34.5 (C10), 34.1 (N-CH3),
31.4 (C90), 29.2 (C80), 29.1 (C30), 27.9 (C20), 27.1 (C70), 26.6 (C40), 22.4
(C100), 14.0 (C11). ESI-MS m/z (rel. int.): [M+H]+ 312 (100). ESI-HRMS
(+) found 312.23169 for C21H30NO [M+H]+, calcd 312.23320.
3.2.7.4.
1-Methyl-2-[(Z)-50-decenyl]-4(1H)-quinolone (8d).
Starting from 7-dodecene-2-one (7d) (1.4 g, 7.7 mmol) in THF
(25 mL), LDA (4.3 mL, 7.7 mmol) and N-methyl isatoic anhydride
(1.03 g, 5.8 mmol) in THF (25 mL). Compound 8d was formed as
yellow oil (0.78 g, 34%). IR (neat, cmꢀ1): 3432, 2926, 2855, 1637,
1597, 1467, 776. 1H NMR d 8.45 (dd, J = 1.4, 8.0 Hz, 1H, H-5),
7.67 (dt, J = 1.4, 8.0 Hz, 1H, H-7), 7.52 (dd, J = 1.4, 8.0 Hz, 1H, H-
8), 7.38 (dt, J = 1.4, 7.8 Hz, 1H, H-6), 6.31 (s, 1H, H-3), 5.40 (m,
1H, H-60), 5.32 (m, 1H, H-50), 3.75 (s, 3H, N-CH3), 2.73 (m, 2H, H-
10), 2.10 (m, 2H, H-40), 2.02 (m, 2H, H-70), 1.69 (quint, J = 7.4 Hz,
2H, H-20), 1.48 (m, 2H, H-30), 1.26–1.35 (m, 4H, H-80-90), 0.87 (t,
J = 7.3 Hz, 3H, H-100). 13C NMR d 177.7 (C4), 155.0 (C2), 141.8
(C8a), 132.1 (C7), 130.8 (C60), 128.6 (C50), 126.6 (C5), 126.2 (C4a),
123.5 (C6), 115.4 (C8), 110.9 (C3), 34.7 (C10), 34.2 (N-CH3), 31.8
(C80), 29.2 (C30), 28.0 (C20), 26.9 (C70), 26.7 (C40), 22.1 (C90), 13.9
(C100). ESI-MS m/z (rel. int.): [M+H]+ 298 (100). ESI-HRMS (+) found
298.21628 for C20H28NO [M+H]+, calcd 298.21654.
3.2.7.8.
1-Methyl-2-[(Z)-30-decenyl]-4(1H)-quinolone (8h).
Starting from 5-dodeceen-2-one (7h) (1.5 g, 8.2 mmol) in THF
(25 mL), LDA (4.6 mL, 8.2 mmol) and N-methyl isatoic anhydride
(1.1 g, 6.2 mmol) in THF (20 mL). Compound 8h was formed as a
light yellow oil (0.91 g, 37%). IR (neat, cmꢀ1): 3426, 2924, 2854,
1635, 1598, 1499, 762. 1H NMR d 8.42 (d, J = 7.8 Hz, 1H, H-5),
7.64 (t, J = 7.6 Hz, 1H, H-7), 7.49 (d, J = 8.0 Hz, 1H, H-8), 7.35 (d,
J = 7.5 Hz, 1H, H-6), 6.25, (s, 1H, H-3), 5.49 (m, 1H, H-40), 5.37 (m,
1H, H-30), 3.73 (s, 3H, N-CH3), 2.74 (t, J = 7.6 Hz, 2H, H-10), 2.40
(m, 2H, H-20), 1.98 (m, 2H, H-50), 1.18–1.31 (m, 8H, H-60-90), 0.84
(t, J = 6.8 Hz, 3H, H-100). 13C NMR d 177.7 (C4), 154.2 (C2), 141.8
(C8a), 132.4 (C40), 132.1 (C7), 126.6 (C5), 126.3 (C4a), 126.2 (C30),
123.4 (C6), 115.3 (C8), 111.1 (C3), 34.6 (C10), 34.2 (N-CH3), 31.6
(C80), 29.4 (C70), 28.9 (C60), 27.3 (C50), 26.2 (C20), 22.5 (C90), 14.0
(C100). ESI-MS m/z (rel. int.): [M+H]+ 298 (100). ESI-HRMS (+) found
298.21594 for C20H28NO [M+H]+, calcd 298.21654.
3.2.7.5. 1-Methyl-2-[(Z)-30-tetradecenyl]-4(1H)-quinolone (8e).
Starting from 5-hexadecen-2-one (7e) (1.5 g, 6.3 mmol) in THF
(25 mL), LDA (3.5 mL, 6.3 mmol) and N-methyl isatoic anhydride
(0.84 g, 4.7 mmol) in THF (20 mL). Compound 8e was formed as a
light yellow solid (1.0 g, 45%). Mp 77–78 °C. IR (cmꢀ1): 3429,
2919, 2852, 1636, 1597, 1472, 773. 1H NMR d 8.41 (d, J = 7.3 Hz,
1H, H-5), 7.64 (t, J = 7.3 Hz, 1H, H-7), 7.49 (d, J = 7.3 Hz, 1H, H-8),
7.35 (t, J = 7.3 Hz, 1H, H-6), 6.27 (s, 1H, H-3), 5.45 (m, 1H, H-40),
5.37 (m, 1H, H-30), 3.73 (s, 3H, N-CH3), 2.74 (t, J = 7.4 Hz, 2H, H-
10), 2.36 (m, 2H, H-20), 1.99 (m, 2H, H-50), 1.17–1.24 (m, 16H, H-
60-130), 0.84 (t, J = 6.6 Hz, 3H, H-140). 13C NMR d 177.7 (C4), 154.3
(C2), 141.8 (C8a), 132.4 (C40), 132.1 (C7), 126.6 (C5), 126.2 (C4a),
126.2 (C30), 123.4 (C6), 115.3 (C8), 111.0 (C3), 34.6 (C10), 34.2 (N-
CH3), 31.8 (C120), 29.5, 29.5, 29.4, 29.3, 29.2, 29.1, 27.3 (C50), 26.2
(C20), 22.6 (C130), 14.1 (C140). ESI-MS m/z (rel. int.): [M+H]+ 354
(100). ESI-HRMS (+) found 354.27838 for C24H36NO [M+H]+, calcd
354.27914.
3.2.7.9. 1-Methyl-2-[(Z)-50-dodecenyl]-4(1H)-quinolone (8i).
Starting from 7-tetradecen-2-one (7i) (0.9 g, 4.3 mmol) in THF
(20 mL), LDA (2.4 mL, 4.3 mmol) and N-methyl isatoic anhydride
(0.57 g, 3.2 mmol) in THF (15 mL). Compound 8i was formed as a
light yellow oil (0.55 g, 39%). IR (neat, cmꢀ1): 3446, 2925, 2853,
1637, 1572, 1467, 776. 1H NMR d 8.45 (d, J = 8.0 Hz, 1H, H-5),
7.68 (t, J = 7.6 Hz, 1H, H-7), 7.60 (d, J = 8.0 Hz, 1H, H-8), 7.39 (t,
J = 7.6 Hz, 1H, H-6), 6.33 (s, 1H. H-3), 5.41 (m, 1H, H-60), 5.32
(m, 1H, H-50), 3.77 (s, 3H, N-CH3), 2.74 (t, J = 7.8 Hz, 2H, H-10),
2.10 (m, 2H, H-40), 2.00 (m, 2H, H-70), 1.71 (quint, J = 7.4 Hz,
2H, H-20), 1.51 (m, 2H, H-30), 1.23–1.36 (m, 8H, H-80-110), 0.86
(t, J = 7.6 Hz, 3H, H-120). 13C NMR d 177.6 (C4), 154.7 (C2),
141.9 (C8a), 132.1 (C7), 130.9 (C60), 128.8 (C50), 126.6 (C5),
126.4 (C4a), 123.4 (C6), 115.3 (C8), 111.1 (C3), 34.7 (C10), 34.2
(N-CH3), 31.7 (C100), 29.6, (C90), 29.2 (C30), 28.9 (C80), 28.1
(C20), 27.3 (C70), 26.7 (C40), 22.6 (C110), 14.1 (C120). ESI-MS m/z
(rel. int.): [M+H]+ 326 (100). ESI-HRMS (+) found 326.24728 for
3.2.7.6. 1-Methyl-2-[(Z)-30-dodecenyl]-4(1H)-quinolone (8f).
Starting from 5-tetradecen-2-one (7f) (1.5 g, 7.1 mmol) in THF
(25 mL), LDA (3.9 mL, 7.1 mmol) and N-methyl isatoic anhydride
(0.95 g, 5.3 mmol) in THF (20 mL). Compound 8f was formed as a
light yellow oil (0.88 g, 38%). IR (neat, cmꢀ1): 3433, 2921, 2852,
1637, 1597, 1467, 772. 1H NMR d 8.44 (d, J = 8.0 Hz, 1H, H-5),
7.66 (t, J = 7.8 Hz, 1H, H-7), 7.51 (d, J = 8.0 Hz, 1H, H-8), 7.37 (t,
J = 7.6 Hz, 1H, H-6), 6.29 (s, 1H, H-3), 5.48 (m, 1H, H-40), 5.38
(m, 1H, H-30), 3.75 (s, 3H, N-CH3), 2.76, (t, J = 7.6 Hz, 2H, H-10),
2.42 (m, 2H, H-20), 1.97 (m, 2H, H-50), 1.18–1.30 (m, 12H, H-60-
110), 0.86 (t, J = 6.7 Hz, 3H, H-120). 13C NMR d 177.7 (C4), 154.3
(C2), 141.8 (C8a), 132.5 (C40), 132.2 (C7), 126.7 (C5), 126.3
(C4a), 126.2 (C30), 123.5 (C6), 115.3 (C8), 111.1 (C3), 34.7 (C10),
34.2 (N-CH3), 31.8 (C100), 29.5 (C90), 29.4 (C80), 29.3 (C70), 29.2
(C60), 27.3 (C50), 26.2 (C20), 22.6 (C110), 14.1 (C120). ESI-MS m/z
(rel. int.): [M+H]+ 326 (100). ESI-HRMS (+) found 326.24728 for
C
22H32NO [M+H]+, calcd 326.24784.
3.2.7.10.
1-Methyl-2-[(Z)-30-tridecenyl]-4(1H)-quinolone (8j).
Starting from 5-pentadecen-2-one (7j) (0.8 g, 3.6 mmol) in THF
(20 mL), LDA (2.0 mL, 3.6 mmol) and N-methyl isatoic anhydride
(0.48 g, 2.7 mmol) in THF (15 mL). Compound 8j was formed as a
light yellow oil (0.46 g, 38%). IR (neat, cmꢀ1): 3421, 2922, 2852,
1637, 1596, 1466, 771. 1H NMR d 8.45 (d, J = 8.0 Hz, 1H, H-5), 7.66
(t, J = 7.6 Hz, 1H, H-7), 7.51 (d, J = 8.0 Hz, 1H, H-8), 7.38 (t,
J = 7.6 Hz, 1H, H-6), 6.29 (s, 1H, H-3), 5.49 (m, 1H, H-40), 5.37 (m,
1H, H-30), 3.78 (s, 3H, N-CH3), 2.78 (t, J = 7.6 Hz, 2H, H-10), 2.44 (m,
2H, H-20), 1.99 (m, 2H, H-50), 1.21–1.31 (m, 14H, H-60-120), 0.86 (t,
J = 6.8 Hz, 3H, H-130). 13C NMR d 177.7 (C4), 154.1 (C2), 141.9
(C8a), 132.5 (C40), 132.1 (C70), 126.7 (C5), 126.4 (C4a), 126.2 (C30),
123.4 (C6), 115.3 (C8), 111.3 (C3), 34.7 (C10), 34.2 (N-CH3), 31.9
(C110), 29.5, 29.5, 29.4, 29.3, 29.3, 27.4 (C50), 26.3 (C20), 22.6 (C120),
14.1 (C130). ESI-MS m/z (rel. int.): [M+H]+ 340 (100). ESI-HRMS (+)
found 340.26285 for C23H34NO [M+H]+, calcd 340.26349.
C
22H32NO [M+H]+, calcd 326.24784.
3.2.7.7. 1-Methyl-2-[(Z)-50-undecenyl]-4(1H)-quinolone (8g).
Starting from 7-tridecen-2-one (7g) (1.5 g, 7.7 mmol) in THF
(25 mL), LDA (4.3 mL, 7.7 mmol) and N-methyl isatoic anhydride
(1.03 g, 5.8 mmol) in THF (20 mL). Compound 8g was formed as a
yellow oil (0.96 g, 40%).14 IR (neat, cmꢀ1): 3427, 2927, 2855,
1635, 1595, 1466, 774. 1H NMR d 8.39 (d, J = 8.5 Hz, 1H, H-5),
7.61 (t, J = 7.6 Hz, 1H, H-7), 7.45 (d, J = 8.5 Hz, 1H, H-8), 7.31 (t,
J = 7.6 Hz, 1H, H-6), 6.20 (s, 1H, H-3), 5.38 (m, 1H, H-60), 5.31
3.2.7.11. 1-Methyl-2-[(Z)-90-octadecenyl]-4(1H)-quinolone (8k).
Starting from 11-eicosen-2-one (7k) (1.5 g, 5.1 mmol) in THF
(25 mL), LDA (2.8 mL, 5.1 mmol) and N-methyl isatoic anhydride

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A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
(0.68 g, 3.8 mmol) in THF (15 mL). Compound 8k was formed as
yellow oil (0.84 g, 40%). IR (neat, cmꢀ1): 3432, 2924, 2853, 1636,
1598, 1467, 761. 1H NMR d 8.40 (d, J = 8.8 Hz, 1H, H-5), 7.61 (t,
J = 8.0 Hz, 1H, H-7), 7.45 (d, J = 8.0 Hz, 1H, H-8), 7.32 (t, J = 7.6 Hz,
1H, H-6), 6.19 (s, 1H, H-3), 5.28–5.37 (m, 2H, H-90,100), 3.68 (s,
3H, N-CH3), 2.65 (t, J = 7.6 Hz, 2H, H-10), 2.00 (m, 4H, H-80,110),
1.63 (quint, J = 7.3 Hz, 2H, H-20), 1.41 (m, 2H, H-30), 1.22–1.35 (m,
20H, H-40-70, 120-170), 0.85 (t, J = 6.7 Hz, 3H, H-180). 13C NMR d
177.6 (C4), 154.7 (C2), 141.8 (C8a), 131.9 (C7), 129.9 (C100),
129.6 (C90), 126.5 (C5), 126.4 (C4a), 123.2 (C6), 115.3 (C8), 110.9
(C3), 34.6 (C10), 34.0 (N-CH3), 31.8 (C160), 29.7, 29.7, 29.4, 29.3,
29.2, 29.2, 29.2, 29.2, 29.1 (C30), 28.4 (C20), 27.1 (C80), 27.1 (C110),
22.6 (C170), 14.0 (C180). ESI-MS m/z (rel. int.): [M+H]+ 410 (100).
ESI-HRMS (+) found 410.34125 for C28H44NO [M+H]+, calcd
410.34174.
(C2), 141.9 (8a), 131.9 (C7), 130.0 (C90), 129.5 (C80), 126.5 (C5),
126.3 (C4a), 123.2 (C6), 115.3 (C8), 110.9 (C3), 34.7 (C10), 34.0 (N-
CH3), 31.8 (C150), 29.7, 29.6, 29.4, 29.2, 29.2, 29.2, 29.1, 29.0, 28.5
(C20), 27.2 (C100), 27.1 (C70), 22.6 (C160), 14.0 (C170). ESI-MS m/z
(rel. int.): [M+H]+ 396 (100). ESI-HRMS (+) found 396.32550 for
C
27H42NO [M+H]+, calcd 396.32609.
3.2.7.15. 1-Methyl-2-[(Z)-80,110-heptadecadienyl]-4(1H)-quino-
lone (8‘o’). Starting from 10,13-nonadecadien-2-one (7‘o’)
(0.50 g, 1.8 mmol) in THF (10 mL), LDA (1.0 mL, 1.8 mmol) and
N-methyl isatoic anhydride (0.24 g, 1.4 mmol) in THF (10 mL).
Compound 8‘o’ was formed as a yellow oil (0.31 g, 42%). IR (neat,
cmꢀ1): 3424, 2926, 2854, 1628, 1599, 1468, 759. 1H NMR d 8.40
(dd, J = 1.5, 8.0 Hz, 1H, H-5), 7.62 (dt, J = 1.5, 8.0 Hz, 1H, H-7),
7.47 (d, J = 8.0 Hz, 1H, H-8), 7.33 (t, J = 7.6 Hz, 1H, H-6), 6.20 (s,
1H, H-3), 5.27–5-39 (m, 4H, H-80, 90, 110, 120), 3.69 (s, 3H, N-CH3),
2.76 (t, J = 7.6 Hz, 2H, H-100), 2.66 (t, J = 7.6 Hz, 2H, H-10), 2.02
(m, 4H, H-70, 130), 1.64 (quint, J = 7.4 Hz, 2H, H-20), 1.21–1.44 (m,
14H, H-30-60, 140-160), 0.86 (t, J = 6.7 Hz, 3H, H-170). 13C NMR d
177.7 (C4), 154.7 (C2), 141.8 (C8a), 131.9 (C7), 130.1 (C120),
129.8 (C80), 128.1 (C90), 127.8 (C110), 126.5 (C5), 126.4 (C4a),
123.2 (C6), 115.3 (C8), 110.9 (C3), 34.6 (C10), 34.0 (N-CH3), 31.4
(C150), 29.5, 29.2, 29.1, 29.1, 29.0, 28.4 (C20), 27.1 (C70) 27.1
(C130), 25.5 (C100), 22.5 (C160), 13.9 (C170). ESI-MS m/z (rel. int.):
[M+H]+ 394 (100). ESI-HRMS (+) found 394.31033 for C27H40NO
[M+H]+, calcd 394.31044.
3.2.7.12.1-Methyl-2-[(Z)-90-nonadecenyl]-4(1H)-quinolone (8‘l’).
Starting from 11-heneicosen-2-one (7‘l’) (1.3 g, 4.2 mmol) in THF
(20 mL), LDA (2.3 mL, 4.2 mmol) and N-methyl isatoic anhydride
(0.56 g, 3.2 mmol) in THF (15 mL). Compound 8‘l’ was formed as
a yellow oil (0.75 g, 42%). IR (neat, cmꢀ1): 3427, 2924, 2853,
1637, 1597, 1467, 776. 1H NMR d 8.44 (dd, J = 1.4, 8.0 Hz, 1H, H-
5), 7.66 (dt, J = 1.4, 8.0 Hz, 1H, H-7), 7.50 (d, J = 8.0 Hz, 1H, H-8),
7.37 (t, J = 8.0 Hz, 1H, H-6), 6.26 (s, 1H, H-3), 5.30–5.39 (m, 2H,
H-90,100), 3.74 (s, 3H, N-CH3), 2.71 (t, J = 8.0 Hz, 2H, H-10), 2.00
(m, 4H, H-80,110), 1.68 (quint, J = 7.4 Hz, 2H, H-20), 1.41 (m, 2H,
H-30), 1.22–1.38 (m, 22H, H-40-70, H-120-180), 0.87 (t, J = 6.6 Hz,
3H, H-190). 13C NMR d 177.7 (C4), 154.7 (C2), 141.9 (C8a), 132.0
(C7), 130.0 (C100), 129.7 (C90), 126.6 (C5), 126.5 (C4a), 123.2 (C6),
115.3 (C8), 111.1 (C3), 34.7 (C10), 34.1 (N-CH3), 31.9 (C170), 29.7,
29.7, 29.6, 29.5, 29.4, 29.3, 29.3, 29.3, 29.2, 29.2, 28.5 (C20), 27.2
(C110), 27.1 (C80), 22.6 (C180), 14.1 (C190). ESI-MS m/z (rel. int.):
[M+H]+ 424 (100). ESI-HRMS (+) found 424.35715 for C29H46NO
[M+H]+, calcd 424.35740.
3.2.8. General procedure for the synthesis of 1-methyl-2-alkyl-
4(1H)-quinolone (9)
A mixture of 1-methyl-2-alkenyl-4(1H)-quinolone (8) (100 mg)
and 10% Pd/C (10 mg, 10% wt. of the alkaloid) in ethanol (1.0 mL)
was stirred for 24 h with continuous supply of hydrogen gas using
a balloon. The mixture was filtered through Celite and Al2O3 and
concentrated in vacuum to give the corresponding saturated alka-
loid as a white solid.
3.2.7.13. 1-Methyl-2-[(Z)-90-eicosenyl]-4(1H)-quinolone (8m).
Starting from 11-docosen-2-one (7m) (1.0 g, 3.1 mmol) in THF
(20 mL), LDA (1.7 mL, 3.1 mmol) and N-methyl isatoic anhydride
(0.42 g, 2.3 mmol) in THF (15 mL). Compound 8m was formed as
a yellow oil (0.50 g, 37%). IR (neat, cmꢀ1): 3430, 2924, 2853,
1628, 1599, 1468, 759. 1H NMR d 8.44 (dd, J = 1.5, 8.0 Hz, 1H, H-
5), 7.65 (dt, J = 1.5, 8.0 Hz, 1H, H-7), 7.50 (d, J = 8.0 Hz, 1H, H-8),
7.37 (t, J = 8.0 Hz, 1H, H-6), 6.26 (s, 1H, H-3), 5.32–5.36 (m, 2H,
H-90,100), 3.74 (s, 3H, N-CH3), 2.71 (t, J = 8.0 Hz, 2H, H-10), 2.01
(m, 4H, H-80,110), 1.68 (quint, J = 7.5 Hz, 2H, H-20), 1.42 (m, 2H,
H-30), 1.22–1.36 (m, 24H, H-40-70, 120-190), 0.87 (t, J = 6.7 Hz, 3H,
H-200). 13C NMR d 177.7 (C4), 154.8 (C2), 141.9 (8a), 132.0 (C7),
130.0 (C100), 129.7 (C90), 126.7 (C5), 126.5 (C4a), 123.3 (C6),
115.3 (C8), 111.1 (C3), 34.8 (C10), 34.1 (N-CH3), 31.9 (C180), 29.7,
29.7, 29.6, 29.6, 29.5, 29.4, 29.3, 29.3, 29.3, 29.2, 29.2 (C30), 28.5
(C20), 27.2 (C110), 27.1 (C80), 22.7 (C190), 14.1 (C200). ESI-MS m/z
(rel. int.): [M+H]+ 438 (100). ESI-HRMS (+) found 438.37350 for
3.2.8.1.1-Methyl-2-tridecyl-4(1H)-quinolone (9a). A white solid
(95 mg, 95%) was formed from l-methyl-2-(40-tridecenyl)-4(1H)-
quinolone (8a). Mp 68–69 °C. IR (cmꢀ1): 3442, 2918, 2852, 1639,
1596, 1470, 774. 1H NMR d 8.42 (dd, J = 1.5, 8.0 Hz, 1H, H-5), 7.63
(dt, J = 1.5, 8.0 Hz, 1H, H-7), 7.48 (d, J = 8.4 Hz, 1H, H-8), 7.34 (t,
J = 7.6 Hz, 1H, H-6), 6.21 (s, 1H, H-3), 3.71 (s, 3H, N-CH3), 2.68 (t,
J = 7.6 Hz, 2H, H-10), 1.66 (quint, J = 7.3 Hz, 2H, H-20), 1.42 (m, 2H,
H-30), 1.22–1.34 (m, 18H, H-40-120), 0.87 (t, J = 6.7 Hz, 3H, H-
130).13C NMR d 177.7 (C4), 154.7 (C2), 141.9 (C8a), 131.9 (C7),
126.6 (C5), 126.4 (C4a), 123.2 (C6), 115.3 (C8), 111.1 (C3), 34.7
(C10), 34.1 (N-CH3), 31.9 (C110), 29.6, 29.6, 29.5, 29.5, 29.4, 29.3,
29.3, 29.2 (C30), 28.5 (C20), 22.6 (C120), 14.1 (C130). ESI-MS m/z
(rel. int.): [M+H]+ 342 (100). ESI-HRMS (+) found 342.27869 for
C23H36NO [M+H]+, calcd 342.27915.
3.2.8.2. 1-Methyl-2-pentadecyl-4(1H)-quinolone (9b). A white
solid (93 mg, 93%) was formed from 1-methyl-2-(50-pentade-
cenyl)-4(1H)-quinolone (8c). Mp 77–79 °C. .IR (cmꢀ1): 3425, 2918,
2851, 1639, 1596, 1470, 774. 1H NMR d 8.43 (dd, J = 1.5, 8.0 Hz,
1H, H-5), 7.64 (dt, J = 1.5, 8.0 Hz, 1H, H-7), 7.49 (d, J = 8.3 Hz, 1H,
H-8), 7.36 (t, J = 8.3 Hz, 1H, H-6), 6.23 (s, 1H, H-3), 3.73 (s, 3H, N-
CH3), 2.69 (t, J = 7.6 Hz, 2H, H-10), 1.67 (quint, J = 7.3 Hz,, 2H, H-
20), 1.42 (m, 2H, H-30), 1.21–1.35 (m, 22H, H-40-140), 0.87 (t,
J = 6.7 Hz, 3H, H-150). 13C NMR d 177.7 (C4), 154.7 (C2), 141.9
(C8a), 131.9 (C7), 126.6 (C5), 126.5 (C4a), 123.3 (C6), 115.3 (C8),
111.1 (C3), 34.7 (C10), 34.1 (N-CH3), 31.9 (C130), 29.7, 29.6, 29.6,
29.6, 29.6, 29.5, 29.4, 29.3, 29.3, 29.2 (C30), 28.5 (C20), 22.6 (C140),
14.1 (C150). ESI-MS m/z (rel. int.): [M+H]+ 370 (100). ESI-HRMS (+)
found 370.30966 for C25H40NO [M+H]+, calcd 370.31044.
C
30H48NO [M+H]+, calcd 438.37304.
3.2.7.14. 1-Methyl-2-[(Z)-80-heptadecenyl]-4(1H)-quinolone(8n).
Starting from 10-nonadecen-2-one (7n) (2.0 g, 7.1 mmol) in THF
(25 mL), LDA (3.9 mL, 7.1 mmol) and N-methyl isatoic anhydride
(0.95 g, 5.3 mmol) in THF (20 mL). Compound 8n was formed as a
yellow oil (1.2 g, 43%). IR (neat, cmꢀ1): 3442, 2925, 2853, 1626,
1599, 1468, 759. 1H NMR d 8.41 (d, J = 8.0 Hz, 1H, H-5), 7.62 (t,
J = 8.0 Hz, 1H, H-7), 7.47 (d, J = 8.0 Hz, 1H, H-8), 7.33 (t, J = 7.6 Hz,
1H, H-6), 6.18 (s, 1H, H-3), 5.35 (m, 1H, H-90), 5.31 (m, 1H, H-80),
3.70 (s, 3H, N-CH3), 2.66 (t, J = 7.6 Hz, 2H, H-10), 1.99 (m, 4H, H-70,
100), 1.65 (quint, J = 7.3 Hz, 2H, H-20), 1.22–1.42 (m, 20H, H-30-60,
110-160), 0.85 (t, J = 6.6 Hz, 3H, H-170). 13C NMR d 177.7 (C4), 154.7

A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
577
3.2.8.3. 1-Methyl-2-heptadecyl-4(1H)-quinolone (9c). A white
solid (91 mg, 91%) was formed from 1-methyl-2-(80-heptadece-
nyl)-4(1H)-quinolone (8n). Mp 94–96 °C. IR (cmꢀ1): 3435, 2917,
2852, 1639, 1596, 1470, 773. 1H NMR d 8.43 (dd, J = 1.5, 8.0 Hz, 1H,
H-5), 7.64 (dt, J = 1.5, 8.0 Hz, 1H, H-7), 7.48 (d, J = 8.5 Hz, 1H, H-8),
7.35 (t, J = 7.4 Hz, 1H, H-6), 6.21 (s, 1H, H-3), 3.72 (s, 3H, N-CH3),
2.69 (t, J = 7.6 Hz, 2H, H-10), 1.65 (quint, J = 7.4 Hz,, 2H, H-20), 1.42
(m, 2H, H-30), 1.22–1.34 (m, 26H, H-40-160), 0.86 (t, J = 6.7 Hz, 3H,
H-170). 13C NMR d 177.7 (C4), 154.7 (C2), 141.9 (C8a), 131.9 (C7),
126.6 (C5), 126.5 (C4a), 123.2 (C6), 115.3 (C8), 111.1 (C3), 34.7 (C-
10), 34.1 (N-CH3), 31.9 (C150), 29.7, 29.7, 29.6, 29.6, 29.6, 29.5, 29.5,
29.5, 29.4, 29.3, 29.3, 29.2 (C30), 28.5 (C20), 22.6 (C160), 14.1 (C170).
ESI-MS m/z (rel. int.): [M+H]+ 398 (100). ESI-HRMS (+) found
398.34131 for C27H44NO [M+H]+, calcd 398.34174.
1H, H-4), 6.03 (bd, J = 16.1 Hz, 1H, H-3), 2.20 (s, 3H, H-1), 2.18
(m, 2H, H-5), 1.44 (m, 2H, H-6), 1.22–1.30 (m, 4H, H-7-8), 0.87 (t,
J = 6.7 Hz, 3H, H-9). 13C NMR d 198.7 (C2), 148.5 (C4), 131.4 (C3),
32.3 (C5), 31.8 (C7), 28.0 (C6), 26.8 (C1), 22.6 (C8), 14.0 (C9).
3.2.12. Synthesis of 1-methyl-2-[(E)-1-alkenyl]-4(1H)-
quinolones (14)
The synthesis was carried out as previously mentioned proce-
dure for the synthesis of the alkaloids (8).
3.2.12.1. 1-Methyl-2-[(E)-10-undecenyl]-4(1H)-quinolone (14a)
Starting from (E)-3-tridecen-2-one (13a) (1.8 g, 9.2 mmol) in THF
(25 mL), LDA (5.1 mL, 9.2 mmol) and N-methyl isatoic anhydride
(1.2 g, 6.9 mmol) in THF (20 mL). Compound 14a was obtained as
a light yellow oil (1.3 g, 45%). IR (neat, cmꢀ1): 3422, 2922, 2853,
1626, 1596, 1468, 762. 1H NMR d 8.41 (d, J = 8.0 Hz, 1H, H-5),
7.63 (t, J = 7.8 Hz, 1H, H-7), 7.45 (d, J = 8.0 Hz, 1H, H-8), 7.33 (t,
J = 7.8 Hz, 1H, H-6), 6.39 (d, J = 15.7 Hz, 1H, H-10), 6.36 (s, 1H, H-
3), 6.32 (dt, J = 15.7, 6.7 Hz, 1H, H-20), 3.72 (s, 3H, N-CH3), 2.25
(m, 2H, H-30), 1.49 (m, 2H, H-40), 1.22–1.37 (m, 12H. H-50-100),
0.87 (t, J = 6.7 Hz, 3H, H-110). 13C NMR d 177.8 (C4), 152.3 (C2),
141.6 (C20), 141.4 (C8a), 132.0 (C7), 126.7 (C4a), 126.5 (C5), 123.9
(C10), 123.2 (C6), 115.4 (C8), 109.6 (C3), 35.4 (N-CH3), 33.1 (C30),
31.8 (C90), 29.4, 29.4, 29.3, 29.1, 28.6 (C40), 22.8 (C100), 14.1
(C110). ESI-MS m/z (rel. int.): [M+H]+ 312 (100). ESI-HRMS (+) found
312.23154 for C21H30NO [M+H]+, calcd 312.23220.
3.2.9. Synthesis of phosphonium salt (11)
A mixture of chloroacetone (10) (20.0 g, 0.22 mol, 1 equiv) and
triphenylphosphine (56.7 g, 0.22 mol, 1 equiv) in CH3CN (200 mL)
was refluxed for 24 h under argon. The solution was cooled at room
temperature and filtered and dried to give acetylmethylenetriphe-
nyl phosphonium chloride as a white precipitate (69.0 g, 88%). 1H
NMR d 7.47–7.83 (m, 15H, 3Ph), 6.07 (bd, J = 11.3 Hz, 2H, H-3),
2.24 (s, 3H, H-1).
3.2.10. Synthesis of methylcarbonylmethylenephosphorane
(12)
To a solution of acetylmethylenetriphenylphosphonium chlo-
ride (11) (69.0 g, 0.2 mol) in water (1.5 L) was added 1 N NaOH
solution (ꢂ170 mL) dropwise with stirring until the pH became
7–8. The resulting precipitate was filtered and dried to give (12)
as a white solid (61.0 g, 96%). 1H NMR d 7.41–7.69 (m, 15H, 3Ph),
3.70 (bd, J = 26.8 Hz, 1H, H-3), 2.09 (s, 3H, H-1). 13C NMR d 190.8
(C2), 128.9–133.0 (C-Ph), 51.5 (C3), 28.4 (C1).
3.2.12.2.
1-Methyl-2-[(E)-10-octenyl]-4(1H)-quinolone (14b)
Starting from (E)-3-decen-2-one (13b) (1.5 g, 9.7 mmol) in THF
(25 mL), LDA (5.4 mL, 9.7 mmol) and N-methyl isatoic anhydride
(1.3 g, 7.3 mmol) in THF (20 mL). Compound 14b was obtained as
yellow oil (1.1 g, 42%). IR (neat, cmꢀ1): 3432, 2927, 2855, 1620,
1596, 1468, 760. 1H NMR d 8.43 (d, J = 8.0 Hz, 1H, H-5), 7.65 (t,
J = 7.6 Hz, 1H, H-7), 7.47 (d, J = 8.0 Hz, 1H, H-8), 7.35 (t, J = 7.6 Hz,
1H, H-6), 6.42 (d, J = 15.3 Hz, 1H, H-10), 6.39 (s, 1H, H-3), 6.34 (dt,
J = 15.3, 6.3 Hz, 1H, H-20), 3.76 (s, 3H, N-CH3), 2.27 (m, 2H, H-30),
1.50 (m, 2H, H-40), 1.27–1.38 (m, 6H, H-50-70), 0.89 (t, J = 6.7 Hz,
3.2.11. General procedure for the synthesis of unsaturated
ketones (13)
A mixture of methylcarbonylmethylenephosphorane (12) (1
equiv) and aldehyde (0.75 equiv) in THF (150 mL) was refluxed
for 48 h in argon. The resulting solution was allowed to cool to
room temperature, concentrated in vacuo and chromatographed
on silica gel (cyclohexane/ethyl aetate 9:1) to afford the corre-
sponding unsaturated ketone (13).
13
3H, H-80). C NMR d 177.8 (C4), 152.4 (C2), 141.8 (C20), 141.5
(C8a), 132.1 (C7), 126.7 (C4a), 126.6 (C5), 123.9 (C10), 123.3 (C6),
115.4 (C8), 109.6 (C3), 35.4 (N-CH3), 33.1 (C30), 31.6 (C60), 28.8
(C50), 28.6 (C40), 22.6 (C70), 14.0 (C80). ESI-MS m/z (rel. int.):
[M+H]+ 270 (100). ESI-HRMS (+) found 270.18546 for C18H24NO
[M+H]+, calcd 270.18527.
3.2.11.1. (E)-3-Tridecen-2-one (13a). Starting from methylcar-
bonylmethylenephosphorane (12) (5.0 g, 15.7 mmol) and decanal
(1.8 g, 11.8 mmol) in THF (150 mL). Compound 13a was formed
as a colourless oil (1.8 g, 59%). 1H NMR d 6.76 (dt, J = 16.1, 6.7 Hz,
1H, H-4), 6.03 (bd, J = 16.1 Hz, 1H, H-3), 2.18 (s, 3H, H-1), 2.16
(m, 2H, H-5), 1.43 (m, 2H, H-6), 1.21–1.29 (m, 12H, H-7-12), 0.84
(t, J = 6.7 Hz, 3H, H-13). 13C NMR d 198.5 (C2), 148.4 (C4), 131.2
(C3), 32.4 (C5), 31.8 (C11), 29.4, 29.3, 29.2, 29.1, 28.0, 26.7 (C1),
22.6 (C12), 14.0 (C13).
3.2.12.3. 1-Methyl-2-[(E)-10-heptenyl]-4(1H)-quinolone (14c)
Starting from (E)-3-nonen-2-one (13c) (1.9 g, 13.6 mmol) in THF
(30 mL), LDA (7.6 mL, 13.6 mmol) and N-methyl isatoic anhydride
(1.8 g, 10.2 mmol). Compound 14c was formed as yellow oil
(1.3 g, 38%). IR (neat, cmꢀ1): 3423, 2927, 2856, 1622, 1596, 1469,
759. 1H NMR d 8.43 (dd, J = 1.6, 8.2 Hz, 1H, H-5), 7.66 (dt, J = 1.6,
6.8 Hz, 1H, H-7), 7.48 (dd, J = 1.6, 8.4 Hz, 1H, H-8), 7.37 (dt,
J = 1.6, 6.7 Hz, 1H, H-6), 6.43 (d, J = 15.2 Hz, 1H, H-10), 6.42 (s, 1H,
H-3), 6.37 (dt, J = 15.2, 6.4 Hz, 1H, H-20), 3.76 (s, 3H, N-CH3), 2.28
(m, 2H, H-30), 1.51 (m, 2H, H-40), 1.34 (m, 4H, H-50,60), 0.92 (t,
J = 6.8 Hz, 3H, H-70). 13C NMR d 177.9 (C4), 152.3 (C2), 141.6
(C20), 141.4 (C8a), 132.1 (C7), 126.6 (C4a), 126.4 (C5), 123.9 (C10),
123.2 (C6), 115.4 (C8), 109.6 (C3), 35.4 (N-CH3), 33.0 (C30), 31.3
(C50), 28.2 (C40), 22.4 (C60), 13.9 (C70). ESI-MS m/z (rel. int.):
[M+H]+ 256 (100). ESI-HRMS (+) found 256.16901 for C17H22NO
[M+H]+, calcd 256.16959.
3.2.11.2. (E)-3-Decen-2-one (13b). Starting from methylcarbon-
ylmethylenephosphorane (12) (5.0 g, 15.7 mmol) and heptanal
(1.3 g, 11.8 mmol) in THF (150 mL). Compound 13b was obtained
as a colourless oil (1.9 g, 79%). 1H NMR d 6.76 (dt, J = 16.1, 6.7 Hz,
1H, H-4), 6.02 (bd, J = 16.1 Hz, 1H, H-3), 2.18 (s, 3H, H-1), 2.16
(m, 2H, H-5), 1.43 (m, 2H, H-6), 1.21–1.28 (m, 6H, H-7-9), 0.85 (t,
J = 6.7 Hz, 3H, H-10). 13C NMR d 198.5 (C2), 148.4 (C4), 131.2
(C3), 32.3 (C5), 31.8 (C8), 29.2, 29.0, 26.8 (C1), 22.6 (C9), 14.0 (C10).
3.2.13. Synthesis of 2-(triphenylphosphoranylidene)-
acetaldehyde (16)
A mixture of 50% aqueous solution of chloroacetaldehyde (15)
(15.7 g, 0.2 mol) and CHCl3 (375 mL) was refluxed using a Dean–
Stark trap at 55 °C. Triphenylphosphine (54.4 g, 0.2 mol) was
3.2.11.3. (E)-3-Nonen-2-one (13c). Starting from methylcarbon-
ylmethylenephosphorane (12) (5.0 g, 15.7 mmol) and hexanal
(1.7 g, 11.8 mmol) in THF (150 mL). Compound 13c was formed
as a colourless oil (1.8 g, 82%). 1H NMR d 6.77 (dt, J = 16.1, 6.7 Hz,

578
A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
added to this solution and refluxed for 24 h. The resulting red solu-
tion was cooled to room temprature, filtered and treated with
water (200 mL). After removing the organic layer, activated char-
coal was added to the aqueous phase and stirred for 45 min. The
resulting brownish solution was filtered and treated with 1 N
NaOH solution as described for compound 12 to give 16 (34.0 g,
53%) as a brown solid.
33.0 (C7), 31.8 (C15), 29.5, 29.5, 29.5, 29.3, 29.2, 29.1, 28.6 (C8),
27.0 (C1), 22.6 (C16), 14.0 (C17).
3.2.16. Synthesis of 1-methyl 2-[(E,E)-10,30-alkadienyl]-4(1H)-
quinolones (19)
The synthesis was carried out as previously mentioned proce-
dure for the synthesis of the alkaloids (8).
3.2.16.1. 1-Methyl-2-[(E,E)-10,30-tetradecadienyl]-4(1H)-quino-
lone (19a). Starting from (E,E)-3,5-hexadecadien-2-one (18a)
(0.80 g, 3.4 mmol) in THF (20 mL), LDA (1.9 mL, 3.4 mmol) and N-
methyl isatoic anhydride (20) (0.45 g, 2.5 mmol) in THF (10 mL).
Compound 19a was obtained as a yellow oil (0.45 g, 38%). IR (neat,
cmꢀ1): 3396, 2925, 1619, 1595, 1467, 758. 1H NMR d 8.45 (dd,
J = 1.4, 8.0 Hz, 1H, H-5), 7.66 (dt, J = 1.4, 8.0 Hz, 1H, H-7), 7.49 (d,
J = 8.6 Hz, 1H, H-8), 7.37 (t, J = 7.6 Hz, 1H, H-6), 6.83 (dd, J = 15.0,
15.0 Hz, 1H, H-20), 6.48 (s, 1H, H-3), 6.44 (d, J = 15.0 Hz, 1H, H-10),
6.25 (dd, J = 15.0, 15.0 Hz, 1H, H-30), 6.06 (m, 1H, H-40), 3.77 (s
3H, N-CH3), 2.18 (m, 2H, H-50), 1.42 (m, 2H, H-60), 1.18–1.36 (m,
14H, H-70-130), 0.88 (t, J = 6.5 Hz, 3H, H-140). 13C NMR d 177.7
(C4), 152.2 (C2), 142.0 (C40), 141.5 (C8a), 139.0 (C20), 132.2 (C7),
128.9 (C30), 126.6 (C4a), 126.5 (C5), 123.4 (C6), 121.9 (C10), 115.5
(C8), 108.8 (C3), 35.5 (N-CH3), 32.9 (C50), 31.8 (C120), 29.6, 29.5,
29.4, 29.3, 29.2, 28.8 (C60), 22.6 (C130), 14.0 (C140). ESI-MS m/z
(rel. int.): [M+H]+ 352 (100). ESI-HRMS (+) found 352.26257 for
3.2.14. General procedure for the synthesis of unsaturated
aldehydes (17)
A mixture of 2-(triphenylphosphoranylidene)acetaldehyde (16)
(1.3 equiv) and aldehyde (1 equiv) in CH3CN (300 mL) was refluxed
for 24 h under argon. The resulting solution was cooled to room
temprature, concentrated and chromatographed on silica gel elut-
ing with cyclohexane/ethyl acetate (1:1) to give the corresponding
a, b-unsaturated aldehyde.
3.2.14.1. (E)-2-Tridecenal (17a). Starting from 2-(triphenylphos-
phoranylidene)acetaldehyde (16) (15.0 g, 49.3 mmol) and undeca-
nal (6.5 g, 38 mmol). Compound 17a was obtained as a colourless
oil (3.1 g, 42%). 1H NMR d 9.48 (d, J = 8.1 Hz, 1H, H-1), 6.83 (dt,
J = 6.7, 15.7 Hz, 1H, H-3), 6.10 (dd, J = 8.1, 15.7 Hz, 1H, H-2), 2.32
(dq, J = 1.2, 6.7 Hz, 2H, H-4), 1.48 (quint, J = 7.3 Hz, 2H, H-5),
1.22–1.34 (m, 14H, H-6-12), 0.86 (t, J = 6.7 Hz, 3H, H-13).13
NMR d 194.0, (C1), 158.9 (C3), 132.9 (C2), 32.7, 31.8 (C11), 29.5,
29.4, 29.3, 29.2, 29.1, 27.8, 22.6 (C12), 14.0 (C13).
C
C
24H34NO [M+H]+, calcd 352.26349.
3.2.14.2. (E)-2-Tetradecenal (17b). Starting from 2-(triphenyl-
phosphoranylidene)acetaldehyde (16) (15.0 g, 49.3 mmol) and
dodecanal (7.0 g, 38 mmol). Compound 17b was formed as a col-
ourless oil (3.5 g, 44%). 1H NMR d 9.49 (d, J = 8.0 Hz, 1H, H-1),
6.83 (dt, J = 6.7, 15.8 Hz, 1H, H-3), 6.10 (dd, J = 8.0, 15.8 Hz, 1H,
H-2), 2.32 (dq, J = 1.2, 6.7 Hz, 2H, H-4), 1.48 (quint, J = 7.3 Hz, 2H,
H-5), 1.21–1.36 (m, 16H, H-6-13), 0.86 (t, J = 6.7 Hz, 3H, H-14).
13C NMR d 194.0 (C1), 158.9 (C3), 132.9 (C2), 32.7, 31.9 (C12),
29.6, 29.4, 29.3, 29.3, 29.3, 29.1, 27.8, 22.6 (C13), 14.0 (C14).
3.2.16.2. 1-Methyl-2-[(E,E)-10,30-pentadecadienyl]-4(1H)-quino-
lone (19b). Starting from (E,E)-3,5-heptadecadien-2-one (18b)
(0.6 g, 2.4 mmol) in THF (20 mL), LDA (1.3 mL, 2.4 mmol) and
N-methyl isatoic anhydride (20) (0.32 g, 1.8 mmol) in THF
(10 mL). Compound 19b was formed as yellow oil (0.38 g,
43%). IR (neat, cmꢀ1): 3420, 2923, 1626, 1596, 1469, 760. 1H
NMR
d 8.44 (dd, J = 1.5, 8.0 Hz, 1H, H-5), 7.66 (dt, J = 1.5,
8.0 Hz, 1H, H-7), 7.49 (d, J = 8.6 Hz, 1H, H-8), 7.38 (t,
J = 7.5 Hz, 1H, H-6), 6.82 (dd, J = 15.0, 15.1 Hz, 1H, H-20), 6.46
(d, J = 15.1 Hz, 1H, H-10), 6.42 (s, 1H, H-3), 6.24 (dd, J, = 15.0,
15.1 Hz, 1H, H-30), 6.04 (m, 1H, H-40), 3.68 (s, 3H, N-CH3),
2.18 (m, 2H, H-50), 1.40 (m, 2H, H-60), 1.21–1.34 (m, 16H, H-
70-140), 0.87 (t, J = 6.7 Hz, 3H, H-150). 13C NMR d 177.7 (C4),
152.1 (C2), 141.8 (C40), 141.5 (C8a), 138.8 (C20), 132.1 (C7),
128.9 (C30), 126.6 (C4a), 126.5 (C5), 123.3 (C6), 122.0 (C10),
115.4 (C8), 108.7 (C3), 35.4 (N-CH3), 32.9 (C50), 31.8 (C130),
29.6, 29.5, 29.5, 29.4, 29.2, 29.2, 28.8 (C-60), 22.6 (C140), 14.0
(C150). ESI-MS m/z (rel. int.): [M+H]+ 366 (100). ESI-HRMS (+)
found 366.27850 for C25H36NO [M+H]+, calcd 366.27914.
3.2.15. General procedure for the synthesis of
unsaturated ketones (18)
a,b,c,d-
This reaction was conducted using the ylide (12) (1 equiv) and
, b-unsaturated aldehyde (17) (0.75 equiv) as previously de-
a
scribed procedure for unsaturated ketone.
3.2.15.1. (E,E)-3,5-Hexadecadien-2-one (18a). Starting from
methylcarbonylmethylenephosphorane (12) (2.4 g, 7.6 mmol) and
2-tridecenal (17a) (1.1 g, 5.6 mmol) in THF (50 mL). Compound
18a was formed as a yellow oil (0.84 g, 64%).1H NMR d 7.09 (dd,
J = 10.1, 15.8, Hz, 1H, H-4), 6.17 (dd, J = 10.1, 15.4, Hz, 1H, H-5),
6.12 (ddd, J = 5.4, 9.0, 15.4 Hz, 1H, H-6), 6.04 (d, J = 15.4 Hz, 1H,
H-3), 2.25 (s, 3H, H-1), 2.15 (m, 2H, H-7), 1.41 (m, 2H, H-8),
1.23–1.32 (m, 14H, H-9-15), 0.87 (t, J = 6.7 Hz, 3H, H-16). 13C
NMR d 198.7 (C2), 145.8 (C5), 144.0 (C4), 128.7 (C6), 128.6 (C3),
33.1 (C7), 31.8 (C14) 29.4, 29.4, 29.3, 29.2, 29.1, 28.6 (C8), 27.0
(C1), 22.6 (C15), 14.0 (C16).
3.3. Evaluation of the antimycobacterial activity
The animycobacterial properties of the synthesized compounds
were determined as previously described.15 The test compounds
initially dissolved in DMSO were diluted in cation adjusted Muel-
ler–Hinton broth (MHB) to give a concentration of 256 mg/L. One
hundred and twenty five microlitre of each test solution were added
to each well containing 125 lL of MHB to achieve a starting concen-
3.2.15.2. (E,E)-3,5-Heptadecdien-2-one (18b). Starting from
methylcarbonylmethylenephosphorane (12) (2.4 g, 7.6 mmol) and
2-tetradecenal (17b) (1.2 g, 5.6 mmol) in THF (50 mL). Compound
18b was obtained as a yellow oil (0.82 g, 59%).1H NMR d 7.17
(dd, J = 10.0, 15.8 Hz, 1H, H-4), 6.26 (dd, J = 10.0, 15.4 Hz, 1H, H-
5), 6.23 (ddd, J = 5.4, 10.0, 15.4 Hz, 1H, H-6), 6.06 (d, J = 15.8 Hz,
1H, H-3), 2.28 (s, 3H, H-1), 2.21 (m, 2H, H-7), 1.46 (m, 2H, H-8),
1.24–1.36 (m, 16H, H-9-16), 0.89 (t, J = 6.9 Hz, 3H, H-17). 13C
NMR d 198.5 (C2), 145.7 (C5), 143.9 (C4), 128.7 (C6), 128.6 (C3),
tration of 128 mg/L. A twofold serial dilution of test solutions was
prepared to get final concentrations ranging from 128–0.25 mg/L.
Mycobacterial strains were cultivated on Columbia blood agar sup-
plemented with 7% defibrinated horse blood. Bacterial suspension
with a turbidity of 0.5 on the MacFarland scale was made in 0.9%
NaCl solution and diluted to give a final inoculum’s density of 5 x
105 cfu/mL. After addition of 125
lL of bacterial inocula into all
wells, except the blank, the plates were incubated at 37 0C for
72 h. The lowest assay concentration of the test compounds that

A. A. Wube et al. / Bioorg. Med. Chem. 19 (2011) 567–579
579
produce complete inhibition of the macroscopic growth (MIC) were
4. Conclusion
detected by addition of 20 lL methanolic solution of tetrazolium
redox dye (MTT, 3.5 mg/mL) followed by incubation at 35 0C for
20 min. Tests were carried out three times in duplicate and
ethambutol, isoniazid and ciprofloxacin were used as positive
controls.
To optimize the antimycobacterial activity of evocarpine ana-
logues, we synthesized a series of 23 new 1-methyl-2-alkenyl-
4(1H)-quinolones 8a–‘o’, 9a–c, 14a–c and 19a–b with seven to
twenty carbons containing aliphatic side chains having one or
two double bonds at various positions. Compounds with monoun-
saturated side chains of 11 – 13 carbons showed the highest activ-
ity with favourable low cytotoxicity. Our findings seem promising
and have provided the bases for further structural modifications on
the aliphatic side chain. Further synthesis of structurally related
compounds is currently in progress.
3.4. Cytotoxicity assay
Cytotoxicity was assessed using the human diploid embryonic
lung cell line MRC-5 as previously described16 with some modifica-
tions. Growth inhibitory effect of respective samples on cells was
measured by XTT proliferation assay (XTT Cell Proliferation Kit II,
Roche Diagnostics, Mannheim, Germany). Fresh stock solutions of
each compound were prepared in ethanol and afterwards diluted
with buffer or water, respectively. Cells were seeded at a concen-
tration of 5 ꢁ 104 cells/well and cultivated for 24 hours in 96-well
Acknowledgement
This work has been financially supported by the Austrian Sci-
ence Fund (FWF), project No. P21152-B18, which is gratefully
acknowledged.
culture plates. Marginal wells were filled with 100 lL of pure med-
ium (MEM) in order to minimize effects of evaporation. Besides,
wells filled with medium were required to determine the back-
ground absorbance caused by non-metabolized XTT. A row of wells
containing cells treated with ethanol (0.1%) served as solvent con-
trol. The other rows of wells containing cells were supplemented
with different concentrations of the respective compound. Each
concentration was tested in triplicate in at least two independent
plates containing different batches of cells (n = 6).
After incubation for 72 h with respective compounds at 37 °C,
5% CO2 in humidified atmosphere, XTT reagent was freshly pre-
pared and added to each well as specified by the manufacturer:
XTT-labelling reagent and electron-coupling reagent were mixed
References and notes
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in a ratio of 50:1 and 50 lL of this mixture were added to each well
of the 96-well plate. The plates were incubated for additional 4 h at
37 °C, 5% CO2 in humidified atmosphere and read out afterwards.
Quantification of cell viability was performed with a microplate
reader at 490 nm with a reference wavelength of 655 nm. Absor-
bance values at both wavelengths were subtracted. The cytotoxic
effect of the treatment was determined as percentage of viability
compared to cells treated with solvent solely.
12. Wube, A. A.; Bucar, F.; Gibbons, S.; Asres, K. Phytochemistry 2005, 66, 2309.
13. Chuang, Wu-Chang; Cheng, Chang-Ming; Chang, Hsien-Chang; Chen, Yuh-Pan;
Sheu, Shuenn-Jyi Planta Med. 1999, 65, 567.
14. Tang, Yuan-Quing; Feng, Xiao-Zhang; Huang, L. Phytochemistry 1996, 43, 719.
15. Schinkovitz, A.; Gibbons, S.; Stavri, M.; Cocksedge, M. J.; Bucar, F. Planta Med.
2003, 69, 369.
Absorbance ðsampleÞ490—655 nm
16. Konkimalla, V. B.; Blunder, M.; Korn, B.; Soomro, S. A.; Jansen, H.; Chang, W.;
Posner, G. H.; Bauer, R.; Efferth, T. Nitric Oxide 2008, 19, 184.
Cell viability ð%Þ ¼
ꢁ 100
Absorbance ðcontrolÞ490—655 nm