Antifungal quinazolinones from marine-derived Bacillus cereus and their preparation

Article abstract of DOI:10.1016/j.bmcl.2011.05.002

Two new quinazolinones alkaloids, R(+)-2-(heptan-3-yl)quinazolin-4(3H)-one (1) and (2R,3′R)+(2S,3′R)-2-(heptan-3-yl)-2,3-dihydroquinazolin- 4(1H)-one (2) (a pair of epimers), as well as seven known analogues, 2-methylquinazolin-4(3H)-one (3), 2-benzylquinazolin-4(3H)-one (4), cyclo-(Pro-Ile), cyclo-(Pro-Leu), cyclo-(Pro-Val), cyclo-(Pro-Phe), and cyclo-(Tyr-Pro) were isolated from the n-butyl alcohol extract of the marine-derived bacterium Bacillus cereus 041381. The new compounds were identified by spectroscopic analysis and chemical synthesis. Four optical isomers 5-8 were also synthesized. Compounds 1-8 all showed moderate antifungal activity against Candida albicans with MIC values of 1.3-15.6 μM. Compound 5 exhibits the most powerful antifungal activity, which may reveal that S-configuration and 2,3-double bond were necessary for antifungal activity, and the racemization at C-2 and C-3′ reduced the antifungal activity.

Full text of DOI:10.1016/j.bmcl.2011.05.002

Bioorganic & Medicinal Chemistry Letters 21 (2011) 4005–4007
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Antifungal quinazolinones from marine-derived Bacillus cereus
and their preparation
Zhihong Xu a, Yapeng Zhang a, Haichao Fu c, Huimin Zhong c, Kui Hong b, , Weiming Zhu a,
⇑
⇑
a Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, People’s Republic of China
b College of Pharmacy, Wuhan University, Wuhan 430071, People’s Republic of China
c College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Two new quinazolinones alkaloids, R(+)-2-(heptan-3-yl)quinazolin-4(3H)-one (1) and (2R,30R)+(2S,30R)-2-
(heptan-3-yl)-2,3-dihydroquinazolin-4(1H)-one (2) (a pair of epimers), as well as seven known analogues,
2-methylquinazolin-4(3H)-one (3), 2-benzylquinazolin-4(3H)-one (4), cyclo-(Pro–Ile), cyclo-(Pro–Leu),
cyclo-(Pro–Val), cyclo-(Pro–Phe), and cyclo-(Tyr–Pro) were isolated from the n-butyl alcohol extract of
the marine-derived bacterium Bacillus cereus 041381. The new compounds were identified by spectro-
scopic analysis and chemical synthesis. Four optical isomers 5ꢀ8 were also synthesized. Compounds
Article history:
Received 29 January 2011
Revised 11 April 2011
Accepted 2 May 2011
Available online 8 May 2011
Keywords:
1ꢀ8 all showed moderate antifungal activity against Candida albicans with MIC values of 1.3ꢀ15.6
lM.
New quinazolinones alkaloids
Antifungal activity
Microbial metabolites
Bacillus cereus
Compound 5 exhibits the most powerful antifungal activity, which may reveal that S-configuration and
2,3-double bond were necessary for antifungal activity, and the racemization at C-2 and C-30 reduced
the antifungal activity.
Ó 2011 Elsevier Ltd. All rights reserved.
Chemical synthesis
Fungi are important opportunistic pathogens of humans, which
could cause superficial or invasive infections. The majority of fun-
gal pathogens include Cryptococcus neoformans and species of Can-
dida and Aspergillus, with Candida albicans the most notable
example of an opportunistic pathogen, causing both superficial
infections and invasive fungal disease in immunocompromised
individuals.1 Unfortunately, the emergence of drug resistance in
pathogenic fungi is all but inevitable.2 Therefore, it is necessary
to find new and efficacious drugs to solve these problems. In our
continuing research on seeking microbial secondary metabolites
with anti-C. albicans activities, a bacteria strain 041381 identified
as Bacillus cereus, was isolated from a sea mud collected in Baima-
jin, Danzhou, Hainan, China. The n-BuOH extract of B. cereus
041381 was found to be active against C. albicans. Chemical inves-
tigation on the secondary metabolites afforded two new quinazoli-
nones alkaloids, R(+)-2-(heptan-3-yl)quinazolin-4(3H)-one (1) and
a mixture of (2R,30R)- and (2S,30R)-2-(heptan-3-yl)-2,3-dihydro-
quinazolin-4(1H)-one (2), along with seven known compounds,
2-methylquinazolin-4(3H)-one (3),3 2-benzylquinazolin-4(3H)-
one (4),3 cyclo-(Pro–Ile),4 cyclo-(Pro–Leu),5 cyclo-(Pro–Val),6 cyclo-
(Pro–Phe),6 and cyclo-(Tyr–Pro).7 Their structures including
absolute configurations were elucidated by spectroscopic analysis
and chemical synthesis. Meanwhile, four optical isomers, S(ꢀ)-2-
(heptan-3-yl)quinazolin-4(3H)-one (5), (2R,30S)+(2S,30S)-2-(hep-
tan-3-yl)-2,3-dihydroquinazolin-4(1H)-one (6), ( )-2-(heptan-3-yl)
quinazolin-4(3H)-one (7), and ( )-2-(heptan-3-yl)-2,3-dihydroqui-
nazolin-4(1H)-one (8), were prepared. These eight quinazolinones
(1ꢀ8) all exhibited antifungal activity against C. albicans with MIC
values of 2.5, 2.5, 15.6, 10.6, 1.3, 5.0, 10.2, 10.1 lM (ketoconazole as
positive control, MIC 0.2
lM), respectively.
O
O
5
3 NH
5
3NH
4a
4a
8a
8a
7
7
1
3'
3'
N
N
H
7'
5'
5'
7'
1
1'
1'
1
5
:
:
R
(+);
(-);
2
6
8
: (2
R
R
,3'
,3'
R
)
+
(2
S
S
,3'
,3'
R
)
S
)
S
: (2
S
)
+
(2
7: ( )
: ( )
O
O
4a
4a
8a
5
5
3NH
3NH
5'
3'
7'
7
7
8a
N
N
1'
1
1
3
4
B. cereus 041381 was cultured under static conditions in a sea-
water based culture medium (4% amidulin and 0.1% yeast powder)
at 28 °C for four days. The n-BuOH extract of the whole fermenta-
tion broth was subjected to extensive chromatography to give the
new compounds 1 and 2 (Supplementary data).
⇑
Corresponding authors. Tel./fax: +86 532 82031268 (W.Z.).
E-mail addresses: kuihong31@gmail.com (K. Hong), weimingzhu@ouc.edu.cn
(W. Zhu).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.05.002

4006
Z. Xu et al. / Bioorg. Med. Chem. Lett. 21 (2011) 4005–4007
Table 1
1H and 13C NMR Data for 1 and 2 (500, 125 MHz, CDCl3, TMS, d ppm)
No
1
2 [(2R,30R)+(2S,30R)]
dC
dH (J in Hz)
dC
dH (J in Hz)
dC
dH (J in Hz)
1
4.09, br s
4.09, br s
2
3
159.0, C
67.3, C
4.96, dd (‘t’ like, 3.7)
5.87, br s
67.3, C
4.96, dd (‘t’ like, 3.7)
5.87, br s
10.3, br s
4
163.2, C
165.5, C
165.4, C
4a
5
6
7
8
8a
10
20
30
40
50
60
70
120.8, C
115.7, C
115.7, C
126.3, CH
126.3, CH
134.7, CH
127.4, CH
149.0, C
12.0, CH3
26.9, CH2
48.5, CH
33.2, CH2
29.6, CH2
22.6, CH2
13.9, CH3
8.28, d (8.0)
7.48, t (7.3)
7.77, t (6.9)
7.73, d (7.6)
128.6, CH
119.1, CH
133.8, CH
114.6, CH
147.8, C
11.9, CH3
22.0, CH2
44.1, CH
28.51, CH2
29.7, CH2
23.01, CH2
14.0, CH3
7.88, d (6.7)
6.84, t (6.8)
7.29, t (7.4)
6.67, d (8.0)
128.6, CH
119.1, CH
133.8, CH
114.6, CH
147.8, C
11.8, CH3
21.9, CH2
44.1, CH2
28.47, CH2
29.6, CH2
22.99, CH2
14.0, CH3
7.88, d (6.7)
6.84, t (6.8)
7.29, t (7.4)
6.67, d (8.0)
0.9, t (7.3)
1.80, m
2.60, m
1.79, m
1.25, m
0.99, t (7.8)
1.40, m; 1.58, m
1.50, m
1.34, m; 1.55, m
1.34, m
0.97, t (7.5)
1.40, m; 1.58, m
1.50, m
1.34, m; 1.55, m
1.34, m
1.32, m
0.85, t (6.8)
1.33, m
0.92, t (6.8)
1.33, m
0.90, t (6.9)
Compound 1 was isolated as a white crystal with ½a D20
ꢁ
+2.1 (c
The absolute configuration of C-30 in 1 was determined by total
synthesis from R(+)- and S(ꢀ)-2-ethylhexanoic acid and the com-
parison of the specific rotation between artificial and natural prod-
ucts. The synthesis work was initiated from the chiral resolution of
( )-2-ethylhexanoic acid by forming diastereomeric salt with R(+)-
1-phenylethanamine.9 R(+)-1-Phenylethanaminium (+)-2-ethyl-
hexanoate was crystallized firstly from petroleum ether, while
R(+)-1-phenylethanaminium (ꢀ)-2-ethylhexanoate was left in the
mother liquor. After acidification by hydrochloric acid, respec-
0.1, acetone).8 Its molecular formula was determined as
C
15H20N2O according to the HRESIMS at m/z 245.1655 [M+H]+
(calcd 245.1654) and NMR data (Table 1). Four aromatic protons
at d 8.28 (1H, d, J = 8.0 Hz, H-5), 7.48 (1H, ‘t’ like, J = 7.3, 7.7 Hz,
H-6), 7.77 (1H, ‘t’ like, J = 7.7, 7.0 Hz, H-7) and 7.73 (1H, d,
J = 7.0 Hz, H-8) revealed the presence of an o-disubstituted ben-
zene nucleus that was further supported by 1H–1H COSY connec-
tions from H-5 to H-8 through H-6 and H-7 (Fig. 1). Besides, the
existence of an amide carbonyl group (d 163.2) and a sp2 quater-
nary carbon (d 159.0) established the nucleus of 1 as quinazolin-
4(3H)-one (Fig. 1).3 The rest atoms were linked as 3-heptanyl that
was deduced by analysis of the upfield 1H and 13C signals and
1H–1H COSY spectra (Fig. 1). The key long-range connections be-
tween H-20 (d 1.80) and H-40 (d 1.79) with the imino carbon (d
159.0) indicated that 3-heptanyl was connected to C-2 of quinazo-
lin-4(3H)-one nucleus. Thus, constitution of 1 was elucidated as 2-
(heptan-3-yl)quinazolin-4(3H)-one.
Mixture 2 was obtained as a white crystal with the molecular
formula C15H22N2O based on the HRESIMS at m/z 247.1819
[M+H]+ (calcd 247.1810), two hydrogen atoms more than that of
compound 1.8 Accordingly, the 1H NMR and 13C NMR spectra of 2
showed resemblance to 1, except that the imino carbon signal at
d 159.0 (C-2) in 1 was replaced by a sp3 methine signal at d 67.3.
In addition, a new NH signal was emerged at d 4.09 and the original
NH signal shifted to upfield (d 5.87). These data supported 2 as the
hydrogenation derivative at C@N double band of 1 that was further
confirmed by the key HMBC correlations from H-1 (d 4.09) to C-4a
(d 115.7) and C-8 (d 114.6), and also by 1H–1H COSY connection be-
tween H-2 (d 4.96) and H-30 (d 1.50). Thus, the constitution of 2
was determined to be 2-(heptan-3-yl)-2,3-dihydroquinazolin-
4(1H)-one. A pair of 13C NMR signals in 3-heptanyl moiety
tively, S(+)-2-ethylhexanoic acid (½a D20
ꢁ
+10.2 (c 2.0, acetone)) and
R(ꢀ)-2-ethylhexanoic acid (½a D20
ꢀ4.4 (c 2.0, acetone)) were recov-
ꢁ
ered with 38% yield (91% ee) and 11% yield (42% ee),10 respectively.
The chemical synthesis of 1 and 2 was outlined in Scheme 1. The
key intermediate, 2-(2-ethylhexanamido)benzamide (9),11 was
prepared from the amidation of o-aminobenzamide with 2-ethyl-
hexanoyl chloride (1a) produced by chloration of 2-ethylhexanoic
acid with oxalyl chloride. Intramolecular condensation of 9 yielded
the target product by reacting with HMDS and I2 in CH2Cl2.12 Using
above method, S(ꢀ)-2-(heptan-3-yl)quinazolin-4(3H)-one (5) (½a D20
ꢁ
ꢀ1.1 (c 1.0, acetone)) and R(+)-2-(heptan-3-yl)quinazolin-4(3H)-
one (½a 2D0
ꢁ
+0.4 (c 1.0, acetone)) were synthesized from S(+)-2-ethyl-
hexanoic acid and R(ꢀ)-2-ethylhexanoic acid, respectively. NMR
and specific rotation comparison between artificial and natural
products revealed that the absolute configuration of 1 was R-.
Therefore, the structure of compound 1 was determined as R(+)-
2-(heptan-3-yl)quinazolin-4(3H)-one.13,14
Reduction of R(+)-2-(heptan-3-yl)quinazolin-4(3H)-one (1) and
S(ꢀ)-2-(heptan-3-yl)quinazolin-4(3H)-one (5) with NaBH4 in HOAc
afforded two pairs of unisolable epimers, (2R,30R)+(2S,30R)-2-
O
CONH2
O
O
7
HO
a
b
5
0
0
3
(C1 ꢂ C7 ) and C-4 (Table 1) suggested 2 as a pair of epimers at
Cl
3'
1
N
5'
7'
C-2 that could not be isolated.
H
1'
1a
9
O
N
O
O
N
O
5
5
NH
NH
c
d
4a
8a
3
3
NH
NH
4a
8a
N
H
7
3'
7
5'
5'
3'
7'
7'
N
H
2
6
: (2R, 3'R)+(2S, 3'R);
: (2R, 3'S)+(2S, 3'S); : (
1'
1'
1
2
1
5
7
: R-(+); : S-(-); : ( )
8
)
1H-1H COSY;
HMBC
Scheme 1. Reagents and conditions: (a) (COCl)2, CH2Cl2, rt; (b) o-aminobenzamide,
Et3N, CH2Cl2, rt; (c) HMDS/I2, CH2Cl2; (d) NaBH4, AcOH, ꢀ10 ꢂ 50 °C.
Figure 1. Key 1H–1H COSY and HMBC correlations of 1 and 2.

Z. Xu et al. / Bioorg. Med. Chem. Lett. 21 (2011) 4005–4007
4007
(heptan-3-yl)-2,3-dihydroquinazolin-4(1H)-one and (2R,30S)+(2S,
30S)-2-(heptan-3-yl)-2,3-dihydroquinazolin-4(1H)-one (6), respec-
tively. The 13C NMR signals of these two pairs of artificial products
(5 mL). The mixture was stirred for another 1 h at rt and concentrated in vacuo.
The obtained residue was dissolved in EtOAc (20 mL) and washed with H2O, 5%
NaHCO3, brine and dried over anhydrous Na2SO4. The concentration was
purified by CC on SiO2 eluting with 4:1 petroleum ether–EtOAc (v/v, 4:1) to
0
0
give the desired 9 as a white crystal (125 mg, 85% yield). mp 152–153 °C; ½a D20
ꢁ
both displayed doublets in 3-heptanyl moiety (C1 –C7 ) and C-4 (Ta-
ble 1). The NMR comparison revealed that the proton signals of 2
were nearly the same to those of synthetic (2R,30R)+(2S,30R)-2-(hep-
tan-3-yl)-2,3-dihydroquinazolin-4(1H)-one and different from
ꢀ1.3 (c 1.0, acetone); 1H NMR (CDCl3, 500 MHz) d: 11.2 (1H, s, H-2), 8.68 (1H, d,
J = 8.4 Hz, H-7), 7.54 (1H, d, J = 8.0 Hz, H-4), 7.49 (1H, t, J = 8.0 Hz, H-5), 7.06
(1H, t, J = 7.7 Hz, H-6), 6.31 (1H, br s, –NH2a), 5.75 (1H, br s, –NH2b), 2.18 (1H,
m, H-30), 1.71 (2H, m, H-20), 1.55ꢂ1.59 (4H, m, H-40, H-50), 1.32 (2H, m, H-60),
0.94 (3H, t, J = 7.5 Hz, H-10), 0.85 (3H, t, J = 6.8 Hz, H-70); ESI-MS m/z 263.2
[M+H]+, 285.1 [M+Na].
those of 6. Therefore, structure of
2 was elucidated as
(2R,30R)+(2S,30R)-2-(heptan-3-yl)-2,3-dihydro-quinazolin-4(1H)-
12. Kshirsagar, U. A.; Mhaske, S. B.; Argade, N. P. Tetrahedron Lett. 2007, 48, 3243.
one.15,16
13. Preparation of R(+)-2-(heptan-3-yl)quinazolin-4(3H)-one (1). To
a stirred
solution of (60 mg, 0.23 mmol) and I2 (175 mg, 0.69 mmol) in CH2Cl2
9
To discuss structure–activity relationship of quinazolinones
and dihydroquinazolinones, two racemic products ( )-2-(hep-
tan-3-yl)quinazolin-4(3H)-one (7) and ( )-2-(heptan-3-yl)-2,
3-dihydroquinazolin-4(1H)-one (8) were also prepared from
( )-2-ethylhexanoic acid by the same procedure.17,18
The antifungal activity of compounds 1ꢀ8 were evaluated by an
agar dilution method.19 Compounds 1ꢀ8 all displayed moderate
growth inhibition on C. albicans, with MIC values of 2.5, 2.5, 15.6,
(10 mL) was added dropwise HMDS (148 mg, 0.92 mmol) at rt and the mixture
was stirred for 12 h. The reaction mixture was diluted with CH2Cl2 (10 mL) and
washed with 5% Na2S2O3 solution, water and brine, and dried over anhydrous
Na2SO4. The concentration was purified by CC on SiO2 eluted with 6:1
petroleum ether–EtOAc to give the synthetic 1 as a white crystal (48 mg, 86%
yield). ½a 2D0
ꢁ
+0.4 (c 1, acetone); NMR data were consistent to the natural.
14. Preparation of S(ꢀ)-2-(heptan-3-yl)quinazolin-4(3H)-one (5). The procedure for
preparation of 1 was followed using S(+)-2-ethylhexanoate (80 mg, 0.56 mmol),
oxalyl chloride (142 mg, 1.12 mmol), o-aminobenzamide (76 mg, 0.56 mmol)
and Et3N (62 mg, 0.62 mmol) to give S(+)-2-(2-ethylhexanamido)benzamide
(115 mg, 80% yiled). mp 148–149 °C; ½a D20
ꢁ
+1.6 (c 1.0, acetone); NMR data was
10.6, 1.3, 5.0, 10.2, and 10.1
lM, respectively (positive control,
M).20 Compound 5 exhibits most powerful
consisitent to 9. S(+)-2-(2-Ethylhexanamido) benzamide (60 mg, 0.23 mmol)
ketoconazole, MIC 0.2
l
reacted with I2 (175 mg, 0.69 mmol) and HMDS (148 mg, 0.92 mmol) in CH2Cl2
antifungal activity, which may reveal that S-configuration and 2,3-
double bond were necessary for antifungal activity, and the race-
mization at C-2 and C-30 reduced the antifungal activity.
to afford compound 5 as a white crystal (47 mg, 84% yield). mp 93–94 °C; ½a D20
ꢁ
ꢀ1.1 (c 1.0, acetone); NMR data was consistent t.
15. Preparation of (2R,30R)+(2S,30R)-2-(heptan-3-yl)-2,3-dihydro- quinazolin-
4(1H)-one (2). To a stirred mixture of R(+)-2-(heptan-3-yl)quinazolin-4(3H)-
one (1) (15 mg, 0.06 mmol) and NaBH4 (23 mg, 0.60 mmol) was added 4 mL
HOAc at ꢀ10 °C and heated to 50 °C for 48 h. The reaction mixture was
quenched with saturated NaHCO3, extracted with EtOAc, dried over Na2SO4.
The concentration was purified by HPLC eluted with MeOH–H2O (v/v 75:25) to
Acknowledgments
This work was supported by grants from National Basic Research
Program of China (No. 2010CB833800), from the National Natural
Science Foundation of China (No. 30973680 & 30670219), from
Special Fund for Marine Scientific Research in the Public Interest
of China (No. 2010418022-3), from PCSIRT (No. IRT0944), and from
Open Research Fund Program of Key Laboratory of Marine Drugs of
MEC (No. 200607).
give the synthetic 2 as a white crystal (7.4 mg, 50%). ½a D20
ꢁ
+1.3 (c 1, acetone); 1
H
NMR (CDCl3, 600 MHz) d: 7.88 (2H, d, J = 7.7 Hz, H-5), 7.30 (2H, t, J = 7.3 Hz, H-
7), 6.84 (2H, t, J = 7.3 Hz, H-6), 6.66 (2H, d, J = 7.7 Hz, H-8), 5.71 (2H, br s, H-3),
4.96 (2H, ‘t’ like, J = 3.7 Hz, H-2), 4.06 (2H, br s, H-1), 1.58 (2H, m, H-20a), 1.55
(2H, m, H-40a), 1.50 (2H, m, H-30), 1.40 (2H, m, H-20b), 1.34 (6H, m, H-40b/H-50),
1.33 (4H, m, H-60), 0.98 (3H, t, J = 7.8 Hz, H-10)/0.96 (3H, t, J = 7.8 Hz, H-10), 0.92
(3H, t, J = 6.9 Hz, H-70)/0.90 (3H, t, J = 6.9 Hz, H-70); 13C NMR (CDCl3, 125 MHz)
d: 165.70/165.66 (C, C-4), 147.9 ꢃ 2 (C, C-8a), 133.9 ꢃ 2 (CH, C-7), 128.6 ꢃ 2
(CH, C-5), 119.2 ꢃ 2 (CH, C-6), 115.8 ꢃ 2 (C, C-4a), 114.7 ꢃ 2 (CH, C-8), 67.4 ꢃ 2
(CH, C-2), 44.2 ꢃ 2 (CH, C-30), 29.8/29.7 (CH2, C-50), 28.6 ꢃ 2 (CH2, C-40),
23.1 ꢃ 2 (CH2, C-60), 22.0 ꢃ 2 (CH2, C-20), 14.1 ꢃ 2 (CH3, C-70), 12.0/11.9 (CH3,
C-10); ESI-MS m/z 247.2 [M+H]+.
Supplementary data
16. Preparation of (2R,30S)+(2S,30S)-2-(heptan-3-yl)-2,3-dihydro- quinazolin-
4(1H)-one (6). The procedure for preparation of 2 was followed using S(ꢀ)-2-
(heptan-3-yl)quinazolin-4(3H)-one (20 mg, 0.082 mmol) and NaBH4 (32 mg,
Supplementary data (1H and 13C NMR, DEPT spectra of com-
pounds 1, 2, 5, 6, 9, and 16S rRNA sequence of B. cereus 041381,
and the isolation procedures of the compounds) associated with
this article can be found, in the online version, at doi:10.1016/
j.bmcl.2011.05.002.
0.82 mmol) to give 6 as a white crystal (10.4 mg, 52% yield). ½a D20
ꢁ
+1.3 (c 1.0,
acetone); 1H NMR (CDCl3, 600 MHz) d: 7.87 (2H, d, J = 7.7 Hz, H-5), 7.28 (2H, t,
J = 7.7 Hz, H-7), 6.82 (2H, t, J = 7.7 Hz, H-6), 6.67 (2H, d, J = 7.7 Hz, H-8), 6.39
(2H, br s, H-3), 4.94 (2H, dd, J = 3.3, 6.6 Hz, H-2), 4.19 (2H, br s, H-1), 1.62 (2H,
m, H-20a), 1.56 (2H, m, H-40a), 1.52 (2H, m, H-20b), 1.45 (2H, m, H-30), 1.39 (2H,
m, H-40b), 1.32 (4H, m, H-50), 1.30 (4H, m, H-60), 0.97 (3H, t, J = 6.6 Hz, H-10)/
0.95 (3H, t, J = 6.6 Hz, H-10), 0.89 (3H, t, J = 6.6 Hz, H-70)/0.88 (3H, t, J = 6.6 Hz,
H-70); 13C NMR (CDCl3, 125 MHz) d: 165.73/165.70 (C, C-4), 147.9 ꢃ 2 (C, C-8a),
133.8 ꢃ 2 (CH, C-7), 128.6 ꢃ 2 (CH, C-5), 119.1 ꢃ 2 (CH, C-6), 115.8 ꢃ 2 (C, C-
4a), 114.7 ꢃ 2 (CH, C-8), 67.4 ꢃ 2 (CH, C-2), 44.2 ꢃ 2 (CH, C-30), 29.8/29.7 (CH2,
C-50), 28.6 ꢃ 2 (CH2, C-40), 23.13/23.09 (CH2, C-60), 22.0 ꢃ 2 (CH2, C-20),
14.1 ꢃ 2 (CH3, C-70), 12.0/11.9 (CH3, C-10); ESI-MS m/z 247.2 [M+H]+.
17. Preparation of ( )-2-(heptan-3-yl)quinazolin-4(3H)-one (7). The procedure for
preparation of 1 was followed using ( )-2-ethylhexanoate (108 mg, 0.75 mmol),
oxalyl chloride (190 mg, 1.5 mmol), o-aminobenzamide (102 mg, 0.75 mmol)
and Et3N (83 mg, 0.83 mmol) to give ( )-2-(2-ethylhexanamido)benzamide
(169 mg, 86% yield). ( )-2-(2-Ethylhexanamido)benzamide (120 mg,
0.46 mmol) reacted with I2 (350 mg, 1.38 mmol) and HMDS (296 mg,
1.84 mmol) in CH2Cl2 to give 7 as a white crystal (95 mg, 85% yield). NMR data
was consistent to 1.
References and notes
1. Richardson, M. D. J. Antimicrob. Chemother. 1991, 28, 1.
2. Morschhauser, J. Fungal Genet. Biol. 2010, 47, 94.
3. Chakrabarty, M.; Batabyal, A.; Morales-Ríos, M. S.; Joseph-Nathan, P. Monatsh.
Chem. 1995, 126, 789.
4. Fdhila, F.; Vázquez, V.; Sánchez, J. L.; Riguera, R. J. Nat. Prod. 2003, 66, 1299.
5. Adamczeski, M.; Reed, A. R.; Crews, P. J. Nat. Prod. 1995, 58, 201.
6. Wang, Y. C.; Zhou, J.; Tan, N. H.; Ding, Z. T.; Jiang, X. Acta Pharm. Sin. 1999, 34, 19.
7. Xiong, J.; Zhou, J.; Dai, H. F.; Tan, N. H.; Ding, Z. T. Acta Bot. Yunnan 2002, 24,
401.
8. R(+)-2-(Heptan-3-yl)quinazolin-4(3H)-one (1): white crystal (MeOH); mp 123–
125 °C; ½a 2D0
ꢁ
+2.1 (c 0.1, acetone); UV (MeOH) kmax (log
max 3177, 3034, 2959, 2906, 1674,
1H (600 MHz, CDCl3) and 13C NMR
(150 MHz, CDCl3) see Table 1. (2R,30R)+(2S,30R)-2-(Heptan-3-yl)-2,3-
dihydroquinazolin-4(1H)-one (2): white crystal (MeOH); +3.9 (c 0.1,
acetone); UV (MeOH) kmax (log ) 221 (4.17), 252 (3.42), 349 (3.18) nm; IR
e) 202 (4.17), 224 (4.23),
265 (3.73), 304 (3.44), 316 (3.35) nm; IR (KBr)
m
1609, 1494, 1465, 1241, 1196, 890, 768 cmꢀ1
;
18. Preparation of ( )-2-(heptan-3-yl)-2,3-dihydroquinazolin-4(1H)-one (8). The
procedure for preparation of
2 was followed using ( )-2-(heptan-3-
½ ꢁ
a 2D0
yl)quinazolin-4(3H)-one (7) (20 mg, 0.082 mmol) and NaBH4 (32 mg,
0.82 mmol) to give 8 as a white powder (9.6 mg, 48% yield).
e
(KBr) mmax 3290, 3063, 2955, 2928, 2867, 1646, 1517, 1489, 1460, 1395, 1312,
19. Zaika, L. L. J. Food Safety 1988, 9, 97.
1262, 1151, 750 cmꢀ1
,
1H (500 MHz, CDCl3) and 13C NMR (125 MHz, CDCl3) see
20. The antifungal activities against Candida albicans were evaluated by an agar
dilution method.19 The tested strain, C. albicans, was cultivated in in YPD agar
plates at 37 °C. Compounds 1ꢀ8 and ketoconazole (positive control) were
Table 1.
9. Zhang, D. T.; Tang, L. D.; Duan, G. Y.; Zhao, G. L.; Xu, W. R.; Meng, L. J.; Wang, J.
W. Chem. Res. Chin. U. 2006, 22, 584.
10. Miura, M.; Toriyama, M.; Motohashi, S. Synth. Commun. 2006, 36, 259.
dissolved in methanol at different concentrations from 10 to 0.078
lg/mL by
the continuous two-fold dilution methods. A 10
lL quantity of test solution
11. Preparation of R(ꢀ)-2-(2-ethylhexanamido)benzamide (9). To
a stirred
was absorbed by a paper disc (5 mm diameter) and placed on the assay plates.
After 12 h incubation, zones of inhibition (mm in diameter) were recorded. The
minimum inhibitory concentrations (MICs) were defined as the lowest
concentration at which no microbial growth could be observed. The MIC
solution of R-(ꢀ)-2-ethylhexanoic acid (80 mg, 0.56 mmol) in CH2Cl2 (10 mL)
at rt was added dropwise oxalyl chloride (142 mg, 1.12 mmol). After stirring
the mixture for 5 h at rt, the solvent was removed in vacuo. The residue was
redissolved in CH2Cl2 (10 mL) and added dropwise to a stirred solution of
o-aminobenzamide (76 mg, 0.56 mmol) and Et3N (62 mg, 0.62 mmol) in CH2Cl2
values of compounds 1ꢀ8 were 2.5, 2.5, 15.6, 10.6, 1.3, 5.0, 10.2, and 10.1
lM,
respectively (ketoconazole with MIC value of 0.2 M).
l