Polycyclic N-heterocyclic compounds. Part 621: Reaction of N-(quinazolin-4-yl)amidine derivatives with hydroxylamine hydrochloride and anti-platelet aggregation activity of the products

Article abstract of DOI:10.1248/cpb.58.369

The reactions of N-(5,6,7,8-tetrahydroquinazolin-4-yl)amidines and their amide oximes with hydroxylamine hydrochloride gave abnormal cyclization products via a ring cleavage of pyrimidine component accompanied with a ring closure of 1,2,4-oxadiazole to gi

Full text of DOI:10.1248/cpb.58.369

March 2010
Chem. Pharm. Bull. 58(3) 369—374 (2010)
369
Polycyclic N-Heterocyclic Compounds. Part 621): Reaction of N-
(Quinazolin-4-yl)amidine Derivatives with Hydroxylamine Hydrochloride
and Anti-platelet Aggregation Activity of the Products
b
Kensuke OKUDA, ,a Ying-Xue ZHANG,b Hiromi OHTOMO,b Takashi HIROTA,b and Kenji SASAKI
*
a Gifu Pharmaceutical University; 1–25–4 Daigaku-nishi, Gifu 501–1196, Japan: and b Faculty of Pharmaceutical
Sciences, Okayama University; 1–1–1 Tsushima-naka, Kita-ku, Okayama 700–8530, Japan.
Received November 2, 2009; accepted December 2, 2009; published online December 9, 2009
The reactions of N-(5,6,7,8-tetrahydroquinazolin-4-yl)amidines and their amide oximes with hydroxylamine
hydrochloride gave abnormal cyclization products via a ring cleavage of pyrimidine component accompanied
with a ring closure of 1,2,4-oxadiazole to give N-[2-([1,2,4]oxadiazol-5-yl)cyclohexen-1-yl]formamide oximes.
Similarly, N-(quinazolin-4-yl)amidines reacted with hydroxylamine hydrochloride gave the same results. The
evaluation of inhibitory activities against platelet aggregation in vitro is also described to show one derivative has
potent activity.
Key words rearrangement; 1,2,4-oxadiazole; anti-platelet aggregation; N-(quinazolin-4-yl)amidine; amide oxime; hydroxyl-
amine hydrochloride
3,5-Disubstituted 1,2,4-oxadiazole is a well utilized scaf- methods.10—12) Amidines 3a, b were prepared by the reaction
fold for medicinal chemistry. A class of 3,5-diphenyl-1,2,4- of 4-amino-5,6,7,8-tetrahydroquinazoline (5) with commer-
oxadiazole based compounds have been identified as potent cially available N,N-dimethylformamide (or acetamide) di-
sphingosine-1-phosphate-1 (S1P1) receptor agonists with methyl acetal in refluxing toluene. Other amidines 3c—g
minimal affinity for the S1P2 and S1P3 receptor subtypes.2) were produced by the reaction of compound 5 with the
Another derivative, 5-(3-chlorothiophen-2-yl)-3-(5-chloropy- Vilsmeier reagent prepared from the corresponding N,N-
ridin-2-yl)-1,2,4-oxadiazole has been identified as a novel dimethylamide and phosphoryl chloride.
apoptosis inducer.3) These two examples demonstrate the po-
tential of 3,5-disubstituted 1,2,4-oxadiazole use in the devel- (RꢁH) the reaction of 3a with 1.2 eq of hydroxylamine hy-
When a hydrogen is attached to the amidine moiety
opment of new pharmaceutics.
drochloride in methanol at room temperature gave the amide
1,2,4-Oxadiazoles4) are usually prepared by 1) Paal–Knorr oxime (6a, 80% yield). 6a was converted to the desired
type ring closure of O-acylamide oximes,5) 2) reaction of 1,2,4-oxadiazole derivative 7a (22% yield) by reaction with
imide equivalents with NH2OH,6) 3) ring closure of N-acyl 6 eq of hydroxylamine hydrochloride in a refluxing methanol
Nꢀ-substituted amidines,7) or 4) 1,3-dipolar cycloaddition of (Chart 1).
nitriles and nitrile oxides.8) Additionally, we have reported
In the H-NMR spectrum of 7a, a characteristic form-
1
the pyrimidine ring opening reaction accompanying the for- amide oxime one-proton doublet (Jꢁ10.0 Hz) appeared at
mation of the 1,2,4-oxadiazole ring to give N-[2-([1,2,4]oxa- 7.47 ppm coupled with an adjacent NH proton (Jꢁ10.0 Hz)
diazol-5-yl)cycloalken-1-yl]formamide oximes (1) by the which was D2O exchangeable. The formamide oxime signal
reaction of tricyclic N-(aliphatic ring-fused pyrimidin-4- changed to a singlet in the presence of D2O. While the 6a
yl)amidine (2) or its amide oxime with hydroxylamine
hydrochloride (Fig. 1).9—12) In this paper, we applied this
reaction to one of the bicyclic N-(aliphatic (or aromatic)
ring-fused pyrimidin-4-yl)amidines, i.e. N-(5,6,7,8-tetrahy-
droquinazolin-4-yl)amidines (3) and N-(quinazolin-4-yl)-
amidines (4). Since current antiplatelet drugs are known to
have certain detrimental side effects and reduced efficacy, we
tested these new analogues for anti-platelet aggregation ac-
tivity.
Results and Discussion
Chemistry First, we dealt with the aliphatic ring-fused
amidines (3). As shown in Chart 1, the requisite amidine 3
starting materials were synthesized by previously reported
Fig. 1. Substrates (2) and Their Rearranged Products (1)
Chart 1. Synthesis of 7
© 2010 Pharmaceutical Society of Japan
∗ To whom correspondence should be addressed. e-mail: okuda@gifu-pu.ac.jp

370
Vol. 58, No. 3
one-proton singlet at H-2 (pyrimidine ring) disappeared. One the present study the fused benzene moiety of quinazoline af-
1,2,4-oxadiazole ring proton was observed at 8.99 ppm as a fected the reactivity by facilitating the nucleophilic attack of
singlet. These results suggest that pyrimidine ring cleavage amide oxime (9) to quinazoline ring. This increased nucle-
and 1,2,4-oxadiazole ring closure occurred when 6a reacted ophilic attack lead to a ring-cleavage and ring-closure reac-
with hydroxylamine hydrochloride.
tion to give the 1,2,4-oxadiazole derivatives (10a). This as-
Reacting alkyl group substituted amidine moieties (RꢁMe sumption is supported by lowest unoccupied molecular or-
and Et) 3b and 3c with 1.1—1.2 eq of hydroxylamine hy- bital (LUMO) energy level comparison of 6a and 9a. Calcu-
drochloride in methanol at room temperature gave alkyl lated LUMO energy of 6a is ꢂ0.6795 eV, whilst that of 9a is
amide oximes 6b (50%) and 6c (42%), respectively. In the ꢂ1.5788 eV.13) Therefore, it is reasonable that 9a is more sus-
case of 3b, we also obtained the minor product 7b (12%). 6b ceptible for nucleophilic attack of amide oxime, because 9a
and 6c were also converted to the desired 1,2,4-oxadiazole is too unstable to isolate.
derivative 7b (77%) and 7c (84%) by reaction with 1.5—2 eq
of hydroxylamine hydrochloride in methanol at room tem- moiety 4b, c also gave the desired oxadiazole 10b, c in 65%
perature. and 76%, respectively, when reacted with 1.5—2 eq of hy-
Amidines with alkyl groups substituted in the amidine
Aryl group substituted amidine moieties 3d—g needed an droxylamine hydrochloride. Finally, aryl group substituted
excess amount of hydroxylamine hydrochloride to consume amidines 4d—g also gave the desired oxadiazole 10d—g
starting materials completely. When 4.6—6 eq of hydroxyl- when reacted with the 5—10 eq of hydroxylamine hydrochlo-
amine hydrochloride were used the reaction did not produce ride.
amide oximes (6d—g), but gave the desired oxadiazole 7d—
g.
Biology Atherothrombosis is characterized by a quick
and unexpected burst of an atherosclerotic plaque and fol-
A tentative explanation for this reactivity difference is as lowing occlusive thrombus formation. It is the main cause of
follows. All amide oximes (6) are expected to dominantly acute ischemic syndromes such as acute coronary syndrome
consist of the less sterically hindered (E)-oximes (Fig. 2).13) or ischemic stroke, which are the major cause of death in the
Isomerization of (E)-oximes to (Z)-oximes must occur to developed world. The most critical step of these diseases is
allow ipso attack of the oxime hydroxy group on the pyrimi- platelet activation and aggregation, therefore antiplatelet
dine ring to start this rearrangement reaction.10—12) In the drugs are used to protect and treat acute ischemic syndromes.
case of hydrogen or alkyl substituted 6a—c, this (E)-oxime is Because current antiplatelet drugs can have detrimental side
rather stable. On the other hand, aryl substituents of 6d—g effects and have low efficacy, we have been exploring an-
caused (Z)-oxime isomerization due to their steric repulsion tiplatelet aggregation agents as possible new drugs.14—21) The
creating the 7d—g.
inhibitory activities of compounds 7a—g and 10a—g against
After our work with aliphatic ring-fused amidines, we fo- platelet aggregation induced by arachidonic acid was assayed
cused our attention on the aromatic ring-fused amidines (4). to demonstrate the possible therapeutic nature of these com-
As shown in Chart 2, the requisite amidines 4 starting mate- pounds.
rials were synthesized by the same method as described
above for amidines 3.
The inhibitory assay was executed by a turbidimetric
method developed by Born and Cross22) using an aggregome-
When a hydrogen is attached to the amidine moiety ter. As shown in Table 1, comparison of the inhibition rate of
(RꢁH) the reaction of 4a with 1.2 eq of hydroxylamine hy- 7a—g at a final concentration of 30 mM with that of Cilosta-
drochloride at room temperature gave the 1,2,4-oxadiazole zol23) revealed that the 4-chlorophenyl derivative 7e (75.2%)
derivative 10a (36%) instead of the amide oxime 9a. This re- had potency comparable to Cilostazol (96.5%). Interestingly,
sult was quite different compared to the case of N-(aliphatic neither phenyl derivative 7d nor 4-fluorophenyl derivative 7f
ring-fused pyrimidin-4-yl)formamidines (2, 3).10—12) In those showed any significant inhibitory activity against platelet ag-
cases, the amide oximes were obtained when a hydrogen or gregation. In addition, none of compounds 10a—g at a final
alkyl group is attached to the amidine moiety. Therefore, in concentration of 30 mM showed any significant inhibition of
platelet aggregation.
In summary, we have developed a method for synthetically
Table 1. Effects of 7a—g and 10a—g on Rabbit Platelet Aggregation in
Vitro
Compound
% inhibition
Compound
% inhibition
Fig. 2. (E,Z)-Isomerization of 6
7a
7b
7c
7d
7e
7f
ꢂ0.9ꢃ18.3
42.6ꢃ14.8
13.7ꢃ27.8
16.5ꢃ13.3
75.2ꢃ10.8*
3.6ꢃ2.6
10a
10b
10c
10d
10e
10f
13.9ꢃ3.3
ꢂ2.5ꢃ1.8
8.8ꢃ8.3
ꢂ20.5ꢃ25.1
13.0ꢃ9.6
ꢂ6.0ꢃ9.7
14.2ꢃ3.2
7g
10.7ꢃ9.6
10g
Cilostazol
96.5ꢃ1.3*
Data represent % inhibition of the vehicle control group (meanꢃS.E. of 3 experi-
ments). * Means significantly different from the vehicle control group at pꢄ0.01 (Dun-
nett’s multiple range test).
Chart 2. Synthesis of 10

March 2010
371
(82.8 mg, 24%) as colorless fine crystals, mp 119—120 °C. 1H-NMR
(CDCl3) d: 1.79 (4H, m, H-6, 7), 2.55 (2H, m, H-5), 2.78 (2H, m, H-8), 3.10
(6H, br s, NMe2), 7.15—7.35 (5H, m, Ph), 8.26 (1H, s, H-2). FAB-MS m/z:
281 (MHꢅ). Anal. Calcd for C17H20N4: C, 72.83; H, 7.19; N, 19.98. Found:
C, 72.48; H, 7.01; N, 19.91.
producing various N-[2-(3-alkyl(or aryl)[1,2,4]oxadiazol-5-
yl)cyclohexen-1-yl (or phenyl)]formamide oximes (7, 10)
through the reaction of N-(5,6,7,8-tetrahydroquinazolin-4-
yl)amidines (3) or N-(quinazolin-4-yl)amidines (4) with hy-
droxylamine hydrochloride via a ring cleavage of a pyrimi-
dine component accompanied with a ring closure of 1,2,4-
oxadiazole. Compound 7e showed considerable inhibitory
activity against platelet aggregation comparable to clinically
used Cilostazol. We are currently exploring their structure–
activity relationships for further elucidation of anti-platelet
aggregation compounds.
N1,N1-Dimethyl-N2-(5,6,7,8-tetrahydroquinazolin-4-yl)-4-chlorobenz-
amidine (3e) To a dry CHCl3 solution of 5 (300 mg, 2.01 mmol) were
added N,N-dimethyl-4-chlorobenzamide (442 mg, 2.41 mmol), POCl3
(0.28 ml, 3.00 mmol), and triethylamine (1.00 ml, 7.17 mmol) sequentially,
and the reaction mixture was refluxed for 24 h. After the workup procedure
described above, the residue was purified by silica gel column chromatogra-
phy (ethyl acetate/n-hexane, 1 : 1) to give 3e (123.7 mg, 20%) as a colorless
oil. 1H-NMR (CDCl3) d: 1.80 (4H, m, H-6, 7), 2.55 (2H, m, H-5), 2.80 (2H,
m, H-8), 3.10 (6H, br s, NMe2), 7.15 (2H, d, Jꢁ8.5 Hz, 3ꢀ,5ꢀ-Ph), 7.30 (2H,
m, 2ꢀ,6ꢀ-Ph), 8.27 (1H, s, H-2). FAB-MS m/z: 315 (MHꢅ), 317 (MHꢅꢅ2).
Anal. Calcd for C17H19ClN4·0.3AcOEt: C, 64.06; H, 6.32; N, 16.42. Found:
C, 63.74; H, 6.36; N, 16.76.
Experimental
All melting points were determined on a Yanagimoto micro-melting point
apparatus, and are uncorrected. Elemental analyses were performed on a
Yanagimoto MT-5 CHN Corder elemental analyzer. The FAB-mass and EI-
mass spectra were obtained on a VG 70 mass spectrometer and m-nitroben-
zyl alcohol or glycerol was used as the matrix. The IR spectra were recorded
on a Japan Spectroscopic FT/IR-200 spectrophotometer with KBr and fre-
N1,N1-Dimethyl-N2-(5,6,7,8-tetrahydroquinazolin-4-yl)-4-fluorobenz-
amidine (3f) To a dry CHCl3 solution of 5 (350 mg, 2.35 mmol) were
added N,N-dimethyl-4-fluorobenzamide (471 mg, 2.82 mmol), POCl3
(0.28 ml, 3.00 mmol), and triethylamine (1.00 ml, 7.17 mmol) sequentially,
and the reaction mixture was refluxed for 24 h. After the workup procedure
described above, the residue was purified by silica gel column chromatogra-
phy (acetone/n-hexane, 1 : 2) to give 3f (88.9 mg, 13%) as a colorless oil. 1H-
NMR (CDCl3) d: 1.77 (4H, m, H-6, 7), 2.50 (2H, m, H-5), 2.70 (2H, m, H-
8), 3.04 (6H, br s, NMe2), 6.96 (2H, m, 3ꢀ,5ꢀ-Ph), 7.18 (2H, m, 2ꢀ,6ꢀ-Ph),
8.32 (1H, s, H-2). FAB-MS m/z: 299 (MHꢅ). Anal. Calcd for
C17H19FN4·1/3H2O: C, 67.09; H, 6.51; N, 18.41. Found: C, 67.13; H, 6.53;
N, 18.03.
1
quencies are expressed in cmꢂ1. The H-NMR spectra were recorded on a
Varian VXR-200 instrument operating at 200 MHz with tetramethylsilane as
an internal standard. Chemical shifts are given in ppm (d) and J values in
Hz, and the signals are designated as follows: s, singlet; d, doublet; dd, dou-
ble doublet; t, triplet; q, quartet; br, broad; m, multiplet. Column chromatog-
raphy was performed on silica gel (IR-60-63-210-W, Daiso) or aluminium
oxide active neutral (Merck). TLC was carried out on Kieselgel 60F254
(Merck).
N1,N1-Dimethyl-N2-(5,6,7,8-tetrahydroquinazolin-4-yl)-3-methylbenz-
amidine (3g) To a dry CHCl3 solution of 5 (250 mg, 1.68 mmol) were
added N,N-dimethyl-3-methylbenzamide (328 mg, 2.01 mmol), POCl3
(0.20 ml, 2.15 mmol), and triethylamine (0.45 ml, 3.23 mmol) sequentially,
and the reaction mixture was refluxed for 24 h. After the workup procedure
described above, the residue was purified by silica gel column chromatogra-
phy (acetone/n-hexane, 1 : 4), then recrystallized from petroleum ether to
N1,N1-Dimethyl-N2-(5,6,7,8-tetrahydroquinazolin-4-yl)formamidine
(3a) 4-Amino-5,6,7,8-tetrahydroquinazoline (5, 400 mg, 2.68 mmol) and
N,N-dimethylformamide dimethyl acetal (383 mg, 3.21 mmol) in dry toluene
(40 ml) was refluxed for 9 h. After evaporation of reaction mixture, the
residue was recrystallized from n-hexane to give 3a (408 mg, 74%) as color-
less needles, mp 67—69 °C. 1H-NMR (CDCl3) d: 1.86 (4H, m, H-6, 7), 2.74
(4H, m, H-5, 8), 3.13 (6H, s, NMe2), 8.52, 8.54 (each 1H, each s, H-2,
CHNMe2). FAB-MS m/z: 205 (MHꢅ). Anal. Calcd for C11H16N4: C, 64.68;
H, 7.89; N, 27.43. Found: C, 64.54; H, 7.74; N, 27.36.
1
give 3g (142.4 mg, 29%) as colorless fine crystals, mp 91—92 °C. H-NMR
(CDCl3) d: 1.76 (4H, m, H-6, 7), 2.27 (3H, s, Me), 2.51 (2H, m, H-5), 2.67
(2H, m, H-8), 3.02 (6H, br s, NMe2), 6.91—7.18 (4H, m, Ph), 8.33 (1H, s,
H-2). FAB-MS m/z: 295 (MHꢅ). Anal. Calcd for C18H22N4: C, 73.44; H,
7.53; N, 19.03. Found: C, 73.67; H, 7.64; N, 19.17.
N1,N1-Dimethyl-N2-(5,6,7,8-tetrahydroquinazolin-4-yl)acetamidine
(3b) 5 (400 mg, 2.68 mmol) and N,N-dimethylacetamide dimethyl acetal
(535 mg, 4.02 mmol) in dry toluene (40 ml) was refluxed for 33 h. After
evaporation of reaction mixture, the residue was purified by neutral alumina
column chromatography (ethyl acetate/n-hexane, 1 : 2) to give 3b (189.6 mg,
32%) as a colorless oil. 1H-NMR (CDCl3) d: 1.82 (4H, m, H-6, 7), 2.04 (3H,
s, Me), 2.50 (2H, t, Jꢁ5.7 Hz, H-5), 2.78 (2H, t, Jꢁ5.7 Hz, H-8), 3.09 (6H,
s, NMe2), 8.57 (1H, s, H-2). FAB-MS m/z: 219 (MHꢅ). Anal. Calcd for
C12H18N4·0.5H2O: C, 63.41; H, 8.43; N, 24.65. Found: C, 63.57; H, 8.10; N,
24.56.
N-(5,6,7,8-Tetrahydroquinazolin-4-yl)formamide Oxime (6a) To a
solution of 3a (142 mg, 0.70 mmol) in dry methanol (6.0 ml) was added
NH2OH·HCl (58.0 mg, 0.84 mmol), and the reaction mixture was stirred at
room temperature for 4 h. Water was added, and then it was made basic with
sat. NaHCO3 aq. The precipitate was filtered, washed with water then recrys-
tallized from methanol to give 6a (106.3 mg, 80%) as colorless needles, mp
1
199—201 °C. H-NMR (DMSO-d6) d: 1.77 (4H, m, H-6, 7), 2.51 (2H, m,
H-5), 2.68 (2H, m, H-8), 7.99 (2H, s, changed to 1H after addition of D2O,
NHCHꢁNO), 8.45 (1H, s, H-2), 10.72 (1H, s, D2O exchangeable, OH). IR
(KBr) cmꢂ1: 3420, 3130 (NH or OH). FAB-MS m/z: 193 (MHꢅ). Anal.
Calcd for C9H12N4O: C, 56.24; H, 6.29; N, 29.15. Found: C, 55.97; H, 6.35;
N, 29.12.
General Procedure for the Preparation of 3c—g To a solution of 5 in
dry CHCl3 (ca. 20 ml) were added N,N-dimethylalkyl (or aryl) amide,
POCl3, and triethylamine sequentially, and the reaction mixture was re-
fluxed. Water was added, and then it was made basic with sat. NaHCO3 aq.,
then extracted with CHCl3. The organic phase was washed with sat. brine,
dried over Na2SO4, then evaporated in vacuo. The residue was purified by
column chromatography and/or recrystallization to give 3.
N-(5,6,7,8-Tetrahydroquinazolin-4-yl)acetamide Oxime (6b) and N-[2-
(3-Methyl[1,2,4]oxadiazol-5-yl)cyclohexen-1-yl]formamide Oxime (7b)
To a solution of 3b (160 mg, 0.733 mmol) in dry methanol (6.0 ml) was
added NH2OH·HCl (56.0 mg, 0.806 mmol), and the reaction mixture was
stirred at room temperature for 14 h. Water was added, and then it was made
basic with sat. NaHCO3 aq. The precipitate was filtered, washed with water
then recrystallized from methanol to give 6b (75.8 mg, 50%) as colorless
needles, mp 117—118 °C. 1H-NMR (DMSO-d6) d: 1.78 (4H, m, H-6, 7),
2.32 (3H, s, Me), 2.45 (2H, m, H-5), 2.67 (2H, m, H-8), 7.95 (1H, s, D2O
exchangable, NH), 8.43 (1H, s, H-2), 10.52 (1H, s, D2O exchangeable, OH).
IR (KBr) cmꢂ1: 3380, 3130 (NH or OH). FAB-MS m/z: 207 (MHꢅ). Anal.
Calcd for C10H14N4O: C, 58.24; H, 6.84; N, 27.17. Found: C, 57.98; H, 6.77;
N, 27.20. The mother liquid was evaporated and the residue was recrystal-
lized from methanol to give 7b (12%) as colorless needles, mp 188—
191 °C. 1H-NMR (DMSO-d6) d: 1.68 (4H, m, H-4, 5), 2.33 (3H, s, Me),
2.45, 2.58 (each 2H, each m, H-3, 6), 7.45 (1H, d, Jꢁ10.0 Hz, changed to
singlet after addition of D2O, NHCHꢁNO), 10.36 (1H, s, D2O exchange-
able, OH), 11.06 (1H, d, Jꢁ10.0 Hz, D2O exchangeable, NH). IR (KBr)
cmꢂ1: 3280, 3150 (br, NH or OH). FAB-MS m/z: 223 (MHꢅ). Anal. Calcd
for C10H14N4O2: C, 54.04; H, 6.35; N, 25.21. Found: C, 53.73; H, 6.24; N,
24.91.
N1,N1-Dimethyl-N2-(5,6,7,8-tetrahydroquinazolin-4-yl)propionami-
dine (3c) To a dry CHCl3 solution of 5 (2.00 g, 13.4 mmol) were added
N,N-dimethylpropionamide (1.49 g, 14.7 mmol), POCl3 (1.90 ml, 20.4
mmol), and triethylamine (4.15 ml, 29.8 mmol) sequentially, and the reac-
tion mixture was refluxed for 35 h. After the workup procedure described
above, the residue was purified by neutral alumina column chromatography
(ethyl acetate/n-hexane, 1 : 3) to give 3c (1.72 g, 55%) as colorless fine crys-
1
tals, mp 48—50 °C. H-NMR (CDCl3) d: 1.07 (3H, t, Jꢁ7.7 Hz, Me), 1.83
(4H, m, H-6, 7), 2.48 (4H, m, H-5, –CH2Me), 2.78 (2H, t, Jꢁ5.8 Hz, H-8),
3.08 (6H, s, NMe2), 8.57 (1H, s, H-2). FAB-MS m/z: 233 (MHꢅ). Anal.
Calcd for C13H20N4·0.25H2O: C, 65.93; H, 8.72; N, 23.66. Found: C, 66.17;
H, 8.50; N, 23.73.
N1,N1-Dimethyl-N2-(5,6,7,8-tetrahydroquinazolin-4-yl)benzamidine
(3d) To a dry CHCl3 solution of 5 (180 mg, 1.21 mmol) were added N,N-
dimethylbenzamide (180 mg, 1.21 mmol), POCl3 (0.12 ml, 1.29 mmol), and
triethylamine (0.55 ml, 3.94 mmol) sequentially, and the reaction mixture
was refluxed for 24 h. After the workup procedure described above, the
residue was purified by silica gel column chromatography (acetone/n-
hexane, 1 : 3), then recrystallized from ethyl acetate–n-hexane to give 3d

372
N-(5,6,7,8-Tetrahydroquinazolin-4-yl)propionamide Oxime (6c) To a
Vol. 58, No. 3
MS m/z: 319 (MHꢅ), 321 (MHꢅꢅ2). Anal. Calcd for C15H15ClN4O2: C,
56.52; H, 4.74; N, 17.58. Found: C, 56.33; H, 4.80; N, 17.44.
solution of 3c (279 mg, 1.20 mmol) in dry methanol (10 ml) was added
NH2OH·HCl (100 mg, 1.44 mmol), and the reaction mixture was stirred at
N-{2-[3-(4-Fluorophenyl)[1,2,4]oxadiazol-5-yl]cyclohexen-1-yl}form-
room temperature for 20 h. Water was added, and then it was made basic amide Oxime (7f) 3f (107.9 mg, 0.36 mmol) was allowed to react with
with sat. NaHCO3 aq. The precipitate was filtered, washed with water then NH2OH·HCl (151 mg, 2.17 mmol) in dry methanol (5.0 ml) for 16 h. 7f
recrystallized from methanol to give 6c (110.3 mg, 42%) as colorless fine
crystals, mp 200—203 °C. H-NMR (DMSO-d6) d: 1.06 (3H, t, Jꢁ7.4 Hz,
Me), 1.78 (4H, m, H-6, 7), 2.50 (2H, m, H-5), 2.67 (2H, m, H-8), 2.87 (2H,
(99.4 mg, 91%) was obtained as colorless needles, mp 197—199 °C. 1H-
NMR (DMSO-d6) d: 1.73 (4H, m, H-4, 5), 2.51, 2.64 (each 2H, each m, H-
3, 6), 7.37 (2H, d, Jꢁ8.9 Hz, Ph-3ꢀ, 5ꢀ), 7.57 (1H, d, Jꢁ9.9 Hz, changed to
1
q, Jꢁ7.4 Hz, CH2Me), 7.89 (1H, s, D2O exchangable, NH), 8.43 (1H, s, H- singlet after addition of D2O, NHCHꢁNO), 8.17 (2H, m, Ph-2ꢀ, 6ꢀ), 10.68
2), 10.60 (1H, s, D2O exchangeable, OH). IR (KBr) cmꢂ1: 3380, 3130 (NH (1H, s, D2O exchangeable, OH), 11.60 (1H, d, Jꢁ9.9 Hz, D2O exchangeable,
or OH). FAB-MS m/z: 221 (MHꢅ). Anal. Calcd for C11H16N4O: C, 59.98; H, NH). IR (KBr) cmꢂ1: 3200 (br, NH or OH). FAB-MS m/z: 303 (MHꢅ). Anal.
7.32; N, 25.44. Found: C, 59.59; H, 7.17; N, 25.18.
Calcd for C15H15FN4O2: C, 59.60; H, 5.00; N, 18.53. Found: C, 59.45; H,
N-[2-([1,2,4]Oxadiazol-5-yl)cyclohexen-1-yl]formamide Oxime (7a) 5.07; N, 18.51.
To a solution of 6a (360 mg, 1.87 mmol) in dry methanol (50 ml) was added
N-{2-[3-(3-Methylphenyl)[1,2,4]oxadiazol-5-yl]cyclohexen-1-yl}form-
NH2OH·HCl (782 mg, 11.3 mmol), and the reaction mixture was refluxed amide Oxime (7g) 3g (117 mg, 0.397 mmol) was allowed to react with
for 24 h. Water was added, and then it was made basic with sat. NaHCO3 aq., NH2OH·HCl (166 mg, 2.39 mmol) in dry methanol (5.0 ml) for 4 h. 7g
then extracted with CHCl3. Organic phase was washed with sat. brine, dried (101.4 mg, 77%) was obtained as colorless needles, mp 205—206 °C. 1H-
over Na2SO4, then evaporated in vacuo. The residue was purified by silica NMR (DMSO-d6) d: 1.73 (4H, m, H-4, 5), 2.40 (3H, s, Me), 2.52, 2.64
gel column chromatography (ethyl acetate/n-hexane, 1 : 2), then recrystal-
lized from methanol to give 7a (87.1 mg, 22%) as colorless needles, mp
(each 2H, each m, H-3, 6), 7.40 (2H, m, Ph-4ꢀ, 5ꢀ), 7.56 (1H, d, Jꢁ10.0 Hz,
changed to singlet after addition of D2O, NHCHꢁNO), 7.88 (1H, m, Ph-6ꢀ),
168—170 °C. 1H-NMR (DMSO-d6) d: 1.69 (4H, m, H-4, 5), 2.49, 2.60 7.97 (1H, br s, Ph-2ꢀ), 10.74 (1H, s, D2O exchangeable, OH), 11.66 (1H, d,
(each 2H, each m, H-3, 6), 7.47 (1H, d, Jꢁ10.0 Hz, changed to singlet after
Jꢁ10.0 Hz, D2O exchangeable, NH). IR (KBr) cmꢂ1: 3340 (br, NH or OH).
addition of D2O, NHCHꢁNO), 8.99 (1H, s, H-3ꢀ), 10.43 (1H, s, D2O ex- FAB-MS m/z: 299 (MHꢅ). Anal. Calcd for C16H18N4O2·CH3OH: C, 61.80;
changeable, OH), 11.09 (1H, d, Jꢁ10.0 Hz, D2O exchangeable, NH). IR H, 6.71; N, 16.96. Found: C, 62.04; H, 6.75; N, 17.16.
(KBr) cmꢂ1: 3240, 3150 (br, NH or OH). FAB-MS m/z: 209 (MHꢅ). Anal.
N1,N1-Dimethyl-N2-(quinazolin-4-yl)formamidine (4a) 4-Amino-
Calcd for C9H12N4O2·0.2H2O: C, 51.03; H, 5.90; N, 26.45. Found: C, 51.34; quinazoline (8, 400 mg, 2.76 mmol) and N,N-dimethylformamide dimethyl
H, 5.90; N, 26.78.
acetal (390 mg, 3.27 mmol) in dry toluene (30 ml) was refluxed for 8 h. After
N-[2-(3-Methyl[1,2,4]oxadiazol-5-yl)cyclohexen-1-yl]formamide evaporation of reaction mixture, the residue was recrystallized from n-
Oxime (7b) To a solution of 6b (63.0 mg, 0.31 mmol) in dry methanol
(20 ml) was added NH2OH·HCl (32.0 mg, 0.46 mmol), and the reaction
hexane to give 4a (410 mg, 74%) as colorless fine crystals, mp 75—76 °C
1
(lit.24) 69 °C). H-NMR (CDCl3) d: 3.27 (3H, s, NMe), 3.31 (3H, s, NMe),
mixture was stirred at room temperature for 3 h. Water was added, and then 7.48—7.59 (1H, m, H-6), 7.75—7.87 (1H, m, H-7), 7.92 (1H, br d,
it was made basic with sat. NaHCO3 aq. The precipitate was filtered, washed Jꢁ7.8 Hz, H-5), 8.52 (1H, dd, Jꢁ8.4, 1.4 Hz, H-8), 8.80 (1H, s, H-2), 8.90
with water and then recrystallized from methanol to give 7b (52.0 mg, 77%)
as colorless needles. The spectroscopic properties were identical to those for 65.98; H, 6.04; N, 27.98. Found: C, 65.76; H, 6.07; N, 27.98.
7b from 3b described above.
N1,N1-Dimethyl-N2-(quinazolin-4-yl)acetamidine (4b)
N-[2-(3-Ethyl[1,2,4]oxadiazol-5-yl)cyclohexen-1-yl]formamide Oxime 2.76 mmol) and N,N-dimethylacetamide dimethyl acetal (550 mg,
(1H, s, CHNMe2). FAB-MS m/z: 201 (MHꢅ). Anal. Calcd for C11H12N4: C,
8
(400 mg,
(7c) To a solution of 6c (25.0 mg, 0.11 mmol) in dry methanol (5.0 ml) was
added NH2OH·HCl (15.0 mg, 0.22 mmol), and the reaction mixture was
4.13 mmol) in dry toluene (30 ml) was refluxed for 12 h. After evaporation
of reaction mixture, the residue was purified by silica gel column chro-
stirred at room temperature for 6 h. Water was added, and then it was made matography (ethyl acetate/n-hexane, 5 : 2) to give 4b (320 mg, 54%) as col-
1
basic with sat. NaHCO3 aq. The precipitate was filtered, washed with water orless crystals, mp 76—78 °C. H-NMR (CDCl3) d: 2.30 (3H, s, Me), 3.25
and then recrystallized from methanol to give 7c (22.4 mg, 84%) as colorless
needles, mp 181—182 °C. H-NMR (DMSO-d6) d: 1.26 (3H, t, Jꢁ7.5 Hz,
Me), 1.69 (4H, m, H-4, 5), 2.45, 2.58 (each 2H, each m, H-3, 6), 2.73 (2H,
q, Jꢁ7.5 Hz, CH2Me), 7.45 (1H, d, Jꢁ10.0 Hz, changed to singlet after ad-
dition of D2O, NHCHꢁNO), 10.37 (1H, s, D2O exchangeable, OH), 11.60
(6H, br s, NMe2), 7.44—7.54 (1H, m, H-6), 7.72—7.83 (1H, m, H-7), 7.90
(1H, d, Jꢁ8.2 Hz, H-5), 8.21 (1H, dd, Jꢁ8.2, 1.4 Hz, H-8), 8.80 (1H, s, H-
2). FAB-MS m/z: 215 (MHꢅ). Anal. Calcd for C12H14N4: C, 67.27; H, 6.59;
N, 26.15. Found: C, 67.21; H, 6.52; N, 26.08.
1
General Procedure for the Preparation of 4c—g To a solution of 8 in
(1H, d, Jꢁ10.0 Hz, D2O exchangeable, NH). IR (KBr) cmꢂ1: 3220 (br, NH dry CHCl3 were added N,N-dimethyamide, POCl3, and triethylamine se-
or OH). FAB-MS m/z: 237 (MHꢅ). Anal. Calcd for C11H16N4O2: C, 55.92; quentially, and the reaction mixture was refluxed. Water was added, and then
H, 6.83; N, 23.71. Found: C, 55.73; H, 6.72; N, 23.55.
it was made basic with sat. NaHCO3 aq., and then extracted with CHCl3. Or-
ganic phase was washed with sat. brine, dried over Na2SO4, then evaporated
in vacuo. The residue was purified by column chromatography and/or re-
crystallization to give 4.
General Procedure for the Reaction of 3d—g with NH2OH·HCl to
Give 7d—g To a solution of amidine (3) in dry methanol was added
NH2OH·HCl, and the reaction mixture was stirred at room temperature.
Water was added, and then it was made basic with sat. NaHCO3 aq. The pre-
N1,N1-Dimethyl-N2-(quinazolin-4-yl)propionamidine (4c) To a solu-
cipitate was filtered, washed with water and then recrystallized from tion of 8 (2.20 g, 15.2 mmol) in dry CHCl3 (50 ml) were added N,N-di-
methanol to give 7.
methylpropionamide (1.69 g, 16.7 mmol), POCl3 (2.15 ml, 23.1 mmol), and
N-[2-(3-Phenyl[1,2,4]oxadiazol-5-yl)cyclohexen-1-yl]formamide triethylamine (6.40 ml, 45.9 mmol) sequentially, and the reaction mixture
Oxime (7d) 3d (63.7 mg, 0.227 mmol) was allowed to react with was refluxed for 30 h. After the workup procedure described above, the
NH2OH·HCl (72.0 mg, 1.04 mmol) in dry methanol (5.0 ml) for 9 h. 7d residue was purified by silica gel column chromatography (acetone/
(48.3 mg, 75%) was obtained as colorless needles, mp 201—203 °C. 1H- n-hexane, 1 : 4) to give 4c (830 mg, 24%) as a colorless oil.25) 1H-NMR
NMR (DMSO-d6) d: 1.70 (4H, m, H-4, 5), 2.49, 2.62 (each 2H, each m, H-
3, 6), 7.55 (1H, d, Jꢁ10.0 Hz, changed to singlet after addition of D2O,
(CDCl3) d: 1.14 (3H, t, Jꢁ7.6 Hz, Me), 2.68 (2H, q, Jꢁ7.6 Hz, CH2Me),
3.21 (6H, s, NMe2), 7.42—7.52 (1H, m, H-6), 7.71—7.81 (1H, m, H-7),
NHCHꢁNO), 7.44—7.63 (3H, m, Ph-3ꢀ,4ꢀ, 5ꢀ), 8.12 (2H, dd, Jꢁ7.6, 7.84 (1H, d, Jꢁ8.3 Hz, H-5), 8.17 (1H, dd, Jꢁ8.3, 1.4 Hz, H-8), 8.83 (1H, s,
1.6 Hz, Ph-2ꢀ, 6ꢀ), 10.69 (1H, br s, D2O exchangeable, OH), 11.62 (1H, d, H-2). FAB-MS m/z: 229 (MHꢅ).
Jꢁ10.0 Hz, D2O exchangeable, NH). IR (KBr) cmꢂ1: 3200, 3100 (br, NH or
N1,N1-Dimethyl-N2-(quinazolin-4-yl)benzamidine (4d) To a solution
OH). FAB-MS m/z: 285 (MHꢅ). Anal. Calcd for C15H16N4O2: C, 63.37; H, of 8 (200 mg, 1.38 mmol) in dry CHCl3 (20 ml) were added N,N-dimethyl-
5.67; N, 19.71. Found: C, 63.43; H, 5.83; N, 19.83.
benzamide (245 mg, 1.64 mmol), POCl3 (0.20 ml, 2.1 mmol), and triethyl-
N-{2-[3-(4-Chlorophenyl)[1,2,4]oxadiazol-5-yl]cyclohexen-1-yl}form- amine (0.65 ml, 4.7 mmol) sequentially, and the reaction mixture was re-
amide Oxime (7e) 3e (342 mg, 1.09 mmol) was allowed to react with fluxed for 26 h. After the workup procedure described above, the residue was
NH2OH·HCl (453 mg, 6.52 mmol) in dry methanol (5.0 ml) for 20 h. 7e purified by silica gel column chromatography (acetone/n-hexane, 1 : 2), then
(297.6 mg, 86%) was obtained as colorless needles, mp 213—214 °C. 1H- recrystallized from ethyl acetate–n-hexane to give 4d (65.7 mg, 17%) as col-
NMR (DMSO-d6) d: 1.73 (4H, m, H-4, 5), 2.52, 2.64 (each 2H, each m, H-
3, 6), 7.57 (1H, d, Jꢁ10.0 Hz, changed to singlet after addition of D2O,
NHCHꢁNO), 7.60 (2H, d, Jꢁ8.5 Hz, Ph-3ꢀ, 5ꢀ), 8.11 (2H, d, Jꢁ8.5 Hz, Ph-
2ꢀ, 6ꢀ), 10.69 (1H, s, D2O exchangeable, OH), 11.61 (1H, d, Jꢁ10.0 Hz,
orless fine crystals, mp 78—79 °C. 1H-NMR (CDCl3) d: 3.37 (3H, s, NMe),
3.54 (3H, s, NMe), 7.32—7.57 (3H, m, H-3ꢀ, 4ꢀ, 5ꢀ), 7.62—7.74 (3H, m, H-
2ꢀ, 6ꢀ, 6), 7.92 (1H, br t, Jꢁ7.7 Hz, H-7), 8.17 (1H, d, Jꢁ8.4 Hz, H-5), 8.30
(1H, s, H-2), 8.37 (1H, d, Jꢁ7.7 Hz, H-8). FAB-MS m/z: 277 (MHꢅ). Anal.
D2O exchangeable, NH). IR (KBr) cmꢂ1: 3300, 3170 (br, NH or OH). FAB- Calcd for C17H16N4: C, 73.89; H, 5.84; N, 20.28. Found: C, 73.93; H, 6.15;

March 2010
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N, 20.25.
Anal. Calcd for C11H12N4O2: C, 56.89; H, 5.21; N, 24.12. Found: C, 56.65;
H, 5.30; N, 23.97.
N-[2-(3-Phenyl[1,2,4]oxadiazol-5-yl)phenyl]formamide Oxime (10d)
N1,N1-Dimethyl-N2-(quinazolin-4-yl)-4-chlorobenzamidine (4e) To a
solution of 8 (2.00 g, 13.8 mmol) in dry CHCl3 (60 ml) were added N,N-
dimethyl-4-chlorobenzamide (2.78 g, 15.1 mmol), POCl3 (1.95 ml, 20.9 4d (41.0 mg, 0.148 mmol) was allowed to react with NH2OH·HCl (63.0 mg,
mmol), and triethylamine (7.25 ml, 52.0 mmol) sequentially, and the reaction 0.907 mmol) in dry methanol (5.0 ml) for 48 h. 10d (9.9 mg, 24%) was ob-
mixture was refluxed for 39 h. After the workup procedure described above, tained as a white powder, mp 250—253 °C. 1H-NMR (DMSO-d6) d: 7.11
the residue was purified by silica gel column chromatography (ethyl (1H, br t, Jꢁ6.8 Hz, H-4), 7.55–7.72 (5H, m, H-5, 6, 3ꢀ, 4ꢀ, 5ꢀ), 8.01 (1H, d,
acetate/n-hexane, 1 : 1) to give 4e (360 mg, 8.4%) as a colorless oil. 1H-
NMR (CDCl3) d: 3.03 (3H, s, NMe), 3.36 (3H, s, NMe), 7.21 (4H, s, H-2ꢀ,
Jꢁ10.0 Hz, changed to singlet after addition of D2O, NHCHꢁNO), 8.11
(1H, br d, Jꢁ6.8 Hz, H-3), 8.20 (2H, m, H-2ꢀ, 6ꢀ), 10.67 (1H, s, D2O ex-
3ꢀ, 5ꢀ, 6ꢀ), 7.48—7.58 (1H, m, H-6), 7.72—7.82 (1H, m, H-7), 7.85 (1H, changeable, OH), 11.08 (1H, d, Jꢁ10.0 Hz, D2O exchangeable, NH). IR
dd, Jꢁ8.2, 1.3 Hz, H-5), 8.25 (1H, dd, Jꢁ8.4, 1.4 Hz, H-8), 8.52 (1H, s,
(KBr) cmꢂ1: 3220 (br) (NH or OH). EI-MS m/z: 280 (Mꢅ). Anal. Calcd for
H-2). FAB-MS m/z: 311 (MHꢅ), 313 (MHꢅꢅ2). Anal. Calcd for C15H12N4O2: C, 64.28; H, 4.32; N, 19.99. Found: C, 64.03; H, 4.59; N,
C17H15ClN4·0.25AcOEt: C, 64.96; H, 5.15; N, 16.83. Found: C, 65.19; H, 19.68.
5.39; N, 16.86.
N-{2-[3-(4-Chlorophenyl)[1,2,4]oxadiazol-5-yl]phenyl}formamide
Oxime (10e) 4e (257 mg, 0.827 mmol) was allowed to react with
N1,N1-Dimethyl-N2-(quinazolin-4-yl)-4-fluorobenzamidine (4f) To a
solution of 8 (2.20 g, 15.2 mmol) in dry CHCl3 (60 ml) were added N,N- NH2OH·HCl (345 mg, 4.96 mmol) in dry methanol (10 ml) for 19 h. 10e
dimethyl-4-fluorobenzamide (2.79 g, 16.7 mmol), POCl3 (2.15 ml,
(85.2 mg, 33%) was obtained as colorless needles, mp 245—247 °C. 1H-
23.1 mmol), and triethylamine (6.40 ml, 45.9 mmol) sequentially, and the re- NMR (DMSO-d6) d: 7.11 (1H, m, H-4), 7.58—7.73 (4H, m, H-5, 6, 3ꢀ, 5ꢀ),
action mixture was refluxed for 36 h. After the workup procedure described 8.01 (1H, d, Jꢁ9.9 Hz, changed to singlet after addition of D2O,
above, the residue was purified by silica gel column chromatography (ethyl NHCHꢁNO), 8.10 (1H, dd, Jꢁ7.8, 1.4 Hz, H-3), 8.16 (2H, m, H-2ꢀ, 6ꢀ),
acetate/n-hexane, 1 : 1) to give 4f (450 mg, 10%) as a colorless oil. 1H-NMR
(CDCl3) d: 3.06 (3H, br s, NMe), 3.37 (3H, br s, NMe), 6.88—7.00 (2H, m,
10.64 (1H, s, D2O exchangeable, OH), 11.04 (1H, d, Jꢁ9.9 Hz, D2O ex-
changeable, NH). IR (KBr) cmꢂ1: 3220, 3140 (br) (NH or OH). FAB-MS
H-3ꢀ, 5ꢀ), 7.23—7.34 (2H, m, H-2ꢀ, 6ꢀ), 7.48—7.58 (1H, m, H-6), 7.72— m/z: 315 (MHꢅ), 317(MHꢅꢅ2). Anal. Calcd for C15H11ClN4O2: C, 57.24; H,
7.82 (1H, m, H-7), 7.86 (1H, dd, Jꢁ8.3, 1.3 Hz, H-5), 8.25 (1H, dd, Jꢁ8.4, 3.52; N, 17.80. Found: C, 57.03; H, 3.84; N, 17.65.
1.3 Hz, H-8), 8.51 (1H, s, H-2). FAB-MS m/z: 295 (MHꢅ). Anal. Calcd for
N-{2-[3-(4-Fluorophenyl)[1,2,4]oxadiazol-5-yl]phenyl}formamide
C17H15FN4·0.25AcOEt: C, 68.34; H, 5.42; N, 17.71. Found: C, 68.29; H, Oxime (10f) 4f (468 mg, 1.59 mmol) was allowed to react with
5.63; N, 18.06.
NH2OH·HCl (664 mg, 9.56 mmol) in dry methanol (10 ml) for 6 h. 10f
N1,N1-Dimethyl-N2-(quinazolin-4-yl)-3-methylbenzamidine (4g) To a
(124.8 mg, 26%) was obtained as colorless needles, mp 165—168 °C. 1H-
solution of 8 (2.15 g, 14.8 mmol) in dry CHCl3 (60 ml) were added N,N- NMR (DMSO-d6) d: 7.09 (1H, m, H-4), 7.42 (2H, m, H-3ꢀ, 5ꢀ), 7.56—7.73
dimethyl-3-methylbenzamide (2.66 g, 16.3 mmol), POCl3 (1.70 ml, 18.2 (2H, m, H-5, 6), 8.00 (1H, d, Jꢁ10.0 Hz, changed to singlet after addition of
mmol), and triethylamine (6.25 ml, 44.8 mmol) sequentially, and the reaction D2O, NHCHꢁNO), 8.10 (1H, br d, Jꢁ7.7, Hz, H-3), 8.24 (2H, m, H-2ꢀ, 6ꢀ),
mixture was refluxed for 24 h. After the workup procedure described above, 10.63 (1H, s, D2O exchangeable, OH), 11.04 (1H, d, Jꢁ10.0 Hz, D2O ex-
the residue was purified by silica gel column chromatography (acetone/ethyl changeable, NH). IR (KBr) cmꢂ1: 3220, 3130 (br) (NH or OH). FAB-MS
acetate/cyclohexane, 1 : 3 : 1), then recrystallized from ethyl acetate– m/z: 299 (MHꢅ). Anal. Calcd for C15H11FN4O2: C, 60.40; H, 3.72; N, 18.78.
1
n-hexane to give 4g (590 mg, 14%) as colorless needles. H-NMR (CDCl3) Found: C, 60.23; H, 4.07; N, 18.78.
d: 2.21 (3H, s, Me), 2.99 (3H, br s, NMe), 3.32 (3H, br s, NMe), 6.91—7.12
N-{2-[3-(3-Methylphenyl)[1,2,4]oxadiazol-5-yl]phenyl}formamide
(4H, m, H-2ꢀ, 4ꢀ, 5ꢀ, 6ꢀ), 7.43—7.56 (1H, m, H-6), 7.68—7.81 (2H, m, H-5, Oxime (10g) 4g (186.7 mg, 0.643 mmol) was allowed to react with
7), 8.24 (1H, d, Jꢁ8.4 Hz, H-8), 8.56 (1H, s, H-2). FAB-MS m/z: 291 NH2OH·HCl (447 mg, 6.43 mmol) in dry methanol (15 ml) for 9 h. 10g
(MHꢅ). Anal. Calcd for C18H18N4·0.5H2O: C, 72.22; H, 6.40; N, 18.71. (74.4 mg, 39%) was obtained as colorless needles, mp 255—257 °C. 1H-
Found: C, 72.06; H, 6.44; N, 18.64.
General Procedure for the Reaction of 4 with NH2OH·HCl to give 10 4ꢀ, 5ꢀ), 7.68 (2H, m, H-5, 6), 8.02 (1H, d, Jꢁ10.0 Hz, changed to singlet
To a solution of amidine (4) in dry methanol was added NH2OH·HCl, and after addition of D2O, NHCHꢁNO), 8.06 (3H, m, H-3, 2ꢀ, 6ꢀ), 10.74 (1H, s,
NMR (DMSO-d6) d: 2.43 (3H, s, Me), 7.10 (1H, m, H-4), 7.46 (2H, m, H-
the reaction mixture was stirred at room temperature. Water was added, and D2O exchangeable, OH), 11.12 (1H, d, Jꢁ10.0 Hz, D2O exchangeable, NH).
then it was made basic with sat. NaHCO3 aq. The precipitate was filtered, IR (KBr) cmꢂ1: 3210 (br) (NH or OH). FAB-MS m/z: 295 (MHꢅ). Anal.
washed with water then recrystallized from methanol to give 10.
N-[2-([1,2,4]Oxadiazol-5-yl)phenyl]formamide Oxime
(145 mg, 0.724 mmol) was allowed to react with NH2OH·HCl (61.0 mg,
Calcd for C16H14N4O2: C, 65.30; H, 4.79; N, 19.04. Found: C, 65.02; H,
(10a) 4a 4.94; N, 18.89.
Preparation of Platelet Blood was collected from a male Albino rabbit
0.878 mmol) in dry methanol (10 ml) for 5 h. 10a (53.4 mg, 36%) was ob- (3—3.5 kg weight) with 0.1 volume of 3.8% sodium citrate as the anticoagu-
1
tained as colorless needles, mp 165—167 °C. H-NMR (DMSO-d6) d: 7.09 lant. After mixing, platelet rich plasma (PRP) was obtained by removing
(1H, m, H-4), 7.55—7.69 (2H, m, H-5, 6), 7.92 (1H, d, Jꢁ10.1 Hz, changed
to singlet after addition of D2O, NHCHꢁNO), 8.08 (1H, d, Jꢁ7.6 Hz, H-3),
erythrocytes and leukocytes by centrifugation (4 °C, 1000 rpm, 10 min).
Platelet poor plasma (PPP) was prepared by further centrifugation (4 °C,
9.29 (1H, s, H-3ꢀ), 10.46 (1H, s, D2O exchangeable, OH), 10.55 (1H, d, 3000 rpm, 15 min). The PRP was diluted by PPP to be 3.0ꢆ105 cells/ml, and
Jꢁ10.1 Hz, D2O exchangeable, NH). IR (KBr) cmꢂ1: 3260, 3130 (NH or then used for the aggregation.
OH). FAB-MS m/z: 205 (MHꢅ). Anal. Calcd for C9H8N4O2: C, 52.94; H,
3.95; N, 27.44. Found: C, 52.69; H, 4.19; N, 27.35.
N-[2-(3-Methyl[1,2,4]oxadiazol-5-yl)phenyl]formamide Oxime (10b) and 10a—g (2 ml) (DMSO solution) was added, followed by an addition of
4b (250 mg, 1.17 mmol) was allowed to react with NH2OH·HCl (122 mg,
Measurement of Platelet Aggregation The plasma described above
(223 ml) was preincubated at 37 °C for 2 min. Synthetic compounds 7a—g
aggregating agent 25 ml (arachidonic acid 25 mg/ml) 1 min later. Platelet
1.76 mmol) in dry methanol (8.0 ml) for 19 h. 10b (166.3 mg, 65%) was ob- aggregation was measured by continuous recording of light transmission
1
tained as colorless needles, mp 189—191 °C. H-NMR (DMSO-d6) d: 2.45 through plasma for 10 min using an aggregometer (Sysmex, AA-100) at
(3H, s, Me), 7.07 (1H, m, H-4), 7.53—7.68 (2H, m, H-5, 6), 7.90 (1H, d, 37 °C. Cilostazol23) was used as a positive control. All compounds were used
Jꢁ10.0 Hz, changed to singlet after addition of D2O, NHCHꢁNO), 8.02
at a 30 mM final concentration. The inhibition rate was calculated according
(1H, d, Jꢁ7.7 Hz, H-3), 10.41 (1H, s, D2O exchangeable, OH), 10.54 (1H, d, to the method already described.14)
Jꢁ10.0 Hz, D2O exchangeable, NH). IR (KBr) cmꢂ1: 3220 (br) (NH or OH).
FAB-MS m/z: 219 (MHꢅ). Anal. Calcd for C10H10N4O2·0.1H2O: C, 54.59;
H, 4.67; N, 25.47. Found: C, 54.61; H, 4.80; N, 25.49.
Acknowledgements We are grateful to the SC-NMR Laboratory of
Okayama University for 200 MHz 1H-NMR experiments. We also thank
N-[2-(3-Ethyl[1,2,4]oxadiazol-5-yl)phenyl]formamide Oxime (10c) David A. Kingery (Department of Molecular Biophysics and Biochemistry,
4c (360 mg, 1.58 mmol) was allowed to react with NH2OH·HCl (220 mg, Yale University) and Dr. K. L. Kirk (NIDDK, NIH) for helpful comments on
3.17 mmol) in dry methanol (8.0 ml) for 19 h. 10c (277 mg, 76%) was ob- the manuscript.
1
tained as colorless needles, mp 189—190 °C. H-NMR (DMSO-d6) d: 1.32
(3H, t, Jꢁ7.5 Hz, Me), 2.82 (2H, q, Jꢁ7.5 Hz, CH2Me), 7.05 (1H, m, H-4),
7.52—7.68 (2H, m, H-5, 6), 7.90 (1H, d, Jꢁ10.1 Hz, changed to singlet after
addition of D2O, NHCHꢁNO), 8.02 (1H, d, Jꢁ8.2 Hz, H-3), 10.41 (1H, s,
D2O exchangeable, OH), 10.71 (1H, d, Jꢁ10.1 Hz, D2O exchangeable, NH).
IR (KBr) cmꢂ1: 3240, 3170, 3130 (NH or OH). FAB-MS m/z: 233 (MHꢅ).
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