N-monocarbamoyl derivatives of symmetrical diamines with antiviral activity

Article abstract of DOI:10.1248/cpb.55.1406

Some new N-monocarbamoyl symmetrical diamines have been prepared by the addition of symmetrical amines to isocyanates or isothiocyanates. 2,6-Diaminopyridine (1), (1R,2R)-1,2-diaminocyclohexane [(1R,2R)-2], meso-1,2-diaminocyclohexane (meso-2), or (1R,2R)

Full text of DOI:10.1248/cpb.55.1406

1406
Notes
Chem. Pharm. Bull. 55(9) 1406—1411 (2007)
Vol. 55, No. 9
N-Monocarbamoyl Derivatives of Symmetrical Diamines with Antiviral
Activity
Nobuko MIBU,a Kazumi YOKOMIZO,b Takeshi MIYATA,b and Kunihiro SUMOTO*,a
a Faculty of Pharmaceutical Sciences, Fukuoka University; 8–19–1 Nanakuma, Jonan-ku, Fukuoka 814–0180, Japan: and
b Faculty of Pharmaceutical Sciences, Sojo University; 4–22–1 Ikeda, Kumamoto 862–0082, Japan.
Received May 15, 2007; accepted June 25, 2007
Some new N-monocarbamoyl symmetrical diamines have been prepared by the addition of symmetrical
amines to isocyanates or isothiocyanates. 2,6-Diaminopyridine (1), (1R,2R)-1,2-diaminocyclohexane [(1R,2R)-2],
meso-1,2-diaminocyclohexane (meso-2), or (1R,2R)-1,2-diphenylethylenediamine (3) were used as the starting
symmetrical diamine frameworks. All of the newly synthesized compounds were subjected to an evaluation of
antiviral activity with herpes simplex virus (HSV)-1. N-Monocarbamoyl 2,6-diaminopyridines (5a, b) showed sig-
nificant antiviral activity (EC50ꢀ17.0, 6.2 mg/ml) comparable to that of N-monododecanoyl 2,6-diaminopyridine
(A2). As a result, compound 5a showed a better selectivity index (CC50/EC50ꢀca. 10.0) than that of A2.
Key words symmetrical diamine; 2,6-diaminopyridine; 1,2-diaminocyclohexane; urea; anti-herpes simplex virus (HSV)-1;
plaque reduction assay
The continuing search for antiviral compounds has identi- Results and Discussion
fied N-monoacylated 2,6-diaminopyridines (A1—3) as a
Synthesis of N-Monocarbamoyl Derivatives of Symmet-
novel class of anti-herpes simplex virus (HSV)-1 agents rical Diamines [(5a—c), (1R,2R)-6(a—c), cis-6c, (1R,2R)-
(Chart 1).1) Some of the derivatives of urea, thiourea, and 7b—c] The above target compounds have been prepared by
their related molecules are known to be important structural the reaction of the symmetrical diamines [2,6-diaminopyri-
components in biological processes2,3) such as antiviral activ- dine (DAP, 1), (1R,2R)-1,2-diaminocyclohexane [(1R,2R)-2],
ity.2,4—6) In connection with previous studies on the search meso-1,2-diaminocyclohexane (meso-2), and (1R,2R)-1,2-
for antiviral compounds, the recent focus has been on the diphenylethylenediamine (3)] with the corresponding iso-
symmetrical chiral diamines and some achiral diamine deriv- cyanate (4a), or isothiocyanates (4b, c) (Chart 2). The reac-
atives.
tion, which involved the simple refluxing of an equimolar
This paper reports the synthesis and properties of the N- amount of DAP (1) and 1-adamantyl isocyanate (4a) in dry
monocarbamoyl derivatives obtained by the addition of di- tetrahydrofuran (THF) or dry pyridine required a long reac-
amines to isocyanates or isothiocyanates. In addition, this tion time to generate the target compound (5a) and resulted
study documents the results of their antiviral [anti-herpes in a low yield (entries 1, 2). Similarly, the reaction of DAP
simplex virus (HSV)-1] activity.
with an equimolar amount of 1-adamantyl isothiocyanate
(4b) or 3,4-dimethoxyphenyl isothiocyanate (4c) in common
organic solvents also gave the product 5b or 5c, in low yields
(10—23%, see entries 5, 6, 8 in Table 1). In both reactions,
for the preparation of 5a (entries 1, 2), there was a gradual
disappearance of the starting materials (4a and DAP) and the
formation of N,Nꢀ-disubstituted diaminopyridine could not
be detected by monitoring with thin layer chromatography
(TLC). The change of the ratio of diamine : isocyanate (1 : 2)
resulted in the formation of N-monosubstituted diaminopyri-
Chart 1
Chart 2
∗ To whom correspondence should be addressed. e-mail: kunihiro@cis.fukuoka-u.ac.jp
© 2007 Pharmaceutical Society of Japan

September 2007
1407
Table 1. N-Monocarbamoyl Derivatives (5—7) from the Reactions of Iso(thio)cyanates with Symmetrical Diamines
Ratio of
Entry
Diamine
Reagent
Product
Yield %
Additive
Conditions
diamine (HCl) : reagent : additive
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
1
1
1
1
1
1
4a
4a
4a
4a
4b
4b
4c
4c
4a
4a
4a
4a
4b
4c
4c
4b
4c
5a
5a
5a
5a
5b
5b
5c
5c
27
25
69
70
23
10
61
17
11a)
39a)
8a)
66
57
67
91
48
76
1 : 1 : 0
1 : 1 : 0
1 : 2 : 0
1 : 1 : 2.2
1 : 1 : 0
1 : 1 : 0
1.4 : 1 : 0
1 : 1 : 0
1 : 1 : 0
1 : 1 : 0
1 : 1 : 0
1 : 0.95 : 1
1 : 0.93 : 0
1 : 1 : 0
1 : 1 : 0
1 : 1 : 0
1 : 1 : 0
Reflux, 3 d, dry THF
Reflux, 2 d, dry pyridine
Reflux, 12 d, THF
rt, 1 h (pretreatment), rt, 10 min, dry THF, N2
Reflux, 5 d, dry DME
Reflux, 2 d, toluene, N2
ꢂ10—0 °C, 1 d, dry CH2Cl2–EtOH, N2
rt, 1 h, reflux 18 h, CH2Cl2
rt, 17 h, dry CH2Cl2
rt, 1 h, reflux 1 h, dry CH3CN
rt, 0.5 h, reflux 0.5 h, dry THF
rt, 1 h (pretreatment), rt, 1 h, THF, N2
rt, 1 d, dry CH2Cl2
n-BuLi
1·HCl
1
(1R,2R)-2
(1R,2R)-2
(1R,2R)-2
(1R,2R)-2
(1R,2R)-2
(1R,2R)-2
meso-2
(1R,2R)-3
(1R,2R)-3
(1R,2R)-6a
(1R,2R)-6a
(1R,2R)-6a
(1R,2R)-6a
(1R,2R)-6b
(1R,2R)-6c
cis-6c
9-BBN
rt, 1 d, CH2Cl2, N2
rt, 1 d, CH2Cl2, N2
rt, 1 d, CH2Cl2, N2
rt, 17 h, CH2Cl2, N2
(1R,2R)-7b
(1R,2R)-7c
a) Additional N,Nꢀ-disubstituted derivative (8a) is also obtained in 54, 26, and 60% yield in entries 9, 10, and 11, respectively.
dine (5a) with a 69% yield (entry 3). The reactivity of the mental). In order to improve the yields of the monosubsti-
aromatic amines as an electrophile was weaker than that of tuted products (6), the procedure for selective monoacylation
the aliphatic amines, and the steric factor (bulkiness of the of symmetrical diamines reported by Zhang Z. et al.10) was
adamantyl group) apparently decreased the accessibility of employed. In order to form a simple associative complex of
the electrophiles to iso(thio)cyanate functionality in the mol- diamine (1R,2R)-2, one equivalent of Lewis acid [9-borabi-
ecules of 4a and 4b. In order to enhance the reactivity, the cyclo[3.3.1]nonane (9-BBN)] was added to a diamine in
protocol used in the preparation of the monobenzoylated de- THF. The mixture was stirred for 1 h at room temperature.
rivatives from acylation of the symmetrical diamines accord- After the addition of isocyante 4a to this pretreated solution
ing to the procedure reported by Wang et al.7) was success- with stirring, the resulted mixture was kept another 1 h. After
fully applied. Therefore, one equivalent of isocyanate (4a) workup, the desired product was obtained in 66% (entry 12;
was added to the pretreated DAP with 2 eq of n-butyllithium Method C). In the reactions with 4c, the diamine meso-2 pro-
to generate a dianion of DAP, at room temperature, resulting ceeded more easily to generate the product cis-6c in a 91%
in the preferential formation of the N-monosubstituted prod- yield (entry 15) than the diamine (1R,2R)-2 (entry 14).11,12)
uct 5a in excellent yield (70%, entry 4; Method A). DAP was Using (1R,2R)-3 as a diamine, the isothiourea derivatives
also found to react fairly slowly with 4c, similar to the cases (1R,2R)-7b and (1R,2R)-7c were also synthesized from the
of 4a and 4b. Therefore, the procedure was also attempted by reactions with isothiocyanates (4b, c) in 48% and 76%
starting with DAP monohydrochloride to iso(thio)cyanates to yields, respectively (entries 16, 17). In order to increase the
prepare N-monosubstituted diamines.8) By the deactivation of solubility in water for bioassay, the compounds (1R,2R)-6c
one nitrogen lone pair of diamines, monoammonium salt was and (1R,2R)-7c were treated with 10% HCl in ethanol to
found to be superior in terms of the preferential formation transform the corresponding hydrochlorides (see Experimen-
procedure of N-monocarbamoyl diamines. This procedure tal).
was successful in the reaction of DAP with 4c for the prepa-
ration of 5c (see, entry 7; Method B). In the reactions of spectroscopic and elemental analyses (Tables 2—4).
DAP with 4a and 4b, unfortunately, this procedure was not Evaluation of Antiviral Activities The anti-HSV-1 ac-
The structures of the target compounds were confirmed by
very efficient. It is possible that the poor results in these tivities of the target N-monosubstituted diamines were esti-
cases may be due to the steric bulkiness of the adamantyl mated using a plaque reduction assay in Vero cells.13) For the
group in 4a and 4b. In addition, an equilibrium state of the active compounds [5a, b and (1R,2R)-6a], their cytotoxic ac-
mono ammonium ion of the diamines between the diammo- tivities were also evaluated. The obtained 50% effective con-
nium ion in the solution may also be another factor for the centration (EC50) and 50% cytotoxic concentration (CC50)
deactivation of the diamine’s reactivity.9) In the case of di- values for the synthesized compounds are listed in Table 5.
amine (1R,2R)-1,2-diaminocyclohexane [(1R,2R)-2], the re- The data for the N-long alkyl chain monoacylated derivative
actions with iso(thio)cyanates 4b, c proceeded more rapidly of diaminopyridine A2 are also listed in Table 5.1) The N-
than those of DAP with 4b, c to produce the N-monocar- monosubstituted 2,6-diaminopyridines (5a, b) showed a sig-
bamoyl diamines (1R,2R)-6b and (1R,2R)-6c, in a 57% and nificant anti-HSV-1 activity (EC50ꢁ17.0, 6.2 mg/ml). Al-
67% yield, respectively (entries 13, 14). The reactions with though compound 5a showed lower activity against HSV-1
isocyanate 4a gave N-monocarbamoyl diamine (1R,2R)-6a in than that of acyclovir (ED50ꢁ0.2—0.9 mg/ml),1) it possessed
low yields by the above procedure, and other attempts for the a comparable potency and a lower cytotoxicity in comparison
preparation of N-monocarbamoyl diamines also resulted in to that of A2, thus resulting in a better selectivity index
low yields, associated with the formation of N,Nꢀ-dicar- (CC50/EC50ꢁca. 10.0) than A2 (CC50/EC50ꢁ3.3). Compound
bamoyl diamine 8a (entries 9—11 in Table 1, and see Experi- 5b has higher antiviral activity in comparison to A2, and

1408
Vol. 55, No. 9
Table 2. Physical Data of N-Monocarbamoyl Derivatives (5—7) from the Reactions of Iso(thio)cyanates with Diamine Derivatives
Analysis (%)
Calcd (Found)
mp (°C)
(Recryst solvent)
Formula HR-MS m/z
IR (cmꢂ1
(KBr)
)
Compd.
Formula
Calcd (Found)
C
H
N
5a
220—224
(EtOH–CH2Cl2)
C16H22N4O·0.1H2O
C16H22N4S
66.69
(66.61
7.76
7.76
19.44
19.35)
C16H23N4O (MꢃH)ꢃ
287.1872
3475, 3380, 3220,
3085 (NH2, NH)
1685 (CꢁO)
3490, 3320, 3205
(NH2, NH)
(287.1873)
5b
209—210
(EtOH)
63.54
(63.72
7.33
7.33
18.52
18.24)
C16H23N4S (MꢃH)ꢃ
303.1643
(303.1637)
1450, 1240 (NH–CꢁS)
3480, 3365, 3295
(NH2, NH)
5c
242—244
(CH2Cl2)
C14H16N4O2S
55.25
(55.05
5.30
5.27
18.41
18.34)
C14H17N4O2S (MꢃH)ꢃ
305.1072
(305.1074)
1510, 1230 (NH–CꢁS)
3855, 3355 br
(1R,2R)-6a
(1R,2R)-6b
(1R,2R)-6c
cis-6c
248—252 decn.
(CH2Cl2)
C17H29N3O·0.3H2O
C17H29N3S·0.9H2O
68.79
(68.72
10.05
10.00
14.16
13.90)
C17H30N3O (MꢃH)ꢃ
292.2389
(NH2, NH)
(292.2392)
1630 (CꢁO)
125—128
(EtCN)
63.08
(62.95
9.59
9.60
12.98
13.04)
C17H30N3S (MꢃH)ꢃ
308.2160
3305, 3295, 3145,
3065 (NH2, NH)
1555, 1305 br (NH–CꢁS)
3340, 3290 (NH2)
(NH2, NH)
1510, 1235 br (NH–CꢁS)
3360, 3340, 3280
(NH2, NH)
1515, 1235 (NH–CꢁS)
3380, 3280
(NH2, NH)
1520, 1225 (NH–CꢁS)
3345 br
(308.2161)
168—170
(CH2Cl2)
C15H23N3O2S·0.4H2O 56.90
(56.93
7.58
7.29
13.27
13.17)
C15H24N3O2S (MꢃH)ꢃ
310.1589
(310.1591)
109—110
(AcOEt–iPr2O)
C15H23N3O2S
C25H31N3S
58.22
(58.18
7.49
7.47
13.58
13.33)
C15H24N3O2S (MꢃH)ꢃ
310.1589
(310.1587)
(1R,2R)-7b
(1R,2R)-7c
81—84a)
74.03
(73.82
7.70
7.69
10.36
10.56)
C25H32N3S2 (MꢃH)ꢃ
406.2317
(406.2317)
78—82
(EtOH)
C23H25N3O2S·0.2H2O 67.19
(67.24
6.23
6.28
10.22
10.14)
C23H26N3O2S (MꢃH)ꢃ
408.1746
(NH2, NH)
(408.1736)
1510, 1235 (NH–CꢁS)
a) Analytical sample (1R,2R)-7b was obtained by silica-gel chromatography using acetonitrile as an eluent.
Table 3. 13C-NMR Spectral Data of N-Monocarbamoyl 2,6-Diaminopyridine, 1,2-Diaminocyclohexane, and 1,2-Diphenylethylenediamine (5—7)
C No.
5a
5b
5c
(1R,2R)-6a
(1R,2R)-6b
(1R,2R)-6c
cis-6c
(1R,2R)-7b
(1R,2R)-7c
Pyridine ring or
C1a)
—
—
—
56.34
61.51
56.21
34.79
24.82
24.74
32.24
—
61.10
53.94
55.25
49.72
31.86
20.28
22.97
27.15
—
64.41
59.52
—
63.68
cycylohexane ring C2
152.36
98.12
152.39
99.04
139.55
100.80
156.54
—
152.31
98.89
139.77
101.42
157.19
—
56.00
59.66
or ethylene chain C3
34.67
34.60
—
—
C4
C5
C6
138.83
99.48
24.91
24.53 or 24.68
24.68 or 24.53
31.23
—
25.18
—
—
153.39
157.43
—
33.12
—
—
–NHCO–
158.1
—
—
—
–NHCS–
176.83
178.17
—
181.24
180.52
179.75
180.49
181.18
C of adamantyl or
phenyl
28.87 (c),
36.05 (a),
41.62 (b),
49.79 (d)
28.94 (c), 109.91 (C2ꢀ),
35.98 (a), 111.55 (C5ꢀ),
40.45 (b), 117.13 (C6ꢀ),
53.51 (d) 132.48 (C1ꢀ),
146.52 (C4ꢀ),
29.60 (c),
36.51 (a),
42.51 (b),
50.93 (d)
29.53 (c), 109.17 (C2ꢀ), 109.23 (C2ꢀ), 29.36 (c),
36.24 (a), 112.03 (C5ꢀ), 111.63 (C5ꢀ), 35.99 (a),
42.07 (b), 116.08 (C6ꢀ), 117.31 (C6ꢀ), 41.93 (b),
54.08 (d) 132.38 (C1ꢀ), 129.78 (C1ꢀ), 53.75 (d),
on C6H3(OMe)2
109.99 (C2ꢀ),
111.65 (C5ꢀ),
118.44 (C6ꢀ),
146.11 (C4ꢀ), 147.75 (C4ꢀ), 126.36, 126.41 (o-), 129.32 (C1ꢀ),
148.20 (C3ꢀ)
148.62 (C3ꢀ)
149.59 (C3ꢀ) 127.28, 127.56 (p-), 148.41 (C4ꢀ),
128.43, 128.63 (m-), 149.81 (C3ꢀ),
140.32, 141.36 (on
C1,2)
on Ph
126.57, 126.67 (o-),
127.52, 127.80 (p-),
128.48, 128.68 (m-),
139.58 (on C2),
140.76 (on C1),
56.07 (on C3ꢀ),
56.11 (on C4ꢀ)
CDCl3
–OCH3
Solvent
—
—
55.67,
55.84
—
—
55.64,
55.99b)
CDCl3
—
55.89
DMSO-d6
DMSO-d6 DMSO-d6
CDCl3
CDCl3
DMSO-d6
CDCl3
a) Corresponding to N1 in the case of pyridine. b) Overlapped with the other signals.

September 2007
1409

1410
Vol. 55, No. 9
Table 5. Antiviral Activity of N-Monocarbamoyl Derivatives (5—7) of
used without further purification.
Symmetrical Diamines
General Procedure for Addition of Isocyanate or Isothiocyanate to
Diamines A solution of an iso(thio)cyanate (a proper molar ratio listed in
Table 1) in a proper solvent (5—10 ml) was added to a stirring solution of an
appropriate diamine (1—3, 2 mmol) in the same solvent (10—20 ml), and
this mixture was stirred for the indicated time and temperature (in Table 1).
In some entries, the experiment was carried out under an N2 atmosphere.
After the evaporation of the solvent, purification by centrifugal or flash col-
umn chromatography (SiO2, EtOH or EtOH–CH2Cl2 as solvent) produced
the target products (5—7). Recrystallization from a proper solvent afforded
an analytically pure sample (see Tables 1, 2). The purification of the com-
pound (1R,2R)-7b was carried out by centrifugal chromatography.
Method A: Preparation of N-(6-Amino-2-pyridinyl)-Nꢁ-tricyclo-
[3.3.1.13,7]dec-1-ylurea (5a) Based on the protocol reported by Wang T. et
al.,7) 1.6 M n-BuLi in n-hexane (1.71 ml, 2.73 mmol, 220 mol%) was added
to a stirred solution of 2,6-diaminopyridine (1; 135 mg, 1.24 mmol,
100 mol%) in dry THF (6 ml) under N2 atmosphere at room temperature.
After stirring for 1 h, 1-adamantyl isocyanate (4a; 220 mg, 1.24 mmol,
100 mol%) was added to this solution, and the resulting mixture was then
stirred for an additional 10 min. The reaction mixture was quenched with
MeOH (4 ml) and the solvents were evaporated. The residue was extracted
with EtOAc (3ꢄ25 ml). The organic layer was dried over MgSO4 and
concentrated to yield the crude product 5a. Recrystallization from
EtOH–CH2Cl2 gave analytically pure 5a (249 mg, 70% yield).
EC50 (mg/ml)
CC50 (mg/ml)
CC50/EC50
5a
5b
5c
17.0
6.2
ꢅ40
42
ꢅ40
ꢅ40
ꢅ40
ꢅ40
ꢅ40
15.3
170
ca. 10.0
15.0
2.4
b)
b)
(1R,2R)-6a
(1R,2R)-6b
(1R,2R)-6c ·HCl
cis-6c
(1R,2R)-7b
(1R,2R)-7c ·HCl
A2a)
250
ca. 5.0 (6.0)
b)
b)
b)
b)
b)
b)
b)
b)
b)
b)
50.0
3.3
a) N-(6-Amino-2-pyridinyl)dodecanamide (A2) was reported.1) b) CC50 values
and selectivity indexes (CC50/EC50) for these compounds were not determined.
showed a high cytotoxic activity, thus resulting in a lower
selectivity index (CC50/EC50ꢁ2.4). Compound (1R,2R)-6a
showed considerable degree of antiviral activity and had less
cytotoxicity than that of A2, and the selectivity index was ca.
5.0—6.0. The other synthesized compounds listed in Table 5
were unfortunately inactive against HSV-1 at the concentra-
tion of 40 mg/ml.
Method B: Preparation of N-(3,4-Dimethoxyphenyl)-Nꢁ-(6-amino-2-
pyridinyl)-thiourea (5c) 2,6-Diaminopyridine monohydrochloride was
prepared by adding one equivalent of 10% hydrochloric acid in ethanol. Re-
crystallization from i-PrOH generated the monohydrochloride of 2,6-di-
These observations demonstrate that the derivatives of aminopyridine (1·HCl) in 73% yield, as a green solid, mp 153—154 °C.14,15)
FAB-MS m/z: 110 (MꢃꢃH). IR (KBr) cmꢂ1: 3370, 3190 (NH2), ca. 3000
DAP (5a, b) possess a higher antiviral activity than the com-
pounds [6 and (1R,2R)-7] derived from aliphatic 1,2-di-
aminocyclohexanes and 1,2-diaminoethanes. In comparison
(NH3ꢃ), 1645 (N–H). 1H-NMR (DMSO-d6) d: 5.91 (2H, d, Jꢁ8.2 Hz, H3,5),
7.33 (4H, br s, NH2), 7.48 (1H, t, Jꢁ8.2 Hz, H4), 13.04 (1H, br s, HCl). 13C-
NMR (DMSO-d6) dC: 94.89 (C3,5), 144.68 (C4), 151.96 (C2,6). Anal.
to prototype A2, compound 5a actually showed identical an-
tiviral activities, and the replacement of the long-chain alkyl
substituent in the adamantyl-amino group resulted in the at-
tenuation of the cytotoxicity (CC50ꢁ170 mg/ml for 5a). Com-
pound (1R,2R)-6a with an adamantyl-urea moiety showed a
lower cytotoxicity and antiviral potency than compound 5a.
The sulfur analog 5b resulted in an increased cytotoxicity as
shown in Table 5. The CC50 values for the other N-monosub-
stituted 1,2-diamine derivatives [5c, (1R,2R)-6b, c, cis-6c,
and (1R,2R)-7b, c] were not evaluated, because there were no
significant antiviral activities over a dose of 40 mg/ml. How-
ever, these data demonstrate that the mono-substituted
aliphatic 1,2-diaminocyclohexane derivatives exhibit a ten-
dency toward lower antiviral activity in comparison to the N-
monosubstituted aromatic diamine derivatives.
Calcd for C5H7N3·HCl·0.7H2O: C, 37.96; H, 5.99; N, 26.56. Found: C,
37.84; H, 5.89; N, 26.83. The addition of isothiocyanate 4c to this diamine
monohydrochloride was carried out according to the procedure described by
Bied C. et al.8) Therefore, 2,6-diaminopyridine·HCl·0.7H2O (1·HCl;
443 mg, 2.8 mmol, 140 mol%) in dry CH2Cl2–EtOH (50 ml, 10 ml) was
placed in a round-bottomed flask under an N2 atmosphere at ꢂ10 °C. A so-
lution of 3,4-dimethoxyphenyl isothiocyanate (4c) in dry CH2Cl2 (15 ml)
was added dropwise. After stirring overnight at ꢂ10—10 °C, the solution
was then washed with aqueous Na2CO3 (20 ml) to remove the excess unre-
acted diamine hydrochloride. The organic layer was dried over MgSO4 and
then the solvent was evaporated. The residue was recrystallized from CH2Cl2
to produce the product 5c in a 61% yield.
Method C: Preparation of N-[(1R,2R)-2-Aminocyclohexyl]-Nꢁ-tricy-
clo[3.3.1.13,7]dec-1-ylurea [(1R,2R)-6a] A solution of 0.4 M 9-BBN in
hexanes (10 ml, 4.0 mmol, 100 mol%) was added to a stirred solution of
(1R,2R)-2 (457 mg, 4.0 mmol, 100 mol%) in THF (60 ml) at room tempera-
ture under N2 atmosphere. After stirring for 1 h, 1-adamantyl isocyanate (5a;
674 mg, 3.8 mmol, 95 mol%) was added and the reaction mixture was stirred
This study showed that the derivatives of DAP 5a showed for an additional 1 h. In order to dissociate the complex with 9-BBN from
product, 1 M aqueous HCl (17 ml) was added, and the mixture was stirred at
room temperature overnight. Neutralization, extraction with CH2Cl2, and
then purification by open column chromatography (SiO2, EtOH) produced
the same level of significant anti-HSV-1 activity and less cy-
totoxicity, providing a new candidate for antiviral leads. Fur-
ther synthetic application of the above information and bio-
logical studies on related compounds are in progress.
the compound (1R,2R)-6a in a 66% yield (see Table 1).
The physical and spectroscopic (1H-, 13C-NMR) data for the prepared
compounds (5—7) are summarized in Tables 2—4.
Experimental
The HCl salts (1R,2R)-6c and (1R,2R)-7c were also obtained by the reac-
tions from the corresponding compounds with a large excess of 10% HCl in
The melting points were determined using a micro melting point appara-
tus (Yanagimoto MP-S3) without correction. IR spectra were measured by EtOH. In addition, recrystallization produced the desired salts.
Shimadzu FTIR-8100 IR spectrophotometer. Low- and high-resolution mass
Compound (1R,2R)-6c·HCl: mp 218—220 °C (from EtOH): HR positive
spectra (LR-MS and HR-MS) were taken by JEOL JMS HX-110 double-fo- ion FAB-MS: Calcd for C15H24N3O2S (MꢃH)ꢃ: 310.1589. Found: 310.1591.
ꢃ
cusing model equipped with a FAB ion source interfaced with a JEOL JMA-
IR (KBr) cmꢂ1: 3205 br (NH3 salt), 1510, 1230 (NH–CꢁS). 1H-NMR
1
DA 7000 data system. H- and 13C-NMR spectra were obtained by JEOL (DMSO-d6) d: ca. 1.20 (1H, m, H5), ca. 1.25 (1H, m, H4), ca. 1.30 (1H, m,
JNM A-500. Chemical shifts were expressed in d ppm downfield from an in- H6), ca. 1.43 (1H, m, H3), 1.68 (1H, m, H5), 1.70 (1H, m, H4), 1.97 (1H, d,
1
ternal tetramethylsilane (TMS) signal for H-NMR and the carbon signal of
the corresponding solvent [CDCl3 (77.00 ppm), CD3OD (49.00 ppm), and
Jꢁ13.7 Hz, H6), 2.04 (1H, d, Jꢁ13.7 Hz, H3), 3.09 (1H, dt, Jꢁ10.8, 0.4 Hz,
H2), 3.73 (3H, s, OCH3 on C3ꢀ), 3.74 (3H, s, OCH3 on C4ꢀ), ca. 4.38 (1H,
dimethyl sulfoxide (DMSO)-d6 (39.50 ppm)] for 13C-NMR. Microanalyses m, H1), 6.88 (1H, dd, Jꢁ8.5, 1.8 Hz, H6ꢀ), 6.91 (1H, d, Jꢁ8.5 Hz, H5ꢀ),
were performed with a Yanaco MT-6 CHN corder. Routine monitoring of re- 7.18 (1H, br s, H2ꢀ), 7.85 (1H, d, Jꢁ7.9 Hz, Ch-NH–), 7.99 (2H, br s, NH2),
actions was carried out using precoated Kieselgel 60F254 plates (E. Merck). 9.73 (1H, br s, Ar-NH–). 13C-NMR (DMSO-d6) dC: 23.27 (C4), 24.01
Centrifugal, flash column, or open column chromatography was performed (C5), 29.42 (C3), 30.76 (C6), 52.87 (C2), 55.20 (C1), 55.57 (OCH3 on C3ꢀ),
on silica gel (Able-Biott, Fuji Silysia FL40D, or Wako gel LP-40, respec- 55.80 (OCH3 on C4ꢀ), 109.20 (C2ꢀ), 111.87 (C5ꢀ), 116.03 (C6ꢀ), 132.02
tively) with a UV detector. Commercially available starting materials were (C1ꢀ), 146.15 (C4ꢀ), 148.46 (C3ꢀ), 180.63 (CꢁS). Anal. Calcd for

September 2007
1411
C15H23N3O2S·HCl: C, 52.09; H, 6.99; N, 12.15. Found: C, 51.93; H, 6.91;
N, 12.15.
Sumoto K., Chem. Pharm. Bull., 55, 111—114 (2007) and related ref-
erences cited therein.
Compound (1R,2R)-7c·HCl: mp 194—198 °C (from EtOH): HR positive
2) Kumamoto K., Misawa Y., Tokita S., Kubo Y., Kotsuki H., Tetrahe-
dron Lett., 43, 1035—1038 (2002) and references are cited therein.
3) Soledade C., Pedras M., Jha M., Bioorg. Med. Chem., 14, 4958—4979
(2006).
4) Sarkis G. Y., Faisal E. D., J. Heterocycl. Chem., 22, 137—140 (1985).
5) Venkatachalam T. K., Sudbeck E. A., Uckun F. M., Tetrahedron Lett.,
42, 6629—6632 (2001).
6) Orzeszko B., Kazimierczuk Z., Maurin J. K., Laudy A. E., Starosciak
B. J., Vilpo J., Vilpo L., Balzarini J., Orzeszko A., Farmaco, 59, 929—
937 (2004).
7) Wang T., Zhang Z., Meanwell N. A., J. Org. Chem., 64, 7661—7662
(1999).
ion FAB-MS: Calcd for C23H26N3O2S (MꢃH)ꢃ: 408.1746. Found: 408.1747.
ꢃ
IR (KBr) cmꢂ1: 3315 (NH), 3000 br (NH3 salt), 1515, 1235 (NH–CꢁS).
1H-NMR (CD3OD) d: 3.73 (3H, s, OCH3 on C3ꢀ), 3.84 (3H, s, OCH3 on
C4ꢀ), 4.81(1H, d, Jꢁ10.4 Hz, H2), 6.34 (1H, d, Jꢁ10.4 Hz, H1), 6.84 (1H,
dd, Jꢁ8.4, 2.3 Hz, H6ꢀ), 6.95 (1H, d, Jꢁ8.5 Hz, H5ꢀ), ca. 6.96 (1H, br s,
H2ꢀ), 7.17—7.20 (2H, m, o-Ph on C1), 7.21—7.24 (3H, m, p-,m-Ph on C1),
7.30—7.34 (5H, m, C6H5 on C2). 13C-NMR (CD3OD) dC: 56.53 (OCH3 on
C3ꢀ), 56.77(OCH3 on C4ꢀ), 60.64 (C2), 62.86 (C1), 110.94 (C2ꢀ), 113.16
(C5ꢀ), 118.78 (C6ꢀ), 128.99 (o-Ph on C1), 129.23 (o-Ph on C2), 129.49 (p-
Ph on C1), 129.83 (m-Ph on C1), 130.07 (m-Ph on C2), 130.47 (p-Ph on
C2), 132.28 (C1ꢀ), 135.24 (Ph on C2), 138.02 (Ph on C1), 148.96 (on C4ꢀ),
150.48 (on C3ꢀ), 183.46 (CꢁS). Anal. Calcd for C23H25N3O2S·HCl: C,
62.22; H, 5.90; N, 9.46. Found: C, 62.08; H, 5.86; N, 9.41.
8) Bied C., Moreau J. J. E., Man M. W. C., Tetrahedron: Asymmetry, 12,
329—336 (2001).
Formation of Bis-ureido: N,Nꢂ-(1R,2R)-1,2-Cyclohexanediylbis[Nꢂ-
tricyclo[3.3.1.13,7]dec-1-ylurea] (8a) At the end of the reactions between
(1R,2R)-2 and 4a in the dry solvent (CH2Cl2, CH3CN, or THF for entries 9,
9) In the reaction of 4c with DAP·HCl, we used the DAP salt elucidated
by an elemental analysis and spectroscopic data as the starting material
(see Experimental; Method B).
10, 11, respectively in Table 1) the precipitated material formed in the reac- 10) Zhang Z., Yin Z., Meanwell N. A., Kadow J. F., Wang T., Org. Lett., 5,
tion mixture. The crude material was then filtered and purified by recrystal-
lization from EtOH or flash chromatography (SiO2, EtOH) to produce 8a as
a white powder; mp 303—304 °C (from EtOH): HR positive ion FAB-MS:
3399—3402 (2003).
11) As an explanation of the difference in the stability of the products be-
tween cis-6c and (1R,2R)-6c, one could consider that the product cis-
6c probably has the chair conformation with the amino group in an
axial position and the thiourea group in an equatorial position predom-
inantly. However, the product from (1R,2R)-2 (trans isomer of 1,2-di-
aminocyclohexane) requires both amino and thiourea group in the
equatorial orientation. The fact that this diequatorial conformer is
more stable than the former conformer of cis-6c by the steric hin-
drance could be estimated by the energy calculation of these conform-
ers using the computer program CAChe version 6.1.12 (Fujitsu Lim-
ited, 2004). The results of calculation showed that minimized strain en-
ergy for (1R,2R)-6c (ꢂ30.63 kcal/mol) is lower than that of cis-6c
(ꢂ30.47 kcal/mol) by an energy difference of 0.16 kcal/mol, and also
showed the ratio of 1 : 1.3 [(1R,2R)-6c : cis-6c]. The diamine meso-2 is
more reactive than one of (1R,2R)-2, however, reported pKa, 9.77 for
(1R,2R)-2 and 9.80 for meso-2, respectively,12) the values are very
close. This may indicate that the pKa values contribute very little to the
reactivity of diamines.
Calcd for C28H45N4O2 (Mꢃ): 469.3543. Found: 469.3545. IR (KBr) cmꢂ1
:
3355, 3325 (NH), 1630 (CꢁO). 1H-NMR (CDCl3) d: 1.1—1.3 (4H, m,
H3—6), 1.66 (12H, br s, a in adamantyl), 1.65—1.75 (2H, m, H4,5), 1.95
(12H, d, Jꢁ2.8 Hz, b in adamantyl), 1.9—2.05 (2H, m, H3,6), 2.06 (6H, br s,
c in adamantyl), 3.3—3.4 (2H, m, H1,2), 4.5 (2H, br s, NH), 5.1 (2H, br s,
NH). 13C-NMR (CDCl3) dC: 24.99 (C4,5), 29.60 (c in adamantyl), 33.23
(C3,6), 36.49 (a in adamantyl), 42.54 (b in adamantyl), 51.07 (d in
adamantyl), 54.78 (C1,2), 158.29 (CꢁO). Anal. Calcd for C28H44N4O2: C,
71.76; H, 9.46; N, 11.95. Found: C, 71.56; H, 9.65; N, 11.92. The filtrate
was evaporated under reduced pressure. The purification of the residue gave
the compound (1R,2R)-6a in the yields listed in Table 1 (entries 9—11).
Antiviral Activity Assay and Cytotoxicity of Target Compounds (5—
7) The antiviral activities of the compounds were measured using a plaque
reduction assay13) as described in a previous paper.1) The calculated EC50
values for the tested compounds are summarized in Table 5. The cytotoxicity
of the compounds 5a, b, and (1R,2R)-6a were determined by the method de-
scribed in a previous paper. The calculated cytotoxicity (CC50) values for the 12) Perrin D. D., Aust. J. Chem., 17, 484—488 (1964).
tested compounds are summarized in Table 5. 13) Schinazi R. F., Peters J., Williams C., Chance D., Nahmias A., Antimi-
crob. Agents Chemother., 22, 499—507 (1982).
Acknowledgments We thank Ms. Chie Fujita and Ms. Sayaka Ueno for 14) Melting point of 81—83 °C has been reported for 2,6-diaminopyri-
their valuable technical assistance.
dine·HCl as crystallized one from EtOH, which changed to 156—
157 °C after heating for 2 h at 75 °C.15)
References and Notes
1) Mibu N., Yokomizo K., Kashige N., Miake F., Miyata T., Uyeda M.,
15) Bernstein J., Stearns B., Dexter M., Lott W. A., J. Am. Chem. Soc., 69,
1147—1150 (1947).