Influence of 2-substituent on the activity of imidazo[1,2-a] pyridine derivatives against human cytomegalovirus

Article abstract of DOI:10.1016/S0968-0896(01)00347-9

The synthesis of various 2-substituted imidazo[1,2-a]pyridine bearing a thioether side chain in position 3 was reported. The new compounds were characterized by ¹H and ¹³C NMR spectra. A conformational study was obtained by X-ray crystallographic analysis for 2-biphen-4-ylimidazopyridine 7. The antiviral activity against human cytomegalovirus (HCMV) was investigated. It was strongly influenced by the nature of C-2 substituent. Copyright

Full text of DOI:10.1016/S0968-0896(01)00347-9

Bioorganic & Medicinal Chemistry 10 (2002) 941–946
Influence of 2-Substituent on the Activity of Imidazo[1,2-a]
Pyridine Derivatives Against Human Cytomegalovirus
Sylvie Mavel,a Jean-Louis Renou,a Christophe Galtier,a Hassan Allouchi,b
Robert Snoeck,c Graciella Andrei,c Erik De Clercq,c Jan Balzarinic and Alain Gueiffiera,*
a
´
´
Laboratoire de Chimie Therapeutique, Faculte de Pharmacie, 31 Av. Monge, 37200 Tours, France
b
´
Laboratoire de Chimie Physique, Faculte de Pharmacie, 31 Av. Monge, 37200 Tours, France
cRega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium
Received 18 June 2001; accepted 1 October 2001
Abstract—The synthesis of various 2-substituted imidazo[1,2-a]pyridine bearing a thioether side chain in position 3 was reported.
1
The new compounds were characterized by H and 13C NMR spectra. A conformational study was obtained by X-ray crystal-
lographic analysis for 2-biphen-4-ylimidazopyridine 7. The antiviral activity against human cytomegalovirus (HCMV) was investi-
gated. It was strongly influenced by the nature of C-2 substituent. # 2002 Elsevier Science Ltd. All rights reserved.
Introduction
Results and Discussion
Chemistry
Human cytomegalovirus (HCMV) is a highly prevalent
member of the herpesvirus family responsible for severe
illness in newborns1 and immunosuppressed patients,
where it can lead to gastrointestinal infections, retinitis,
pneumonitis, and encephalopathy.2
Condensation of 2-amino-4-picoline with the suitable
bromoacetyl compound in refluxing ethanol in the usual
manner gave the attempted imidazo[1,2-a]pyridine deri-
vatives 1a–k (Scheme 1), in moderate to good yield (not
optimized, Table 1). Using formaldehyde in acetic acid
medium, hydroxymethylation in position 3 gave com-
pounds 2a–k, generally in good yields (Table 1). Upon
the nature of the 2-substituent, the reaction began
smoothly at room (or eventually higher) temperature,
and progressive heating was necessary in order to avoid
the formation of by-products (Table 1). The thioethers
3–14 were obtained using benzyl or phenethylmercaptan
in acetic acid medium at 100 ꢁC. Yields and melting
point were listed in Table 2. The structural determina-
In previous communications, we have reported the
synthesis and the antiviral activities of imidazo[1,2-
a]pyridine derivatives bearing a 3-alkyl or 3-arylalkyl-
thiomethyl side chain.3ꢀ6 Some of these compounds
were shown to be potent inhibitors of HCMV. In these
studies, we were principally interested by studying the
influence of the pyridinic substituent on the antiviral
activity. It appeared that 7-methyl, 8-methyl and 6-
bromo-8-methylimidazo[1,2-a] pyridine derivatives (I,
II, III, Fig. 1) were potent inhibitors of HCMV. At this
point, only little information on the influence of the 2-
substitution was obtained. A phenyl group (compound
IV) was found to diminish activity.6 We have now syn-
thesized and determined the antiviral activity of 2-alkyl,
cycloalkyl, aryl and heteroaryl substituted derivatives.
1H and 13C NMR were determined together with X-ray
crystal structure of one derivative. The biological activ-
ity is described too.
1
tion of all the new structures was achieved by H and
13C spectroscopy and when necessary, for quaternary
*Corresponding author. Tel.: +33-2-4736-7138; fax: +33-2-4736-
7239; e-mail: gueiffier@univ-tours.fr
Figure 1.
0968-0896/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(01)00347-9

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S. Mavel et al. / Bioorg. Med. Chem. 10 (2002) 941–946
Scheme 1. Reagents and conditions: (i) a-halogenocarbonyl derivative, EtOH, 4 h, reflux; (ii) HCHO, AcOH, AcONa, 20 ꢁC–reflux, 1–4 h; (iii)
C6H5CH2SH or C6H5(CH2)2SH, AcOH, 100 ꢁC, 4 h.
carbons, by LRHETCOR. For the final thioethers 3–14,
the spectroscopic data were given in Tables 2 and 3.
For these reasons, we did not look further into the
activities for this compound. The bond lengths and
bond angles are given in Tables 5 and 6, respectively.
The interesting torsion angles which entirely define the
molecule conformation are as follows:
Antiviral assays
None of the synthesized compound showed appreciable
activity against human immunodeficiency virus (HIV-1
and HIV-2) in MT-4 cell cultures (data not shown). The
antiviral activity of compounds 3–14 against human
cytomegalovirus are indicated in Table 4.
N1–C2–C10–C20
ꢀ41.2 (3)ꢁ C3–C9–S10–C11
78.0 (2)
C30–C40– C70–C80 147.5 (2)ꢁ C9–S10–C11–C100 67.3 (2)
N4–C3–C9–S10
65.0 (2)ꢁ
C10–C11–C100–C20 111.5 (2)
These data agree quite well with those obtained pre-
viously in the same series.9,10
Crystal structure analysis
The biphenyl compound 7 gave suitable crystals. The
solid-state conformation of compound 7 with thermal
ellipsoid representation and the labeling of non-hydro-
gen atoms7 is presented in Figure 2. It should be noted
that the homologue of 7 in the 2-phenylimidazopyridine
series was inactive.6 Moreover, with regard to molecular
modeling studies on imidazo[1,2-a]pyridine,8 it seemed
that the thioether side chain on C-3 is in an orientation
perpendicular to the direction of the C(2)-H bond for
active compounds. For compounds which presented
poor antiviral activity, the thioether side chain con-
formation was parallel to the C-2 extra cyclic bond, as it
was evident on the crystallographic data obtained for 7.
Structure–activity relationship
Introduction of an alkyl group in position 2 (12, 13)
slightly enhanced the activity against HCMV, but also
the cytotoxicity. The trifluoromethyl derivative 11
emerged as the most potent compound with an
improvement of the antiviral activity by a factor 2- to 4-
fold in comparison with I, and decreased cytotoxicity.
As reported for the 2-phenyl compound IV,6 the furan-
2-yl compound 5 was inactive, and the pyridin-3-yl
derivative 9 was poorly active. In contrast, all the other
compounds, with aryl group in 2 position, showed
Table 1. Physical data of 1, conditions for the synthesis and physical data of 2
Yield %
Mp (ꢁC)
Temperature (ꢁC)
Time (h)
Yield (%)
Mp (ꢁC)
1a
1b
1c
1d
1e
1f
1g
1h
1i
75
37
54
77
48
13
12
40
36
67
39
124–126 (lit.:21 129)
149–151 (lit.:22 155)
199–201
2a
2b
2c
2d
2e
2f
2g
2h
2i
Reflux
Room temperature
1
2
4
1
3
2
4
3
3
3
1
76
51
57
75
90
42
53
70
46
43
79
205–207
155–157
221–223
>260
182–184
162–164
243–245
175–177
159–161
230–232
182–184
50
50
Reflux
60
60
100
50
50
50
221–223 (lit.:23 217)
183–185
72–74
165–167
145–146 (lit.:24 145)
96–98
147–146
1j
1k
2j
2k
113–115

S. Mavel et al. / Bioorg. Med. Chem. 10 (2002) 941–946
943
Table 2. Physical data and 1H NMR spectral data of thioethers 3–14 in CDCl3, chemical shifta
Yield % Mp (ꢁC)
H-5
7.70
H-6
6.61
H-8
H alkyl
H aryl
0
7.07 (dd, J4 ,5 =5.0, J3 ,4 =3.6, H-4 ), 7.25 (m, 3Harom, H-50),
0
0
0
0
3
4
95
90–92
7.26 br.s
2.40 (s, CH3),
3.68 (s, SCH2),
4.18 (s, CH2S)
2.40 (s, CH3),
2.70 (m, 2CH2),
4.26 (s, CH2S)
0
0
7.29 (dd, J3 ,4 =3.6, J3 ,5 =1.1, H-3 ), 7.34 (m, 2Harom
0
0
0
J5,6=7.1 J5,6=7.1,
J6,8=1.7
7.91
J5,6=7.0 J5,6=7.0,
J6,8=1.7
)
0
0
0
0
7.01 (m, 2Harom), 7.15 (dd, J4 ,5 =5.1, J3 ,4 =3.6, H-4 ),
0
70
93–95
6.65
7.38 br.s
7.25 (m, H-50, 2Harom),
7.38 (m, H-8,400, H-50), 7.51 (dd, J3 ,4 =3.6,
0
0
0
0
0
J3 ,5 =1.2, H-3 )
0
0
0
0
0
5
72
75
42
56
57
37
20
73
149–151
142–144
136–138
118–119
189–191
135–137
106–108
66–68
7.83
J5,6=7.0
6.88
J5,6=7.0
7.35 s
2.42 (s, CH3),
3.65 (s, SCH2),
4.35 (s, CH2S)
2.46 (s, CH3),
3.69 (s, SCH2),
4.20 (s, CH2S)
2.46 (s, CH3),
3.70 (s, SCH2),
4.17 (s, CH2S)
2.33 (s, CH3),
3.60 (s, SCH2),
4.72 (s, CH2S)
2.26 (s, CH3),
3.56 (s, SCH2),
3.91 (s, CH2S)
2.21 (s, CH3),
3.53 (s, SCH2),
3.86 (s, CH2S)
2.42 (s, CH3),
3.70 (s, SCH2),
4.12 (s, CH2S)
1.45 (s, 3CH3),
2.35 (s, CH3),
3.79 (s, SCH2),
4.05 (s, CH2S)
1.79 (m, 4CH),
2.10 (m, 6CH2),
2.38 (s, CH3),
3.80 (s, SCH2),
4.10 (s, CH2S)
0.70 (m, CH2),
0.99 (m, CH2),
1.43 (s, CH3),
2.36 (s, CH3),
3.78 (s, SCH2),
4.08 (s, CH2S)
6.52 (dd, J3 ,4 =3.4, J4 ,5 =1.8, 0H-4 ), 6.88 (d, 1H,
0
J3 ,4 =3.4, H-3 ),
0
0
0
0
7.24 (m, 5Harom), 7.43 (d, J4 ,5 =1.8, H-5 )
7.19 (m, 5Harom), 7.55 (m, H-30,40), 7.90 (m, H-50,60,70,80),
8.25 (s, H-10)
6
7.78
6.68
7.45br.s
7.45 br.s
7.29 br.s
7.25 br.s
7.19 br.s
7.32 s
J5,6=7.0 J5,6=7.0,
J6,8=1.8
7.78
J5,6=7.0
7
6.68
J5,6=7.0
7.17 (m, 5Harom), 7.91 (m, 5Harom)
0
0
0
0
0
0
0
7.10 (m, 6Harom), 7.68 (td, J4 ,3 =J4 ,5 =7.8, J4 ,6 =1.8, H-4 ),
8
7.81
J5,6=7.0
6.56
J5,6=7.0
0
0
0
0
0
0
8.14 (ddd, J3 ,4 =7.8, J3 ,5 =1.2, J3 ,6 =1.0, H-3 ),
0
8.41 (m, H-60)
0
7.20 (m, 5Harom, H-50), 7.91 (d, J4 ,5 =8.0, H-4 ),
0
0
9
7.56
J5,6=7.0
6.49
J5,6=7.0
0 0
0 0
8.48 (d, J5 ,6 =4.8, H-6 ), 8.96 (br.s, H-2 )
0 0
0 0 0 0
7.15 (m, 5Harom), 7.44 (d, J2 ,3 =J5 ,6 =5.0, H-3 ,5 ),
10
11
12
7.51
J5,6=6.8
6.45
J5,6=6.8
0 0
0 0 0 0
8.42 (d, J2 ,3 =J5 ,6 =5.0, H-2 ,6 )
7.77
J5,6=7.0
6.72
J5,6=7.0
7.26 (m, 5Harom
)
)
7.40
6.50
7.33 br.s
7.37 (m, 5Harom
J5,6=7.0 J5,6=7.0,
J6,8=1.4
13
14
64
34
Oil
7.48
6.53
7.46 br.s
7.27 br.s
7.41 (m, 5Harom
)
J5,6=7.0 J5,6=7.0,
J6,8=1.6
74–76
7.57
6.53
7.36 (m, 5Harom
)
J5,6=6.9 J5,6=6.9,
J6,8=1.5
as are in ppm, H–H coupling constants J are in Hz. Multiplicity of coupling are given: s, singlet; br. s, broad singlet; d, doublet; dd, doublet of
doublet; m, multiplet.
Figure 2. Ellipsoid representation and atomic labeling of 7 (probability 50%).

944
S. Mavel et al. / Bioorg. Med. Chem. 10 (2002) 941–946
Table 3. 13C NMR spectral data of thioethers 3–14 in CDCl3
a
C-2
C-3
C-5
C-6
C-7
C-8
C-8a
C-alkyl
C- aryl
3
4
137.3
114.3 122.5 114.9 135.3 115.7 144.8 20.8 (CH3),
24.2 (CH2S),
35.7 (SCH2)
114.2 123.4 114.9 136.0 115.7 145.5 21.4 (CH3),
124.4 (C-30), 125.0 (C-50), 126.6 (C -400), 127.3 (C-40), 128.0 (2Carom),
128.4 (2Carom), 136.8 (C-100), 137.8 (C-20)
137.3
125.1(C-30), 125.6 (C-50), 126.3 (C-400), 127.8 (C -40), 128.4 (2Carom),
128.5 (2Carom), 138.5 (C -100), 140.0 (C-20)
25.4 (CH2S),
33.0 (CH2),
36.4 (CH2)
114.2 123.3 114.7 135.4 115.6 145.8 21.3 (CH3),
5
136.1
143.7
143.4
141.5
140.2
140.3
107.9 (C-30), 111.4 (C-40), 126.8 (C-400), 128.3 (2Carom),
128.7 (2Carom), 137.8 (C-100), 141.9 (C-50), 149.8 (C-20)
24.4 (CH2S),
35.6 (SCH2)
6
114.5 122.9 114.6 135.4 115.5 145.4 21.1 (CH3),
24.7 (CH2S),
36.1 (SCH2)
114.5 123.1 114.7 135.7 115.7 145.1 21.2 (CH3),
125.8 (C-60, 70), 126.1, 126.8, 127.0, 127.4 (4Carom) 128.0, 128.2 (4Carom),
128.5 (C-200, 600), 131.5, 132.6, 133.2 (C-20,4a0,8a0), 137.6 (C-100)
7
126.9 (2Carom), 127.0 (1Carom), 127.2 (2Carom), 128.4 (2Carom),
128.6 (2Carom), 128.7 (5Carom), 133.0 (C-40), 137.5 (C-1000),
140.2, 140.6 (C-10, 100)
121.9, 122.0 (C-30, 50), 126.6 (C-400), 128.2 (2Carom), 128.6 (2Carom),
136.4 (C-40), 138.3 (C-100), 148.7 (C-60), 154.3 (C-20)
24.7 (CH2S),
36.2 (SCH2)
8
118.0 123.5 114.8 135.8 115.9 145.3 21.3 (CH3),
24.7 (CH2S),
35.6 (SCH2)
114.8 123.1 114.6 135.6 115.4 145.3 20.9 (CH3),
9
122.8 (C-50), 126.8 (C-400), 128.1 (2Carom), 128.3 (2Carom), 129.9 (C-30),
135.0 (C-40), 137.1 (C-100), 148.2 (C-60), 148.7 (C-20)
24.2 (CH2S),
36.0 (SCH2)
10
11
12
115.9 122.8 115.0 136.1 115.7 145.4 21.0 (CH3),
24.1 (CH2S),
36.2 (SCH2)
118.2 123.6 116.2 137.3 116.6 145.2 21.2 (CH3),
122.0 (C-30,50), 127.1 (C-400), 128.3, 128.6 (C-30, 50, 200, 600),
137.1 (C-100), 141.5 (C-40), 149.6 (C-20,60)
132.8
J=36.7 Hz
122.3 (CF3, J=270Hz), 127.1 (C-40),
128.4, 128.6 (4Carom), 137.1(C-10)
23.6 (CH2S),
36.2 (SCH2)
152.2
111.9 121.9 113.6 133.8 114.9 143.5 20.7 (CH3),
25.0 (CH2S),
126.7 (C-40), 128.1, 128.5 (4Carom), 137.5 (C-10)
126.7 (C-40), 128.0, 128.5 (4Carom), 137.6 (C-10)
30.5 (3CH3),
32.9 (C),
36.4 (SCH2)
112.0 121.9 113.5 133.8 115.0 143.7 20.7 (CH3),
13
14
152.1
25.1(CH2S),
28.3 (3CH2),
35.2 (SCH2),
36.4 (4CH),
41.9 (3CH2)
114.3 122.5 114.0 134.7 115.0 144.1 13.2 (2CH2),
148.5
126.9 (C-40), 128.2 (2Carom), 128.6 (2Carom), 137.6 (C-10)
14.3 (C),
20.9 (CH3),
24.1 (CH3),
25.4 (CH2S),
36.5 (SCH2)
aChemical shift d are in ppm.
Table 4. Anti-HCMV activities and cytotoxic properties of test compounds in human embryonic lung (HEL) cells
Compd
Antiviral activity
Cytostatic and cytotoxic activity
HCMV AD-169
strain IC50 (mg/mL)
HCV Davis strain
IC50 (mg/mL)a
Cell morphology
MCC (mg/mL)b
Cell growth
CC50 (mg/mL)c
I
II
III
3
4
5
6
8
9
10
3.5
0.12
>20
2.7
3.5
0.12
>20
7.0
1.6
>50
1.2
0.95
50
>5
NDd
50
5
>50
>5
45
>50
>50
14
14
>50
16
1.1
>50
>0.5
0.6
10
3.2
>50
ꢂ2
ꢂ20
ꢂ50
ꢂ50
ꢂ50
5
50
>50
>50
>50
11
11
12
0.95
1.0
1.5
1.2
13
14
>0.5
2.0
1.3
>0.5
5.0
5
0.68
2
10
ꢂ20
>50
>50
>50
>50
50
Ganciclovir
Cidofovir
0.17
aCompound concentration required to inhibit virus-induced cytopathicity by 50%.
bMinimum cytotoxic concentration that causes a micro-scopically detectable alteration of cell morphology.
cCytostatic concentration required to reduce cell growth by 50%.
dNot determined.

S. Mavel et al. / Bioorg. Med. Chem. 10 (2002) 941–946
945
Table 5. Bond lengths (A), and standard-deviations for compound 7
Table 6. Bond angles (ꢁ) and standard-deviations for compound 7
N1–C8a
N1–C2
C2–C3
1.327(3)
1.369(3)
1.383(3)
1.475(3)
1.383(2)
1.483(3)
1.371(2)
1.392(2)
1.347(3)
1.423(3)
1.361(3)
1.500(3)
1.407(3)
1.822(2)
1.814(3)
1.495(3)
1.391(3)
1.394(3)
C20–C30
C30–C40
C40–C50
C40–C70
C50–C60
C70–C120
C70–C80
C80–C90
C90–C100
C100–C110
C110–C1020 0
C100–C600
C100–C200
C200–C3
C300–C400
C400–C500
C500–C600
1.375(3)
1.395(3)
1.394(3)
1.480(3)
1.374(3)
1.386(3)
1.396(3)
1.375(3)
1.374(4)
1.374(4)
1.380(3)
1.384(3)
1.388(3)
1.383(4)
1.356(4)
1.377(4)
1.370(4)
C8a–N1–C2
N1–C2–C3
N1–C2–C10
C3–C2–C10
N4–C3–C2
N4–C3–C9
C2–C3–C9
C5–N4–C3
C5–N4–C8a
C3–N4–C8a
C6–C5–N4
C5–C6–C7
C8–C7–C6
C8–C7–C12
C6–C7–C12
C7–C8–C8a
N1–C8a–N4
N1–C8a–C8
N4–C8a–C8
C3–C9–S10
C11–S10–C9
C100–C11–S10
C20–C10–C60
C20–C10–C2
105.33(16)
111.90(17)
119.52(17)
128.55(18)
104.50(16)
121.90(16)
133.49(18)
131.11(16)
121.57(16)
107.32(15)
119.22(18)
121.78(19)
118.25(19)
121.39(19)
120.35(19)
120.91(18)
110.93(16)
130.82(18)
118.23(17)
115.21(13)
101.79(11)
114.90(16)
117.41(18)
120.09(17)
C60–C10–C2
C30–C20–C10
C20–C30–C40
C50–C40–C30
C50–C40–C70
C30–C40–C70
C60–C50–C40
C50–C60–C10
C120–C70–C80
C120–C70–C40
C80–C70–C40
C90–C80–C70
C80–C90–C100
C90–C100–C110
C100–C110–C120
C110–C120–C70
C600–C100–C200
C600–C100–C11
C200–C100–C11
C300–C200–C100
C400–C300–C200
C300–C400–C500
C600–C500–C400
C500–C600–C100
122.44(18)
121.11(17)
121.71(18)
116.91(18)
121.72(17)
121.35(17)
121.47(18)
121.36(18)
117.54(19)
121.33(17)
121.12(18)
121.0(2)
120.6(2)
119.3(2)
120.4(2)
121.2(2)
117.6(2)
121.6(2)
120.9(2)
121.1(2)
C2–C10
C3–N4
C3–C9
N4–C5
N4–C8a
C5–C6
C6–C7
C7–C8
C7–C12
C8–C8a
C9–S10
S10–C11
C11–C100
C10–C20
C10–C60
120.2(2)
119.5(2)
120.7(2)
120.9(2)
improved antiviral potency. In particular, the thien-2-yl
3 and pyridin-4-yl 10 showed comparable activity with
I. The napht-2-yl 6 and pyridin-2-yl 8 appeared to be as
potent as 11 but 6 was also quite cytotoxic.
General procedure for hydroxymethylation to give (2)
Conclusion
A mixture of imidazo[1,2-a]pyridine (20 mmol), formal-
dehyde 37% in water (10 eqviv), acetic acid (3 mL) and
sodium acetate (4.3 g) was stirred at room temperature
or heated for the time reported in Table 2. After cool-
ing, when necessary, the solution was made alkaline
with 2 N sodium hydroxyde. The solution was extracted
with dichloromethane and the organic layers dried over
calcium chloride. After evaporation under vacuo the
residue was chromatographed on neutral alumina eluted
with dichloromethane/methanol (99:1 v/v).
In this work, we have shown that the substituent at the
2 position strongly influences the activity of these com-
pounds against human cytomegalovirus as well as their
cytotoxicity. For the pyridin-2-, 3- and 4-yl derivatives,
it was demonstrated that the position of the nitrogen
plays a crucial role for an optimal interaction with the
target virus (HCMV).
Experimental
General procedure for the thioethers (3–14)
General details
To a solution of the alcohol (500 mg) in acetic acid (5
mL) was added the suitable thiol (0.9 eqviv). The result-
ing mixture was heated at 100 ꢁC for 4 h. After cooling,
the solution was made alkaline with 2 N sodium hydrox-
ide and extracted with dichloromethane. After drying
on calcium chloride the organic layer was evaporated
under vacuo, and the residue was chromatographed on
neutral alumina eluted with dichloromethane.
Melting points were determined on a Kofler hotstage
apparatus and are uncorrected. Elemental analysis were
performed by Microanalytical Center, ENSCM, Mon-
tpellier and the analytical results obtained were within
ꢃ0.4% of the theoretical values. NMR spectra were
recorded on Bruker DPX 200 (SAVIT, 37200 Tours) or
AM 400 WB spectrometer. The following a-halogen-
ocarbonyl compound were synthesized according to
cited references: 2-bromoacetylthiophene,11 2-bromo-
acetylpyridine,12 3-bromoacetylpyridine,13 4-bromoace-
tyl-pyridine,12 1-bromoacetyl-1-methylcyclopropane.14
X-ray diffraction
Colorless crystals were grown by slow evaporation of
dichlomethane solution at 293 K. The crystal used for
X-ray measurement was lamellar, with as dimensions:
0.05ꢄ0.28ꢄ0.38 mm. The studied compound,
C28H24N2S, Mx=420.55 g molꢀ1 crystallizes in the tri-
clinic system, space group P-1 (Z=2). The unit cell
parameters were obtained by least-square fit of the set-
ting angles of 25 reflections and are as follow:
a=9.399(1), b=10.274(2), c=12.324(3) A, a=101.99(2),
b=101.57(1) and g=104.36(1)ꢁ with a cell volume of
1087.1(4) A3. The calculated density equaled to 1.29 g
cmꢀ3. The linear absorption coefficient was m=1.44
mmꢀ1 for the l(CuKa) radiation (l=1.54178 A). The
diffracted intensities were collected with a CAD-4
General procedure for cyclisation to give (1)
To a solution of 2-amino-4-picoline (0.1 mol) in ethanol
(100 mL) was added the a-halogeno carbonyl derivative
(0.1 mol) and the resulting mixture was refluxed for 4 h.
After cooling the solution was evaporated to dryness.
The residue was treated with water, made alkaline with
sodium carbonate and extracted with dichloromethane.
The organic layers were dried over calcium chloride,
filtered, and after evaporation under vacuo, the residue
was chromatographed on neutral alumina eluted with
dichloromethane.

946
S. Mavel et al. / Bioorg. Med. Chem. 10 (2002) 941–946
Enraf-Nonius diffractometer equipped with a graphite
monochromator for ymax=60ꢁ:ꢀ10ꢅhꢅ10, 0ꢅkꢅ11,
ꢀ13ꢅlꢅ13 and a o ꢀ2y scan. Three standard reflec-
tions were used to monitor the data collection and
detect any decrease of intensity (5 1ꢀ9, 3 5ꢀ6, 4 4ꢀ1);
the crystal absorption correction was performed using
the ꢀ scan technique.15 There were 3191 independent
reflections of which 2642 were considered as observed
(Iꢂ2s(I) and Rint=0.029). The crystal structure was
solved and refined by full-matrix anisotropic least-
squares on F2 with using the SHELX97 program.16
Scattering factors were taken from the International
Tables for Crystallography.17 The hydrogen atoms were
introduced in their theoretical positions and allowed to
ride with the atoms to which they are attached. The final
reliability factors are: R=0.038, wR=0.096 and the
goodness of fit on F2 was equal to 1.032. The weight was
equal to: w=1/[s2(Fo2)+(0.0383P)2+0.3458P] where
P=(Fo2 +2Fc2)/3. The minimum and maximum resi-
dual density were:-0.180 and 0.196 e.Aꢀ3, respectively.
zoek (FWO), Vlaanderen and the Geconcerteerde
Onderzoeksacties (GOA), Vlaamse Gemeenschap.
References and Notes
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Human cytomegalovirus (HCMV) (AD-169, Davis)
strains were exposed to human embryonic lung HEL
cell cultures. Briefly, confluent cell cultures in microtiter
trays were inoculated with 100 plaque forming units
(PFU). After 1 h virus adsorption, residual virus was
removed, and the cell cultures were incubated in the
presence of varying concentrations (400, 200, 100, . . .mg/
mL) of the test compounds. Viral cytopathicity was
recorded as soon as it reached completion in the control
virus-infected cell cultures. Inhibition of HCMV by the
test compounds was compared with cidofovir and gan-
ciclovir as the reference compounds. Antiviral activity is
expressed as the compound concentration required to
inhibit viral cytopathicity by 50% (IC50).
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34, 1295.
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Cytostatic activity assays
The cytostatic assays were performed as previously
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Acknowledgements
We thank Anita Campsand Lies Vandenheurck for
excellent technical assistance and Doctor J. C. Debouzy
(CRSSA, La Tronche, France) for performing 400 MHz
spectra of 1c. These investigations were supported by
grants from the Fonds voor Wetenschappelijk Onder-