Table 1.

Structures, antitrypanosomal activities, and selectivities of thiazole derivatives 1-26

Compd	R2	T. b. rhodesiense a		Cytotox.b
		IC50c (μM)	SId	IC50c (μM)
1	phenyl	0.632	162	103
2	3-cyanophenyl	1.90	69	131
3	4-cyanophenyl	42.7	1	44.1
4	4-(trifluoromethyl)phenyl	145	<1	24.6
5	3-nitrophenyl	2.72	47	127
6	4-nitrophenyl	29.3	>9	>255
7	3-methoxyphenyl	6.11	11	69.2
8	4-methoxyphenyl	18.3	5	99.7
9	2-fluorophenyl	0.156	624	97.2
10	3-fluorophenyl	0.233	239	55.8
11	4-fluorophenyl	0.218	1130	247
12	3-chlorophenyl	0.452	125	56.4
13	4-chlorophenyl	13.3	7	95.9
14	3-bromophenyl	0.553	94	51.9
15	4-bromophenyl	34.7	1	46.3
16	2,4-difluorophenyl	0.162	>1590	>257
17	2,5-difluorophenyl	1.63	40	65.3
18	2,6-difluorophenyl	1.22	133	162
19	3,4-difluorophenyl	0.145	211	30.6
20	3,5-difluorophenyl	1.62	36	58.1
21	2,4,5-trifluorophenyl	2.13	116	248
22	2-furanyl	2.53	53	134
23	2-thiophenyl	1.62	63	102
24	2-pyridyl	3.63	57	209
25	3-pyridyl	4.64	45	207
26	4-pyridyl	10.3	21	217
pentamidine		2.8	11400	31.8
melarsoprol		4.0	1280	5.12
podophyllotoxin				0.017

^aTrypanosoma brucei rhodesiense (STIB900)²³

^bCytotoxicity to L6 rat myoblast cells²³

^cThe IC₅₀ values are the mean of two independent assays. Coefficients of variation were less than 50%.

^dSelectivity index for T. b. rhodesiense expressed as the ratio IC₅₀ (L6 cells) / IC₅₀ (T. b. rhodesiense). Values are rounded to the nearest integer or to the third significant figure.