Table 1. In vitro structure–activity relationships of N-benzylidene-N′-thiazol-2-yl-hydrazines.

Compound number	R1	R2	R3	R4	R5	R6	Inhibition (%)
							MtbLeuRS	MtbMetRS
1 a	C6H4-4-Br	H	H	NO2	OH	OCH3	113 ± 14 (5)	110 ± 6 (3)
2	C6H4-4-NO2	H	H	NO2	OH	OCH3	103 ± 9 (5)	94 ± 23 (4)
3	C6H4-4-F	H	H	Br	OCH3	H	109 ± 3 (2)	121 ± 8 (2)
4	C6H3-2,4-dCl	H	H	H	C(O)OH	H	101 ± 4 (2)	92 ± 4 (2)
5	C6H4-3-NO2	H	Br	H	H	H	80 ± 12 (2)	93 ± 10 (2)
6	C6H4-3-NO2	H	H	OC6H5	H	H	11 ± 15 (2)	65 ± 15 (2)
7	C6H4-3-NO2	H	H	H	C2H5	H	3 ± 23 (2)	27 ± 9 (2)
8 a	C6H5	H	H	NO2	OH	H	53 ± 10 (2)	72 ± 16 (2)
9 a	C6H5	CH3	H	OH	H	H	65 ± 18 (2)	112 ± 13 (2)
10 a	C6H5	H	H	H	N(CH3)CH3	H	65 ± 18 (2)	122.7 ± 0.3 (2)
11	C6H5	H	OH	H	H	H	7 ± 8 (2)	51 ± 4 (2)
12	3-Pyridyl	H	OCH3	H	H	OCH3	74 ± 4 (2)	115 ± 13 (2)
13	CH2C(O)OC2H5	H	H	H	C(O)OH	H	12 ± 4 (2)	22 ± 6 (2)
14	CH3	C(O)OC2H5	CF3	H	H	H	34 ± 3 (2)	45 ± 4 (2)
15	CH3	C(O)OC2H5	H	Br	OH	Br	55 ± 4 (2)	51 ± 17 (4)
16	CH3	C(O)OC2H5	H	Br	OH	OCH3	54 ± 9 (2)	94 ± 5 (2)
17 a	CH3	C(O)OC2H5	H	H	Br	H	39 ± 8 (2)	111 ± 6 (2)
18	CH3	C(O)OC2H5	Br	H	H	H	67 ± 15 (2)	99 ± 13 (2)
19	CH3	C(O)OC2H5	H	H	C(O)OH	H	–7 ± 11 (2)	6 ± 8 (2)
20	CH3	C(O)OC2H5	H	OH	H	H	1 ± 2 (2)	71 ± 11 (2)
21	CH3	C(O)OC2H5	H	H	H	H	19 ± 1 (2)	73 ± 13 (2)
22 a	CH3	C(O)OCH3	H	H	Br	H	46 ± 1 (2)	88 ± 18 (2)
23	CH3	C(O)OCH3	H	H	C(O)OH	H	12 ± 1 (2)	–11 ± 3 (2)
24	CH3	C(O)OCH3	H	H	NO2	H	88 ± 1 (2)	75 ± 12 (3)
25 a	CH3	C(O)CH3	H	OCH3	OCH2C6H4–2Cl	H	87 ± 21 (5)	113 ± 3 (2)
26	CH3	C(O)CH3	H	H	OC2H5	H	20 ± 11 (2)	53 ± 0 (2)
27	CH3	CH3	H	H	OCH3	H	1 ± 10 (2)	1 ± 8 (2)
28	CH3	H	OCH3	OCH3	H	H	17 ± 8 (3)	25 ± 12 (2)
29	CH3	H	H	H	C(O)OH	H	–4 ± 17 (2)	–22 ± 2 (2)
30	CH3	H	H	H	NO2	H	20 ± 6 (2)	92 ± 3 (2)
31 a	H	H	H	OCH3	OC(O)C6H3–2,4-dCl	H	73 ± 16 (2)	142 ± 2 (2)
32 a	H	H	H	Br	OCH2C6H5	OCH3	55 ± 6 (2)	106 ± 1 (2)
33 a	H	H	H	OCH3	OCH2C6H4–2-Cl	H	64 ± 1 (2)	102 ± 2 (2)
34	H	H	H	Br	OCH3	H	29 ± 11 (2)	90 ± 23 (4)
35	CH3	H	OH	H	H	Br	39 ± 3 (2)	113 ± 11 (2)
36	H	H	H	OCH3	OC6H13	H	47 ± 6 (2)	62 ± 5 (2)
37	H	H	NO2	H	H	H	45 ± 35 (4)	51 ± 25 (4)

^aCompounds that affected the steps downstream of the aminoacylation reaction in the assays (inorganic pyrophosphatase activity and/or development of BIOMOL® GREEN signal).