Further SAR exploring the role of chirality and substitution on the phenyl ring. IC₅₀ values were determined against E. coli DNA gyrase in a supercoiling assay.

Compound	R 1	R 2	IC50a (μM)
28			76
29			36
30			180
31			41
32			45
33			41
34			62
35			>200

^aIC₅₀ values were the mean of 2 or 3 different experiments. Error limits are not given, as the gel-based assays used are at best semi-quantitative.