Preliminary differentiating screening of the antibacterial and antifungal activity of a series of diastereomeric cis/trans-3-aryl(heteroaryl)-3,4-dihydroisocoumarin-4-carboxylic acids (3a- i) was performed by the agar diffusion method against twelve microorganism strains of different taxonomic groups. S. aureus and A. niger were the most sensitive strains to the antibiotic effect of the tested compounds, both inhibited by 10 of 12 compounds. The most potent antibacterial agent was cis-3-phenyl-3,4-dihydroisocoumarin-4-carboxylic acid (cis-3a), exhibiting activity against all seven bacterial test strains

The reaction between homophthalic anhydride and cyclohexanone was examined both in the presence of DMAP or BF3·Et2O complex as a catalyst. The latter yielded (±)‐1‐oxo‐1H‐spiro[benzo[c]pyran‐3(4H), 1′‐cyclohexane]‐4‐carboxylic acid (3) in a higher yield (82 %). A series of new (±)‐4‐(N,N‐disubstituted‐1‐carbamoyl)‐1H‐spiro[benzo[c]pyran‐3(4H),1′‐cyclohexane]‐1‐ones (5a‐h) were synthesized from the parent acid 3 by a two‐step reaction. Differentiating microbial screening was performed for most of the synthesized compounds against twelve microorganisms belonging to different taxonomic groups. The spiro acid 3 was active against all bacterial strains with MIC ≥ 20 μg/ml against B. subtillis and P. vulgaris. E. coli was the most sensitive strain to the antibacterial effect of the tested compounds.

±)-1H-Spiro[benzo[c]pyran-3(4H),1'-cyclohexane]-1-ones. -Title compounds (V) are obtained by a three-step procedure starting from homophthalic anhydride (I) and cyclohexanone (II). Most of the products are screened for antimicrobial effects. (III) is active against B. subtilis and P. vulgaris. -(BOGDANOV, M. G.; GOCHEVA, B. T.; DIMITROVA, D. B.; PALAMAREVA*, M. D.; J. Heterocycl. Chem. 44 (2007) 3, 673-677; Fac. Chem., Univ. Sofia, BG-1126 Sofia, Bulg.; Eng.) -H. Haber 39-122