New isochromans.: 1.: Synthesis and antimicrobial activity of 4-substituted (±)-1H-spiro[benzo[c]pyran-3(4H), 1′-cyclohexane]-1-ones

The reaction between homophthalic anhydride and cyclohexanone was examined both in the presence of DMAP or BF3 center dot 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-carbarnoyl)-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 mu g/ml against B. subtillis and P. vulgaris. E. coli was the most sensitive strain to the antibacterial effect of the tested compounds.