Intramolecular 4π photocyclization of chalconoid-like compounds in solution and antimicrobial activities

Two new (2 and 8) and eight known (1, 3–7, 9 and 10) o-, m-, p-nitro, -methoxy and -methyl substituted chalconoid and alnustone-like compounds with a skeleton of (2E,4E)-1,5-diarylpenta-2,4-dien-1-one (1–10) were synthesized and their 4n(π) photocyclization reaction gave 10 new o-, m-, p-nitro, -methoxy and -methyl substituted cis-3-benzoyl-4-phenylcyclobutenes (11–20), stereoselectively, as major products in solution. The antimicrobial activities of all the compounds were also investigated. They showed antibacterial activity against Gram-positive bacteria, moderate antibacterial activity against Gram-negative bacteria, but no antifungal activity was observed against yeast-like fungi.