Usnic acid, a dibenzofuran, was originally isolated from lichens producing secondary metabolites, and is well known as an antibiotic, but is also endowed with several other interesting properties. Thus, the goal of this paper is the design of new usnic acid derivatives and evaluation of their antimicrobial activity. All newly synthesized compounds possess good antibacterial activity with MIC ranging from 1.02-50.93 × 10 mmol mL and MBC from 2.05-70.57 × 10 mmol mL. The most sensitive bacterial species was , while and were the most resistant among the ATCC strains, and MRSA was the most resistant among all tested bacteria (ATCC and clinical isolates). Their antifungal activity was very strong (MIC = 0.35-7.53 × 10 mmol mL and MFC = 0.70-15.05 × 10 mmol mL) - better than those of reference compounds and usnic acid itself. The most sensitive fungal species was , while var. appeared to be the most resistant. It should be mentioned that in general most of the compounds showed weaker antibacterial activity, but better antifungal properties than usnic acid itself. The results allow us to conclude that the title compounds are good lead compounds for novel more active antibacterial drugs. On the other hand, these compounds are very promising as antifungals.
For
the first time, the possibility of photocyclization of the
1,3,5-hexatriene system containing a fragment of allomaltol was demonstrated.
A preparative method for the synthesis of previously unknown benzo[5,6]chromeno[8,7-d]oxazole-2,7(3H)-diones was developed
based on the investigated photoreaction. A distinctive feature of
this approach is the modification of the starting terarylenes aimed
at blocking the competitive process leading to side reactions of the
pyranone fragment. It was shown that the proposed photocyclization
of substituted oxazol-2-ones can be used for the photogeneration of
biologically active alcohols and various acids. The structure of one
of the cyclization products was determined by X-ray diffraction.
A convenient approach to the synthesis of the previously unknown 7H‐furo[3,2‐b]pyran‐7‐ones based on the intramolecular cyclization of carbonyl derivatives of 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one has been elaborated. Key intermediates in the synthesis of the target 7H‐furo[3,2‐b]pyran‐7‐ones are 3‐hydroxy‐6‐methyl‐2‐(2‐oxo‐2‐arylethyl)‐4H‐pyran‐4‐ones. They are formed as a result of multicomponent condensation of 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one with arylglyoxals and 4‐methoxyaniline.
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