Synthesis and biological evaluation of novel ( l)-α-amino acid methyl ester, heteroalkyl, and aryl substituted 1,4-naphthoquinone derivatives as antifungal and antibacterial agents

The synthesis, antifungal, and antibacterial activities of 3– 15 are described. A series of ( S)- N-(1,4-naphthoquinon-2-yl)-α-amino acid methyl esters 3– 9, 2- N, N-dialkylamino-1,4-naphthoquinones 10– 11 and 2-hydroxy-3-(2′-mercaptoimidazolyl)-1,4-naphthoquinones and their cyclic analogs 12– 15 were synthesized and evaluated for antifungal and antibacterial activities. The structure–activity relationships of these compounds were studied and the results show that the compounds 9b and 13c exhibited in vitro antifungal activity against Candida albicans, Cryptococcus neoformans, and Sporothrix schenckii, whereas compound 6a showed in vitro antibacterial activity against Streptococcus faecalis, K. pneumoniae, Escherichia coli, and Staphylococcus aureus.