Cobalt mediated ring contraction reaction of lapachol and initial antibacterial evaluation of naphthoquinones derived from lapachol

The synthesis of 2-hydroxy-2-(3-methylbut- 2-enyl)-2H-indene-1,3-dione 3, from lapachol which involves a ring contraction via the Hooker intermediate 1,2-dihydroxy-2-(3-methylbut-2-en-1-yl)-3-oxo-2,3-dihydro- 1H-indene-1- carboxylic acid 2 is described. Different pyranonaphthoquinone derivatives, obtained in our previous synthetic work, were screened for antimycobacterial (Mycobacterium tuberculosis) activity and against resistant strains of Gram-positive (Bacillus cereus and Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The results indicated significant activity of all the tested samples against M. tuberculosis and only moderate activity against the Gram-positive and Gram-negative bacteria. © Springer Science+Business Media, LLC 2011.