Substituted tubaic acids, new oxidative rotenoid metabolites from Lonchocarpus nicou

The chemical study of Lonchocarpus nicou roots benzene extract afforded the new (−)-rotoic acid and (−)-deguoic acid. Biogenetically, these natural products are probably located between the parent rotenoids rotenone and deguelin, respectively, and the corresponding free tubaic acids. A lipophile extract of Lonchocarpus nicou roots afforded two likely O-substituted isomers of the known tubaic acids. Spectroscopic analysis assigned to the former, named (−)-rotoic acid, the new 4-(2,3-dihydro-6,7-dimethoxychromon-3-oxy) tubaic acid structure which differs from (−)-deguoic acid, the latter, by the β-tubaic acid part. Biogenetically, the two compounds could be considered as resulting from the parent rotenone and deguelin, respectively, by oxidative ring-C cleavage.