Meliaceous Limonoids: Chemistry and Biological Activities

Some of the important naturally occurring limonoids from Meliaceae discovered in the last six decades, from 1942 to June 30, 2010, and their various bioactivities, are discussed. The cedrelone-class limonoids are characterized as the 5,6-enol-7-one derivatives and Burke et al. presented the chemical correlation of anthothecol with hirtin. Under mildly acid conditions, the first stage of the ring-opening of havanensin gives a 15-hydroxy-14- carbonium ion, which then either undergoes Wagner-Meerwein rearrangement or loses a proton to give a 15-ketone enolate and involves participation of the oxygenated function at C-7. The photooxidation of salannin and nimbin by UV light in the presence of oxygen led to more polar unstable intermediates that rearranged on silica gel to two final products in which the furan ring had been oxidized to isomeric hydroxybutenolides.