Semi-synthetic modification of nimbolide to 6-homodesacetylnimbin and 6-desacetylnimbin and their cytotoxic studies

A new C-seco tetranortriterpenoid named as 6-homodesacetylnimbin 2, has been synthesised for the first time through semi-synthetic modification of nimbolide 1, a potent molecule with anticancer activity. Attempts were made to transesterify the -COOMe moiety in nimbolide using titanium (IV) isopropoxide and ethanol so as to obtain a molecule with -COOEt moiety. However, a novel product was envisaged during the course of the reaction, which was identified as 6-homodesacetylnimbin, a higher homologue of 6-desacetylnimbin 3 through spectroscopic and crystallographic methods. Also, 6-desacetylnimbin has been synthesised through acid hydrolysis of nimbolide. The compounds were screened for their cytotoxic properties through brine shrimp lethality bioassay method using Artemia salina.