Application of radical reactions in the organic synthesis for the formation of carbon-carbon bond has dramatically increased over the last fifteen years by virtue of their high degree of chemo-, regio- and stereoselectivity. The present thesis entitled "Radical Cyclisation based Approaches to 9-pupukeanone and Lignan Precursors" describes the application of radical reactions in the synthesis of isotwistane carbon framework present in pupukeananes, and b-arylmethylbutyrolactones, established precursors of various types of lignans. For convenience, the results are presented in two chapters, & ( I ) Radical annulation approach to chiral analogues of 9-pupukeanones; (2) Synthesis of (+-)-enterolactone and lignan precursors; and an appendix entitled 'Chiral synthons from (R)- carvone'. In each Chapter the compounds are sequentially numbered (bold and double underlined), and references are marked sequentially as superscripts and listed at the end of the Chapter. All the figures were obtained by direct xerox of the originaltNMR and muss spectra, and in some of them uninformative areas have been cut to save the space.