This thesis describes novel diastereoselective group selective processes for the desymmetrisation of cyclohexa-1,4-dienes, and their application to target synthesis of the cladiellin diterpenes. In addition, an enantioselective approach to batzelladine C methyl ester is described, permitting stereochemical assignment of batzelladine C. Chapter 1 describes the use of diastereoselective iodocyclisation reactions for the desymmetrisation of cyclohexa-1,4-dienes, and also details a novel epoxidation-cyclisation transformation, enabling the formation of up to six contiguous stereogenic centres, selectively, in a single step. Chapter 2 introduces the cladiellin diterpenes and describes the application of novel diastereoselective Prins chemistry for the synthesis of a model of the cladiellin core. Chapter 3 describes our attempts at elaborating the cladiellin model to approach the cladiellin framework and discusses an unexpected but interesting Prins cyclisation/rearrangement process. Chapter 4 describes an enantioselective synthesis of batzelladine C methyl ester, permitting assignment of the relative and absolute stereochemistry of batzelladine C.