Organic synthesis, with the invention of new synthetic strategies and technologies, has evolved from largely empirical approaches for the preparation of relatively simple molecules to sophisticated strategies for the construction of molecules with considerable structural and functional complexity. Organic synthesis is employed to synthesize the natural product and its analogs for the discovery of new drugs. The development of new synthetic methodologies in the course of total synthesis is imperative for the efficient synthesis of drug candidates. Apart from the practical applications, the pursuit of efficient syntheses of complex natural products is both gratifying and truly enjoyable.;Chapter One describes the development of annulation reaction for the construction of five-, six- and seven-membered rings. Chapter Two describes a direct approach to the synthesis of methyllycaconitine, a representative of the aconitine alkaloids. The numbering of the compounds, schemes and references are independent in each section.