The goal of our research program involves the chemical synthesis of complex natural products of importance in biology and human medicine. At the core of this research program is the development of new synthetic strategies and methods guided by the study of chemical reactivity and mechanism. A major emphasis involves the efficient synthesis of complex oligosaccharides and glycoconjugates that are of value as immunostimulants in therapeutic and prophylactic vaccines. We have developed a series of new methods for oligosaccharide construction allowing for the synthesis of complex saponin adjuvants and subunit antigen glycopeptide constructs, whose potential for anti-cancer and anti-viral vaccine therapies are being investigated. We are also engaged in the synthesis of complex anti-tumor and anti-viral alkaloids, enabled by the development of novel heterocyle annulation strategies.