Synthesis of Guanidines in Solution

The guanidinium group is a typical functional group in molecules with physiological or biological activity. Its geometry and physiochemical properties are of importance for molecular recognition processes. We discuss in this review modern synthetic methods for the introduction of the guanidinium group and focus our survey on examples from natural product synthesis and drug synthesis. The presented methods are sufficiently mild and selective to allow guanidylation of more complex structures.