Oligo‐ and Polygermanes

Germanium is a trace element and germanium compounds are not frequently found in natural environment. The most popular compound containing germanium in nature is germanium dioxide and its physiological effect on erythropoietic properties was reported in 1920s. However, germanium dioxide has fatal toxicity in high amounts. Dr. Asai thought that water soluble compound of germanium would be safe and useful for health care, and together with his collaborators synthesized a water soluble organogermanium compound, called Ge-132, over 50 years ago. Ge-132 has very high safety and now is used as food ingredient for supplements or cosmetic materials and called Asaigermanium. After Asaigermanium was synthesized, many other types of organogermanium compounds were produced. Several organogermanium compounds were studied for their potential medical use. However, most were not suitable for medical development. In this chapter, we discuss bioactive organogermanium compounds with a particular focus on Asaigermanium.