Synthesis of lesquerella‐based bisphosphonates

Hydroxy fatty acids (HFAs) have found wide use in today's market, ranging from industrial materials to pharmaceuticals. Castor oil, which is obtained from castor seeds, has served as a primary source of the most common HFA, ricinoleic acid, but also contains several undesirable compounds which pose severe health risks, the most notable being ricin, an unusually stable, toxic protein. A promising HFA alternative is lesquerella oil, an oil obtained from seeds of the Lesquerella fendleri species. Lesquerella oil is mainly comprised of lesquerolic acid, an HFA that is structurally similar to ricinoleic acid, the only difference being that lesquerolic acid possesses two additional methylene groups on the carboxyl end of the molecule. In addition, the bisphosphonate moiety has been shown to display interesting biological activities, primarily as osteoporosis drugs and anti‐cancer therapeutics. The synthesis of lesquerella‐based bisphosphonates, both an unsaturated and saturated series, have been produced in high yields and high purity and are reported here.