Leonurine
Leonurine is a pseudoalkaloid that has been isolated from
Leonotis leonurus,
Leonotis nepetifolia, Leonotis artemisia, Leonurus cardiaca, Leonurus sibiricus, as well as other plants of family Lamiaceae. Leonurine is easily extracted into water.Leonurine can be synthesized starting from eudesmic acid. Reaction with sulfuric acid produces syringic acid. Protection with ethyl chloroformate followed by reaction with thionyl chloride SOCl2 and then tetrahydrofuran yields 4-carboethoxysyringic acid 4-chloro-1-butyl ester. The chloride is then converted to an amino group via a Gabriel synthesis with potassium pthalimide) followed by hydrazinolysis. The final step is reaction of the amine with S-methylisothiourea hemisulfate salt.
