Preparation of semisynthetic (+)-tubocurarine chloride

Semisynthetic (+)-tubocurarine chloride (II) was prepared by monoquaternization of (+)-tubocurine. The method involved treating (+)-tubocurine with a 0.5 M equivalent of hydrochloric acid prior to quaternization with methyl iodide, followed by neutralization and iodide-chloride ion-exchange. Column chromatography and crystallization procedures were utilized for pure semisynthetic II preparation. The neuromuscular junction blocking activities of the semisynthetic and commercial II were determined by the in vivo cat hypoglossal nerve-tongue muscle preparation. No delectable differences among physical constants, spectral data, and neuromuscular junction blocking activities were noted between the commercial product and the semisynthetic II. This result substantiates the chemical and biological data for the well-accepted new formula for II. The unexplained M + n14 mass spectral peaks shown by the curare-type bases are characteristic of the molecular species rather than a result of contaminants.