Diastereoselective synthesis of cularine alkaloids via enium ions and an easy entry to isoquinolines by aza-Wittig electrocyclic ring closure.
In preliminary communications, we reported the diastereoselective synthesis of cularine and sarcocapnine via the intramolecular ring closure of nitrenium and oxenium ions, a new highly diastereoselective reductive methylation with (+)-8-phenylmenthyl chloroacetate followed by reduction with sodium borohydride, and a facile entry to the isoquinoline precursors by aza-Wittig electrocyclic ring closure. We now report the full details of the syntheses of (+)-O-demethylcularine, (+)-cularine, (+)-sarcocapnidine, (+)-sarcocapnine, and (+)-crassifoline and describe different methods of synthesis of their precursors.
Rodrigues
J Augusto R
JA
Universidade Estadual de Campinas, Instituto de Quimica, 13.083-970 Campinas, Brazil.
Abramovitch
Rudolph A
RA
de Sousa
Joana D F
JD
Leiva
Genaro C
GC
D000085:Acetates / Q000737:chemistry; D000470:Alkaloids / Q000138:chemical synthesis*; D002412:Cations / Q000737:chemistry; D003500:Cyclization; D005609:Free Radicals / Q000737:chemistry; D007546:Isoquinolines / Q000138:chemical synthesis*; D008745:Methylation; D015394:Molecular Structure; D010082:Oxepins / Q000138:chemical synthesis; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013696:Temperature; D013997:Time Factors
D000085:Acetates; D000470:Alkaloids; D002412:Cations; D005609:Free Radicals; D007546:Isoquinolines; D010082:Oxepins; C006972:chloroacetic acid; C064577:cularine