A novel oxidation stage in the chemistry of protoberberine alkaloids. Synthesis of 7,8-dehydroberbines
摘要:
1,2-substituted berbines, such as (-)-caseamine, (-)-caseadine and (-)-O-methylcaseadine, are partially oxidized by iodine to the 7,8-dehydroberbines, while the 2,3-substituted berbines are oxidized all the way to the protoberberinium salts. This different behaviour is interpreted in terms of the preferred cis or trans B/C quinolizidine conformation of the starting berbines.