Protoberberines from Reissert-Compounds.Part IX [1].An Alternative Approach to Dibenzoquinolizine- and Isoquinonaphthyridin-13a-carboxylic Acids,a Novel Synthesis of Alangimarine

摘要

3,4-Dihydroisoquinoline-Reissert-compounds were alkylated to 1-benzyl- and 1-picolyl-derivatives,which in turn could selectively be hydrolized yielding various carboxylic acids,among others certain amino acids related to 3',4'-deoxynorlaudanosoline carboxylic acid (DNLCA).These on treating with ethanolic KOH underwent cyclization to dibenzoquinolizine- and isoquinonaphthyridine-13a-carboxylic acids.Alternatively this cyclization also could be achieved by a more convenient one-pot procedure starting from the same dihydro-Reissert-compounds.Thermal decarboxylation afforded among others the alangia alkaloids alangimarine and dihydroalangimarine.