Protoberberine ausReissert-Verbindungen, 5. Mitt.: Synthese des (�)-Bharatamins

Recent Strategies for the Synthesis of Protoberberines and Protoberberine Type Compounds

“…Subsequent reductive methylation of 78a or 78b with methyllithium affords the partially or totally deoxygenated coralynes 79a and 79b, which are not accessable by the classical coralyne reaction [41]. Further reduction of the coralynes 79a and 79b with NaBH 4 results in B/C-trans fused 8-ß-methyldibenzo[a,g]quinolizidines 80a and 80b [39], while bharatamine 81b, the sole protoberberine alkaloid with lacking O-functions in ring D, is available by combined LiAlH 4 /NaBH 4 reduction of 78d followed by cleavage of the benzylether 81a [42]. Contrastly, the isoquinonaphthyridinone 78f fails to give a corresponding reduction product, only the 9,10,11,12-tetrahydro derivative 82 is formed by catalytic hydrogenation.…”

“…A new class of dimeric alkaloids represents the benzyltetrahydroisoquinoline-protoberberine-derivative longiberine (42) and its methylether (43) isolated from Thalictrum longistylum (Ranunculaceae) ( Table 1). …”

The asymmetric synthesis of (R)-(+)- and (S)-(−)-O-methylbharatamine

“…1). [3][4][5][6][7][8][9][10][11][12] Until now, only racemic bharatamine 1 has been synthesized [13][14][15][16][17] with no synthesis of this protoberberine alkaloid in its optically active form being published. Among the different methods developed for the construction of a protoberberine skeleton, a growing interest in the lateral metallation methodology 18 has been observed over the last decade.…”