Berberine and coptisine free bases

The free bases of protoberberine alkaloids berberine and coptisine and related compounds have been examined. The H-1 and C-13 NMR data of 8-hydroxy-7,8-dihydroberberine (2a), 8-hydroxy-7,8-dihydrocoptisine (2b), bis(7,8-dihydroberberin-8-yl) ether (3a), 8-oxoberberine (5a), and 8-oxocoptisine (5b) as well as X-ray data of compounds 2a, 5a, and 5b are reported and discussed. (C) 2003 Elsevier B.V. All rights reserved.