TOTAL SYNTHESES OF MACROCYCLIC MARINE ALKALOIDS, HALICLAMINE-A AND HALICLAMINE-B - A CONVENIENT AND EXPEDITIOUS ASSEMBLY OF 3-SUBSTITUTED PYRIDINE-DERIVATIVES WITH DIFFERENT ALKYL CHAINS TO THE BISPYRIDINIUM MACROCYCLE

The total syntheses of haliclamines A (1) and B (2), macrocyclic marin e alkaloids closely related to the key bisdihydropyridine intermediate 3 of the biogenetically unique manzamine family, have efficiently bee n achieved via stepwise controlled inter- and intramolecular N-alkylat ions of 3-alkylpyridine derivatives such as 40 and 41. The general syn thetic methodology toward the bispyridinium macrocycle 44, a key bioge netic equivalent of the polycyclic marine alkaloids, has been proposed through the total syntheses. (C) 1998 Elsevier Science Ltd. All right s reserved.