Synthesis of didemnolines A-D, N9-substituted β-carboline alkaloids from the marine ascidian Didemnum sp.

Article abstract of DOI:10.1016/S0040-4020(98)01100-4

Didemnolines A-D (1-4) were synthesized and their structures were confirmed through comparisons of data for the synthetic material with those obtained for natural 1-4. The synthesis of didemnolines A (1) and C (3) involved the coupling of 1-[(benzyloxy)methyl]-4-chloromethyl-5- (thiomethyl)imidazole (6) with 7-bromo-β-carboline (5), while didemnolines B (2) and D (4) were formed through the analogous coupling of 6 with norharmon (7). Intermediate 6 was efficiently prepared from 1-[(benzyloxy)methyl]- 2,4,5-tribromoimidazole using a sequential one-pot halogen-metal exchange reaction and 7-Br-β-carboline was synthesized using a new approach.