Synthesis of vinca alkloids and related compounds. 90.~1 new results in the synthesis of alkaloids with the aspidospermane skeleton. First total synthesis of (±)-3-oxominovincine

摘要

The tryptamine derivative 1 readily reacted with methyl 4-acethyl-5-bromopent-4-enoate (9) that had been built from 2,4-pentanedione. On intramolecular dehydration and subsequent [4+2] cycloaddition, the reaction product 10 gave the epimers 12 and 13 having the D-secoaspidospermane skeleton. Compound 12 directly and 13 after epimerization yielded (±)-3-oxominovincine (14). Regioselective reduction of 14 furnsihed (±)-minovincine (17).