Synthesis of Vinca Alkaloids and Related Compounds. Part 106. An Efficient Convergent Synthetic Pathway to Build Up the Ibophyllidine Skeleton II. Total Synthesis of (±)-Deethylibophyllidine and (±)-14-Epi-deethylibophyllidine
Starting from 5-ethyldihydrofuran-2(3H)-one (9) we prepared aldehydes (6 and 7) which, in a [4+2] cycloaddition reactions with the tryptamine derivative (8) gave, as a final step, compounds (13 and 22) having D-seco-pseudoaspidospermane skeleton. We synthesized (±)-20-epiibophyllidine (4) via the benzoate ester (15) or the mesylate (17) of alcohol (14) which had been obtained from 13, while the catalytic