Synthesis of vinca alkaloids and related compounds. Part 105: Efficient convergent synthetic pathway to the ibophyllidine skeleton and synthesis of (±)-19-hydroxy-ibophyllidine and (±)-19-hydroxy-20-epiibophyllidine

Abstract

Starting from methyl-5-oxohexanoate we produced the appropriately functionalized aldehyde, which, after having been allowed to react with the tryptamine derivative in a [4+2] cycloaddition reaction as the final step, yielded the molecule containing a D-seco-aspidospermane skeleton. From the latter we could successfully produce a 1:1 mixture of protected epimers, the desilylation reaction of the protected molecules gave the alkaloids (±)-19-hydroxy-ibophyllidine and (±)-19-hydroxy-20-epiibophyllidine in good yield.