Revisiting the Reduction of Vinpocetine

Hydrogenation of the semisynthetic vinca alkaloid vinpocetine produces two epimers that have previously been investigated as chiral additives. However, the absence of a full characterization generated some ambiguities in their stereochemical identification. In this study, computational methods, NMR analysis, and X-ray crystallography were employed to clarify and revise the previously reported assignment. Additionally, various methods for the reduction of the 16,17-double bond of vinpocetine are explored. A comparative analysis of epimer formation ratios with the corresponding alcohols is presented, supported by a detailed NMR characterization of these previously unexplored alkaloids.