The first stereoselective synthesis of lippidulcines A, B and C has been accomplished starting from (+)-hernandulcin, which has been prepared on a multigram scale. The previously assigned absolute configurations have been confirmed. The key steps of this synthesis are based on a modified version of the Kornblum-DeLaMare rearrangement, and on a highly regioselective and stereoselective ketone reduction with the MeCBS reagent. The taste evaluations indicate that none of these sesquiterpenes are sweet, instead the lippidulcine A is a cooling agent with a mint after taste.
Keywords: ADH ketone reduction; Corey–Bakshi–Shibata reduction; Kornblum–DeLaMare rearrangement; Saegusa–Larock; cooling agent; dehydrogenation; hernandulcin; lippidulcines.