Studies on oxidation of ergot alkaloids: oxidation and desaturation of dihydrolysergol-stereochemical requirements

A new method for the oxidation of ergoline alcohols to aldehydes was found (TFFA-DMSO, -78 °C, then DIPEA). Structural features of ergolines required for successful C7-C8 double bond introduction via Polonovski-Potier reaction of respective 6-N-oxides were defined and experimentally confirmed: (i) the presence of electron-withdrawing group at C-8; (ii) trans-diaxial orientation of N6-O and C7-H bonds (both requirements are fulfilled for dihydrolyserg-17-al and its 2,4-dinitrophenyl hydrazone prepared in this work).