Säurekatalysierte Umlagerung von 7‐Hydroxy‐royleanon in ein 20(10→9) abeo ‐Abietan‐Derivat und zwei Phenalenone

Acid‐catalyzed rearrangement of 7‐hydroxyroyleanone into a 20(10→9) abeo ‐abietane derivative and two phenalenones Short treatment of either horminone ( 1b ), taxoquinone ( 1a ), 6,7‐dehydroroyleanone ( 3 ) or 6β‐hydroxyroyleanone ( 1c ) with 80% H 2 SO 4 at 0° leads to a mixture of rearranged products. Two of the structures, determined by X‐ray‐cristallography, were found to be (9 R , 10 R )‐20(10→9)‐ abeo ‐12‐hydroxy‐5,7, 12‐abietatriene‐11,14‐dione ( 4 ) and 9‐isopropyl‐2,2,5‐trimethyl‐8 H ‐phenaleno[1,9‐ bc ]furan‐8‐one ( 5 ), and the third compound, isolated in very small amounts, has been provisionally identified as 3‐hydroxy‐9‐isopropyl‐2,2,5‐trimethyl‐8 H ‐phenaleno[1,9‐ bc ]furan‐8‐one ( 6 ) from the spectroscopic data.