Radikalische Cyclisierung von Dienen, VI. Totalsynthese von (−)‐Coriolin und (−)‐Epicoriolin aus (S)‐(+)‐Carvon

Radical‐Type Cyclization of Dines, VI. – Total Synthesis of (−)‐Coriolin and (−)‐Epicoriolin from (S)‐(+)‐Carvone (3aR,4S,6aS)‐(+)‐4‐(4‐Methoxybenzyloxy)‐6a‐methyl‐3,3a,4,6a‐tetrahydro‐2H‐cyclopenta[b]furan‐2‐one (10) and (3aR,3bR,4R,6aS,7S,7aS)‐(−)‐decahydro‐4,7‐dihydroxy‐3a,5,5‐trimethyl‐3‐methylene‐2H‐cyclopenta[a]pentalen‐2‐one (21) are the key intermediates in the synthesis of the title compounds 1 and 1a. Enantiomerically pure 10 is produced from (S)‐(+)‐carvone (4) in seven straightforward reactions. Compound 21 is produced from 10 by analogy with the method developed for the synthesis of (−)‐hirsutene. Through the introduction of the double bond into 21 via the silylenolether 23 one arrives at precoriolin 25, which is converted into (−)‐coriolin (1) and the C‐3 epimer (−)‐epicoriolin (1a) (63:37) with hydrogen peroxide. The structures of 1 and 1a were confirmed via X‐ray crystallography.