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Total Synthesis of (+)-Ryanodol
A 15-Step Synthesis of (+)-Ryanodol.
17 November 2016 (online)
Key words(+)-ryanodol - (+)-anhydroryanodol - Pauson–Khand reaction - reductive cyclization - selenium dioxide oxidation
(+)-Ryanodol is a highly oxidized complex diterpenoid and the hydrolysis product of ryanodine. It modulates intracellular Ca2+ channels, albeit with lower affinity than the parent natural product. Reisman and co-workers completed the synthesis of (+)-ryanodol in only 15 steps from (S)-pulegone.
Key intermediate G was assembled in seven steps from (S)-pulegone and transformed into enone H by a highly diastereoselective Pauson–Khand reaction. Treatment of tetracycle H with SeO2 under strictly anhydrous conditions led to the simultaneous installation of three oxygen functionalities. (+)-Anhydroryanodol was finally converted into (+)-ryanodol by epoxidation and reductive cyclization.