OsO4-Catalyzed Diastereoselective Formation of cis-Tetrahydrofurans
D. J. Donohoe*, S. Butterworth
Oxford University, UK
21 September 2005 (online)
This paper highlights a highly diastereoselective cyclization to form enantiopure cis-tetrahydrofuran through a 1,2-diol. The enantioenriched diols were synthesized from Sharpless asymmetric dihydroxylation (AD) methodology. It was found that addition of a sacrificial alkene such as isoprene coupled with the oxidant Me3NO in acidic conditions is essential for complete conversion if a catalytic amount of OsO4 was used. Both the yield and selectivity were relatively insensitive to the substitution pattern of the substrates, providing useful flexibility in designing natural product syntheses. This methodology was efficiently applied to an enantioselective formal synthesis of (+)-cis-solamin, in which a key intermediate was prepared in three steps in 70% overall yield (90% ee), significantly higher than in the previous literature method.