OsO₄-Catalyzed Diastereoselective Formation of cis-Tetrahydrofurans

Significance

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.