Stereoselective synthesis of iriomoteolide-1a hemiketal core

A stereoselective synthesis of the cyclic hemiketal core of iriometeolide-1a (1) is described. The key step involves a Sakurai reaction of allylsilane 4 and aldehyde 5, which bears a chiral α-tertiary center. Mild TES deprotection of β,γ-unsaturated ketone 23 led to concomitant cyclization to produce the fully intact hemiketal core 2.