A short and flexible route to tetrahydropyran-4-ones via conjugated nitrile oxides cycloaddition and oxa-Michael cyclization: a concise diastereoselective total synthesis of (±)-diospongin A.

A short and flexible [3+2+1] synthetic strategy was developed for the synthesis of substituted tetrahydropyran-4-ones, featuring [3+2]-cycloaddition of α,β-unsaturated nitrile oxides and alkenes and oxa-Michael cyclization in a 6-endo-trig fashion. The efficiency of this synthetic strategy was further demonstrated by the concise total synthesis of (±)-diospongin A in 8 steps with 20.2% yield.