Solid-Phase Total Synthesis of the Pentacyclic System Lamellarins U and L^†

A total solid-phase synthesis of lamellarins U and L has been achieved. The conversion of an aldehyde group into a formate by a Baeyer−Villiger reaction and a intramolecular [3 + 2] cycloaddition of a 3,4-dihydroisoquinolinium salt over a triple bond comprise the key steps of the process. Each transformation has been controlled with the proper spectroscopic and analytical methods.