First asymmetric synthesis of a differentially silyl-protected tris(alkynyl) methyl methyl ether

For an improved synthesis of the recently described expanded octamethoxycubane with a central C-56 core, formally obtained by inserting buta- 1,3-diynediylmoieties into all C(sp(3)) C( sp(3)) bonds of octamethoxycubane, the preparation of the optically pure methyl ether of a differentially silyl-protected trispropargylic alcohol was required. The key step of the preparation involved a diastereoselective addition of a lithium acetylide to an optically active alkynyl ketone under Cram chelation control.