Rapid Two‐Directional Synthesis of the F–J Fragment of the Gambieric Acids by Iterative Double Ring‐Closing Metathesis

D-glucal is the starting point for the efficient synthesis of the F–J fragment of the gambieric acids (see scheme). The H-ring diol was subjected to double two-directional alkynyl ether formation, carbocupration ring-closing metathesis, and hydroboration. The tricyclic G–I diol was then converted into the F–J fragment by a sequence that involves another double two-directional ring-closing metathesis reaction.