Convergent stereospecific total synthesis of monocillin I and radicicol: some simplifications and improvements

A much improved and reliable access to the macrolide 9, key-intermediate in our synthesis of monocillin I and radicicol is reported, via a modification of our first synthesis. The formation of the conjugated E,Z-dienone trans-epoxide is now achieved in a much higher yield, in a stereospecific reaction, by elimination of the methanesulfonate ester of the 6′-OH of the intermediate macrolide. It is also shown that the configuration of the 6′-OH has no significant incidence on all the steps leading to 9, and that consequently the two diastereoisomers 12, epimeric at 6′, can be used for the synthesis of radicicol.