Chemoselectivity of the Ru-catalyzed cycloisomerization reaction for the synthesis of dihydropyrans; application to the synthesis of L-forosamine.

The chemoselectivity of a Ru-catalyzed cycloisomerization reaction has been established. The preference for O- capture of the vinylidene intermediate allows for the synthesis of 4-aminodihydropyrans that are valuable synthetic intermediates. The synthetic utility of these structures has been demonstrated in the synthesis of l-forosamine.