Efficient Asymmetric Synthesisof Oseltamivir from d-Mannitol

A highly practical asymmetric synthesis of oseltamivir has been accomplished in 18 steps from D-mannitol without any chromatographic purification, which features intramolecular aldol condensation of dialdehyde with a 3-pentyl ether moiety in constructing densely functionalized cyclohexene ring of oseltamivir.