A concise and practical synthesis of oseltamivir phosphate(Tamiflu) from d-mannose

A short and practical synthesis of oseltamivir phosphate was accomplished in 11 steps from inexpensive and abundant starting material, d-mannose. This synthetic route featured an intramolecular Horner–Wadsworth–Emmons reaction as the key step to furnish the cyclohexene ring product. The hydroxyl group was converted stereo specifically into an amino group by oxidation to the ketone and reductive amination whereas the second amino group was introduced by azide substitution of a hydroxyl group. This synthesis provided an economical and practical alternative for the synthesis of Tamiflu.