Synthesis and evaluation of fluorinated sialic acid derivatives as novel 'mechanism-based' neuraminidase inhibitors

Abstract

Increasing drug resistance towards the front line influenza neuraminidase inhibitor Oseltamivir (Tamiflu, Roche) has recently been reported, emphasising the need to perform further studies to gain insight into receptor ligand interactions.

Recently, influenza neuraminidase activity has been tackled using a novel class of mechanism based inactivator, which incorporates fluorine atoms at positions C2 and C3 of sialic acid. These inactivators are anticipated to be less susceptible to drug induced resistance as they target essential catalytic amino acids. However, individual hydrogen bonding interactions formed between these inactivators and the neuraminidase in both the Michaelis complex and at the transition state remain unclear.

The aim of this project is to synthesise a series of monodeoxygenated 2,3difluoroNacetylneuraminic acid derivatives, designed to probe the importance of individual hydrogen bonding interactions towards transition state stabilisation.

The syntheses of the four novel monodeoxygenated 2,3difluorosialic acid inactivators at position C4,C7, C8 and C9 deploying a Barton-McCombie protocol were accomplished. The time-dependant inactivation of wild type influenza neuraminidase N9 G70C by these monodeoxygenated 2,3difluorosialic acid inactivators was tested in a fluorescent kinetic assay. Further biochemical evaluation (performed by our collaborators) in IC50 measurements against a panel of influenza viruses including wild types (wt.) and Oseltamivir resistant mutants showed potent inhibition of influenza B and H1N1 strains.

We also wished to develop a further understanding of the effects of the monodeoxygenated 2,3difluorosialic acid inactivators upon inactivation on a physical basis. Hence, we will discuss Xray crystallographic structures, (obtained by our collaborators) of influenza neuraminidase N9 in complex with the monodeoxygenated 2,3difluorosialic acid inactivators.

Date of Award	1 Nov 2011
Original language	English
Awarding Institution	University of Bath
Supervisor	Andrew Watts (Supervisor) & Stephen Husbands (Supervisor)