A Simple and Efficient Stereoselective Synthesis of a 2,3‐Difluorosialic acid‐based influenza virus neuraminidase inhibitor

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3‐Fluoroneuraminosyl fluorides are invaluable probes for studying the catalytic mechanism of sialidases (neuraminidases), and as sialidase inhibitors. Significantly, when a C‐3 equatorial fluorine is installed on a C‐4 functionalised N‐acylneuraminic acid (Neu)–based template, the compounds are potent and selective inhibitors of both influenza and parainfluenza sialidases, and of virus replication. Typically, the reported syntheses of 3‐fluoroneuraminosyl fluorides involve either an enzymatic or a chemical synthesis that have uncontrolled stereoselectivity in the introduction of fluorine at C‐3 of Neu and consequently yield a mixture of C‐3 ax and C‐3 eq fluoro derivatives. We now report a simple approach for the exquisitely stereo‐controlled introduction of the C‐3 equatorial fluorine on Neu by incorporation of steric bulk at C‐4. Through this method, we have elaborated a novel synthetic route that exclusively produces the potent anti‐influenza drug candidate; 2,3‐difluoro‐zanamivir analogue with C‐3 eq fluoride.