4 fluoro-Dolutegravir

4-Fluoro-Dolutegravir is a synthetic byproduct formed via unintended fluorination at the 4-position of the naphthyridine core during Dolutegravir synthesis. It retains the 5-methyl-1,6-naphthyridine-2,4-diamine pharmacophore but incorporates a 4-fluoro substituent, which disrupts the hydrogen-bonding capacity critical for integrase inhibition. The molecule features a pyrimidin-4-ylmethyl side chain linked to the naphthyridine ring, with the fluoro group inducing conformational rigidity. This impurity arises from competitive electrophilic fluorination during late-stage aromatic substitution. It functions as an HPLC reference standard for quantifying this specific synthetic variant in Dolutegravir API batches.