Synthetic pathway for obtaining EN 292685: Treatment of amino acid (I) with CbzOSu affords the protected amino acid (II), which is further protected by means of Boc2O to yield derivative (III). Condensation of amino acid (III) with N,O-dimethyl hydroxylamine by means of BOP and DIEA provides hydroxamic ester (IV), which is then subjected to hydrogenolysis over Pd/C in CHCl3 for selective deprotection, furnishing compound (V). Coupling of (V) to intermediate (VI) affords derivative (VII), which is then coupled to lithium derivative (VIII) to give protected compound (IX). Finally, the Boc group of (IX) is removed by treatment with TFA.
Synthesis of intermediate (VI): Treatment of pyridone (X) with diphenyl phosphoryl azide (DPPA) followed by reaction with benzyl alcohol affords the protected derivative (XI), which then reacts with tert-butyl bromoacetate (XII) by means of Cs2CO3 to provide the acetate derivative (XIII). Hydrogenation of (XIII) over Pd/C allows Cbz removal, giving amine (XIV), which is then condensed with iodo derivative (XV) to furnish sulfonamide compound (XVI). Finally, hydrolysis of (XVI) is achieved by treatment with TFA to afford the target intermediate (VI).