The condensation of 1-cyclopropyl-6,7,8-trifluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (I) with 2-(formylamino-methyl)- morpholine (II) by means of 1,8-diazabicyclo[5.4.0]-7-undecene (DABU) in refluxing acetonitrile gives the formamido derivative (III), which is then hydrolyzed with concentrated HCl in refluxing methanol.
A new synthesis for Y-26611 has been reported: The reaction of 4-benzyl-2-(chloromethyl)morpholine (I) with potassium phthalimide (II) in refluxing DMF gives 4-benzyl-2-(phthalimidomethyl)morpholine (III), which is treated with hydrazine hydrate in refluxing ethanol yielding 2-(aminomethyl)-4-benzylmorpholine (IV). The acetylation of (IV) with acetic anhydride in cool toluene affords 2-(acetamidomethyl)-4-benzylmorpholine (V), which is debenzylated by hydrogenation with hydrazine hydrate over Pd/C in isopropanol to give 2-(acetamidomethyl)morpholine (VI). The condensation of (VI) with 1-cyclopropyl-6,7,8-trifluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (VII) by means of triethylamine in refluxing acetonitrile yields 7-[2-(acetamidomethyl)morpholin-4-yl]-1-cyclopropyl-6,8-difluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (VIII), which is finally deacetylated with refluxing aqueous HCl.