合成路线图解说明: Maltol (I) was protected as the benzyl ether (II) by means of benzyl chloride, and subsequently treated with 1-(2-aminoethyl)piperidine (III) in refluxing ethanol to produce the substituted pyridone (IV). The benzyl protecting group of (IV) was finally removed with boron tribromide, yielding the title hydroxypyridone, which was isolated as the dihydrobromide salt. |