合成路线1

A new synthesis of lafutidine has been described: The condensation of 2-bromopyridine-4-carbaldehyde ethylene ketal (I) with 4-(tetrahydropyranyloxy)-2(Z)-buten-1-ol (II) by means of NaOH, K2CO3 and tetrabutylammonium bisulfate in refluxing toluene gives the corresponding substitution product (III), which by treatment with pyridinium p-toluenesulfonate (PPTS) in hot ethanol yields the 2(Z)-butenol (IV). The reaction of (IV) with SOCl2 and then with potassium phthalimide (V) affords the substituted phthalimide (VI), which by treatment with hydrazine hydrate in refluxing methanol gives the 2(Z)-butenamine (VII). The condensation of (VII) with 2-(2-furylmethylsulfinyl)acetic acid 4-nitrophenyl ester (VIII) in THF yields the expected amide (IX), which is treated with p-toluenesulfonic acid in refluxing acetone/water to eliminate the ethylene ketal protecting group yilding the aldehyde (X). Finally, this compound is reductocondensed with piperidine (XI) by means of NaBH4 in ethanol.