合成路线1

The protection of 3-piperidinol (I) with tert-butoxycarbonyl anhydride or benzyloxycarbonyl chloride gives the corresponding protected piperidine (II), which is oxidized with CrO3 and acetic anhydride in pyridine yielding the piperidinone (III). The condensation of (III) with phosphinate (IV) and triethylamine at 100 C affords the alpha-hydroxyphosphinate (V), which is acylated with methoxalyl chloride (VI) and DMAP giving the methoxalyl ester (VII). The reduction of (VII) with tributyl in hydride and AIBN yields the protected phophinate (VIII), which is finally deprotected and hydrolyzed with 6M HCl.