合成路线1

An enantioselective synthesis of the (3R,4R)-isomer has also been reported. Quaternization of 3-(methoxycarbonylamino)-4-methylpyridine (VII) with benzyl chloride in toluene at 80 °C, followed by reduction of the resulting pyridinium salt (VIII) with NaBH4 in ethanol, yields the tetrahydropyridine (IX). Enantioselective hydrogenation of (IX) in the presence of chiral rhodium catalyst in ethanol, and subsequent purification of the obtained piperidine by crystallization as the corresponding di-p-toluoyltartrate salt, provides the pure (3R,4R)-enantiomer (X). This is then condensed with 2,4-dichloro-7H-pyrrolo[2,3-d]pyrimidine (XI) by means of K2CO3 in boiling water to give the tertiary amine (XII), which is subjected to simultaneous debenzylation and dechlorination by means of H2 and Pd(OH)2/C to yield the deprotected piperidine (XIII) (2). This compound is finally condensed with cyanoacetyl chloride (VI) (prepared from cyanoacetic acid [XIV] and oxalyl chloride) by means of triethylamine in dichloromethane to obtain the chiral CP-690550 (2, 3). Scheme 2.