合成路线1

(S)-5-(Hydroxymethyl)-2-pyrrolidinone (I) was condensed with benzaldehyde in the presence of p-toluenesulfonic acid, and the resulting oxazolidine (II) was hydrogenated over Pd/C to afford the N-benzyl pyrrolidinone (III). Treatment of alcohol (III) with I2 and triphenylphosphine gave iodide (IV), which was reduced to the methyl pyrrolidinone (V) employing NaBH4 in HMPT. An azido group was introduced at position 3 of pyrrolidinone (V) by treatment with 2,4,6-triisopropylbenzenesulfonyl azide in the presence of LDA, and the resulting trans-azide (VI) was subsequently epimerized to the cis-isomer (VII) by means of NaOEt in EtOH. Reduction of the azido group of (VII) to the corresponding amine (VIII) was carried out by catalytic hydrogenation over Pd/C, and further treatment with Boc2O provided the tert-butyl carbamate (IX). The N-benzyl group was then removed by means of lithium metal in liquid ammonia to afford (X).