We report an efficient protocol for synthesis of methyl 2-[(tert-butoxycarbonyl) amino]-3-hydroxy-3-phenylpropanoate (Erythro (±)) by simple reduction and methyl 2-[(tert-butoxycarbonyl) amino]-3-hydroxy-3-phenylpropanoate (Threo (±)) by inversion method. The erythro (±) isomer has been obtained in excellent yield (93%) using sodium borohydride in methanol at -40°C. The erythro isomer has been effectively converted into its threo (±) with 100% efficiency, by inversion, using methanesulfonyl chloride, cesium acetate and crown ether-18-6. The salient features of this method include cost effectiveness, excellent yields and scope for large-scale synthesis, which makes the method an attractive addition to the applicable methodologies.

中文翻译：

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2-[(叔丁氧羰基)氨基]-3-羟基-3-苯基丙酸甲酯：还原法合成赤型 (±) 异构体和反转法合成苏型 (±) 异构体

我们报告了一种通过简单还原和甲基 2-[(tert-butoxycarbonyl)amino]-3 合成 2-[(tert-butoxycarbonyl)amino]-3-hydroxy-3-phenylpropanoate (Erythro (±)) 的有效方案-羟基-3-苯基丙酸酯（Threo（±））通过反转法。使用硼氢化钠的甲醇溶液在 -40°C 下以优异的产率 (93%) 获得赤型 (±) 异构体。通过使用甲磺酰氯、乙酸铯和冠醚-18-6 的转化，赤型异构体已有效地转化为其苏型 (±)，效率为 100%。该方法的显着特点包括成本效益、出色的产率和大规模合成的范围，这使得该方法成为适用方法的一个有吸引力的补充。