A scalable and chromatography-free synthesis of enantiopure N-Boc-trans-4-methyl-l-prolinol (1) on the multi-gram scale is described. Two shortest possible routes have been developed using commercially available and inexpensive amino acids such as 4-hydroxy-l-proline and l-pyroglutamic acid to afford 1 (>99% purity by high-performance liquid chromatography) with a moderate yield. This chiral precursor can act as a promising building block by providing practical access to a diverse array of 4-alkyl-l-prolines.

中文翻译：

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对映体纯 N-Boc-反式-4-甲基-L-脯氨醇的短且可扩展合成

描述了数克规模的对映体纯N -Boc-反式-4-甲基-l-脯氨醇 ( 1 )的可扩展且无色谱合成。已经使用市售且廉价的氨基酸（例如 4-羟基-l-脯氨酸和l-焦谷氨酸）开发了两条最短的可能路线，以中等收率提供1（>99% 纯度，通过高效液相色谱法测定）。这种手性前体可以通过提供对各种 4-烷基-l-脯氨酸的实用途径来充当有前途的构建块。