A new synthesis of (S)-3-amino-4-methoxy-butan-1-ol is reported. The synthesis is based on the preparation of the primary, nonprotected enamine of the commercially available β-keto ester methyl 4-methoxy-3-oxo-butanoate and asymmetric catalytic enamine hydrogenation using a Ru-MeOBIPHEP catalyst. Alternatively, the process is performed by asymmetric catalytic reductive amination of the β-keto ester with ammonium acetate and hydrogen using a similar Ru catalyst. Both process versions provided initial ee values of 97−98% which were upgraded to ≥99% by product crystallization. Ester to alcohol conversion was best accomplished by LiBH₄ reduction after transitory Boc protection of the amino group.

中文翻译：

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还原胺化法不对称合成（S）-3-氨基-4-甲氧基丁氧基-1-醇

报道了（S）-3-氨基-4-甲氧基-丁-1-醇的新合成。该合成是基于制备可商购的β-酮酯4-甲氧基-3-氧代丁酸甲酯的伯胺，未保护的烯胺和使用Ru-MeOBIPHEP催化剂进行不对称催化烯胺加氢。或者，该方法通过使用类似的Ru催化剂通过β-酮酯与乙酸铵和氢的不对称催化还原胺化来进行。两种工艺版本均提供了97-98％的初始ee值，通过产品结晶可将其提高到≥99％。氨基的短暂Boc保护后，通过LiBH ₄还原可以最好地实现酯到醇的转化。