Highly efficient and enantioselective syntheses of (2S,3R)-3-alkyl- and alkenylglutamates from Fmoc-protected Garner’s aldehyde
作者:Ryan Moreira、Scott D. Taylor
DOI:10.1007/s00726-020-02868-7
日期:2020.7
3R)-3-alkyl/alkenylglutamates, including the biologically significant amino acid, (2S,3R)-3-methylglutamate, protected for Fmoc SPPS, is reported. Overall yields range from 52–65%. Key to the success of these syntheses was the development of a high-yielding 2-step synthesis of Fmoc Garner’s aldehyde followed by a Horner–Wadsworth–Emmons reaction to give the corresponding Fmoc Garner’s enoate in a 94% yield. The
(2S,3R)-3-烷基/烯基谷氨酸的6步对映选择性合成,包括具有生物意义的氨基酸(2S,3R据报道,针对Fmoc SPPS保护的)-3-甲基谷氨酸。总产量在52–65%之间。这些合成成功的关键是开发了高产率的两步合成Fmoc Garner醛,然后进行了Horner-Wadsworth-Emmons反应,以94%的产率得到了相应的Fmoc Garner的烯酸酯。探索了非对映选择性的1,4-二烷基铜酸锂加到Fmoc Garner的烯酸酯中。当使用二乙基铜酸锂和以前报道的将二烷基铜酸锂1,4-加到Boc或Cbz保护的Garner烯酸酯中的条件下,会发生明显的分解。通过对该反应的优化研究,得出了一系列可靠的条件,从而解决了先前报道的条件的缺点。在这种情况下,高度非对映选择性(大多数情况下> 20:1)1 二烷基/二烯基锂碳酸锂与Fmoc Garner烯酸酯的4加成反应以76-99%的产率实现。所得的1