<i>C</i>-Alkylation of Peptides through Polylithiated and LiCl-Solvated Derivatives Containing Sarcosine Li-Enolate Units
作者:Dieter Seebach、Hans Bossler、Hansjörg Gründler、Shin-Ichiro Shoda、Roland Wenger
DOI:10.1002/hlca.19910740121
日期:1991.1.30
respectively), and thus C-alkylated on sarcosine (Sar) moieties with MeI and allyl or PhCH2Br. The polylithiated species are solubilized in THF, and their reactivity modified by excess base (lithium diisopropylamide (LDA)), by added LiCl, and/or the cosolvent N,N′-dimethylpropyleneurea (DMPU). Optimization of the reaction conditions for methylation in the cases of 7b (Table 3) and 12b (Scheme 8) gave products
三肽和六肽衍生物Boc-Gly-Sar-MeLeu-OH(5b),Boc-Ala-Sar-Sar-OH(6b),Boc-Ala-Sar-MeLeu-OH(7b)和Boc-Abu-Sar -OH -MeLeu-Val-MeLeu-Ala-OH(12b)可以被多去质子化(分别为三硫代和五硫代衍生物K和P),并因此在肌氨酸(Sar)部分上用MeI和烯丙基或PhCH 2 Br进行C-烷基化。将多晶化的物质溶解在THF中,并通过添加过量的碱(二异丙基氨基锂(LDA)),添加的LiCl和/或助溶剂N,N来改变其反应活性。′-二甲基丙烯脲(DMPU)。优化7b(表3)和12b(方案8)情况下的甲基化反应条件,得到的产物中,离析物的Sar残基已转化为Me-D-Ala单元,产率为80(9c / 8c)和67%(14c / 13c),非对映选择性约为ca。4:1。三肽5b和6b仅包含一个立体生成中心,观察到选