Transesterifications with 1,8-Diazabicyclo[5.4.0]undec-7-ene/Lithium Bromide (DBU/LiBr) - Also Applicable to Cleavage of Peptides from Resins inMerrifleld Syntheses
作者:Dieter Scebach、Adrian Thaler、Denis Blaser、Soo Y. Ko
DOI:10.1002/hlca.19910740520
日期:1991.8.7
amidine base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and LiBr (preferably 0,5 and 5 equiv., resp.) turns out to be a highly efficient catalyst (at 0–25°) for saponifications (in THF/H2O) and transesterifications (in ROH). The scope and limitations of the method are determined using ca. two dozens of different ester/alcohol combinations (Schemes 2 and 3). The investigation is focused on peptides as substrates
base碱的1,8-二氮杂双环[5.4.0]十一碳-7-烯(DBU)和LiBr(最好分别为0.5和5当量)的混合物被证明是一种高效催化剂(0时) –25°)用于皂化(在THF / H 2 O中)和酯交换(在ROH中)。该方法的范围和局限性由ca确定。两种不同的酯/醇组合(方案2和3)。研究集中在肽作为底物上。在精心控制的条件下,N -Boc-和N不会发生准分子反应-Z-保护的肽酯,当是甲基,乙基,异丙基或烯丙基酯的产物时,如含多达六个氨基酸的肽所示,C端带有Ala,Len MeLeu,Asp(OEt)或Tyr (方案3以及表1和2)。Bom-Leu-Ala-Gly-Val-OR和Boc-Leu-Ala-Gly-Phe-OR(R = H,Me)从PAM和Wang树脂中水解和酯基转移(R = H,Me)(0–25°下1–8 h ,通过这种方法可以在不致使C端立体异构中心发生差向异构的情况下,获