Zn-Catalyzed<i>tert</i>-Butyl Nicotinate-Directed Amide Cleavage as a Biomimic of Metallo-Exopeptidase Activity
作者:Clarence C. D. Wybon、Carl Mensch、Charlie Hollanders、Charlène Gadais、Wouter A. Herrebout、Steven Ballet、Bert U. W. Maes
DOI:10.1021/acscatal.7b02599
日期:2018.1.5
A two-step catalytic amide-to-ester transformation of primary amides under mild reaction conditions has been developed. A tert-butyl nicotinate (tBu nic) directing group is easily introduced onto primary amides viaPd-catalyzed amidation with tert-butyl 2-chloronicotinate. A weak base (Cs2CO3 or K2CO3) at 40–50 °C can be used provided that 1,1′-bis(dicyclohexylphosphino)ferrocene is selected as ligand
已经开发了在温和的反应条件下伯酰胺的两步催化酰胺转化为酯的方法。甲叔丁基烟酸甲酯(吨卜NIC)指示组很容易通过Pd催化的酰胺化与引入到伯酰胺叔丁基2-氯烟。如果选择1,1'-双(二环己基膦基)二茂铁作为配体,则可以使用40–50°C的弱碱(Cs 2 CO 3或K 2 CO 3)。所述吨卜NIC活化酰胺随后允许的Zn(OAc)2催化的醇解nonsolvolytic在吨在中性反应条件下于40–60°C的BuOAc。激活机制是仿生的:在引导基团中吡啶的C3酯取代基构成了适合Zn螯合的反式构象异构体,C═O酰胺-Zn-N引导基团,并且Zn配位醇还被激活为亲核试剂通过氢键与催化剂的乙酸酯配体键合。另外,乙酸盐配体有助于分子内O至N质子转移。化学选择性相对于其他官能团以及与具有挑战性的反应伙伴(如肽,糖和固醇)的相容性说明了这种两步酰胺裂解方法的合成适用性。该Ť卜NIC酰胺在裂解前不需要纯化。初步实验
Convenient one-pot esterification of N-protected aminoacids via isopropenyl chloroformate activation.
ZEGGAF, CH.;PONCET, J.;JOUIN, P.;DUFOUR, M. -N.;CASTRO, B., TETRAHEDRON, 45,(1989) N6, C. 5039-5050
作者:ZEGGAF, CH.、PONCET, J.、JOUIN, P.、DUFOUR, M. -N.、CASTRO, B.
DOI:——
日期:——
Isopropenyl chlorocarbonate (IPCC)1 in amino acid and peptide chemistry: Esterification of N-protected amino acids; Application to the synthesis of the depsipeptide valinomycin
Esterification of N-protected α-amino acids was achieved via isopropenyl chlorocarbonate (IPCC) activation. In situ alcoholysis of the unstable mixed anhydride intermediate was catalyzed by 4-(dimethylamino)pyridine (DMAP). Competing isopropenyl ester formation was negligible when using methylene chloride as the solvent. A variety of esters from primary and secondary alcohols were obtained with good