directly introduce these acyl moieties by an enzyme-catalyzed reaction of 2a with the corresponding activated esters. This new approach was based on the regioselective introduction of a methyl malonate residue at the CH2OH of the sugar moiety by catalysis with the protease subtilisin ( 22a). The mixed diester 22a was then subjected to chemoselective hydrolysis of the methoxycarbonyl function by another
Enols of Amides Activated by the 2,2,2-Trichloroethoxycarbonyl Group
作者:Ahmad Basheer、Zvi Rappoport
DOI:10.1021/jo030266z
日期:2004.2.1
Reaction of isocyanates XNCO (X = Ar, i-Pr, t-Bu) with CH2(Y)CO2CH2CCl3 (Y = CO2Me, CO2CH2CCl3, CN) gave 15 amides XNHCOCH(Y)CO2CH2CCl3 (6) or enols of amides XNHC(OH)C(Y)CO2CH2CCl3 (5) systems. The amide/enol ratios in solution depend strongly on the substituent Y and the solvent and mildly on the substituent X. The percentage of enol for group Y increases according to Y = CN > CO2CH2CCl3 > CO2Me
异氰酸酯XNCO(X = Ar,i- Pr,t- Bu)与CH 2(Y)CO 2 CH 2 CCl 3(Y = CO 2 Me,CO 2 CH 2 CCl 3,CN)反应生成15个酰胺XNHCOCH( Y)CO 2 CH 2 CCl 3(6)或酰胺的烯醇XNHC(OH)C(Y)CO 2 CH 2 CCl 3(5)系统。溶液中的酰胺/烯醇比率在很大程度上取决于取代基Y和溶剂,在轻微程度上取决于取代基X。Y基团的烯醇百分比根据Y = CN> CO 2 CH 2 CCl 3 > CO 2 Me的增加而增加。按照CCl 4 > C 6 D 6 > CDCl 3 > THF- d 8 > CD 3 CN> DMSO- d 6的溶剂。在最酸性的系统中(Y = CN),在中等极性的溶剂中观察到酰胺/烯醇交换,而在DMSO- d 6中观察到电离到共轭碱。发现具有Y = CN,X =i- Pr的化合物的固态
Stoll, Gerhard; Frank, Juergen; Musso, Hans, Liebigs Annalen der Chemie, 1986, # 11, p. 1968 - 1989
作者:Stoll, Gerhard、Frank, Juergen、Musso, Hans、Henke, Henning、Herrendorf, Wolfgang