2-acilaminoacritlatos en cicloadiciones [2+2]síntesis de alfa, beta-C4Ser

Resumo

First, we have optimized the termal [2+2] cycloaddition between methyl 2-acetamideacrylate and ketene diethyl acetal. The reaction gives rise to a new substituted cyclobutane skeleton that can be transformed to obtain several protected (1R*, 2R*)-c4Ser. The other stereoisomer, protected (1R*, 2S*)-c4Ser was obtained from an intermediate product, after having inverted a secondary alcohol. The zwitterionic mechanism proposed for the thermal [2+2] cycloaddition between acrylates and ketene diethyl acetal was verified at the B3LYP/6-31+G theory level for optimized geometries using the Gaussian 98 package. In the other hand, we could see that in the presence of Lewis acids, the reaction between methyl 2-acetamideacrylate and ketene diethyl acetal led to a cyclohexane ring wich has incorporated one electron-poor acceptor alkene and two electron-rich donor alkenes. Also, the reaction between methyl 2-acetamideacrylate and ethyl vinyl ether in the presence of bulky aluminium Lewis acid furnished one of the two possible stereoisomers, depending on the Lewis acid employed. We have studied the versatility of this reaction with several alkyl vinyl ethers, mono and disubstituted. Following the last method, we have synthesized several a,b-c4Ser derivatives, protected in the right way to be used as starting material for the synthesis of new peptides, glycoaminoacids or glycopeptides. Also we introduce quirality in the acceptor and the donor olefin leading to promising results.