Activation of d-Asparagine and d-Glutamine Derivatives Using the Mitsunobu Reaction

Seven d-amino acid derivatives having reactive side chains have been activated to afford their respective 3,5-dinitrobenzyl esters using the Mitsunobu reaction. This esterification was found to be difficult using traditional methods involving 3,5-dinitrobenzyl chloride under alkaline conditions. The conversion of a tRNA to the respective d-glutaminyl-tRNA using d-glutamine 3,5-dinitrobenzyl ester was catalyzed by a flexizyme, followed by purification to remove all the unacylated tRNAs and other byproducts. Both d- and l-glutamine were incorporated from their aminoacyl-tRNAs into a model peptide structurally related to IFN-β.