Synthesis of β-(S-methyl)thioaspartic acid and derivatives

β-(S-Methyl)thioaspartic acid occurs as a posttranslational modification at position 88 in Escherichia coli ribosomal protein S12, a position that is a mutational hotspot resulting in both antibiotic-resistant and antibiotic-sensitive phenotypes. Critical to research designed to determine the biological function of β-(S-methyl)thioaspartic acid will be the availability of synthetic β-(S-methyl)thioaspartic acid as well as derivatives designed for peptide incorporation. We report here the synthesis of β-(S-methyl)thioaspartic acid and derivatives. The installation of the β-methylthio moiety into the aspartic acid structure was accomplished by electrophilic sulfenylation of N-protected-l-aspartic acid derivatives with 2,4-dinitrophenyl methyl disulfide. Following this key transformation, we were able to prepare protected β-(S-methyl)thioaspartic acid derivative suitable for peptide coupling.

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