New building blocks for peptide and depsipeptide synthesis: hexafluoroacetone protected l-homoisoserine and d,l-homoisocysteine derivatives

Hexafluoroacetone as Protecting and Activating Reagent: New Routes to Amino, Hydroxy, and Mercapto Acids and Their Application for Peptide and Glyco- and Depsipeptide Modification

“…When the catalytic decomposition of the diazoketones is carried out in tert -butyl alcohol, the tert -butyl esters are formed. The ω-carboxy-protected species can be deblocked and activated as ω-carboxylic acid chlorides by heating in the presence of an excess of thionyl chloride in an one-pot procedure (Scheme ) 28 …”

“…Analogously, HFA-2-methylisoserine was obtained from citramalic acid and HFA-isocysteine from mercaptosuccinic acid . Efficient syntheses (section 4.5) of the homologues HFA-homoisoserine, the nonnatural amino acids HFA-homoisocysteine, , and HFA-2-methylhomoisoserine are described. , N α -Methyl-2,3-diaminopropionic acid was found in a variety of natural products, like in the peptide antibiotic TAN -1057, which is active against Staphylococcus aureus . The HFA route gives rise to derivatives of N α -methyl-2,3-diaminopropionic acid and its homologues .…”

“…The ω-carboxy-protected species can be deblocked and activated as ω-carboxylic acid chlorides by heating in the presence of an excess of thionyl chloride in an one-pot procedure (Scheme 28). 80 5. ω-Isocyanates from r-Functionalized r,ω-Dicarboxylic Acids…”