Among many hurdles in synthesizing proteo-
glycan glycopeptides, one challenge is the incorporation of
aspartic acid in the peptide backbone and acid sensitive
O
-
sulfated glycan chains. To overcome this, a new strategy was
developed utilizing homoserine as an aspartic acid precursor.
The conversion of homoserine to aspartic acid in the
glycopeptide was successfully accomplished by late stage
oxidation using (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl
(TEMPO) and bis(acetoxy)iodobenzene (BAIB). This is the
fi
rst time that a glycopeptide containing aspartic acid and an
O-sulfated glycan was synthesized.