2,3,4,6-Tetra-O-acetyl-a-D-mannopyranosyl-Fmoc serine (CAS# 118358-80-8) is a an fmoc-protected, and glycosylated form of L-serine (S270995) used in the synthetic preparation of peptides and peptide fragments, such as the synthesis of homogeneously glycosylated insulin for use as an oral medication for diabetics.