, Volume 20, Issue 1, pp 365-378
Date: 08 Nov 2012

Synthesis of peptide–cellulose conjugate mediated by a soluble cellulose derivative having β-Ala esters (II): conjugates with O-phospho-l-serine-containing peptides

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A synthetic route is described here for novel peptide-cellulose conjugates containing O-phospho-l-serine. First, Boc-Ser(PO3Ph2) and the related dipeptides, Boc-Ser(PO3Ph2)-Asp(OBzl) and Boc-Asp(OBzl)-Ser(PO3Ph2), were synthesized by adopting the phosphoryl-protection strategy. The condensation reaction between the α-carboxyl group of the protected Boc-Ser(PO3Ph2) and the β-amino groups of β-Ala-Cellulose using isobutyl chloroformate and N-methylmorpholine yielded the product conjugate, N β -[Boc-Ser(PO3Ph2)]-β-Ala-Cellulose. The degree of substitution of Boc-Ser(PO3Ph2) towards the β-amino groups of β-Ala-Cellulose was estimated as DS N  = 0.75 (maximum, 1.0). Similar reactions between β-Ala-Cellulose and two kinds of protected dipeptides, Boc-Asp(OBzl)-Ser(PO3Ph2) and Boc-Ser(PO3Ph2)-Asp(OBzl), gave the corresponding conjugates, and the DS N was estimated to be 0.95 and 0.69, respectively. The phenyl, benzyl, and Boc groups were removed in one-pot using the Pt2O catalyst in 50 % trifluoroacetic acid/acetic acid. The 31P-NMR and UV–Visible spectra indicated the complete deprotection without any observable elimination of the phosphorylated peptides.