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A Method for Solid-Phase Synthesis of Oligonucleotide 5‘-Peptide-Conjugates Using Acid-Labile α-Amino Protections
journal contribution
posted on 2004-11-03, 00:00 authored by Simone Zaramella, Esther Yeheskiely, Roger StrömbergWe describe the development of a solid-phase technique for the synthesis of 5‘-peptide−oligonucleotide conjugates (POCs) with a uniform protection strategy for the nucleic acid and the peptide
fragments. On the α-amino function, the amino acid building blocks were protected with the 2-(biphenyl-4-yl)propan-2-yloxycarbonyl (Bpoc) group. This protection is removed during the stepwise peptide elongation
by the same acidic conditions used for removal of the dimethoxytrityl (DMT) group used in the oligonucleotide
assembly (3% trichloroacetic acid, 2 min). The 2-(3,5-dimethoxyphenyl)propan-2-yloxycarbonyl (Ddz) group
was also tested. With this somewhat more stable group, a prolonged contact with the acid (at least 16 min)
was required for accomplishing complete α-amino deprotection, which resulted in some degree of
depurination of the acid-sensitive DNA chain. Base-labile acyl protections were adopted for the side-chains
of histidine, lysine, and the nucleobase amino functions. These were all removed in the final deblocking
step by ammonolysis. This uniform protection scheme for the peptide and the oligonucleotide enabled the
total stepwise synthesis of model conjugates in the 3‘ → N direction with high efficiency and purity.