Synthesis of oxy-peptide nucleic acids with mixed sequences.

Syntheses of N-Fmoc delta-amino acids with an ether linkage in the main chain and six different nucleobases on the side chain, Fmoc-NH-C*H(CH2-CH2-B)-CH2-O-CH2-COOH (B = N6-benzoyladenine, thymine, uracil, N-benzoylcytosine, guanine, and N2-isobutyrylguanine) are described. The delta-amino acids were prepared through 8-12 step synthesis starting from L-homoserine and could be linked together to form novel peptide nucleic acids (oxy-PNAs = OPNAs) by solid-phase peptide synthesis.