alpha-PNA: A novel peptide nucleic acid analogue of DNA

Peptide nucleic acid (PNA) analogues of DNA have attracted interest as potential pharmacological regulators of gene expression since they have the capacity to invade duplex DNA forming Watson-Crick base paired PNA:DNA heteroduplexes. Unfortunately, strand invasion is limited to homopurine and homopyrimidine sequences and there is the need to explore further PNA analogues for the purpose of expanding the strand invasion alphabet. Accordingly, we have designed a true peptide mimic of DNA (designated alpha-PNA) involving novel L-alpha-amino acids, with side chains comprising the four DNA bases attached via an ethylene linkage, interspaced with glycine. The four base-containing amino acids have been synthesized from N-Boc-L-homoserine, via alkylation of the appropriate base with the key intermediate (S)-2-(N-Boc-amino)-4-bromobutyric acid methyl ester followed by hydrolysis. These amino acids have been incorporated into alpha-PNA oligomers using both solution and solid phase methods.