This application relates to monomers of the general formula (I) for the preparation of PNA (peptide nucleic acid) oligomers and provides method for the synthesis of both predefined sequence PNA oligomers and random sequence PNA oligomers:
1
wherein
R1, R2, R3, R4, R5 is independently H, halogen, C
1
-C
4
alkyl, nitro, nitrile, C
1
-C
4
alkoxy, halogenated C
1
-C
4
alkyl, or halogenated C
1
-C
4
alkoxy, wherein at least one of R1, R3, and R5 is nitro;
R6 is H or protected or unprotected side chain of natural or unnatural &agr;-amino acid; and
B is a natural or unnatural nucleobase, wherein when said nucleobase has an exocyclic amino function, said function is protected by protecting group which is labile to acids but stable to weak to medium bases.