Nucleo--Amino Acids: Synthesis and Oligomerization to -Homoalanyl-PNA

Abstract

The synthesis of thyminyl-, uracilyl-, cytosinyl-, and guaninyl-β3-amino acids and the oligomerization of the cytosinyl- and guaninyl-β3-amino acids to β-homoalanyl-PNA are presented. The pyrimidinyl nucleobases were connected to the γ-position of β-homoalanine by Mitsunobu reaction with a β-homoserine derivative or by nucleophilic substitution of methanesulfonates. For the preparation of the guaninyl-β3-amino acid, a β-lactam route was established that might be of interest also for the synthesis of other β3-amino acid derivatives. The cytosinyl and guaninyl building blocks were oligomerized to hexamers. They form quite stable self-pairing complexes in H2O as indicated by temperature dependent UV and CD spectroscopy.