Synthesis of a Peptidoyl RNA Hairpin via a Combination of Solid‐Phase and Template‐Directed Chain Assembly

Peptidoyl RNAs are the products of ribosome‐free, single‐nucleotide translation. They contain a peptide in the backbone of the oligoribonucleotide and are interesting from a synthetic and a bioorganic point of view. A synthesis of a stabilized version of peptidoyl RNA, with an amide bond between the C‐terminus of a peptide and a 3′‐amino‐2′,3′‐dideoxynucleoside in the RNA chain was developed. The preferred synthetic route used an N‐Teoc‐protected aminonucleoside support and involved a solution‐phase coupling of the amino‐terminal oligonucleotide to a dipeptido dinucleotide. Exploratory UV‐melting and NMR analysis of the hairpin 5′‐UUGGCGAAAGCdC‐LeuLeu‐AA‐3′ indicated that the peptide‐linked RNA segments do not fold in a cooperative fashion. The synthetic access to doubly RNA‐linked peptides on a scale sufficient for structural biology opens the door to the exploration of their structural and biochemical properties.