# Conception and Synthesis of Sequence‐Coded Morpholinos

## TL;DR

Researchers developed a new method to create sequence-defined morpholino oligomers, which can store and decode digital information.

## Contribution

The study introduces a binary alphabet system for synthesizing sequence-coded morpholino oligomers, enabling digital data storage.

## Key findings

- A binary alphabet of morpholino comonomers was successfully synthesized and used to create sequence-defined oligomers.
- Uniform coded sequences were achieved by adding a capping step during synthesis.
- Tandem mass spectrometry confirmed full sequence coverage and the ability to decode stored binary messages.

## Abstract

Solid‐phase morpholino chemistry was explored as a new route to synthesize abiological sequence‐defined oligomers. Two comonomers, 0 and 1 containing (i) a chlorophosphoramidate reactive function, (ii) a trityl‐protected morpholine, and (iii) a coding substituent (H or CH3 for 0 and 1, respectively) on the morpholine ring were first synthesized and characterized. This binary alphabet was afterwards tested for the synthesis of digitally‐encoded oligomers with different lengths and sequences. The oligomers were prepared on a modified polystyrene resin, cleaved, and characterized by liquid chromatography mass spectrometry. When using a repetitive cycle containing only morpholino coupling and trityl deprotection steps, the formed oligomers were not uniform. Thus, an additional capping step was added. In these conditions, uniform coded sequences were prepared in most cases. Furthermore, the oligomers were analyzed by tandem mass spectrometry. In the studied collision‐induced dissociation conditions, the repeat units of the oligomers undergo two main‐chain fragmentations and full sequence coverage was observed for all studied sequences. Therefore, the binary messages stored in the oligomers could be decoded and retrieved in all cases.

Morpholino oligomer chemistry, which relies on the coupling of a chlorophosphoramidate group with the secondary amine of a morpholine ring, has been to date only explored for the synthesis of xeno nucleic acids. Here, we report that it can also be used for the design of digital polymers. Oligomers with different sizes and sequences were synthesized using a binary monomer alphabet.