I'm an oldfag chemist and back in the day I worked on a novel therapeutic treatment called antisense. It was a reactive DNA backbone on a chain of nucleotides the were meant to make the body fight certain cancers and eliminate things like specific proteins cancers used during mitosis.

Anyway one of the big hurdles in producing these drugs was the chiral nature the bonds of these lab produced oligos had, wherein one would want a single left handed chain and end up with 2^52 different compounds.

After some digging I can't find any reasonable solution to the stereochemical issue that was ever discovered. This was the issue with Thalidomide btw, a racemic compound that one enantiomer was supposedly the cause of the birth defect.

My question, if anyone knows, when the mRNA vaccines are produced, in what is typically described as using an "mRNA synthesizer" how do they deal with, if at all, the stereochemistry?