If amino acids can only be made where there is no free oxygen in the atmosphere, and porphyrins can only be made when there is free oxygen, then these things needed by every cell could not have existed together to form the first cell! What’s more, many of these compounds are antagonistic. They will combine and destroy each other—anywhere except within a living cell.
What does this mean? Simply that to make DNA, you have to have DNA in the first place! You have to have the DNA code within the cell before you can make more DNA code. Without the complete code in the first place, there is no way to make the code necessary for every living cell!
