Define synthetic.
The BHA and BHT (preservative) were probably synthesized in a chemical plant.
The metal oxides and potassium chloride would have come from natural sources like seawater and rocks. I have no idea why most of that would be in pizza dough. Titanium dioxide is a white pigment used in paints so maybe it's for coloration. As for the rest?
The ferrous sulfate
might be in there as an iron supplement, but that's me stabbing the dark. Same for the magnesium oxide. Magnesium is good for you but I'm not sure that's why it's in the dough
Xanthan gum is produced by bacteria and, by the by, can be purchased in a health food store. It's often used as a thickening and/or emulsifying agent. Monostearate is a conjugate base for stearic acid, which is a fatty acid and used for purposes similar to xanthan gum. It's extracted from animal fat. Sodium ascorbate is the conjugate base for vitamin C and some of it will convert to vitamin C once it's in solution. Sodium citrate is the conjugate base for citric acid. I'm not entirely sure why those are in your pizza dough though neither of these is bad for you (quite the contrary, though you produce your own citric acid). Not sure where they came from. Maybe they were synthesized, though it's also possible they were purified out of something that lived. Not sure why they're in your pizza dough. Potassium chloride can come from saltwater or a rock and it's a common way to take in potassium, which you need to live (though too much will give you a heart attack). Not sure why that's in your pizza dough either. Ditto for sodium nitrite and sodium aluminum phosphate.
Generally, chemical companies use the most cost effective means available to make their products and that often involves extracting them from natural sources. Just because it has a chemistry class name doesn't mean it was pieced together, atom by atom, in a lab. That said, it's wise to know what you're eating. Titanium dioxide probably won't hurt you, but why ingest it at all, you know?
By the way, it's not that hard to make your own pizza dough.