Walter White here. Organic chemistry can turn pretty much any molecule into a related molecule if you have enough time and patience. You want to purchase a precursor that's nearly the same as your desired product but also one that takes the fewest reactions to get there. I don't know how many reactions you would need to turn this into this but it's definitely possible.

Historical myth: The rumor started in the 1990s–2000s on drug forums (and later persisted on places like Reddit) because people noticed the close structural relationship and assumed “just swap the side chain.” In reality, pharmaceutical companies start from opium-derived precursors (thebaine → oxycodone → etc.) or full total synthesis — they never use naloxone as a starting material to make oxymorphone.

A lot of opioids are fairly related, Oxycodone and Oxymorphone can be used as precursors to make Nalaxone and vice versa. I recall Four Thieves Vinegar Collective doing a similar trick though I don't remember what the actual precursor was.