A typical 15,000 BTU A/C unit requires 2400 watts (Camping World info). Camping World also suggests a generator of at least 3500 watts to run that A/C.
Running that A/C with an inverter and alternator requires an inverter of at least 3000 watts and an alternator that ALWAYS puts out at least 200 amps even at idle. I don't think you can find a normal alternator that can generate that many amps.
It might be possible if you can find a 5000 BTU A/C for an RV but that is not much cooling power.
Before proceeding with this, I would strongly recommend doing a lot more research including checking out how engine RPM affects the power output of your alternator.
Advanced RV Sprinter