You didn't specify if you are doing a nail down application. Most manufacturers will not approve particleboard underlayment for 3/4" strip flooring because it will not hold nails or glue. Before you proceed, call your manufacturer representative or floor reseller to determine if the particleboard underlayment affects warranty.
Drywall compound is not appropriate as a floor leveler. There are compounds made specifically for this purpose.
Best approach would be to replace particleboard with plywood underlayment after leveling subfloor with appropriate compound. You can use rosin paper or felt under the wood floor and nail per mfg recommendation.