Paul didn't teach anything that Christ didn't teach. Jesus was basically a Pharisee, he was a teacher of the law. He presented himself that way, and those listening to him treated him that way. He just taught in a different context- he taught the Law to Jews who were already in agreement with the Law. Paul was the apostle to the Gentiles, so he was teaching what Christ taught to people who didn't know the Law, who were in a Greek environment with a Greek mindset. They were both teaching to the same end though- "Love the Lord your God with all your heart, soul, strength and mind." To Jews, that meant to accept the prophesied Messiah. To Greeks, that meant accept Christ as your Saviour and tell the world about him. They taught the same thing.