The pilot recently purchased the tailwheel airplane; however, he did not possess a tailwheel endorsement and was receiving flight instruction in his airplane. The pilot stated that he landed on a turf runway, and shortly after touchdown, the airplane rolled about 800 feet and the left main landing gear contacted a divot in the turf, which caused the airplane to yaw left. He tried to correct the yaw by applying right rudder and brake. The flight instructor then also applied rudder, aileron, and elevator control; however, they were unable to regain control and the airplane ground-looped. The impact resulted in substantial damage to the right wing, right main landing gear, and right side fuselage. The pilot further stated that the wind was calm and the airplane did not experience any preimpact mechanical malfunctions.