The commercial pilot was practicing touch-and-go landings in the tailwheel equipped airplane. He reported that the wind direction changed to a quartering tailwind after the airplane touched down. The pilot stated that he then lost directional control of the airplane and did not believe he had sufficient engine power to recover. During the accident sequence the left main landing gear failed and the airplane ground looped, resulting in substantial damage to the left wing and horizontal stabilizer. The pilot stated that the airplane and engine had no mechanical failures or malfunctions prior to the accident.