Cut tenderloin crosswise into 8 pieces. Place each piece between 2 sheets of heavy duty plastic wrap; pound each piece to 1/2-inch thickness. Combine salt, thyme, pepper, and allspice; rub over both sides of pork.
Heat a large skillet over medium-high heat. Lightly coat with olive oil. Add pork to pan, and cook for 2 minutes on each side or until done. Remove pork from pan; keep warm.
Reduce heat to medium. Add shallots and butter to pan; cook 2 minutes, stirring occasionally. Add brown sugar and vinegar to pan; cook 30 seconds or until sugar melts, stirring constantly. Spoon sauce over pork (about 1 T. per medallion).
Calories 226; Fat 6.4g; Protein 32.3g; Carb 7.3g; Sodium 371mg