Combine vinegar, ginger, rosemary, sugar substitute, pepper flakes and salt in a small bowl. Slowly whisk in oil in a steady stream until dressing thickens.
2
Brush chicken with 1 tablespoons of dressing and let marinate for 1 hour. Set remaining dressing aside.
3
Heat grill to medium-high after 50 minutes of marinating. Season chicken with salt and pepper and grill for 15 minutes, turning once halfway through cooking time, until just cooked through. Remove chicken from grill and place on a platter to rest.