Preheat oven to 350 degrees. Line muffin pans with paper liners. Lightly spray cups with non stick cooking spray. In a large bowl, combine cake mix, buttermilk, oil, egg whites, and vanillla; beat at low speed with electric mixer for 30 seconds, or until moistened. Increas speed to medium; beat for 2 minutes. Devide batter evenly among prepared muffin cups, filling about two- thirds full. Bake for 20 to 24 minutes, or until a wooden pick inserted in the center comes out clean. Cool in pans for 15 minutes. Remove from pans, and cool completely on wire racks (about 45 minutes). In a small bowl, stir together frosting and coconut extract. Spread frosting evenly over cupcakes. Sprinkle with coconut flakes.