Preheat the oven to 375°F. Wipe the chicken with a paper towel. Mix the butter, mustard, vinegar, salt, and cayenne, and rub the mixture all over the skin side of the chicken. Place the quarters, skin side up, in a shallow roasting pan. Sprinkle evenly with the crumbs and bake for about 40 minutes, or until a meat thermometer registers 170°F in the breast meat, 185°F in the dark meat.