Bring wine, sugar, shallot, garlic, rosemary, 1 1/2 teaspoons kosher salt and 1/2 teaspoon pepper to a boil in medium saucepan. Simmer over medium-low heat until thickened and reduced to about 3/4 cup, about 12 minutes. Let wine mixture cool completely.
Pour wine mixture into a medium bowl. Add the chicken pieces, cover and marinate mixture for 1 hour.
Preheat oven to 400 degrees F. Cover the top insert of a 2 piece broiler pan with foil, place on bottom pan. Evenly space the chicken on the pan skin-side up, reserving marinade. Roast the chicken until cooked through about 40 minutes.
Meanwhile, pour the reserved marinade into a small skillet and add the grapes. Bring mixture to a rolling boil, and cook until the grapes are tender, about 5 minutes. Baste the chicken with the grape mixture, including both the grapes and the liquid every 15 minutes until the chicken and grapes are glazed and the chicken is cooked through, about 40 minutes. Serve.
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