Halve the endives lengthwise. Melt the butter, sugar, and vinegar to caramel in a large saute pan, and then add the wine. Lay in the endive, cut side down. Season the endive with salt, and pepper, cover the pan with foil, and cook over medium-low heat, turning a few times, until very tender, about 20 to 30 minutes. While the endive cooks, cut the skin off the oranges with a knife, to expose the flesh, then remove the sections, holding the oranges over a bowl to catch the juices. Add the juices to the endive, but reserve the sections until the very end. When the endives are soft, uncover the pan, and continue cooking, turning the endives occasionally, to reduce the liquid to a glaze and caramelize the endives. At the last minute, add the orange sections to heat through, and serve.