In a large nonreactive saucepan, combine the wine and sugar and bring to a simmer over moderate heat. Stir briefly to dissolve the sugar.
Peel the pears; if they don't stand upright, trim the bottoms slightly. Stand the pears in the saucepan and add just enough water to cover them. Place a heatproof plate on top of the pears to help keep them submerged in the liquid. Bring to a simmer over moderately high heat and cook until the pears are tender when pierced with a knife, about 20 minutes.
Using a slotted spoon, transfer the pears to a plate and let the poaching liquid cool completely. Return the pears to the cooled liquid, re-cover them with the plate and refrigerate for at least 3 hours or overnight.
Transfer the pears to a platter or plates. Strain the poaching liquid into a clean nonreactive saucepan and boil over high heat until syrupy, about 35 minutes. Spoon the syrup over the pears.