In a saucepan, combine the sugar, basil leaves, half of the peach nectar and lemon juice. Bring to a simmer, crushing the basil leaves with the back of a spoon to release their flavor. Simmer just long enough to melt the sugar, then remove from the heat and allow to cool.
Strain the basil mixture into a pitcher filled with ice cubes. Pour in wine and remaining peach nectar. Stir briefly and serve.