In a small saucepan, bring vinegar to a boil; cook 10-15 minutes or until liquid is reduced to 3 tablespoons. Remove from heat.
Brush oil over both sides of baguette slices. Grill, uncovered, over medium heat until golden brown on both sides. Grill nectarines 45-60 seconds on each side or until tender and lightly browned. Cool slightly.
Spread goat cheese over toasts. Cut nectarines into thick slices; arrange over cheese. Drizzle with balsamic syrup; sprinkle with basil. Serve immediately.