Preheat oven to 425° F. Place the sugar and syrup in a small heavy saucepan and cook over low heat, stirring constantly until it becomes thick. Once it has thickened, gradually add the eggs, stirring quickly. Remove the mixture from the heat and add the butter, vanilla, and pecans.
Pour the mixture into pie crust. Bake for 10 minutes, then lower the temperature to 325° F. and bake for an additional 30 minutes.