Preheat oven to 350 °F (177 °C). Bring frozen pie crust out of freezer and set aside.
In a large bowl, whisk together sugar, corn syrup, and flour. Add eggs in, one at a time, and whisk together until well incorporated. Add in the crushed pineapples, vanilla, and sweetened coconut flakes. Whisk well to combine.
Pour batter into pie crust and using a pastry brush, brush the top with the melted butter.