In a large saucepan of boiling salted water, cook pasta until al dente.
Meanwhile, in a small nonstick skillet, melt half the butter over medium. Add garlic and pinch of red-pepper flakes; cook until fragrant, 1 minute. Raise heat to medium-high; add wine. Cook until reduced by 1/3, about 1 minute. Add shrimp and season with salt and pepper; cook until opaque throughout, 1 to 2 minutes. Remove skillet from heat; swirl in lemon juice and remaining butter. Add pasta and toss to combine. Serve topped with parsley.