Put clams into large pan and cover with water. Pour in the salt, stir, and refrigerate 30 mins. Heat olive oil over medium heat in a large pan. Add garlic and red pepper flakes; saute about 2 minutes. Add tomato puree and wine, bring to a boil, reduce heat and simmer 5 minutes. Drain clams in a colander and rinse well. Put clams into the sauce with half of the parsley. Bring to a boil, reduce heat to medium, cover and cook about 7 mins, or until clam shells have opened. Discard any clams not opened. Remove clams with slotted spoon, place in bowl, cover with foil. Drain pasta and put into the sauce. Stir for about 3 mins, so that pasta absorbs some of the sauce. Toss with the remaining parsely, the parmesan, and clams. Serve on heated plates or pasta bowls.