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AMA Arch Intern Med. 1951;88(3):296-309. doi:10.1001/archinte.1951.03810090027003.
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THE FIRST synthesis of the 4-hydroxycoumarin anticoagulant No. 63, a compound chemically related to bishydroxycoumarin (dicumarol® 3,3′-methylenebis [4-hydroxycoumarin] ), was by Dr. Myoshi Ikawa in 1942 in Dr. Karl Paul Link's laboratory.1 It is a colorless and stable product which is readily prepared in pure form, and its solubility in water is of the order of 1/100 that of bishydroxycoumarin. Chemically anticoagulant No. 63 is 2-methyl-2-methoxy-4-phenyl-5-oxodihydropyrano-(3,2-c) (1) benzopyran. In work done by Scheel2 in the mouse, rat, rabbit, and dog, attention was given not only to activity per se, as reflected by the prolongation of the 12.5% plasma-prothrombin time, but also to the time and site of appearance of visible hemorrhage and the survival time resulting from continued administration of various coumarin anticoagulants. He concluded that 4-hydroxycoumarin anticoagulant No. 63 was a strong competitor, if not an agent superior, to bishydroxycoumarin. In dogs and in human beings this anticoagulant was


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