Acyclic tautomer (left) and cyclic hemiketal tautomer (right) X-ray crystallographic studies of<unk>  show that it exists in tautomeric form, as the cyclic hemiketal, which is formed from the 4-hydroxycoumarin and the ketone in the 3-position substituent. However, the existence of many 4-hydroxycoumadin anticoagulants (for example phenprocoumon) that possess no ketone group in the 3-substituent to form such a structure, suggests that the hemiketal must tautomerise to the 4-hydroxy form in order for<unk>  to be active. Stereochemistry<unk>  contains a stereocenter and consists of two enantiomers. This is a racemate, i.e., a 1: 1 mixture of ( R ) – and the ( S ) – form: Enantiomers of<unk>  200 px CAS Number: 5543-58-8 200 px CAS Number: 5543-57-7
Warfarin
Palladin
Clopidogrel
Ticlopidine
Apixaban
Ticagrelor
Heparin
Dabigatran