Assertion: warfarin | /r/HasProperty | active
Facets:
Source sentences:
text: 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 warfarin to be active.