monocarboxylic acid azabicycloalkane thiabicycloalkane ureas biotins Compounds containing a biotin (5-[(3a<i>S</i>,4<i>S</i>,6a<i>R</i>)-2-oxohexahydro-1<em>H</em>-thieno[3,4-<em>d</em>]imidazol-4-yl]pentanoic acid) skeleton.