Glycoluril derivatives bearing free ureidyl groups (1) and bis (cyclic ethers)(2) are the fundamental building blocks for the synthesis of cucurbituril, its derivatives, and its congeners. The known derivatives of 1 and 2 fall into two main classes—those bearing alkyl or aryl functional groups on their convex face. In this paper we present a third class of glycolurils, namely those bearing substituents that are electron withdrawing in character. ...