Receptor molecules with large cavities synthesized by the combination of building blocks that already possess a cavity, viz. calixarenes and resorcinarenes, are described. These receptor molecules are synthesized by reaction of one or two upper rim 1,2-difunctionalized calixarene fragments oriented either endo or exo toward a cavitand unit. The endo:exo ratio depends on the substituents at the 3- and 4-positions of the calixarenes. These novel receptor molecules complex steroids with association constants of (0.9−9.5) × 102 M-1 in CDCl3.
Higler, I., Timmerman, P., Verboom, W., & Reinhoudt, D. N. (1996). Combination of calixarenes and resorcinarenes for the complexation of steroids. Journal of organic chemistry, 61(17), 5920-5931. https://doi.org/10.1021/jo960256g