{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T02:58:45Z","timestamp":1790305125434,"version":"4.1.0"},"reference-count":55,"publisher":"Wiley","issue":"15","license":[{"start":{"date-parts":[[2015,2,17]],"date-time":"2015-02-17T00:00:00Z","timestamp":1424131200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Angew Chem Int Ed"],"published-print":{"date-parts":[[2015,4,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Exceptionally powerful anion receptors have been constructed by placing squaramide groups in axial positions on a steroidal framework. The steroid preorganizes the squaramide NH groups such that they can act cooperatively on a bound anion, while maintaining solubility in nonpolar media. The acidic NH groups confer higher affinities than previously\u2010used ureas or thioureas. Binding constants exceeding 10<jats:sup>14<\/jats:sup>\u2009<jats:sc>M<\/jats:sc><jats:sup>\u22121<\/jats:sup> have been measured for tetraethylammonium salts in chloroform by employing a variation of Cram\u2019s extraction procedure. The receptors have also been studied as transmembrane anion carriers in unilamellar vesicles. Unusually their activities do not correlate with anion affinities, thus suggesting an upper limit for binding strength in the design of anion carriers.<\/jats:p>","DOI":"10.1002\/anie.201411805","type":"journal-article","created":{"date-parts":[[2015,2,17]],"date-time":"2015-02-17T15:54:26Z","timestamp":1424188466000},"page":"4592-4596","source":"Crossref","is-referenced-by-count":129,"title":["High\u2010Affinity Anion Binding by Steroidal Squaramide Receptors"],"prefix":"10.1002","volume":"54","author":[{"given":"Sophie J.","family":"Edwards","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hennie","family":"Valkenier","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nathalie","family":"Busschaert","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Philip 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methyl ester analogues were also prepared in some cases but proved insoluble in chloroform."},{"key":"e_1_2_2_26_2","doi-asserted-by":"publisher","DOI":"10.1039\/a701949a"},{"key":"e_1_2_2_27_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja026022y"},{"key":"e_1_2_2_28_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja016796z"},{"key":"e_1_2_2_29_2","unstructured":"For further details of synthesis binding and transport studies see the Supporting Information."},{"key":"e_1_2_2_30_2","doi-asserted-by":"publisher","DOI":"10.1021\/ol102294g"},{"key":"e_1_2_2_30_3","doi-asserted-by":"publisher","DOI":"10.1039\/c2md20011b"},{"key":"e_1_2_2_31_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00959a040"},{"key":"e_1_2_2_32_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00450a026"},{"key":"e_1_2_2_33_2","doi-asserted-by":"publisher","DOI":"10.1002\/1521-3765(20020503)8:9<2197::AID-CHEM2197>3.0.CO;2-J"},{"key":"e_1_2_2_34_2","unstructured":"Evidence for aggregation was obtained from the titrations versus Bu4N+Cl\u2212in CDCl3 where some NH groups were observed to shift upfield (see Figure\u2005S8\/S10 Supporting Information). This shift implies that the protons were moving from one hydrogen\u2010bonded environment (presumably an aggregate) to another (the chloride complex)."},{"key":"e_1_2_2_35_2","doi-asserted-by":"publisher","DOI":"10.1002\/anie.200351957"},{"key":"e_1_2_2_35_3","doi-asserted-by":"publisher","DOI":"10.1002\/ange.200351957"},{"key":"e_1_2_2_36_2","doi-asserted-by":"publisher","DOI":"10.1039\/b927005a"},{"key":"e_1_2_2_37_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja1076102"},{"key":"e_1_2_2_38_2","doi-asserted-by":"publisher","DOI":"10.1039\/b414589e"},{"key":"e_1_2_2_39_2","unstructured":"An alternative explanation is that aggregation in the membrane lowers activities. 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