Stereochemical Preference of 2'-​Deoxycytidine for Chiral Bis(diamido)​-​bridged Basket Resorcin[4]​arenes

Bis(diamido)​-​bridged basket resorcin[4]​arene and its enantiomer proved able to interact with 2'-​deoxycytidine () and pyrimidine nucleoside analogs in dimethyl sulfoxide (DMSO) solution. In such a solvent, the resorcinarene hosts adopt a preferential 1,​3-​alternate-​like conformation, with a larger cavity delimited by two syn 3,​5-​dimethoxyphenyl moieties, and two external pockets, each delimited by the other 3,​5-​dimethoxyphenyl group and its diamido arm (the wing)​. Complexation phenomena were investigated by nuclear magnetic resonance (NMR) methods, including (1) H NMR DOSY and 1D ROESY experiments, and molecular modeling. Heteroassociation constants of [] and [] diastereoisomeric complexes were obtained from diffusion data by single point measurements, and from nonlinear fitting of (1) H NMR chemical shifts. Selective proton relaxation rate measurements allowed us to significantly discriminate the two complexes by identifying two different interaction sites of the guest in the resorcin[4]​arene host, depending on its configuration.