The synthesis of the first phosphorylated derivatives of p-tert-butylthiocalix[4]arene was achieved by reaction with phosphorus trichloride. The product containing two cyclic P(III) atoms is not hydrolytically stable. The flattened 1,2-alternate conformation of a P(IV) derivative was established by 1H, 13C, 31P NMR experiments and X-ray analysis
