Synthesis of C-alkyl Calix[4]arenes. 4. Design, synthesis and computational studies of novel chiral amido[4]resorcinarenes

In extending our studies involving BF3·Et2O-catalyzed reaction of cinnamic acid analogues, we have shown that amido derivatives also can afford [4]resorcinarene octamethyl ethers. Subsequently, chiral monomeric amides, derived from the mixed anhydride of cinnamic acid and l- or d-valine, upon treatment with BF3·Et2O, yielded for the first time chiral amido [4]resorcinarenes in enantiomerically pure forms. Four stereoisomers were isolated, and three of them were attributed the flattened-cone, chair, and 1,2-alternate conformations. The major product was assigned a novel chairlike structure, namely flattened partial cone 1. The flattened-cone stereoisomer, which was indicated by molecular modeling studies to be the most stable, became the major product under more drastic experimental conditions. Chromatographic studies on chiral phases revealed that the above tetramers could be used for the enantiodiscrimination of racemic molecules.