Improved acylation rates within cyclodextrin complexes from flexible capping of the cyclodextrin and from adjustment of the substrate geometry

Structure of a complex of cycloheptaamylose with 1-adamantanecarboxylic acid

“…Our structural results are in agreement with and in disagreement with Breslow et al (1980). The cycloheptaamylose cavity is large enough to accommodate completely the 1-adamantanecarboxylic acid.…”

“…6 shows how completely the guests are enclosed. In our discussion of the benzoic acids and their orientation in the cycloheptaamylose dimer (Hamilton, Sabesan & Steinrauf, 1981) we concluded that dimer formation is equivalent to the 'capping' of the cycloheptaamylose by chemical modification as described by Breslow et al (1980). In the crystal structure the access of the water is restricted at the secondary hydroxyl end of the cycloheptaamylose by the dimer 'cap' and the 1-adamantanecarboxylic acid orients itself so that the carboxylic acid group can be solvated at the open primary hydroxyl end.…”

“…However, as pointed out by Breslow, Czarniecki, Emert & Hamaguchi (1980), true enzymes often achieve ratios of 105-101° or greater. They suggested, on the basis of model building, that substrates such as tert-butylphenyl acetate can bind fully in the cavity in the complex but they are pulled up partly out of the cavity by formation of the tetrahedral intermediate.…”

“…On the basis of binding studies and model building they have proposed that in the complex of 1-adamantanecarboxylic acid with cycloheptaamylose only half of the adamantane moiety would be enclosed by the cycloheptaamylose. Breslow et al (1980) discussed the kinetic results of ester hydrolysis of two adamantane derivatives on the basis of this model. In contrast, proposed that the cycloheptaamylose cavity would be large enough to accommodate almost completely 1-adamantanecarboxylic acid.…”

Synthesis of novel chiral, cage-annulated macrocycles

“…3 The ability of optically active host systems of this type (i) to discriminate between the enantiomers of guest alkylammonium salts and (ii) to function as catalysts for a variety of organic reactions suggests their potential use as enzyme mimics. 4 A particularly interesting group of chiral crown ethers contains carbohydrate units as the source of chirality. Compounds of this type have been reported by Stoddart,3a,b Penades, 5 and more recently by Seebach and coworkers.…”