Chiral recognition based on enantioselective interactions of propranolol enantiomers with cyclosophoraoses isolated from Rhizobium meliloti

Cyclosophoraoses isolated from Rhizobium meliloti , as an NMR chiral shift agent, were used to discriminate propranolol enantiomers. Continuous variation plot made from the complex of cyclosophoraoses with propranolol showed that the diastereomeric complex had predominantly 1:1 stoichiometry through UV spectroscopic analysis. The chiral recognition of propranolol enantiomers by cyclosophoraoses was investigated through the determination of binding constant based on the 13 C NMR chemical shift changes. The averaged K obs values from the plots were 55.7 M −1 for ( R )‐(+)‐propranolol and 36.6 M −1 for ( S )‐(–)‐propranolol, respectively. Enantioselectivity (α = K R (+) / K S ( – ) ) of 1.52 was then obtained. Computational calculation also revealed that ( R )‐(+) propranolol was more tightly bound with cyclosophoraose than ( S )‐(–)‐propranolol due to the enhanced van der Waals interaction. Chirality 16:204–210, 2004. © 2004 Wiley‐Liss, Inc.