Stereoisomeric flavour compounds LXXIV: 2-phenylpropanol, 2-phenylpropanal and 2-phenylpropanal dimethyl acetal: structure elucidation and structure-function relationship

The direct enantioseparation of 2-phenylpropanol, 2-phenylpropanal and 2-phenylpropanal dimethyl acetal was achieved, using enantioselective gas chromatography and heptakis-[2,3-di-0-acetyl-6-0-tert.butyldimethylsilyl]--cyclodextrin (DIAC--CD) or octakis-[2,3-di-0-acetyl-6-0-tert.butyldimethylsilyl]--cyclodex-trin (DIAC--CD) as the chiral stationary phase. Their odour characteristics and threshold values were investigated by enantioselective gas chromatography/olfactometry. Starting from commercially available (R)-2-phenylpropionic acid, enantiopure (R)-configured reference compounds were synthesized.     

Integrated Simulated Moving Bed Processes for Production of Single Enantiomers

Based on the assumption of true moving bed processes it was demonstrated that integration of a racemization reaction into a continuous chromatographic process can improve the production of single enantiomers. In view of possible practical implementations, the analysis is extended to more realistic simulated moving bed (SMB) processes. Superstructures of SMB‐based systems are defined that reflect the three general concepts of flow sheet, partial, and total process integration. Process candidates are generated by simultaneously optimizing process structure and operating conditions. Optimal process setups are determined under idealized conditions as a function of the purity requirement. The best performance is achieved by fully integrated processes. These are compared under more realistic conditions to units with side reactors. The results indicate that a simple fully integrated SMB system with three zones is a particularly promising new process option. The new concept is investigated in detail to identify relevant practical aspects.     

Stereoselective release behaviors of imprinted bead matrices

In this work, the stereoselective release behaviors of “low”-swelling molecularly imprinted polymer (MIP) bead matrices in pressed-coat tablet type were studied. Either R-propranolol selective MIP or S-propranolol selective MIP was combined with excipients and racemic propranolol and fabricated into the matrix. Subsequently, the release of different propranolol enantiomers from the matrices was examined. Also, the microscopic structure of the hydrated “low”-swelling MIP matrix was determined using a cryogenic scanning electron microscope in order to compare with that of the hydrated “high”-swelling MIP matrix. In vitro release profiles of the “low”-swelling matrices showed a difference in the release of enantiomers, in that the non-template isomer was released faster than the template isomer. However, in the last phase of dissolution this difference reduced and later reversed, resulting at last in the type of specificity being similar to that obtained previously with “high”-swelling MIP matrices.

n summary, MIP beads can be fashioned into matrices and incorporated into different formulations to regulate the resultant stereoselectivity. From the behaviors of stereoselective release observed in MIP matrices, we can conclude that the enantioselective-controlled delivery mechanism of MIPs via formulations depends on the relative affinity of the enantiomer for the template sites, as well as the nature of the polymer, such as hydrophobicity and swellability.     

Semiochemicals via epoxide inversion

A sequence of reactions is presented for inverting the configurations of both epoxide carbons in 1,2-disubstituted epoxides. As examples, (+)-disparlure was converted to its enantiomer, (–)-disparlure, andexo-endo conversion of a cyclohexene oxide was demonstrated.     

Chiral separation of ketoprofen racemate by using chirex® 3005 and kromasil® CHI-II chiral column

Ketoprofen is a non-steroid anti-inflammatory drug (NSAID) that has analgesic, anti-inflammatory and antipyretic properties, of which pharmacological activity has been contributed mainly by the S-ketoprofen enantiomer. To gain highly purified S-ketoprofen enantiomer from ketoprofen racemate, suitable stationary phase was investigated by comparing R-type naphthylglycine and 3,5-dinitrobenzoic acid of Chirex® 3005 and O,O′-bis(4-tertbutyl-benzoyl)-N and N′-diallyl-L-tartardiamide of Kromasil® CHI-II. S-ketoprofen enantiomer was successfully isolated by using the Kromasil column as well as the mobile phase of hexane/tert-butyl methyl ether/acetic acid (v/v)= 60/40/0.1. Equilibrium constants of R-and S-ketoprofen were obtained by pulsed injection method (PIM) at various concentrations of ketoprofen racemate and loading sample amounts, which serve the basic information on overloading sample volume and amounts. A volume of 100 ml containing 3.0 mg of ketoprofen racemate to Kromasil column (250 mm×4.6 mm) resulted in 85% recovery of injected sample under an high concentration (30 mg/ml) feed condition.     

Andrena wilkella male bees discriminate between enantiomers of cephalic secretion components

Diastereomers of the spiroacetal, 2,8-dimethyl-1,7-dioxaspiro [5.5]undecane, represent main components of the cephalic secretion from males of the solitary bee,Andrena wilkella. The major compound proved to be of high enantiomeric purity, showing (2S,6R,8S) configuration. Only the naturally occurring enantiomer attracted patrolling males in the field; its antipode was behaviorally inactive and in a racemic mixture did not inhibit response. The (E,Z) diastereomers were also found to be almost inactive. EAG studies gave the same result as the behavioral tests. The biological function of the spiroacetal is discussed in view of the evolution of the mating behavior inA. wilkella.     

Stereoselective Release Behaviors of Imprinted Bead Matrices

ABSTRACT

In this work, the stereoselective release behaviors of “low”-swelling molecularly imprinted polymer (MIP) bead matrices in pressed-coat tablet type were studied. Either R-propranolol selective MIP or S-propranolol selective MIP was combined with excipients and racemic propranolol and fabricated into the matrix. Subsequently, the release of different propranolol enantiomers from the matrices was examined. Also, the microscopic structure of the hydrated “low”-swelling MIP matrix was determined using a cryogenic scanning electron microscope in order to compare with that of the hydrated “high”-swelling MIP matrix. In vitro release profiles of the “low”-swelling matrices showed a difference in the release of enantiomers, in that the non-template isomer was released faster than the template isomer. However, in the last phase of dissolution this difference reduced and later reversed, resulting at last in the type of specificity being similar to that obtained previously with “high”-swelling MIP matrices.

n summary, MIP beads can be fashioned into matrices and incorporated into different formulations to regulate the resultant stereoselectivity. From the behaviors of stereoselective release observed in MIP matrices, we can conclude that the enantioselective-controlled delivery mechanism of MIPs via formulations depends on the relative affinity of the enantiomer for the template sites, as well as the nature of the polymer, such as hydrophobicity and swellability.     

l-薄荷醇的制备及检测方法研究进展

本文阐述了1-薄荷醇的结构、理化性质及其应用现状,介绍了最新的制备和检测方法,展望了其发展的前景,并着重介绍了酶拆分技术应用于1-薄荷醇制备的研究进展。