Chiral recognition ability and solvent versatility of bonded amylose tris(3,5‐dimethylphenylcarbamate) chiral stationary phase: Enantioselective liquid chromatographic resolution of racemic N‐alkylated barbiturates and thalidomide analogs

Abstract

The chiral recognition ability and solvent versatility of a new chiral stationary phase containing amylose 3,5-dimethylphenylcarabamate immobilized onto silica gel (CHIRALPAK IA) is investigated. Thus, the direct enantioselective separation of a set of racemic N-alkylated barbiturates and 3-alkylated analogs of thalidomide was conducted using different nonstandard solvents as eluent and diluent, respectively in high-performance liquid chromatography (HPLC). The separation, resolution, and elution order of the investigated compounds were compared on both immobilized and coated amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases (Chiralpak IA and Chiralpak AD, respectively) using a mixture of n-hexane/2-propanol (90:10 v/v) as mobile phase with different flow-rates and fixed UV detection at 254 nm. The effect of the immobilization of the amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase on silica (Chiralpak IA) on the chiral recognition ability was noted as the bonded phase (Chiralpak IA) was superior in chiral recognition and possesses a higher resolving power in most of the reported cases than the coated one (Chiralpak AD). A few racemates were not or poorly resolved on the immobilized Chiralpak IA or the coated Chiralpak AD when using standard solvents were most efficiently resolved on the immobilized Chiralpak IA upon using nonstandard solvents. Furthermore, the immobilized phase withstands the nonstandard (prohibited) HPLC solvents such as dichloromethane, ethyl acetate, tetrahydrofuran, methyl-tert-butyl ether, and others when used as eluents or as a dissolving agent for the analyte itself. The direct analysis of a real sample extracted from plasma using DCM on Chiralpak IA is also shown.

Naturally Occurring and Related Synthetic Cannabinoids and their Potential Therapeutic Applications

“…Com- mercially available examples include Chiralpak AD, containing amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) coated on macroporous silica gel (10 !m), and Chiralpak IA, containing ADMPC immobilized on macroporous silica gel (5 !m) (Diacel Chemical Co.) Fig. (5) [38]. Encapsulation of the derivatized polysaccharide, which is not bonded to the substrate, may prevent conversion of (1) to (4a).…”

Study of enantioselectivity on an immobilized amylose carbamate stationary phase under subcritical fluid chromatography

“…The most versatile chiral stationary phases are the ones derived from cellulose and amylose . The problem with these stationary phases stem from the fact that they are adsorbed onto a silica matrix, which limits the possibilities of using a variety of mobile phases that can elute out the chiral phase . This impediment was alleviated by chemically immobilizing them to the silica matrix.…”

Enantioseparation Properties of the Biselector Chiral Stationary Phase Derived from Amylose Tris(phenylcarbamate) and Amylose Tris(benzoate)

“…Owing to its accessibility and the satisfactory chiral recognition ability of its derivatives, amylose has been extensively employed to prepare chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) [1][2][3]. The chiral columns known as CHIRALPAK AD and CHIRAL-PAK AD-H (Daicel, Japan), AmyCoat (Kromasil, Sweden) and Lux Amylose-2 (Phenomenex, USA) are commercially available.…”