Guoliang Yi

Novel cyclodextrin-oligosiloxane copolymers and their use as stationary phases for separating enantiomers in open tubular column supercritical fluid chromatography

Abstract New stationary phases composed of cyclodextrin-oligosiloxane copolymers for open tubular column supercritical fluid chromatography have been developed. These phases allow the separation of enantiomers of a variety of chiral organic solutes.

Evaluation of β-cyclodextrin-based chiral stationary phases for capillary column supercritical fluid chromatography

Abstract The Chromatographic performance of two series of chiral stationary phases (CSPs) based on β-cyclodextrin, one copolymeric and one side-arm substituted, was investigated to improve the applicability of cyclodextrin-based CSPs in open-tubular column supercritical fluid chromatography. For the side-arm approach, the influence on performance of different amount of cyclodextrin in the CSP, attachment of the cyclodextrin at the wide or narrow opening, different substituents on the cyclodextrin, the structure of the spacer and the film thickness was studied. The immobilization of these CSPs was also investigated. In addition, the chromatographic performance in gas and supercritical fluid chromatography of one of these CSPs was compared at optimal conditions using test solutes having relatively large differences in size and functionality.

Large-rim-tethered permethyl-substituted β-cyclodextrin polysiloxanes for use as chiral stationary phases in open tubular column chromatography

Abstract 3-O-(p-Allyloxybenzoyl)heptakis(2,6-di-O-methyl)-β-cyclodextrin, which was used for preparation of permethylated 3-O-(p-allyloxybenzoyl)-β-cyclodextrin (4), was produced in a 15% yield by a monoesterification of heptakis(2,6-di-O-methyl)-β-cyclodextrin. Heptakis[6-O-(tert.-butyl)dimethylsilyl]-β-cyclodextrin was regioselectively monoesterified with p-allyloxybenzoyl chloride or p-(tert.-butyl)benzoyl chloride to yield 2-O-(p-allyloxybenzoyl)heptakis[6-O-(tert.-butyl)dimethylsilyl]-β-cyclodextrin (6) or 2-O-[p-(tert.-butyl)benzoyl]heptakis [6-O-(tert.-butyl)dimethylsilyl]-β-cyclodextrin (7). Compound 6 was acylated to give tridecaacetate 8, which was deprotected and methylated, to give 2A-O-(p-allyloxybenzoyl)heptakis(3-O-acetyl-6-O-methyl)- 2B,2C,2D,2E,2F,2G-hexa-O-acetyl-β-cyclodextrin (10). Both 6 and 7 were methylated, following by deprotection and methylation (on the 6-position), to give permethylated 2A-O-(p-allyloxybenzoyl)-β-cyclodextrin (15) and permethylated 2A-O-[p-(tert.-butyl)benzoyl]-β-cyclodextrin (16), respectively. Then, 16 was treated with lithium aluminum hydride to form monoalcohol, which was transformed into permethylated 2A-O-(p-allyloxybenzyl)-β-cyclodextrin (18) by a nucleophilic substitution reaction. Four new permethyl- or per(methyl/acetyl)-substituted β-cyclodextrin-bound methylpolysiloxanes were prepared by a hydrosilylation reaction of the monoalkenyl-substituted β-cyclodextrin derivatives 4, 10, 15 and 18 with a specially prepared hydromethylpolysiloxane. The polymeric phases provide excellent enantiomeric separations of a variety of chiral solutes in open tubular column supercritical fluid chromatography and gas chromatography.