Whelk-O 1 phase

Fig. n. Systematic representation of the functional groups of the Whelk-O 1 phase and an analyte. The stereoselective interaction may rely on n-n interactions and/or hydrogen bonds and dipole-dipole interactions. 

Fig. 5. The stmcture of the chiral selector in the Whelk-O-1 chiral stationary phase.

Alcohols and ketones, arylnaphthalenes Whelk-O 1 and poly Whelk-O (= its polysil-oxane borne analog) Subcritical carbon dioxide-based mobile phase at cryogenic temperatures 166... 

The application of the reciprocality concept has led to the design of various phases of the Ji-donor/acceptor type [61, 62]. One successful phase is the Whelk-O 1 CSP developed by Pirkle and Welch [63-65]. 

Hi) n-electron acceptor/yc-electron donor stationary phases l-(3,5-Dinitrobenzamido)-l,2,3,4-tetrahydrophenanthrene W-(3,5-Dinitrobenzoyl)-l,2-diphenyl-1.2-diaminoethane yV-(3,5-Dinitrobenzoyl)-l,2-diaminocyclohexane yV-(3,5-DinitrobenzoyI)-(l-naphthyl)glycine amide Whelk-O 1 ULMO DACH DNB CHIREX 3005... 

Recently, two examples of the separation of enantiomers using CCC have been published (Fig. 1-2). The complete enantiomeric separation of commercial d,l-kynurenine (2) with bovine serum albumin (BSA) as a chiral selector in an aqueous-aqueous polymer phase system was achieved within 3.5 h [128]. Moreover, the chiral resolution of 100 mg of an estrogen receptor partial agonist (7-DMO, 3) was performed using a sulfated (3-cyclodextrin [129, 130], while previous attempts with unsubstituted cyclodextrin were not successful [124]. The same authors described the partial resolution of a glucose-6-phosphatase inhibitor (4) with a Whelk-O derivative as chiral selector (5) [129]. 

Pirkle and coworkers [59] compared retention and selectivity factors between HPLC and SFC using Poly Whelk-O chiral stationary phases and a-naphthyl-1-ethylamine carbamates. The results indicate that both retention and selectivity factors in SFC were higher than those in HPLC. This can be mainly attributed to the weaker solvating power of the carbon dioxide supercritical fluid as compared to a liquid such as methanol or hexane. 

In deacylation, as the enzyme cleaved the phenylacyl group, phenylacetic acid was formed, which lowered the pH of the reaction medium. Base was added to maintain the starting pH. (Note Use of ammonium hydroxide led to the formation of desilylated byproducts desilylation was eliminated when bicarbonates were used.) This approach was not required in the acylation reaction. At pH above 7.5 the (R)-and (S)-amines are practically insoluble in water. Organic solvents were used to extract the free amines from the aqueous reaction medium at pH 8.0. p-Fluoro-benzoyl, 1-naphthoyl, and phenylacetyl derivatives of the racemic amine were prepared and their behavior on the chiral HPLC column was studied. Based on ease of preparation and HPLC analysis, the 1-naphthoyl derivatives (Fig. 7) were preferred. Reversed phase HPLC analysis on a Vydac-C18 analytical column used a gradient of acetonitrile (0.1% triethylamine) in water (0.05% phosphoric acid) to quantify the total amide in the reaction mixture. Chiral HPLC analysis on (S,S) Whelk-O Chiral column used isopropanol hexane (30 70) as a solvent system to separate and quantify the (R)- and (S)-enantiomers. 

Enantiomeric separation of nonpharmaceutical compounds include IV-alkyl-Af-methylaniline W-oxides (ethyl to butyl plus isomers) on a Chiralcel OD column. (A = 210 nm) using 1% to 3% ethanol in hexane [143]. Carrea et al. [144] separated the enantiomers of various substituted chromium and magnesium tricarbonyl metallocenes ( / -benzene and -cyclopentadiene) on a Chiralcel OD column (A = 315 run) with an isocratic mobile phase that varied from 1% to 10% ethanol in hexane depending on the enantiomeric pair involved. Chromium tricarbonyl compounds complexed with a variety of ij -arenes were separated on a Whelk-O column (A = 315 nm) using a 20/80 IPA/hexane as the mobile phase [145]. 

---