Correlation of structure and retention behaviour in reversed- phase high-performance liquid chromatography

Relationship between retention characteristics and physicochemical parameters of solutes on porous graphitized carbon column

The retention of 44 barbituric acid derivatives was determined on porous graphitized carbon (PGC) column using dioxane water mixtures as eluents. Linear correlations were calculated between the logarithm of the capacity factor and the dioxane concentration in the eluent. Free Wilson analysis combined with stepwise regression analysis was used to elucidate the role of individual substituents in the retention behaviour. Calculations indicated that the apolar substituents lie parallel to the surface of PGC surface increasing in this manner the retention and--as opposed to the retention characteristics of traditional reversed-phase supports--the position of substituents also exerts a marked influence on the retention.

Neoglycopeptide synthesis and purification in multi-gram scale: preparation of O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-N alpha-fluoren-9-yl-methoxycarbonyl-hydroxyproline and its use in the pilot-scale synthesis of the potent analgesic glycopeptide O1.5-beta-D-galactopyranosyl [DMet2, Hyp5]enkephalinamide

The preparation of a beta-galactosylated hydroxyproline derivative and its use in the multi-gram solid-phase synthesis of the potent analgesic neoglycopeptide O1.5-beta-D-galactopyranosyl [D-Met2, Hyp5]enkephalinamide is described in this paper. The most closely related impurities have been identified, isolated and characterized. Significant aspects of the synthesis and purification affecting yields and purity of both the building block and the target neoglycopeptide are discussed.

Correlation of structure and retention behaviour in reversed-phase high-performance liquid chromatography. II. Methionine-enkephalin-related glycoconjugates

Reversed-phase high-performance liquid chromatographic elution data for methionine-enkephalin-related glycoconjugates were analysed as a function of the identity and position of the sugar-peptide linkage. It was shown that binding to the column could be correlated with the degree of sugar moiety protection. Replacement of either the phenylalanine or methionine residue in the peptide backbone of the glycoconjugates with its D-enantiomer leads to a considerably stronger retention on a reversed-phase column. The dependence of retention times on the methanol concentration in the mobile phase suggested that, under the conditions studied, there are different retention mechanisms for glycopeptides containing unprotected sugar moieties in the molecule.