Acyl Migrations in Partially Acylated, Polyhydroxylic Systems¹

Chromatographic investigation on acyl migration in betacyanins and their decarboxylated derivatives

“…The acyl migration is proved to be intramolecular, therefore, mechanisms involved with hydrolysis and re-esterification are not important in the process [25]. Hence, the free carboxyls in the acylating moieties in phyllocactin and hylocerenin as well as their derivatives do not take part in the rearrangement.…”

Kinetic studies on the intramolecular acyl migration of β-1-O-acyl glucuronides: Application to the glucuronides of (R)- and (S)-ketoprofen, (R)- and (S)-hydroxy-ketoprofen metabolites, and tolmetin by1H-NMR spectroscopy

“…Electronic factors from the drug are therefore a major determinant of the reactivity. Steric factors are also very important, as bulky groups in close vicinity to the ester linkage can hinder nucleophilic attack from the adjacent hydroxyl group, thus impeding formation of the ortho-ester intermediate (Figure 1), which is a necessary step for the initiation of the migration (Doerschuk 1952). Correlations have been found between experimentally derived rates and certain calculated molecular properties, although firm structure-reactivity relationships have not been established (Nicholls et al 1996;Gavaghan 1997;Vanderhoeven et al 2004a).…”

“…The acyl group migrates from hydroxyl to adjacent hydroxyl at the C-2, C-3 and C-4 positions of the glucuronide ring and thus 2-O-, 3-O-and 4-O-acyl positional isomers appear sequentially (Bradow et al 1989;Akira et al 1997Akira et al , 2002 (Figure 1). The phenomenon of acyl migration has been shown by 14 C labelling experiments to occur intramolecularly via an ortho-ester intermediate (Doerschuk 1952). After acyl migration, the positional isomers readily ring open and undergo mutarotation to give rise to -and -anomeric mixtures at C-1 on the sugar ring.…”

Liquid Chromatography–Mass Spectrometric Analysis of Lipids Present in Human Meibomian Gland Secretions

“…Fragment m/z 663.6 with all likelihood was identified as a product of DA dehydration ([M-H 2 O + H] + , theoretical mass 663.6), while ion m/z 369.5 was a product of neutral loss of arachidic acid residue (molecular weight 312.3). Because (a) the tested compound was a mixture of two positional isomers of DA (1,2-and 1,3-DA), and (b) 1,2-and 1,3-diacyl glycerols (DAG) are known to rapidly undergo spontaneous positional isomerization[32,33] via acyl-migration, their order of elution remained unknown.…”