Diastereochemical differentiation of bicyclic diols using metal complexation and collision‐induced dissociation mass spectrometry

Abstract

Metal complex formation was investigated for di-exo-, di-endo- and trans-2,3- and 2,5-disubstituted trinorbornanediols, and di-exo- and di-endo- 2,3-disubstituted camphanediols using different divalent transition metals (Co(2+), Ni(2+), Cu(2+)) and electrospray ionization quadrupole ion trap mass spectrometry. Many metal-coordinated complex ions were formed for cobalt and nickel: [2M+Met](2+), [3M+Met](2+), [M-H+Met](+), [2M-H+Met](+), [M+MetX](+), [2M+MetX](+) and [3M-H+Co](+), where M is the diol, Met is the metal used and X is the counter ion (acetate, chloride, nitrate). Copper showed the weakest formation of metal complexes with di-exo-2,3-disubstituted trinorbornanediol yielding only the minor singly charged ions [M-H+Cu](+), [2M-H+Cu](+) and [2M+CuX](+). No clear differences were noted for cobalt complex formation, especially for cis-2,3-disubstituted isomers. However, 2,5-disubstituted trinorbornanediols showed moderate diastereomeric differentiation because of the unidentate nature of the sterically more hindered exo-isomer. trans-Isomers gave rise to abundant [3M-H+Co](+) ion products, which may be considered a characteristic ion for bicyclo[221]heptane trans-2,3- and trans-2,5-diols. To differentiate cis-2,3-isomers, the collision-induced dissociation (CID) products for [3M+Co](2+), [M+CoOAc](+), [2M-H+Co](+) and [2M+CoOAc](+) cobalt complexes were investigated. The results of the CID of the monomeric and dimeric metal adduct complexes [M+CoOAc](+) and [2M-H+Co](+) were stereochemically controlled and could be used for stereochemical differentiation of the compounds investigated. In addition, the structures and relative energies of some complex ions were studied using hybrid density functional theory calculations.

Differentiation of Isomeric HydroxypyridineN-Oxides Using Metal Complexation and Electrospray Ionization Mass Spectrometry

“…Within the past decade, alkali, alkaline earth, and transition metal ions have been extensively used in ESI for many types of compounds. For example, metal ions have been successfully used for stereochemical differentiation by tandem mass spectrometry of some bicyclic diols [2] and glycosyl dithioacetals [3].…”

Noncovalent Complexation of Monoamine Neurotransmitters and Related Ammonium Ions by Tetramethoxy Tetraglucosylcalix[4]arene

“…The ion then fragmented further. Dissociation of the complexes of trimethyl ammonium ions (11)(12)(13)(14), on the other hand, led to [Guest] + ions (as expected since there is no mobile proton in the alkyl ammonium ion structure). Except for the relatively small betaine (11), the complexes of GABA and trimethyl ammonium compounds dissociated with relatively low energy, and there were no significant differences between their E com 50% values (Figure 4a).…”

“…Among the aliphatic guests (10)(11)(12)(13)(14), the binding affinity of glucosylcalixarene toward the compounds followed the order GABA (10) 9 carnitine (14) 9 carbamylcholine (13) 9 betaine (11) 9 acetylcholine (12) (Figure 3). This affinity order further emphasizes the importance of hydrogen bonding group for formation of a stable complex (13 versus 12 and 11 versus 14).…”

“…Dynamic nature and reversible binding are important properties of host-guest complexes when synthetic hosts are designed for applications related to molecular transport (10) and trimethyl ammonium compounds (11)(12)(13)(14) and (b) neurotransmitter ammonium ions and related ammonium ions (2-9). The E com 50% values are presented in parentheses (eV) + and 300 s for the complexes of 1, ND 3 as reagent).…”

“…The ability of synthetic receptors to function as artificial enzymes or ion channels [1][2][3], to sense biologically important ions [4,5], to improve chromatographic separation [6][7][8][9][10][11][12][13], and to solubilize, stabilize, and transport drugs is being explored [14,15]. The design of synthetic receptors for host-guest systems is challenging, however, because of the many factors requiring adjustment for selective complexation.…”