Electrospray ionization mass spectrometric analysis of newly synthesized α,β‐unsaturated γ‐lactones fused to sugars

Abstract

Knowledge of the fragmentation mechanisms of lactones and their behaviour under electrospray ionization (ESI) conditions can be extended to larger and more complex natural products that contain an alpha,beta-unsaturated gamma-lactone moiety in their structure. Moreover, little is known about the gas-phase behaviour of alpha,beta-unsaturated gamma-lactones linked or fused to sugars. Therefore, five alpha,beta-unsaturated gamma-lactones (butenolides) fused to a pyranose ring, recently synthesized compounds with potential relevance regarding their biological properties, were investigated using ESI-MS and ESI-MS/MS in both positive and negative ion modes. Their fragmentation mechanisms and product ion structures were compared. It was observed that two isomers could be unambiguously distinguished in the negative ion mode by the fragmentation pathways of their deprotonated molecules as well as in the positive ion mode by the fragmentation pathways of either the protonated or the sodiated molecule. Fragmentation mechanisms are proposed taking into account the MS/MS data and semi-empirical calculations using the PM6 Hamiltonean. The semi-empirical calculations were also very useful in determining the most probable protonation and cationization sites.

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometric and semi‐empirical calculations study of five isoflavone aglycones

“…Semi‐empirical calculations were performed to support the proposed fragmentation mechanisms. These computational methodologies have been used successfully in a wide variety of MS studies, including the fragmentation under electrospray ionization (ESI) conditions of flavonoids19, 29–32 and α,β‐unsaturated γ‐lactones fused to furanose rings,33 the fragmentation under electron ionization (EI) conditions of buspirone,34 complexation studies,35, 36 the evaluation of the strength of non‐covalent interactions37 and the study of fullerene derivatives 38…”

Applications of Tandem Mass Spectrometry: From Structural Analysis to Fundamental Studies

“…In this study (Madeira, Rosa et al 2010) we came across an interesting behaviour of two of the compounds studied (structures depicted in Fig. 13), that are isomers.…”

“…We will present some examples of the application of tandem mass spectrometry together with collision induced dissociation to study the gas-phase behaviour of some aniline derivatives (Madeira 2010), , -unsaturated -lactones fused to sugars (Madeira, Rosa et al 2010) and isoflavone aglycones. (Madeira, Borges et al)…”

Furanose C—C‐linked γ‐lactones: a combined ESI FTICR MS and semi‐empirical calculations study

“…[20 -23] The fragmentation pathways of five-membered ring lactones using electrospray ionization mass spectrometry have already been reported. [19,24] Recently we reported the gas-phase behaviour of α,β-unsaturated γ -lactones fused to pyranose rings, [25] nevertheless, studies on the gas-phase behaviour of monosaccharide derivatives of this type are still lacking. In fact, studies that deal with the gas-phase behaviour of monosaccharides are scarce.…”

“…These inexpensive computational methodologies have been successfully employed in mass spectrometry studies, for example in the fragmentation of flavonoids and flavonoid diglycosides [31,32] and, more recently, α,β-unsaturated γ -lactones fused to pyranose units. [25] Furthermore, semi-empirical calculations were used in complexation studies, [33,34] in the evaluation of the strength of non-covalent interactions, [35] establishment of fragmentation pathways under EI conditions [36] and in the study of fullerene derivatives. [37] The fragmentation pathways are greatly influenced by the type of precursor ion, and several studies have shown that protonated species fragment more readily than metalcationized ones since the metal cationization alters the stability of the product ions.…”