New Fragmentation Process in Mass Spectrometry of Carbonyl Compounds with a δ-Silyl Group

Hwu, Jih Ru; Wu, I-Fay; Shiao, Shui-Sheng; Tseng, Wen Nan; Huang, Jow Lay; Chen, Buh-Luen

doi:10.1021/om980804b

Cited by 5 publications

(3 citation statements)

References 21 publications

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“…Similar to the results for compounds 1-12, the elimination of the methyl radical (M-15) that forms product-ions as 25 (Scheme 2, X = H) followed by the loss of an ethylene molecule leads to the base peaks with structure identical to 28. The EI mass spectra of all bisHAPs studied (13-24) lacked the odd-electron molecular ions (Tables 2 and 3, SF [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The molecular masses of these compounds were confirmed by GC/ MS(CI) (SF 41-43).…”

Section: Resultsmentioning

confidence: 93%

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GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

Picazas-Márquez

Sierra

Nova

et al. 2016

J. Am. Soc. Mass Spectrom.

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Section: Resultsmentioning

confidence: 93%

“…Therefore, it seems less probable than the proposed mechanism pathway in Scheme 3. It is remarkable that although some heteroatom transfers have been reported as examples of the hetero McLafferty rearrangement [35][36][37][38][39], no data for similar iodine consecutive transfers have been described in the literature.…”

Section: Resultsmentioning

confidence: 99%

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

Picazas-Márquez

Sierra

Nova

et al. 2016

J. Am. Soc. Mass Spectrom.

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“…The latter was certainly the most favored since the loss of ethylene from TMSE ester has already been described in EI-MS according to the six-membered McLafferty rearrangement. 11 The CAD mass spectrum of 1 also displayed the acylium ion issued from the loss of the trimethylsilylethyl alcohol. Compounds bearing multiple protecting groups were subjected to successive CAD of increasing energy to compare the lability of the TMSE ester towards Boc, Fmoc and Z.…”

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confidence: 99%

JMS Letters

et al. 2002

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ESI mass spectrometry of amino acid trimethylsilylethyl estersIn complex peptide synthesis, such as cyclopeptides 1,2 and cyclodepsipeptides, 3 multiple protection strategies are required to build the desired structure. 4 Exotic protecting groups cleaved under unusual conditions are chosen to mask a specific reactive site. Among such protections, trimethylsilylethyl (TMSE) esters were found satisfactory in terms of compatibility with classical solidphase urethane protections such as tert-butyloxycarbonyl (Boc) or 9-fluorenylmethoxycarbonyl (Fmoc) groups. Indeed, silyl esters are selectively deprotected in the presence of a Boc group using tetrabutylammonium fluoride. 5 NaH deprotection ensures selectivity with fluoride-labile Fmoc groups. 6 Soft ionization fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectrometric (MS) techniques are effective analytical tools to identify and sequence peptides. 7 Specific fragmentations encountered in FAB mass spectrometry for the most common protecting groups Boc, 8 Fmoc 9 and Z 10 are also relevant in ESI-MS under collision-activated induced dissociation (CAD) conditions. We investigated the specific fragmentation of the TMSE protecting group in ESI-MS.

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McLafferty Rearrangement

2010

Comprehensive Organic Name Reactions and Reagents

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This reaction is explained as the rearrangement of monounsaturated molecular ion or radical ion with the cleavage of α,β‐bond of the unsaturated system along with the concomitant transfer of a γ hydrogen via a six‐membered transition state by the formation of a pair of unsaturated fragments, regardless of which fragment holds the charge is generally referred to as the McLafferty rearrangement. During the fragmentation, the structural, steric, and electronic factors determine the actual fragmentation paths. The mechanistic feature for carbonyl compounds has been discussed and it is explicated that if the distance between γ‐hydrogen and oxygen are >1.8A°, then McLafferty rearrangement do not occur. It has been found almost all molecular ions of aldehydes, ketones, thioketones, carboxylic acids, and acetates undergo a silyl group migration. Mechanistically, the McLafferty rearrangement can be either concerted with “simultaneous hydrogen transfer and β‐cleavage,” or stepwise with the “initial hydrogen transfer being followed by β‐cleavage”. This rearrangement is useful in structural elucidation using mass spectroscopy as the tool.

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New Fragmentation Process in Mass Spectrometry of Carbonyl Compounds with a δ-Silyl Group

Cited by 5 publications

References 21 publications

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

JMS Letters

McLafferty Rearrangement

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