| Popis: |
Unsaturated 5(4H)-oxazolones lead, by methanolysis, to the corresponding dehydroamino acid derivatives. Interestingly, under atmospheric pressure chemical ionisation (APCI) conditions, the latter give rise, aside from abundant [M+H]+ ions, to [MHCH3OH]+ species, formally corresponding to the protonated oxazolones employed for their synthesis. Retrosynthetic processes have often been described as energetically favoured decompositions of odd-electron molecular ions but never invoked in APCI-activated fragmentations. To investigate this possible retrosynthetic process, occurring also under collisional conditions, some experiments on the deuterated analogues have been undertaken. The breakdown curves of [M+H]+ of oxazolones and [MHCH3OH]+ of the dehydroamino acid derivatives are superimposable, proving their structural identity and giving experimental evidence of the occurrence of a real retrosynthetic process from even-electron protonated molecules. Copyright © 2002 John Wiley & Sons, Ltd. |
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