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The study of electron ionization (EI) induced decomposition patterns is usually undertaken by extensive metastable-ion investigations, mainly depending on spectra of the unimolecular decomposition of parent ions carried out in double-focusing instruments.By such an approach, in the last decades most of the definitive data on ion structures and on the mass spectrometric behaviour of many classes of compounds have been achieved. Unfortunately, single-quadrupole analysers do not give any definitive information on the unimolecular decomposition pathways of selected species; only by collision experiments in triple-stage quadrupolar systems can such data be obtained.','The ion-trap mass spectrometer3 (ITMS) offers a particularly interesting mass spectrometric approach due to its ability to store ions for further experiments, first of all being mass analysis. In particular, the use of a supplementary AC voltage (the so-called 'tickle' voltage) leads to effective collision-induced decompositions of preselected ionic species, even in cases where the energy deposition into the stored ionic species is lower than that usually observed in high-energy collision experiments.For these reasons ITMS seems to be highly promising for ion structure investigations as an alternative to the more complex (and more expensive) systems such as double-focusing sector instruments and triple-stage quadrupoles. In other words, what is usually obtained by the study of natural or collision-induced decomposition in multiple-stage analysers, is achieved in the ITMS by a simple, single-stage device by means of time separation of the different steps, namely electron ionization, ionic species isolation, collision of the preselected ions, mass analysis and detection of the collisioninduced decomposition products.Following our previous mass s ectrometric investigations of flavonoid cornpounds?'in this paper we will discuss the data obtained by ITMS on structure investigation of [M -HI+ ions of chalcone (2-propen-1-ona-1,3-diaphenyl) (l), whose EI mass spectrum has + Partially and preliminarily communicated at the European Meeting on Tandem Mass Spectrometry, Manchester UK, 9-11 July 1990.* Author to whom correspondence should be addressed.already been reported together with those of some of its derivatives.6-8 In such early papers the major fragmentation pathways and rearrangement processes were used to determine the type of chalcone and, in some cases, the position of substituents on the molecular skeleton. Some disagreement was expressed concerning the structure assignment of their [M -H]+ species.Ronayne and co-workers' postulated that the commonly observed intense [M -H]+ ion of chalcone was due to the loss of hydrogen from ring A in the resonance-stabilized flavylium ion structure a. The same mechanism was also proposed by Van

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Aerial parts of Senecio filaginoides yielded two new furanoeremophilane type sesquiterpenoids: 6alpha-acetyloxy-10betaH-furanoeremophil-1-one, 1 and 6alpha-tiglinoyloxy-10betaH-furanoerernophil-1-one, 2. Their structures have been elucidated by spectroscopic data. From roots and aerial parts of S. pinnatus 1alpha-hydroxy-6betaangeloyloxy-10alphaH-furanoeremophil-9-one, 3 has been isolated.

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The electron impact induced fragmentations of chalcone have been studied with the aid of high resolution measurements, using metastable decompositions by linked scans and mass-analysed ion kinetic energy spectroscopy through collisional experiments by ion-trap mass spectrometry and labellng by I3C deuterium. Based on the data obtained, two different mechanisms for the formation of mlz 130 ions have been proposed.The chalconoids' represent an important family of naturally occurring flavonoids and are of general interest because of their implication both in biosynthetic and in biomedical work.'-3 The use of mass spectrometry for structural elucidation of flavonoids has received considerable attention.2 The general fragmentation pattern and some detailed electron impact induced decomposition mechanisms have been already discussed by many authors who have used various mass spectrometric approaches.2,4In chalcones, the major fragmentation pathways and genera1 rearrangement processes can determine, in some cases, the type of chalcone and establish the position(s) of substituents on the molecular skeleton. In a previous paper' we reported and discussed the data obtained by ion-trap mass spectrometry (ITMS) on the [M-HI+ ion of chalcone, whose structure was still a matter of debate. By ITMS, definitive results on the formation mechanism and structure of [M-HI+ ions were achieved, thus proving the value of this technique in structural problems.There is still disagreement in the literature concerning some of the main decomposition routes of chalcone, for example those related to the formation of ions at m/z 130, that are considered to be of diagnostic value from the structural point of view. Thus while Van de Sande et al.,' sustained that this ion originates from a cyclic moiety and has the structure a (see Scheme 1), Rouvier et al.,' in an earlier investigation based on substituted chalcones, had proposed the alternative structure b as making a contribution to the ion of mlz 130.In the present study, in order to gain definitive information on both the formation mechanism and structure of ions of mlz 130, we have investigated differently labelled (D, " C ) and substituted (CH,, F, and C1) compounds (1-11, see Table 1) by means of accurate mass measurements, metastable ion studies (linked scans at constant B21E and mass-analysed ion kinetic energy (MIKE) studies)6 performed on ZAB 2F (VG Analytical, Manchester, UK) and Varian MAT

The electron impact induced fragmentations of the five possible naphthoflavones have been studied with the aid of low-and high-resolution measurements, metastable decompositions and isotope labelling using either deuterium or carbon-13 atoms. All compounds show both the direct expulsion of a CO residue from the carbonyl group and the retro Diels-Alder cleavage. The abundant [M -HI+ ion has been formulated as the substituted P-tropolone species, which, in the case of P-naphthoflavone, is in competition with a pentacyclic species arising from the elimination of H-5 as evidenced in the spectrum of 5-d-P-naphthoflavone. Other previously unsuspected ions are also in evidence. Received