FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRIC AND TANDEM MASS-SPECTROMETRIC INVESTIGATION IN THIOGLYCEROL ON PROTONATED NONCOVALENT ASSOCIATIONSOF B-CYCLODEXTRIN WITH 2-ACETYL, 2-PROPIONYL-1-PYRROLINE AND 5-ACETYL-2,3-DIHYDRO-1,4-THIAZINE, ROAST SMELLING ODORANTS IN FOOD - ROLE OF THE MATRIX

2-Acetyl-1-pyrroline (1), 2-propionyl-1-pyrroline (2) and 5-acetyl-2,3 -dihydro-1,4-thiazine (3), roast smelling odorants in food, form stabl e inclusion compounds with beta-cyclodextrin. Fast atom bombardment (F AB) mass spectra of such complexes in thioglycerol showed abundant [G + Hs + Mr + H](+) ions, where G = guest (1, 2 or 3), Hs = host (beta-c yclodextrin) and Mx = one molecule of matrix, consistent with protonat ed non-covalent three-component adducts, and nearly negligible 1:1 ass ociations of the type [G + Hs + H](+). Collision-activated decompositi on (CAD) experiments indicated that [G + Hs + Mx + H](+) are made of n eutral beta-cyclodextrin and protonated 1:1 guest-matrix adducts. The nature of these latter adducts was investigated by FAB mass spectromet ric experiments on 1, 2 and 3 in thioglycerol without beta-cyclodextri n. In all cases the most intense signals are due to [G + Mx + H](+) an d [G + H](+), with a small contribution of [G + Mx - H2O + H](+) to th e total ion current. CAD experiments on [G + Mx + H](+) afforded proto nated guest molecules as the base peak, consistent with the decomposit ion of protonated non-covalent 1:1 guest-matrix associations, possibly mediated by an intermolecular hydrogen bond. According to these data, there is a significant contribution of non-covalent three-component a ssociations to [G + Hs + Mx + H](+) complexes, although the possibilit y of the formation of covalent guest-matrix adducts is not ruled out d efinitely, as discussed in tbe text. (C) 1997 by John Wiley & Sons, Lt d.