Abstract-The mass spectra of nine compounds belonging to the group of (-)-kauran-16-ols are reported. These compounds differ either by stereochemistry at C,, (I, 11) or by the nature of the substituent at C, (I11 to VIII). In all cases the most characteristic ions correspond to a process in which ring D is split off and lost as a C3H,0 fragment. The nature of the sobstituent R1 at C , can be deduced from such typical ions asshow little difference in their mass spectra; the assignment of configuration at this centre may be reliable only when the spectra of both epimers are compared.
Abstract-The trifluoroacetyl derivatives of alditols are convenient compounds for mass spectrometric investigation as they are easily obtainable and highly volatile. They show simple fragmentation patterns with intensive peaks in the high mass range. Trifluoroacetates of alditols may be used for detection and location of deoxy groups in the molecule.THE SUCCESSFUL development of mass spectrometry1 and mass spectrometry combined with gas liquid chr~matography~,~ (g.1.c.) in carbohydrate field emphasises the need for highly volatile and easily available sugar derivatives with simple fragmentation patterns. Trifluoroacetyl (TFA) derivatives of sugars described by Tatlow* seemed attractive from this point of view and their mass spectra should be apriori simpler than those of acetates5s6 and trimethyl silyl ethers. ' We started our investigation with TFA derivatives of alditols. Our preliminary data as well as the paper8 published recently showed that alditol trifluoroacetates could be readily separated by g.1.c. techniques and hence may be of value for examination by g.l.c./mass spectrometry. We measured the mass spectra of TFA derivatives of glycerol, erythritol, arabinitol, ribitol, xylitol, glucitol, mannitol, galactitol, 1-deoxy-L-mannitol and 2-deoxy-D-arabinohexitol. All the mass spectra except those of glycerol and deoxyhexitol show a molecular peak intense enough for direct molecular weight determination in contrast to the mass spectra of acetates6 and methyl ethersS of alditols. The mass spectra of TFA derivatives of the diastereomeric alditols are all very similar and coincide within the limits of error. The electronimpact fragmentation of alditol trifluoroacetates resemble that of other esters of polyols. The fragmentation of the molecular ion starts from the splitting of the trifluoroacetyl radical and then of molecules of trifluoroacetic acid to give fragments of the C , series (where n is the number of carbon atoms in the original alditol molecule) or from the rupture of one of carbon-carbon bonds to give the primary fragments (Cnp1 -C,). These primary fragments split off sequentially the molecules of trifluoroacetic acid. Thus, the mechanism of fragmentation of trifluoroacetates is analogous to that of esters of other carboxylic acids and can be considered as an example of a McLafferty rearrangement.
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