Deoxy sugars mass spectra

The u-deoxy sugars studied (6-deoxy and 5-deoxy) have intense peaks for the dithioacetal fragment, and also break down to Fragments A, B, and C. < -Deoxyhexose dithioacetals cannot be differentiated from 5-deoxy-hexose dithioacetals. The deoxy function is, apparently, too far removed from the bonds most susceptible to cleavage to have a significant effect. Mass spectrometry can also be useful in the characterization of terminal branched-chain deoxy sugars. The spectrum of 6-deoxy-5-C-methyl-D-xylo-hexose diethyl dithioacetal 1 contains prominent peaks due to Fragments A, B, and C. Apparently, substitution beyond C-4 does not affect... 

Other methods of identification include the customary preparation of derivatives, comparisons with authentic substances whenever possible, and periodate oxidation. Lately, the application of nuclear magnetic resonance spectroscopy has provided an elegant approach to the elucidation of structures and stereochemistry of various deoxy sugars (18). Microcell techniques can provide a spectrum on 5-6 mg. of sample. The practicing chemist is frequently confronted with the problem of having on hand a few milligrams of a product whose structure is unknown. It is especially in such instances that a full appreciation of the functions of mass spectrometry can be developed. 

Holacurtinol (40) is a minor alkaloid. The mass-spectrum showed fragments attributable to successive losses of two molecules of HjO suggesting the presence of two hydroxyl groups. The NMR spectral data showed the presence of the same sugar unit (4-deoxy-4-amino-P-D-cymaropyranose) as in 37 and 39, while the pregnane aglycone portion was similar to that of... 

C-4 consecutive carbon atoms of the ring. In the light of these fragmentations, it is possible to derive valuable information regarding deoxy sugar acetates. In the case of the 6-deoxy 4 and 2-deoxy 5 derivatives, certain peaks are characteristic in their mass spectra (Scheme 5). The peak at m/e 170 in the mass spectrum of 5 is derived from the consecutive carbon atoms C-l-C-4. The most intense peak at m/e 97 is due to the highly stabilized pyronium ion and is displaced to m/e 98 in the mass spectrum of the C-2 deuterio derivative (23). 

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