Combined gas chromatography-mass spectrometry of the inositol trimethylsilyl ethers and acetate esters.

Each of the inositol diastereomers have been subjected to low resolution gas chromatography-mass spectrometry as their hexa-O-trimethylsilyl (TMSi) ethers and as their hexaacetyl esters. The TMSi ethers of the inositols each possess a unique spectrum consisting of the same ions occurring with remarkable variation in intensity. This variation, which is much greater with the inositol TMSi ethers than in the spectra of the inositol acetates, is presumably an expression of the stereochemistry of each isomer exaggerated by the bulky TMSi groups. Using TMSi- d₉, labeling as well as ring labeling with deuterium we identified several fragment ions which are characteristic of the cyclitols. The spectra of the TMSi inositols are compared with the spectra of other TMSi carbohydrates. Two main series of fragmentation processes are observed in the inositol hexaacetates. With the aid of acetyl- d₃ labeling each of these series were found to divide into two more pathways consisting of ions of the same m/ e values but of different structures. These pathways are compared with similar pathways observed in other acetyl carbohydrates. A method is described for the direct conversion of TMSi ethers to acetate esters which has potential usefulness in natural product studies. [ABSTRACT FROM AUTHOR]