n this article

the authors report the electron impact mass spectrometric analysis of six structurally related derivatives of 3

4

6-tri- O-acetyl or benzyl-β-D-mannopyranose 1

2-(methyl orthoacetate) (1～2 )

and3

4

6-tri-O-acetyl-o-acetyl-α-D-glucopyranose 1

2-metyyl or cthylorthoaeetate ) (3～6 ). It was found that the massspectra of 1～6 are much complicated because of the valietips of ismerizations and rearrangements that co-curred during the fragmentation process.