The acetylation of apiitol in the determination of apiose

The complete acetylation of apiitol required 9 h when acetic anhydride at 120 degrees was used and sodium acetate was the catalyst. Both apiitol pentaacetate and apiitol tetraacetate were detected before acetylation was complete. When the reaction was done in dimethyl sulfoxide, with 1-methylimidazole as the catalyst, a third compound was observed, and identified as 1,2,4-tri-O-acetyl-3-C-(acetoxymethyl)-3-O-(methylthiomethyl)-D-glycero- tetrito l [3-O-(methylthiomethyl)apiitol tetraacetate] by gas-liquid chromatography and mass spectrometry. In N,N-dimethylformamide, with 1-methylimidazole as catalyst, the acetylation of apiitol was essentially complete in 4 h at 85 degrees, and the formation of methylthiomethyl ether was avoided. A method for preparing alditol acetates using 1-methylimidazole as the catalyst, and suitable for samples containing apiose as well as ordinary sugars, is described. The separation of apiitol pentaacetate from xylitol pentaacetate by gas-liquid chromatography proved difficult. However, a virtually complete separation of the peracetates of apiitol and xylitol as well as complete separation of those of rhamnitol, fucitol, arabinitol, mannitol, galactitol, glucitol, and myo-inositol, plus apiitol tetraacetate and 3-O-(methylthiomethyl)apiitol tetraacetate, was accomplished with a 30 m x 0.53 mm (i.d.) SP-2380 column in 49 min, and on a 30 m x 0.75 mm (i.d.) SP-2330 column in 82 min. A complete separation of apiitol and xylitol pentaacetates as well as four other alditol peracetates was obtained with a 60 m DB-1 column in 15.2 min, however this column did not resolve the acetates of fucitol and arabinitol. A variety of other columns and column conditions were ineffective.