Trehalose octaacetate

The best yield recorded for a,(8-trehalose octaacetate is 40%, obtained by Sharp and Stacey in 1951. The compound resulted from shaking 2,3,4,6-tetra-0-acetyl-(8-D-glucosyl fluoride with silver carbonate, An-hydrone, and iodine in chloroform for 48 hours. The same compound was obtained from 2,3,4,6-tetra-0-acetyl-(3-D-glucose treated in chloroform with phosphorus pentaoxide. A disaccharide was not produced by the action of sodium on 2,3,4,6-tetra-O-acetyl-a-D-glucosyl bromide at 90-100°. 

In chloroform at 17-25 . Table IX Definitive Chemical Syntheses of a, -Trehalose Octaacetate ... 

There was better agreement with calculations made on the basis of Klyne s rules, except for ,a-trehalose octaacetate. It was assumed that both parts of the trehalose molecule are identical. Moreover, the calculated values agreed more closely with the less positive values reported for a,/3-trehalose octaacetate (see Tables VII and VIII). 

Stjernholm isolated a,a-trehalose from three species of D-glucose-fermenting propionibacteria (P. ardbinosum, P. shermanii, and P. pento-saceum). This identification was proved by formation of the crystalline dihydrate and conversion thereof into the crystalline octaacetate. In proliferating cells, 9% of the fermented D-glucose was converted into a,a-trehalose, and, in resting cells, as much as 30%. After the n-glucose had been utilized, the a,a-trehalose was converted by the bacteria into carbon dioxide, acetic acid, propionic acid, and succinic acid. 

Crystalline a, a-trehalose has been obtained as the dihydrate (m.p. 96-97°) from various natural sources (see Table II), and, in several cases, the identity of the sugar was confirmed by formation of the crystalline octaacetate (see Table III). Preparation of natural a,a-trehalose from vegetable and fungal sources involves extraction with ethanol, liberation from protein by the addition of lead acetate, removal of lead by precipitation with hydrogen sulfide, filtration, and decolorization with carbon. The sugar crystallizes readily from aqueous ethanol. An excellent method... 

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