Psicose acetals

D-ribonyl chloride tetraacetate (IX) with diazomethane. The 1-diazo-l-desoxy-/cefo-D-psicose tetraacetate (X) which was formed was transformed into /ceio-D-psicose pentaacetate (XI) by refluxing with cupric acetate in acetic acid. Deacetylation with barium hydroxide gave D-psicose (I). 

Occurrence. D-Psicose (D-rifeo-hexulose, 30) is produced in the hydrolysis of the antibiotic psicofuranine.147,148 Although the sugar was initially isolated only as the phenylosazone, its identity was proved by synthesis of psicofuranine from tetra-0-acetyl-D-psicosyl chloride. The ketose also occurs in Itea plants, from which it has been isolated as the diisopropylidene acetal.149... 

Preparation. Isomerization of D-allose in anhydrous pyridine gives syrupy d-psicose, which may be isolated as the crystalline l,2 3,4-diisopropylidene acetal.150 D-Psicose is not fermentable by yeast. A review of the chemistry of D-psicose has appeared.151... 

Emil Fischer first described the condensation of D-fructose with acetone in 1895, and most of the early work on cyclic acetals of ketoses was performed with D-fructose. In 1934, Reichstein and Griissner published their classic synthesis of L-ascorbic acid (vitamin C), in which L-sorbose was converted into 2,3 4,6-di-0-isopropylidene-a-L-sorbofuranose or other di-alkylidene acetals. The emphasis of research activity then shifted to L-sorbose, and to the elucidation of an optimal procedure for preparing such diacetals. At about the same time, Levene and Tipson used isopropylidene acetals as derivatives for the purification of L-cri/thro-pentulose (as the di-isopropylidene acetal) and D-thrco-pentulose (as the monoisopropyli-dene acetal). Soon thereafter, Reichstein and coworkers used diisopropylidene acetals of D- and L-psicose, and D-tagatose, to purify the respective sugars. 

Retention Times of Per(trimethylsilyl) Ethers and Other Derivatives of Some Acetals of D-Fructose and D-Psicose... 

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