Psicose synthesis

The synthesis of D-psicose as a colorless sirup ([< ]% + 3.1° in water) by Steiger and Reichstein13 may be regarded as the first authentic preparation of this ketohexose. The Kiliani-Fischer cyanohydrin synthesis furnished D-allonic lactone (VII) from D-ribose. This lactone, on reduction with sodium amalgam, gave D-allose (VIII) which was transformed into D-psicose (I) by refluxing with pyridine. Pyridine had been introduced into the Lobry de Bruyn-Van Ekenstein reaction by Fischer, Danilov and their coworkers.13 ... 

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... 

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. 

The value of the 1,3-dithian route to branched-chain sugar derivatives has been illustrated further by stereospecific syntheses of 3-C-formyl, 3-C-hydroxymethyl, and 3-C-methyl derivatives of D-psicose from the ketone (373) via the dithianyl adduct (374). Addition of nitromethane to (373) gave both 3-C-nitromethyl-o-psicose and -fructose derivatives, which, after separation by chromatography, were reduced to the corresponding 3-C-aminomethyl derivatives. The use of dithianyl derivatives in the synthesis of streptomycin components is dealt with in Chapter 18. 

An improved synthesis of D-psicose from base-catalysed isomerization of D-fructose using calcium ion cation-exchange resin chromatography has been reported. 

---