3-Hexuloses, synthesis

For preparative applications, the expensive and configurationally unstable donor 128 can be simply prepared in situ by the action of ribose 5-phosphate isomerase (EC 5.3.1.6) on D-ribose 5-phosphate (39). This technique was applied to the stereoselective synthesis of d-[1-13C] fructose 6-phosphate 38 from [13C] formaldehyde [376,377] which also included a second enzymatic isomerization of the D-arafrino-3-hexulose 6-phosphate intermediate 129 into the more stable 2-hexulose derivative 38. Notable are the conflicting demands for high substrate levels (necessary to shift the fully reversible multi-component equilibrium) versus the notorious enzyme inactivation that occurs at higher formaldehyde concentrations. 

Mostly the baker s yeast transketolase has been used so far to prepare several valuable ketose sugars and derivatives 141 (cf. Sect. 7). Recently, the transketolase was utilized in the key stereogenic transformation of racemic 2-hydroxybutyraldehyde 142 into the homochiral synthon 5,6-dideoxy-D-t/ireo-hexulose 110 for the chemoenzymatic synthesis of (+ )-exo-brevicomin 107 [314], Transketolase has also been applied for the in-situ generation of Ery4P (35) from Fru6P (38) in a multi-enzymatic synthesis of 34 (Scheme 5). 

I. I. Cubero and M. T. P. Lopez-Espinosa, Branched-chain sugars. 12. Synthesis of 3,4-anhydro-l-deoxy-3-C-methyl-D-hexulose derivatives, Carbohydr. Res., 154 (1986) 71-80. 

C. Fayet and J. Gelas, Synthesis of 3-substituted furans from 3-C-substituted hexuloses, Carbohydr. Res., 155 (1986) 99-106. 

S. I. Angyal and M. E. Evans, Oxidation of carbohydrates with chromium trioxide in acetic acid. III. Synthesis of the 3-hexuloses, Aust. J. Chem., 25 (1972) 1495-1512. 

The Synthesis of 3-Hexuloses. Part II. Derivatives of l-Deoxy-L-arafoo-3-hexulose (Syn. 6-Deoxy-L-lt/xo-4-hexulose), J. W. Bird and J. K. N. Jones, Can.. Chem., 41... 

Conversion of2-Hexuloses into 3-Heptuloses Synthesis of D-manno-3-Heptulose," R. W. Lowe, W. A. Szarek, and J. K. N. Jones, Carbohydr. Res., 28 (1973) 281-293. 

Scheme 44. Chemical synthesis of dTDP-6-deoxy-D-3-hexulose (130)...

Scheme 47. Enzymatic synthesis of dUDP-6-deoxy-4-hexulose 144 from sucrose 141...

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... 

Synthesis of D-lyxo-Hexulose (D-Tagatose) and 1-Deoxy-D-lyxo-hexulose, M. L. Wolfrom and R, B. Bennett,/. Org. Chem., 30, 1284-1287 (1965). 

A novel diacetal of L-xi/lo-3-hexulose has been isolated in the course of studies on a general method for the synthesis of 3-hexuloses by oxidation of fully acetylated, hexitol monoacetals with chromium trioxide. Oxidation of l,2,5,6-tetra-0-acetyl-3,4-0-methylene-D-glucitol with chromium trioxide in acetic acid yielded principally l,2,5,6-tetra-0-acetyl-4-0-formyl-D-nbo-3-hexulose. The material remaining in the mother liquors was saponified with sodium methoxide in methanol and the product treated with acetone containing concentrated sulfuric acid a di-O-isopropylidene derivative, presumably l,2 3,4-di-0-isopropylidene-j8-L-xj/lo-3-hexulofuranose (116), was obtained. 

L-Sorbose a monosaccharide hexulose, 180.16, m.p. 162°C, [a]D - 42.9", present in certain plant juices, e.g. rowan berries, and biosynthesized from t>-sorbitol. L-S. is an intermediate in the commerdal synthesis of ascorbic add. 

Marumo K, Lindquist L. Verma N. Weintraub A, Reeves P, Lindbetg AA. Enzymatic synthesis and isolation of thymidine dipho phate-6-slcoxY D Xy(o-4 hexulose and thymidine diphosphate-L-ihamnose. Eur J Biochem 1992 204 539-545. 

The photochemical and thermal Isomerization of D-arablno-hexulose phenylosazone In solution between the N- and 0-chelate forms (20) and (21) respectively, has been studied In detail, the photo-reaction being a fast efficient method for the synthesis of the 0-chelate. Lifetimes and quantum yields have been reported for... 

---