Gulose preparation

Most substrates, with the exception of hydroxypymvate, have a threo configuration of hydroxyl groups at the C-3 and C-4 positions (139). The new stereocenter formed in TK-catalyzed addition is formed in the threo configuration with high diastereo-selectivity (151). Using TK-catalyzed condensations of hydroxypymvic acid with a number of aldehydes a practical preparative synthesis of L-idose [5934-56-5], L-gulose [6027-89-0], 2-deoxy-L-xylohexose, and... 

Both L-gulose12,13 (9) and D-gulose (d-9, see Ref. 10) have been oxidized with bromine to L- or D-gulonic acid, respectively (see Scheme 1). L-Gulose (9) has been prepared by a number of different procedures. Schemes 2 and 3 show two early procedures that afforded L-gu-lose, but the overall yields were low (<30%). In the first procedure12 (see Scheme 2), D-glucitol (10) was converted into 2,4-O-benzylidene-D-glucitol (11), which was then oxidized with lead tetraacetate to 2,4-O-benzylidene-L-xylose (12). Nitromethane was added to 12 to afford crystalline 13 in 50% yield. Hydrolysis of 13 provided 14, which was treated with sodium hydroxide, followed by sulfuric acid, to afford 9, which was isolated in 52% yield as the 2-benzyl-2-phenylhydrazone. 

It has also been reported that D-galactose can be isomerized with molybdic acid to a mixture containing D-talose and D-gulose, but the yields are low.34-35 A number of derivatives of gulono-1,4-lactone have been prepared that, by reduction, would provide selectively protected derivatives of gulose. These derivatives will be discussed in subsequent Sections of this article. 

A. C. Richardson and H. O. L. Fischer, Cyclization of dialdehydes with nitromethane, Part VI. Preparation of 3- amino-1,6-anhydro-3-deoxy-p-D-gulose, -P-D-altrose and -p-D-idose derivatives and their characterization by means of inversion of mesyloxy groups,./. Am. Chem. Soc., 83 (1961) 1132-1139. 

As discussed in Sect. 3.4, the synthon 20 was prepared from the dibromo-heptonolactone, which in turn was obtained from the cheap commercially available D-g(ycero-D-gM/o-heptono-l,4-lactone (Table 1). The other isomeric dibro-moheptonolactones shown in Table 1, which were prepared from the heptonates, obtained from chain extension of o-mannose and o-galactose, respectively, were also converted into unsaturated bromodeoxyheptonolactones. Finally, we obtained 2-0-acetyl-7-bromo-3,7-dideoxy-D-x7(o-hept-2-enono-l,4-lactone and the corresponding D-/yxo-isomer by the Kiliani extension of o-gulose. These substrates were all cyclized to cyclopentane lactones, stereoisomers of 65 [98]. 

Problem 22.27 Fischer prepared L-gulose by oxidizing o-glucose to two separable lactones of glucaric acid. These were reduced to lactones of gluconic acid, which were further reduced. Give all the structures in these... 

Compound 43 has been prepared from a mixture of L-gulose and L-sorbose, or from L-gulose.293-296 The mixture of L-gulose and L-sorbose... 

Several miscellaneous procedures have been reported for the preparation of L-gulonic acid (47). 5-0-Benzoyl-l,3 2,4-di-0-ethylidene-D-glucitol (72) was oxidized388 with chromium trioxide to 73. After hydrolysis of 73, the L-gulose (45) formed was oxidized369,370 with bromine to 21. As noted in Section III,5b, 3,5 4,6-di-0-ethylidene-L-gu-lonic acid (50) was prepared from 3,5 4,6-di-0-ethylidene-D-gulitol (49) in 50-70% yield. By hydrolysis, 50 afforded333 21. 

By treatment of D-gulose (XVII) or D-idose (XVIII) with warm aqueous barium hydroxide solution Van Ekenstein and Blanksma were able to isolate D-sorbose (II) with a melting point of 165° and [< ]d + 42.9° in water. The aldoses were prepared from D-gulonic and D-idonic lactones obtained by the cyanohydrin synthesis from D-xylose. 

Recently Gatzi and Reichstein28 have prepared D-sorbose by refluxing D-gulose with pyridine and by the action of very dilute potassium hydroxide on D-galactose. The product of the latter reaction was contaminated with a little D-tagatose. 

Deacetylation of tetraacetyl-L-sorbose phenylosazone121 (LII) may involve a Walden inversion on carbon 4 with the formation of an L-hexose phenylosazone dianhydride (LIII). The antipode had been prepared previously from tetraacetyl-D-gulose phenylosazone (synonym, tetra-acetyl-D-sorbose phenylosazone). 

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