D-Gulose

D-Allose D-Altrose D-Glucose -Mannose D-Gulose D-ldose -Galactose D-Talose... 

Carbon atom D-Gulose Me a-D-guIoside D-Mannose Me a-D-mannoside... 

C16H3oOsS2 2,3 4,5-Di-0-isopropylidene-D-gulose diethyl dithioacetal (IPGETA)97... 

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. 

D-Gulose (d-9) has also been prepared24 by the oxidation of 4,6-0-ethylidene-l,2-0-isopropylidene-a-D-galactopyranose (33), followed by reduction (resulting in overall inversion of the configuration of C-3) and hydrolysis. 

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 variety of methods has been developed for the reduction of the gulonolactones and derivatives to D- and L-gulose and the corresponding derivatives. D-Gulono-1,4-lactone (2) was reduced to D-gulose (d-... 

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. 

W. Homer, L. Hough, and A. C. Richardson, Derivatives of 2-amino-2-deoxy-D-gulose Synthetic and conformational studies,/. Chem. Soc., Sect. C (1971) 99-102. 

As a consequence, 4,6-O-isopropylidene derivatives are obtained from D-aldohex-oses this has now been demonstrated not only for D-allose, D-galactose, D-glucose, D-mannose, and D-talose, but also for D-gulose (J. Gelas and D. Horton, unpublished results see also, Ref. 15) it may reasonably be assumed that it will also be found for D-altrose and D-idose. 

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-gu/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 D-mannose and D-galactose, respectively, were also converted into unsaturated bromodeoxyheptonolactones. Finally, we obtained 2-0-acetyl-7-bromo-3,7-dideoxy-D-xyZo-hept-2-enono-l,4-lactone and the corresponding D-/yxo-isomer by the Kiliani extension of D-gulose. These substrates were all cyclized to cyclopentane lactones, stereoisomers of 65 [98]. 

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