1,2-O-Cyclohexylidene-a-D-glucofuranose

The preparation of 1,2-O-cyclohexylidene-a-D-xylofuranose (22) (Expt 5.117) from 1,2-O-cyclohexylidene-a-D-glucofuranose illustrates the use of sodium metaperiodate for the cleavage of carbon-carbon bonds in a-diols (see also Section 4.2.55, p. 454). In this case C-6 is lost as formaldehyde and C-5 is converted into an aldehyde group. This aldehydic product is isolated as a dimer, which is then reduced in methanol solution with sodium borohydride to the xylofuranose derivative (22). 

Di-(1,2-0-cyclohexylidene-a-D-xj/o-pentodialdofuranose-5-hydrate)-5,5 3, 5-dianhydride. Add a solution of 14.3 g (0.061 mol) of sodium metaperiodate in 220 ml of water dropwise to a well-stirred solution of 17.4 g (0.067 mol) of 1,2-O-cyclohexylidene-a-D-glucofuranose (Expt 5.115) in 50 ml of water (1)- Stir for a further 30 minutes and remove the water at a temperature below 50 °C by evaporation under reduced pressure. Extract the solid residue with three 75 ml portions of dichloromethane and dry the combined extracts over magnesium sulphate. Filter and evaporate to give a residue which crystallises spontaneously. After recrystallisation from acetone the dimer has m.p. 182— 183 °C, the yield is 7.9 g (51%). 

It was found that die stereoselectivity of reduction was increased by ethanol, and that (R)-l-phenylethanol was obtained in 70% optical yield when acetophenone (12.5 mmoles) was reduced with an ethanol-modified complex of lithium aluminum hydride with 3-O-benzyl-1,2-O-cyclohexylidene-a-D-glucofuranose prepared from the sugar derivative (26 mmoles), lithium aluminum hydride (58 mmoles), and ethanol (110 mmoles). 

Stereospecific R or S Lithium aluminum hydride-3-O-benzyl-1-2-O-cyclohexylidene-a-D-glucofuranose complex. ,(3-Unsaturated ketones Li (or K) in hexamethylphosphoric triamide and ether. 

Benzyl-1,2-0 -cyclohexylidene-o-glucofuranose 5,6-bis(diphenylphosphinite), G-254 3- O -Benzyl-1,2- O -cyclohexylideneglucofuranose, B-23 5- O -Benzyl-1,2- O -cyclohexylidene-a-D-glucnrono- 1,5-lactone, G-539... 

Although menthyl esters, especially 19, are most often used to prepare sulfoxides, esters derived from optically active alcohols other than menthol have been prepared . Ridley and Smal prepared arenesulfmic esters of 1,2 5,6-di-O-cyclohexylidene-a-D-glucofuranose. Unfortunately, these diastereomers were oils, except for the mesityl derivative, with the major epimer having configuration R at sulfur and so they offered no advantage over the menthyl esters. Separation of the epimers by chromatography failed. 

Benzoyl-l,2 3,5-di-0-benzylidene-a-D-glucofuranose, B-27 3-0-Benzoyl-l,2 4,6-di-0-benzylidene-a-D-glucopyranose, B-26 3-0-Benzoyl-2,5-dibromo-2,5-dideoxy-D-arabinono-l,4-lactone, D-526 3- O -Benzoyl-1,2 5,6-di- O -cyclohexylidene-a-D-glucofuranose, C-190... 

An early approach to the formation of chiral amines by nonenzymatic asymmetric synthesis was the reduction of prochiral ketoximes and their O-tetrahydropyranyl and O-methyl derivatives with lithium aluminum hydride-3-0-benzyl-1,2-0,0-cyclohexylidene-a-D-glucofuranose complex (16)33 in ether and prochiral ketoximes... 

Reduction of ketones with sodium borohydride in the presence of a carboxylic acid and 1,2 5,6-di-0-cyclohexylidene-a -D-glucofuranose gave 35-50% enantiomeric enhancement values.Another group has reported a similar reaction with the corresponding di-O-isopropylidene-glucose derivative and prochiral aromatic ketones. Optical yields of up to 64% were claimed. The chiral reagents appear to be sodium acyloxyborohydrides, which complex with the carbohydrate before reduction takes place. 

Free Sugars and Simple Derivatives Thereof. — Partially deuteriated j8-L-arabino-pyranose and a-L-xylopyranose (n.d. refinement), 1,2-6>-cyclohexylidene- and l,2-O-isopropylidene-0 -D-glucofuranose 3,5,6-phosphites, 5-O-acetyl-l,2 3,4-di-O-isopropylidene-a-D-galactoseptanose, 3,4,6-tri-O-acetyl-l, 2-0-(R )-ethyl-... 

O-Cyclohexylidene 1,2-O-Cyclohexyli-dene-3-deoxy-3-fluoro-a-D-glucofuranose C12H19FO5 262.277... 

Di- O -cyclohexylidene-a-D-allofuranose, C-189 1,2 5,6-Di- 0 -cyclohexylidene-3- C-ethyl-a-D-allofuranose, C-189 l,2 4,5-Di-0-cyclohexylidene-p-D-fructopyranose, F-84 1,2 5,6-Di- 0 -cyclohexylidene-a-D-glucofuranose, C-190 l,2 4,5-Di-0-cyclohexylidene-p-D-eryf/zro -hexo-2,3-diulose-2,6-pyranose, H-86... 

Di-0-cyclohexylidene-a-D-mannopyranosyl chloride, M-42 1,2 5,6-Di-0 -cyclohexylidene-3- O -mesyl-a-D-allofuranose, C-189 l,2 5,6-Di-0-cyclohexylidene-3-C-methyl-a-D-allofuranose, C-189 1,2 3,4-Di-0 -cyclohexylidene-6- O -tosyl-a-D-galactopyranose, G-193 1,2 5,6-Di-0 -cyclohexylidene-3-O -tosyl-a-D-glucofuranose, C-190 l,2 5,6-Di-0-cyclohexylidene-3-C-vinyl-a-D-allofuranose, C-189 l,2 3,5-Di-0-cyclohexylidene-a-D-xylofuranose, C-191 l,2 3,5-Di-(9-cyclohexylidene-a-L-xylofuranose, C-191 Didanosine, D-548 4a,106-Didehydrobergenin, B-29 4, 5 -Didehydro-5 -deoxycytidine, D-333 2, 3 -Didehydro-3 -deoxytliymidine, S-76 4, 5 -Didehydro-5 -deoxyuridine, D-549... 

O -Cyclohexylidene-3- O -methyl-a-D-glucofuranose, M-256 Decyl glucoside p-D-Pyranose-/orm Tetra-Ac, D-19... 

---