Glucitol 2,4-0-benzylidene

Methyl 2-methyl-3-methylthio-4,6-benzylidene-/S-i>-idoside to methyl 2-methyl-3-de8Oxy-4,6-benzylidene-0-D-idoside Methyl 3-methylthio-5-L-xyloside to methyl 3-desoxy-/J-o-xyloside Ethyl thiol-D-ribonate tetraacetate to aldehydo-D-ribose tetraacetate Methyl thiol-D-gluconate pentaacetate to D-glucitol hexaacetate Ethyl tetraacetyl-0-D-glucopyranosyl xanthate to 1,5-anhydro-D-glucitol tetraacetate... 

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. 

The simple cleavage of lactones 1 or 2 with alcohol and acid has not been reported. However, when 1 is treated with benzaldehyde diethyl acetal and hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (47) is formed in >90% yield.77,78 No other isomers were observed, and other acetals of benzaldehyde, as well as aliphatic aldehydes, afford similar products in good yield.77 D Addieco prepared36 similarly protected derivatives of L-gulonic acid by oxidation of l,3 2,4-di-0-ethylidene-D-glucitol (15), followed by esterification of the resulting acid with diazomethane. 

It is noteworthy that saponification of Baker s first compound afforded a 1,5-anhydride, whereas saponification of the corresponding 5,6-anhydro-2,4-0-benzylidene derivative furnished l,3-anhydro-2,4-O-benzylidene-D-glucitol.51... 

A less obvious instance is the acylation of l,5-anhydro-4,6-0-benzylidene-D-glucitol. The 1,5-anhydride has a chair conformation, and the 2- and 3-hydroxyl groups are equatorially attached trans to each other, and are, apparently, essentially equivalent91 However, the 2-benzoate and 2-p-toluenesulfonate were obtained almost exclusively on using the acyl chlorides in pyridine, although in the former acylation, an appreciable proportion of the dibenzoate was formed. 

Under mild conditions, isosorbide (3) is converted into 1,6-dichloro-1,6-dideoxy-D-glucitol (147) by reaction with boron trichloride (Scheme 41). Compound 147, which was not isolated in pure form, was allowed to react with benzaldehyde to afford 2,4-(3-benzylidene-1,6-dichloro-1,6-dideoxy-D-glucitol (148) and 2,4 3,5-di-O-benzylidene-1,6-dichloro-1,6-dideoxy-D-glucitol (149). By this method, the two tetrahydrofuran rings are cleaved in a very mild manner.218... 

With the aid of these rules, we have predicted the structures of the acetals which would be expected to result from the benzylidenation, ethylidenation and methylenation of all the tetritols, pentitols and hexi-tols. As will be seen from Table IV, the predicted structures agree very well with the accepted structures of the compounds. The rules explain, too, the syntheses of 3,5-benzylidene- and 3,5-methylene-gluco-[Pg.180]

A new synthetic approach to D-ribose has recently been made by Sowden.43 In this procedure 4,6-benzylidene-D-glucose (X) was reduced catalytically to 4,6-benzylidene-D-glucitol (XI) which was then oxidized with sodium metaperiodate to 2,4-benzylidene-D-erythrose (XII). Condensation of this latter compound with nitromethane gave a mixture of epimeric, crystalline, substituted C-nitro alcohols, 3,5-benzylidene-1-desoxy-l-nitro-D-arabitol and 3,5-benzylidene-l-desoxy-l-nitro-D-ribitol (XIII). After separation, the appropriate isomer was hydrolyzed to 1-nitro-l-desoxy-D-ribitol (XIV) which, in the form of its sodium salt was decomposed directly to D-ribose (XV), isolated as its benzylphenyl-hydrazone. This synthesis is of interest in that it may be used to obtain D-ribose labeled at carbon 1 with C.14... 

Preparation. L-Xylose has been prepared by periodate oxidation of 2,4-0-benzylidene-D-glucitol followed by acid hydrolysis of the benzylidene group.53... 

Preparation. L-Gulose was prepared by the Sowden and Fischer method from 2,4-O-benzylidene-L-xylose, which can be conveniently prepared from 2,4-0-benzylidene-D-glucitol.116... 

Synonyms Bis-0-(benzylidene)-D-glucitol Bis-o-(phenylmethylene)-D-glucitol D-Glucitol, bis-o-( phenyl methylene)- Sorbitol acetal... 

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