Reaction with methyl xyloside

Reactions with Model Compounds. To test whether carbohydrates were actually reacting with the phenolic resin, the reaction of methyl xyloside (III) and saligenin (V) under neutral conditions was studied. This reaction system was used as a model for the curing reaction. 

Figure 5. TLC on Whatman K5F silica gel of (1) the reaction mixture of saligenin and methyl xyloside heated at 140 °C for 80 minutes and (2) the reaction of saligenin with itself when heated at 140 °C for 60 minutes. The TLC plate was developed in 8% methanol in chloroform and visualized by spraying with 50% concentrated sulfuric acid in ethanol and heating at 140 °C.

The 1H-NMR and 13C-NMR spectra were obtained for each of the three components. The spectra of the components are compared with those of methyl xyloside and saligenin in Tables I and II. The spectra are consistent with the three components having been formed by the reaction of one hydroxyl substituent on methyl xyloside with the methylol group of saligenin to form an ether linkage. Formation of similar compounds has been reported on reacting carbohydrates with vanillyl alcohol (12). 

In an attempt to synthesize 2-desoxy-L-ribose, Mukherjee and Todd68 treated methyl 2,3-anhydro-jS-L-ribopyranoside (LXXII) with sodium thiomethoxide and then reduced the amorphous product. The sulfur-free sirup thus obtained was inert to the action of periodate and is therefore methyl 3-desoxy-/3-L-riboside (ayn., methyl 3-desoxy-/3-L-xyloside) (LXXIV) rather than the desired 2-desoxy derivative. The methylthio intermediate (LXXIII) was consequently a 3-methylthio-L-xylose derivative rather than a 2-methylthio-L-arabinose compound. The presence of a trace of the latter, however, is not wholly excluded since the sirupy desoxypentoside (LXXIV) gave a feeble green coloration in the Keller-Kiliani test, a reaction generally accepted as being specific for 2-desoxy-sugars. 

Honeyman147 reported the synthesis of methyl 2,3-anhydro-/3-L-lyxopyranoside, and claimed that, on alkaline hydrolysis, this gives a 2 1 ratio of L-xyloside L-arabinoside, but these results could not be substantiated by Buchanan and R. Fletcher,68 who recorded different constants for the epoxide and for the disulfonic ester claimed147 to be the starting material for its synthesis. The same epoxide has been synthesized by Reist and coworkers,160 and its properties are in agreement with Buchanan and Fletcher s results. Ethyl or methyl 3,4-anhydro-/3-L-ribopyranoside undergoes substitution at C-4 in all the reactions thus far studied. Neither half-chair conformation would seem to be clearly favored, but the specificity observed can be rationalized by considering the steric and polar interactions that may arise in the transition state substitution at C-3 in conformation 58 would involve marked interactions between the nucleophile and... 

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