Glucose with benzaldehyde

Other procedures frequently adopted involve periodate oxidation of a suitable acetal derivative,63 and borohydride reduction of acetals of lactones.64 It has also proved feasible to interchange acetals by means of acid catalysis55,56 thus, reaction of a 1,2-O-isopropylidene derivative of D-glucose with benzaldehyde and sulfuric acid afforded the corresponding 1,2-O-benzylidene derivative. 

Dehydration [1, 303, after formula (5)]. 4,6-O-Benzylidenc-D-glucose, a cyclic acetal, was introduced by Zervas348 in 1931 and has proved a valuable intermediate in a variety of carbohydrate syntheses. The compound had been prepared previously by reaction of D-glucose with benzaldehyde in suspension with fused zinc chloride in yield of only 42%.34b In a new procedure by Boffi34c the intermolecular dehydration... 

Acetalation. As polyhydroxy compounds, carbohydrates react with aldehydes and ketones to form cycHc acetals (1,13). Examples are the reaction of D-glucose with acetone and a protic or Lewis acid catalyst to form l,2 5,6-di-0-isoprop5lidene-a-D-glucofuranose [582-52-5] and its reaction with benzaldehyde to form 4,6-0-benzyhdene-D-glucopyranose [25152-90-3]. The 4,6-0-(l-carboxyethyhdine) group (related to pymvic acid) occurs naturally in some polysaccharides. 

Partially methylated derivatives of D-glucosone have been prepared by decomposition of the corresponding partially methylated phenylosazones with p-nitrobenzaldehyde osones have been obtained from 5-0-methyl-D-glucose phenylosazone and from 3,4,5-tri-O-methyl-D-glucose phenylosazone in this way.22 Although 6-0-methyl-D-glucose phenylosazone is not altered by heating with benzaldehyde or piperonal in aqueous ethanolic... 

The 4- and 6-OH groups of glucose reacted with benzaldehyde to form the acetal. 

The preparation of methyl 4,6-0-benzylidene-a- and 8-D-glucopyrano-sides by heating benzaldehyde and n-glucose with sodium sulfate at 145° was originally reported by Alberda van Ekenstein and Blanksma. Two isomeric forms of the a-n anomer were described by Irvine and Scott, but their claims have not been convincingly established. Good yields of these compounds have also been obtained by using zinc chloride as a catalyst. 

Agarwal with co-workers [48] mentioned that the rate of phenylacetyl carbinol formation from glucose and benzaldehyde in a 5. cerevisiae catalyzing reaction decreased gradually with time. This study, determining the optimum benzaldehyde concentration, showed that beyond a concentration of 16 mM the rate of benzaldehyde to phenylacetyl carbinol conversion decreased. The process was completely inhibited at benzaldehyde concentrations beyond 20 mM. It was suggested that benzaldehyde concentration be maintained within the range 4-16 mM for maximum rates of conversion. 

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