D tetrabenzoate

Another question concerns the effect of solvent polarity on the conformational equilibrium. The results in Table XIII show for / -D-xylo-pyranose tetrabenzoate (which is approximately a 1 1 mixture of chair conformers in chloroform) that changes in the solvent polarity over a... 

Very efficient reaction occurs when phenyl 1 -thio-/ -D-glucopyranoside and -D-galactopyranoside tetrabenzoates (94 and 95) are treated in refluxing carbon tetrachloride with JV-bromosuccinimide under a heat lamp, and, within 15 minutes, they are converted into products from which the enones 96 and 97 have been obtained by direct crystallization in 76 and 83% yield, respectively (see Scheme 15).20... 

Brigl and Muhlschlegel148 were able to isolate 3,4,5,6-tetra-O-benzoyl-D-glucose diethyl thioacetal from the thioacetal and benzoyl chloride in an aqueous solution of alkali. When the reaction is carried out in pyridine, both the tetra- and the penta-benzoate are obtained. The tetrabenzoate has been described as a convenient intermediate for the synthesis of 2-0-methyl-n-glucose and its derivatives.149 It is somewhat surprising that position 2 should exhibit this resistance to benzoylation, since preferential methylation occurs in this position. A benzoyl migration could possibly explain the anomalous observations. 

Catalytic hydrogenation of LXVI in the presence of Raney nickel and calcium hydroxide afforded methyl 2-desoxy-/3-D-riboside (LXVII). This on hydrolysis with dilute acetic acid yielded 2-desoxy-D-ribose, which was isolated as the aniline 2-desoxy-D-riboside. Likewise dehalo-genation of LXV gave methyl 3-desoxy-/3-D-riboside (LXVIII). The position of the desoxy group in LXVIII was established by hydrolyzing it and hydrogenating the product. The resultant desoxypentitol and its tetrabenzoate were both optically inactive, indicating that the... 

There is abundant information to support the contention that the lower-melting monoisopropylidene-mannitol (m. p. 85°) is the 3,4-derivative. For example, its tetrabenzoate is identical with that obtained by acetonation of 1,2,5,6-tetrabenzoyl-mannitol,11498 the structure of which is based on independent evidence.114 The larger fragment resulting from the oxidative scission of the D-enantiomorph of the isopropylidene-man-nitol with lead tetraacetate is 2,3-isopropylidene-D-//treo-dihydroxy-succinic dialdehyde, characterized by its subsequent conversion into D-i/ireo-tartaric acid.126 When methylated and hydrolyzed, the L-enantio-morph of the monoketal affords a tetramethyl-mannitol, which, in turn, yields dimethyl-L-glyceraldehyde with lead tetraacetate.127 Each of these facts is in itself proof that the acetone residue occupies the 3,4-position in the mannitol molecule. 

The benzoylated D-ribopyranosyl halides appear to be considerably more stable than their acetyl analogs and tribenzoyl-/3-D-ribopyranosyl bromide (XXXIX), obtained in crystalline form through the action of hydrogen bromide on /3-D-ribopyranose tetrabenzoate (XLI) in glacial... 

The reaction of /3-D-ribopyranose tetrabenzoate with hydrogen bromide in glacial acetic acid solution has recently been reinvestigated by Ness, Fletcher and Hudson111 and a new, crystalline tribenzoyl-D-ribopyranosyl bromide, isomeric with that previously known, obtained in 5% yield. In contrast to the major product of the reaction, the new halide proved to have a dextrorotation of [a]20D + 78° in chloroform and, since it reacted readily with methanol to give methyl 0-D-ribo-pyranoside tribenzoate (XLII), it was concluded that it is tribenzoyl-... 

The division of the total computer-memory into sections allows the contents of one section to be added to or subtracted from those of another. This technique may sometimes be used to obtain the spectrum of one component of a mixture by subtraction of the spectrum due to other components from that of the mixture. For example, a 100-MHz spectrum of a-D-ribopyranose tetrabenzoate (1) has been... 

In an extension of the work, treatment of 2-deoxy-/M)- /- /vw -hexopyranose tetraacetate with anhydrous HF yielded a major proportion of 3,4,6-tri-0-acetyl-2-deoxy-a-D-arabmo-hexopyranosyl fluoride, with some of the /i-anomer. However, a similar reaction of 2-deoxy-/ -D-arabmo-hexopyranose tetrabenzoate afforded exclusively 3,4,6-tri-0-benzoyl-2-deoxy-z-D- rai>/n -hexopyranosyl fluoride. The oc anomeric configuration of the major products followed from the large values (38.0-38.3 Hz) of the Fj a coupling constants, the F,. H2c couplings being much smaller (5.0-5.3 Hz). 

The benzoates are more resistant to acid hydrolysis than are the corresponding acetates, but by boiling with hydrochloric acid in acetone the amine radical is removed, giving good yields of n-glucose 2,3,4,6-tetrabenzoate, D-mannose 2,3,4,6-tetrabenzoate, D-xylose 2,3,4-tribenzoate, and D-frue-tose 1,3,4,6-tetrabeiizoate, compounds of known structure, previously prepared and characterized. ... 

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