Deacylation debenzoylation

Benzoates. The selective debenzoylation of sucrose octabenzoate [2425-84-5] using isopropylamine in the absence of solvents caused deacylation in the furanose ring to give 2,3,4,6,1/3/6 -hepta- and 2,3,4,6,1/6 -hexa-O-benzoyl-sucroses in 24.1 and 25.4% after 21 and 80 hours, respectively (54). The unambiguous assignment of partially benzoylated sucrose derivatives was accompHshed by specific isotopic labeling techniques (54). Identification of any benzoylated sucrose derivative can thus be achieved by comparison of its C-nmr carbonyl carbon resonances with those of the assigned octabenzoate derivative after benzoylation with 10 atom % benzoyl—carbonyl chloride in pyridine. 

A nucleoside derivative of 4-acetamido-4-deoxy-D-xyIofuranose was synthesized by a series of reactions. Partial benzoylation of methyl )8-L-arabinopyranoside produces " methyl 2,3-di-0-benzoyl-j3-L-arabinopyranoside. p-Toluenesulfonylation at 0-4, followed by displacement with sodium azide, gives methyl 4-azido-2,3-di-0-benzoyl-4-deoxy-a-D-xylopyranoside. Hydrogenation, debenzoylation, N-acetylation, and acetolysis yield 4-acetamido-l,2,3,5-tetra-0-acetyl-4-deoxy-D-xylofuranose (D-enantiomorph of 191), which reacts in the presence of titanium tetrachloride in chloroform with chloromercuri-(6-benzoyladenine), giving, after deacylation, 9-(4-acetamido-4-deoxy-)8-D-xylofuranosyl)adenine. ... 

With the exception of the Fischer reaction, the general methods employed for the formation of the glycoside bond result in the formation of glycoside acetates (or benzoates). Deacylation is accomplished by treatment with alkali, to which the glycoside bond is stable, unless the bond approximates to the ester type. The original method of deacetylation was by quantitative saponification with sodium hydroxide, potassium hydroxide, or barium hydroxide. It was noted, however, that, in anhydrous media, much less than the theoretical amount of alkali was required, and the reaction has since been made entirely catalyt.ic, with considerable gain in efficiency and convenience. The same methods have been employed for debenzoylation. 

Two studies to date have reported on modifications at both the C-2 and the C-4 positions. In the first of these the taxol isomer with a benzoate at C-4 and an acetate at C-2 was prepared. The 4-deacyl compound 4.3.1.7 was benzoylated at C-4 and then converted to its 2-debenzoyl derivative by reduction with Red-Al. Acetylation at C-2 and side chain attachment completed the synthesis of the analog 4.3.2.9. The product was found to be completely inactive in both tubulin-assembly and cytotoxicity assays (793). 

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