Penta-O-acetyl

From the rearrangement of tetra-O-acetyl-2-hydroxy-D-galactal in boiling acetic acid it was possible to isolate l,2,4,6-tetra-0-acetyl-2,3-dide-h.ydro-3-deoxy-a-jy-threo-hexose (32) (58%) and a small amount of 1,2,3,4,6-penta-O-acetyl-jS-D-galactopyranose. In the reaction mixture the presence of some a-pentaacetate was demonstrated chromatographically but NMR spectroscopy indicated no resonances corresponding to the / anomer of compound 32. These spectral measurements indicate that compound 32 constituted 80% of the mixture of products. 

Alternatively, penta-O-acetyl-galactose can be converted to the known 2,3,4,6-tetra-O-acetylgalactopyranosyl azide59 which after treatment with sodium methoxide in methanol and subsequent pivaloylation with pivaloyl chloride in pyridine, also furnishes the O-pivaloylated galactosyl azide60. 

Penta-O-acetyl-a/de/iycfo-D-glucose 2,4-Di-0-acetyl-6-0-trityl-D-glucopyranose or a/dehydo-D-glucose pentaacetate... 

C16H22O10S 1,2,3,4,6-Penta-O-acetyl-5-thio-0 -D-ghicopyranose (SD-GLPA)324... 

Scheme 9.—Proposed Mechanism for Formation of Cyclobutanol from the Photolysis of 1,3,4,5,6-Penta-O-acetyl-fceto-L-sorbose (18).

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