Methyl uronate, crystal structure

Acetolysis of methyl (methyl 4-0-methyl- -D-glucopyranosid)uronate with acetic acid and a Lewis acid (e.g., BF3.0Et2, AIQ3) gave the acylal (17) in almost quantitative yield. When sulphuric acid was used as catalyst, a number of intermediates such as the mixed acetals (18) could be isolated. The x-ray crystal structure of (f )-(18) is referred to in Chapter 22. 

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