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An alternative synthesis of methyl 2,3-anhydro-4,6-O-benzylidene-α-d-allopyranoside using carbonate esters

✍ Scribed by Harry W.C. Raaijmakers; Binne Zwanenburg; Gordon J.F. Chittenden

Publisher
Elsevier Science
Year
1993
Tongue
English
Weight
583 KB
Volume
238
Category
Article
ISSN
0008-6215

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✦ Synopsis

New simple routes to the title epoxide, using carbonate esters of methyl 4,6-O-benzyiidenea-D-glucopyranoside, are described. Some mechanistic aspects of the reactions are discussed.

Sugar epoxides (oxiranes) are of considerable practical importance'-4. They are usually prepared from sulfonic esters, with unsubstituted or esterified vicinal hydroxyl groups, by treatment with alkali. Methanesulfonic or toluene-p-sulfonic esters are co~on~y employed. Nitric esters behave similarly but are preparatively unattractive. The mechanism and stereochemistry of this process has been discussed comprehensively 3*4.

Alternative syntheses of limited application include treatment of deoxyhalo sugars with alkali3y4, nitrous acid deamination of amino sugars3T4, the treatment of certain diols with t~phenylphosph~e~diethyl azodicarboxylate (DEAD15, the reaction of unsaturated derivatives with peroxy acids or hydrogen peroxide3", and the treatment of some c&-diols with Viehe's salt6.

The chemistry of sugar oxiranes has been reviewed1*2*4. An efficient alternative synthesis of the anhydro-alloside derivative 1 resulted during recent attempts to prepare the cyclic carbonate 2 from the glue&de 3, by base-catalysed ester-exchange with diethyl carbonate. Details of this study and some associated aspects are reported.

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## Abstract Die Methyl‐4,6‐__O__‐benzyliden‐2,3‐di‐__O__‐methylhexopyranoside mit D‐__gluco__‐ (**1**), D‐__altro__‐ (**3**) und D‐__allo__‐Konfiguration (**4**) reagieren mit n‐Butyllithium unter Methanol‐Eliminierung zu Methyl‐4,6‐__O__‐benzyliden‐3‐desoxy‐2‐__O__‐methyl‐α‐D‐__erythro__‐hex‐2‐eno