No abstract

The synthesis of quinic acid (4) oia epoxide 13, starting from shikimic acid (5), is described (Scheme 1). Treatment of 13 with thiophenol yielded not only 17, but also the y-lactones 18 and 19 as result of migration of silyl groups within a cis-and trans-diol system. The conversion provides a direct stereoselective epoxidation of a shikimic-acid derivative as well as an alternative pathway for the preparation of 4. A shorter approach via the disilylated epoxide 22 was unsuccessful because the y-lactone 25 was obtained in place of the desired ci -hydroxy ester 24 (Scheme 2).

No abstract

We report a n unusual rearrangement of a synthetic epoxychorismic acid derivative which provides access to the 6-substituted shikimic acid framework. Photolysis of the pyruvate ester of dimethyl epoxychorismate triggered a n intramolecular Paterno-Buchi photocyclization of the enol pyruvate alkene and the ketone group of the pyruvate ester, leading to a 2,2,3,34etrasubstituted oxetane ring. Upon standing for 1 week in CDC4 or in the presence of CF~COZD, the primary photoproduct underwent a slow epoxide-opening reaction with participation by the oxetane-substituted carbomethoxy group to form a n unusual fused tetracyclic lactone. The chemistry described here suggests a t least one plausible pathway, with appropriate stereoelectronic constraints, by which oxidation of shikimic acid a t C6 might be achieved.

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