Stereoselective Epoxidation and Bromoalkoxylation with 3-Ylidenepyrazine-2,5-diones

Abstract

3-Ylidenepyrazine-2,5-diones 1 were stereoselectively epoxidsed by dimethyldioxirane giving access to spirooxiranes 2 and diols 3. Bromohydroxylation and bromoalkoxylation of 3-ylidenepyrazine-2,5-diones 1 produced high yields of optically active 3-(1-bromoalkyl)pyrazine-2,5-diones 4 with a 3-hydroxy or 3-alkoxy function, respectively. Whereas direct hydrogenation of epoxides 2 afforded epimeric mixtures of 3-(1-hydroxyalkyl)pyrazine-2,5-diones 5 and 6, the highly stereoselective transformation into 5 was possible by primary acid cleavage of the oxirane ring followed by hydrogenation of the resulting keto-enol mixtures 7/8.

Key words

epoxidation - pyrazine-2,5-diones - hydrogenations - amino acid derivatives

References

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Complete crystallographic data (excluding structure factors) have been deposited at the Cambridge Crystallographic Data Centre under the number CCDC-187708. Copies can be obtained free of charge from CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: Int. [phone]; e-mail: [e-mail]].