Enolate ions, preparation conjugate addition

In a formal sense, the reaction of ascorbic acid (11) with various electrophiles may also be regarded as an intramolecular conjugate addition with subsequent alkylation of the intermediate enolate ion. For example, the reaction of 11 with ( )-2-methyl-2-butenenitrile afforded the natural product piptosidin (12), together with its di-epimer 1351. In a quite similar fashion, leucodrin (14) and delesserin (15) were prepared from the corresponding benzyl alcohols52. 

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