✦ LIBER ✦
1,2:5,6-Di-O-isopropylidene-α-D-gulofuranose as a Chiral Auxiliary in the Diastereoselective C Methylation of Ester Enolates. The Influence of the Base on the Stereochemistry of Enolate Formation and Alkylation
✍ Scribed by Mulzer, Johann ;Hiersemann, Martin ;Buschmann, Jürgen ;Luger, Peter
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 551 KB
- Volume
- 1996
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
The C methylation of the carbohydrate‐derived O‐chiral esters 5a‐d to derivatives 8 proceeds with (R) selection of 1:1 to 10:1 and depends primarily on the base used for enolate generation. Lithium 2,2,6,6‐tetramethylpiperide (LTMP) shows the highest and lithium hexamethyldisilazanide (LHMDS) the lowest selection. These results are interpreted in terms of a “post‐enolization complex” involving the lithium amide base.