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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
Author(s) -
Mulzer Johann,
Hiersemann Martin,
Buschmann Jürgen,
Luger Peter
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960502
Subject(s) - chemistry , lithium (medication) , base (topology) , methylation , keto–enol tautomerism , amide , lithium amide , stereochemistry , medicinal chemistry , organic chemistry , enantioselective synthesis , tautomer , biochemistry , catalysis , gene , medicine , mathematical analysis , mathematics , endocrinology
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.