Doubly diastereoselective conjugate addition of homochiral lithium amides to homochiral alpha,beta-unsaturated esters containing cis- and trans-dioxolane units

As part of a long-term goal directed towards the ab initio asymmetric synthesis of unnatural amino sugars, the doubly diastereoselective conjugate addition reactions of the antipodes of lithium N-benzyl-N-(alpha-methylbenzyl) amide to a range of homochiral alpha,beta-unsaturated esters containing ci...

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Published inOrganic & biomolecular chemistry Vol. 7; no. 4; pp. 761 - 776
Main Authors Davies, Stephen G., Durbin, Matthew J., Goddard, Euan C., Kelly, Peter M., Kurosawa, Wataru, Lee, James A., Nicholson, Rebecca L., Price, Paul D., Roberts, Paul M., Russell, Angela J., Scott, Philip M., Smith, Andrew D.
Format Journal Article
LanguageEnglish
Published CAMBRIDGE Royal Soc Chemistry 01.01.2009
Subjects
Amides - chemistry
Amino Acids - chemical synthesis
Chemistry
Chemistry, Organic
Dioxolanes - chemistry
Esters - chemistry
Lithium - chemistry
Physical Sciences
Science & Technology
Stereoisomerism
ASYMMETRIC-SYNTHESIS
ORGANOCOPPER REAGENTS
ACID
DYNAMIC RESOLUTIONS
CONVERSION
PARALLEL KINETIC RESOLUTION
(E)-ALPHA,BETA-UNSATURATED ESTERS
STEREOSELECTIVE-SYNTHESIS
SOLVENT
DIALKYLAMIDES
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Summary:As part of a long-term goal directed towards the ab initio asymmetric synthesis of unnatural amino sugars, the doubly diastereoselective conjugate addition reactions of the antipodes of lithium N-benzyl-N-(alpha-methylbenzyl) amide to a range of homochiral alpha,beta-unsaturated esters containing cis- and trans-dioxolane units was investigated. These reactions resulted in "matching" and "mismatching" effects. In the "matched" cases a single diastereoisomer of the corresponding beta-amino ester (containing three contiguous stereocentres) is produced. Upon conjugate addition to a homochiral alpha,beta-unsaturated ester containing a cis- dioxolane unit, in the "mismatched" case it is the stereocontrol of the substrate which is dominant over that of the lithium amide, whilst upon addition to homochiral alpha,beta-unsaturated esters containing a trans-dioxolane unit the stereocontrol of the homochiral lithium amide is dominant. Hydrogenolytic N-deprotection of the beta-amino ester products of conjugate addition gives access to polyoxygenated beta-amino acid derivatives.
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ISSN:1477-0520
1477-0539
DOI:10.1039/b818298a