Synthèse totale des acides (+) et (–) nonactique à partir de carbohydrates

1981 ◽  
Vol 59 (3) ◽  
pp. 572-583 ◽  
Author(s):  
Robert E. Ireland ◽  
Jean-Paul Vevert
Keyword(s):  
Carbon Atom ◽  
Absolute Configuration ◽  
Claisen Rearrangement ◽  
Sigmatropic Rearrangement ◽  
Chiral Carbon ◽  
Ketene Acetal ◽  
Boat Form ◽  
Aliphatic Esters ◽  
Ketene Acetals

The synthesis of (−) and (+) nonactic acids (2a) and (2b) has been achieved starting from D-mannose (7) and D-gluono-γ-lactone (22) respectively. The key step in the synthesis is the [3,3]-sigmatropic rearrangement of the silylated ketene-acetals IV leading to control of the C-2 configuration of nonactic acid. The ketene-acetals were prepared from aliphatic esters of furanoid-glycals II, which were prepared in ten steps from the carbohydrate precursor. The chiral sites of the glycals arise from the corresponding centres in the starting monosaccharide. This type of ketene-acetal Claisen rearrangement leads to products containing the aldol portion required. At the same time knowledge of the absolute configuration of the chiral carbon atom of nonactic acid allows for the determination of the chair or boat form of the transition state of the [3,3]-sigmatropic rearrangement. [Journal translation]

scholarly journals Stereoselective free radical phenylsulfenylation of a nonactivated δ-carbon atom

2004 ◽  
Vol 69 (10) ◽  
pp. 737-747 ◽  
Author(s):  
Goran Petrovic ◽  
Radomir Saicic ◽  
Ljiljana Dosen-Micovic ◽  
Zivorad Cekovic
Keyword(s):  
Free Radical ◽  
Carbon Atom ◽  
Transition State ◽  
Ab Initio ◽  
Absolute Configuration ◽  
Optical Purity ◽  
Methyl Group ◽  
Chiral Carbon ◽  
The Difference ◽  
High Stereoselectivity

A stereoselective free radical introduction of a phenylthio group onto a nonactivated methyl group in the ?-position, adjacent to a prochiral carbon atom, was achieved by photolysis of (-)-menthyl benzenesulfenate in the presence of hexabutylditin and (1R, 3R, 4S, 8S)-9-phenylthiomenthol (4) was obtained with 91%optical purity. High stereoselectivity of the reaction was calculated (ab initio MP2/6-31G**) to be the consequence of the difference in the transition state eneregies (??G# = 5.08 kJ/mol) favouring 4 relative to (1R,3R,4S,8R)-9-phenylthiomenthol (5). The absolute configuration of a the new chiral carbon atom was confirmed by its correlation with the corresponding menthane-3,9-diol of known stereochemistry.

The generation of C-glycosides through the enolate Claisen rearrangement

1979 ◽  
Vol 57 (13) ◽  
pp. 1743-1745 ◽  
Author(s):  
Robert E. Ireland ◽  
Craig S. Wilcox ◽  
Suvit Thaisrivongs ◽  
Noel R. Vanier
Keyword(s):  
Carboxylic Acids ◽  
Claisen Rearrangement ◽  
Sigmatropic Rearrangements ◽  
Unsaturated Carboxylic Acids ◽  
Aliphatic Esters ◽  
Ketene Acetals ◽  
Silyl Ketene Acetals

The [3,3]-sigmatropic rearrangements of silyl ketene acetals obtained from aliphatic esters of furanoid and pyranoid glycals is described. The heterocyclic γ,δ-unsaturated carboxylic acids II are produced in good yields. A new preparation of furanoid and pyranoid glycals is described.

scholarly journals Rapid Organocatalytic Chirality Analysis of Amines, Amino Acids, Alcohols, Amino Alcohols and Diols with Achiral Iso(thio)cyanate Probes

2021 ◽  
Author(s):  
Eryn Nelson ◽  
Jeffrey S. S. K. Formen ◽  
Christian Wolf
Keyword(s):  
Amino Acids ◽  
Absolute Configuration ◽  
Rapid Determination ◽  
Amino Alcohols ◽  
Enantioselective Synthesis ◽  
Widespread Occurrence ◽  
Chiral Compounds ◽  
New Methods ◽  
The Absolute

The widespread occurrence and significance of chiral compounds does not only require new methods for their enantioselective synthesis but also efficient tools that allow rapid determination of the absolute configuration,...

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