Substitutionen und Additionen an (R)‐2‐tert‐Butyl‐Δ4‐1,3‐oxazolin‐3‐carbonsäure‐methylester

Stucky, G.; Seebàch, Dieter

doi:10.1002/cber.19891221225

Cited by 25 publications

(6 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9). and electrophilic substitution at the C-C double bond by means of lithiation or by direct Vilsmeier formylation (subsequent Wittig olefination produces the electron-rich diene 10) [101,103,140,182,190]. A short review article about 9 has heen published in the Encyclopedia of Reagenis for Organic S,vnthesis [165] this decarboxylation is a simple, easily conducted reaction.…”

Section: Reviewsmentioning

confidence: 99%

“…Top: An acetylenic amino alcohol and a phosphoserine derived from heterocycle 8 [182,195], which is shown in Scheme 16 and derived from serine; an amino diol prepared by addition of the Li threonine derivative from Scheme 16 to acetone, hydrogenation of the double bond, and hydrolysis [140]. Middle: Compounds resulting from addition of dibromocarbene, tetracyanoethylene, and an acyl cyanide to heterocycle 9 ; a product with four neighboring stereogenic centers (two of which are derived from serine) results from hydrogenation of the Diels-Alder adduct of maleic anhydride and diene 10 [192].…”

Section: Reviewsmentioning

confidence: 99%

See 1 more Smart Citation

Self‐Regeneration of Stereocenters (SRS)—Applications, Limitations, and Abandonment of a Synthetic Principle

Seebàch¹,

Sting²,

Hoffmann³

1996

Angew. Chem. Int. Ed. Engl.

Self Cite

520

299

View full text Add to dashboard Cite

In the same manner that the Nasobem, Stiimpke's mythical creature, teaches his child the peculiar way of life of the species Nasobema lyricum, the work of Seebach et al. on the self-regeneration of stereocenters has been governed by a fanciful idea. On the way, many tricks have been learned and much knowledge gained. Finally, they have come back down to earth and find themselves once again in the unimaginative world of enantiomer separation for the synthesis of enantiomerically pure compounds. In order to replace a substituent at a single stereogenic center of a chiral molecule without racemization, a temporary center of chirality is first generated diastereoselectively, the original tetragonal center is then trigonalized by removal of a substituent, a new ligand is introduced, again diastereoselectively, and finally, the temporary center is removed. By means of these four steps (the "Self-Regeneration of Stereocenters", SRS), 2-and 3-amino-, hydroxy-, and sulfanylcarboxylic acids have been successfully alkylated with formation of tertiary carbon centers and without the use of a chiral auxiliary. Use of this methodology has allowed the potential of these inexpensive chiral building blocks to be expanded considerably. This article aims to demonstrate (using, in part, examples from natural product syntheses) that chiral heterocyclic acetals with enamine, enol ether, enolate, dienolate, enoate, radical, and acyliminium functionalities and also those that are potential reactants for Michael additions and pericyclic processes (for example, electron-rich and electronpoor dienophiles and dienes) are now easily accessible, more often than not, in both enantiomeric forms. Stereogenic nitrogen atoms of aziridines, boron atoms of cyclic or linear systems, and stereogenic planes of x-complexes can also be used as the temporary chirality element in other approaches to the realization of the SRS principle. Enantiomerically pure derivatives of, for example, glycine, hydroxy-and sulfanylacetic acid, 3-aminopropanoic acid, and 3-oxocarboxylic acids can be prepared by resolution of racemic mixtures via diastereoisomeric salts or by chromatography on a chiral column. Hence, the extensive reactivity of compounds developed to test the SRS principle and, above all, the outstanding stereoselectivities of the reactions can be put to good use even when no suitable chiral precursor is availabl-ven though this amounts to an abandonment of the principle! The readily available 2-tertbutyl-l,3-imidazolidin-3-one, -0xazolid-in-5-one, -dioxin-3-one, and -hydropyrimidinone (all of which contain a single stereogenic center at the acetal C atom) can thus be used in the preparation of a vast range of 2-amino-and 3-hydroxycarboxylic acids, and no chiral auxiliary has to be removed or regenerated during these procedures. (One example is the synthesis of 4-fluoro-MeBmt, a derivative of the C, amino acid found in cyclosporin.) In the final chapter we will discuss the most useful findings gained from investigations into both the self-regeneration of ste...

show abstract

Section: Reviewsmentioning

confidence: 99%

Section: Reviewsmentioning

confidence: 99%

Self‐Regeneration of Stereocenters (SRS)—Applications, Limitations, and Abandonment of a Synthetic Principle

Seebàch¹,

Sting²,

Hoffmann³

1996

Angew. Chem. Int. Ed. Engl.

Self Cite

520

299

View full text Add to dashboard Cite

show abstract

“…Amino acids have also been used as sources of chirality in the synthesis of (6) and (7). Enantiomerically pure (R)-2-tert-butyl-1,3-oxazoline prepared from serine has been converted to (S)-GABOB in six steps and 23% overall yield [178]. A novel procedure involving the electrochemical oxidation of (S,R)-N-acetyl-4-hydroxyproline (244) in methanol that yields the 2-methoxy derivative (240) as a mixture of diastereoisomers has been reported (Scheme 14.67).…”

Section: B-hydroxy-g-amino Acidsmentioning

confidence: 99%

Synthesis of γ‐Aminobutyric Acid Analogs

Hanrahan

Johnston

2009

Amino Acids, Peptides and Proteins in Organic Chemistry

View full text Add to dashboard Cite

“…Finally, acidic hydrolysis of 486 provided (S)-GABOB 21 in 22% yield (Scheme 122). 191 On the other hand, treatment of commercially available 1,4-oxazin-2-one 479 with DIBAL-H followed by reaction with acetic anhydride gave the corresponding hemiacetal 487a in 84% yield, whereas the reaction of 479 with MeLi or n-BuLi in the presence of CeCl 3 led to hemiacetals 487b,c in 45-73% yield. The reaction of 487a-c with allyltrimethylsilane in the presence of BF 3 AEOEt 2 afforded allyl derivatives 488a-c as a single diastereoisomer.…”

Section: Ab-disubstituted C-amino Acidsmentioning

confidence: 99%