Herstellung von (R,R)‐ oder (S,S)‐2‐Amino‐3‐hydroxycarbonsäuren (allo‐Threonin‐Analoge) durch Acylierung/Reduktion von 2‐t‐Butyl‐3‐methyl‐4‐oxoimidazolidin‐1‐carbonsäure‐t‐butylester (Boc‐BMI)

Blank, Stefan; Seebàch, Dieter

doi:10.1002/jlac.1993199301140

Cited by 21 publications

(3 citation statements)

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“…The complexes can be easily decomposed in MeOH/HCl solution yielding free amino acid using well known procedure . Other commonly used approaches are based on functionalization of natural ( S )‐serine or use the ( S ) enantiomer of the chiral glycine derivative . Both transformations do not involve the α‐carbon stereocenter making only one stereoisomer available.…”

Section: Resultsmentioning

confidence: 99%

Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of Ni^II‐Schiff‐Base Complexes

2019

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A new electrochemical method for stereoselective hydroxyalkylation of glycine in the form of a chiral NiII complex of the Schiff base derived from (S)‐2‐[N‐(N′‐benzylprolyl)amino] benzophenone (GlyNi) is elaborated. The method is technologically simple: galvanostatic electrolysis of GlyNi is performed in a one‐compartment electrochemical cell in an alcohol solution (which serves as a reactant and a solvent simultaneously) in the presence of KOH. High chemical yields of α‐amino‐β‐hydroxy acids (in the form of NiII Schiff base complexes) were obtained for the C1–C3 primary alcohols; for the higher alcohols yields were low. The stereochemical outcome of the process is dependent on the pH of the solution and the reaction time between the end of the electrolysis and the work‐up procedure. Thermodynamically more stable (2R) product (for methanol) and (2R,28S)‐diastereomer (for the homologues) are formed at high pH with high diastereselectivity (de up to 94 %). In the media with low basicity, under kinetic control, the (2S) complex (for methanol) and (2S,28R)‐diastereomer (for higher alcohols) can be obtained (de = 100 %). The correlation between the chemical shift of the H8 proton in the 1H NMR spectra and the configuration of the amino acid α‐stereocenter in the NiII Schiff‐base complexes was established providing a new tool for determination of the absolute configuration of the α‐carbon stereocenter.

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Section: Resultsmentioning

confidence: 99%

Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of Ni^II‐Schiff‐Base Complexes

2019

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“…,Ti [153] Me [153], Bu [153], Ph [153] Me 11531, Bu [153] Me [153] Me [152] Bu [152] Me [179] [258],CH(OH)(C,H,,) [258], CH(Me)Ph [240], CH(Me)CH,NO, 12401, (CH,),Ph [240],CH,CH =CHMe [240]. CH,C(CO,Me)= CH, [240], (CH,),CI [240], (CH,),CI [240] Self-Regeneration of Stereocenters El [82], IPK [82], Bn [82], Et [82].…”

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.

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520

299

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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...

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“…Numerous amino acids, including α-branched ones, have been prepared from Boc-BMI. Only a few examples can be alluded to here: (11) from (S)-(1), EtI, and Br(CH 2 ) 4 Cl; 3 (12) from (S)-(1), 3methylbutanoyl chloride, and Lithium Triethylborohydride; 8 (13) from (R)-(1), butanal, and dibutylcuprate; 12 (14) The method is applicable to the synthesis of amino acids with extremely bulky substituents in the α-position. 4b Chiral Imidazolidinones with Other Substitution Patterns.…”

Section: Alternate Names: N-t-butoxycarbonyl-2-t-butyl-3-methylimid-mentioning

confidence: 99%

t-Butyl 2-t-Butyl-3-methyl-4-oxo-1-imidazolidinecarboxylate

Studer

Seebàch

2001

Encyclopedia of Reagents for Organic Synthesis

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Herstellung von (R,R)‐ oder (S,S)‐2‐Amino‐3‐hydroxycarbonsäuren (allo‐Threonin‐Analoge) durch Acylierung/Reduktion von 2‐t‐Butyl‐3‐methyl‐4‐oxoimidazolidin‐1‐carbonsäure‐t‐butylester (Boc‐BMI)

Cited by 21 publications

References 47 publications

Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of Ni^II‐Schiff‐Base Complexes

Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of Ni^II‐Schiff‐Base Complexes

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

t-Butyl 2-t-Butyl-3-methyl-4-oxo-1-imidazolidinecarboxylate

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Herstellung von (R,R)‐ oder (S,S)‐2‐Amino‐3‐hydroxycarbonsäuren (allo‐Threonin‐Analoge) durch Acylierung/Reduktion von 2‐t‐Butyl‐3‐methyl‐4‐oxoimidazolidin‐1‐carbonsäure‐t‐butylester (Boc‐BMI)

Cited by 21 publications

References 47 publications

Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of NiII‐Schiff‐Base Complexes

Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of NiII‐Schiff‐Base Complexes

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

t-Butyl 2-t-Butyl-3-methyl-4-oxo-1-imidazolidinecarboxylate

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Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of Ni^II‐Schiff‐Base Complexes

Stereoselective Electrosynthesis of β‐Hydroxy‐α‐Amino Acids in the Form of Ni^II‐Schiff‐Base Complexes