Journal ArticleDOI
Stereoselective radical addition of carbon-centred radicals to the dehydroalanine moiety of the chiral nickel(II) complex of the Schiff′s base derived from (S)-2-[N-(N′-benzylprolyl)amino]benzophenone and dehydroalanine
R. G. Gasanov,Lubov V. Il'inskaya,Michail A. Misharin,Victor I. Maleev,Nicolai I. Raevski,Nicolai S. Ikonnikov,S. A. Orlova,N. A. Kuz'mina,Yuri N. Belokon +8 more
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In this paper, a new approach to the asymmetric synthesis of β-substituted α-aminopropanoic acids by 2,2′-azoisobutyronitrile (AIBN) and Bu3SnH-initiated radical addition of Etl, PriBr, ButBr, and PhCH2Br to the dehydroalanine moiety of the NiII complex 1 of a Schiff′s base derived from (S)-o-[N-(N′-benzylprolyl)amino]benzophenoneAbstract:
A new approach to the asymmetric synthesis of β-substituted α-aminopropanoic acids by 2,2′-azoisobutyronitrile (AIBN) and Bu3SnH-initiated radical addition of Etl, PriBr, ButBr, and PhCH2Br to the dehydroalanine moiety of the NiII complex 1 of a Schiff′s base derived from (S)-o-[N-(N′-benzylprolyl)amino]benzophenone (BPB) and dehydroalanine is described. The radical addition produced a mixture of diastereoisomeric complexes 4a–d with a 40–90% excess of (S,S)diastereoisomers over the (S,R)-ones, giving the reaction products in almost quantitative yields. The diastereoselectivity of the reaction depended on the size of the entering radicals, the most effective asymmetric induction being achieved for the But radical addition. Enantiomerically pure ‘(S)-2-amino3-(tert-butyl)propanoic acid’[(S)-γ-methylleucine] and the chiral auxiliary BPB were recovered from compound 4d after its decomposition with HCl. The reactivities of the carbon–centred radicals towards the carbon-carbon double bond in the amino acid moiety of the complex 1 was quantitatively established by using ESR spectroscopy in the spin-trap technique.read more
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Free-radical reactions in the synthesis of alpha -amino acids and derivatives
Journal ArticleDOI
Advances in radical conjugate additions
TL;DR: The field of radical conjugate additions, including both intramolecular and intermolecular examples, is reviewed in this paper, where the authors highlight the applications in total synthesis.
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Access to Enantioenriched α-Amino Esters via Rhodium-Catalyzed 1,4-Addition/Enantioselective Protonation
TL;DR: Deuterium labeling experiments revealed an unusual mechanism involving a hydride transfer from the amido substituent to the alpha carbon explaining the high levels of enantioselectivity attained in controlling this alpha chiral center.
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Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 3: Michael addition reactions and miscellaneous transformations
Jose Luis Acena,Alexander E. Sorochinsky,Alexander E. Sorochinsky,Alexander E. Sorochinsky,Vadim A. Soloshonok,Vadim A. Soloshonok +5 more
TL;DR: A chiral auxiliary can be used as a part of nucleophilic glycine Ni(II) complex, Michael acceptor or both, leading to the conditions of matching vs. mismatching stereochemical preferences.
Journal ArticleDOI
Iron-Catalyzed Diastereoselective Synthesis of Unnatural Chiral Amino Acid Derivatives
TL;DR: The protocol uses inexpensive iron salt as the catalyst, readily available 2-phthaloyl acrylamide and alkenes as the starting materials, and phenylsilane as the reductant, and the reactions were performed well in mixed solvent of 1,2-dichloroethane and ethylene glycol at room temperature.
References
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Radical reactions in natural product synthesis
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Asymmetric thermal reactions with oppolzer's camphor sultam
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Photochemistry of metal-metal bonded complexes. II. Photochemistry of rhenium and manganese carbonyl complexes containing a metal-metal bond
Mark S. Wrighton,David S. Ginley +1 more
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Absolute rate constants for reaction of phenyl, 2,2-dimethylvinyl, cyclopropyl, and neopentyl radicals with tri-n-butylstannane. Comparison of the radical trapping abilities of tri-n-butylstannane and -germane
Linda J. Johnston,Janusz Lusztyk,Danial D. M. Wayner,A. N. Abeywickreyma,A. L. J. Beckwith,Juan C. Scaiano,Keith U. Ingold +6 more
TL;DR: Le tributylgermane est un donneur d'hydrogene, considerablement plus pauvre, aux radicaux alkyles que le Tributylstannane as mentioned in this paper.