- Preparation of labeled aromatic amino acids: Via late-stage18F-fluorination of chiral nickel and copper complexes
-
A general protocol for the preparation of 18F-labeled AAAs and α-methyl-AAAs applying alcohol-enhanced Cu-mediated radiofluorination of Bpin-substituted chiral complexes using Ni/Cu-BPX templates as double protecting groups is reported. The chiral auxiliaries are easily accessible from commercially available starting materials in a few synthetic steps. The versatility of the method was demonstrated by the high-yielding preparation of a series of [18F]F-AAAs and the successful implementation of the protocol into automated radiosynthesis modules. This journal is
- Craig, Austin,Kolks, Niklas,Urusova, Elizaveta A.,Zischler, Johannes,Brugger, Melanie,Endepols, Heike,Neumaier, Bernd,Zlatopolskiy, Boris D.
-
p. 9505 - 9508
(2020/09/03)
-
- A NOVEL APPLICATION OF THE CHIRAL REAGENT (S)-2-N-(N'-BENZYLPROLYL)-AMINOBENZALDEHYDE: SYNTHESIS OF OPTICALLY PURE α-METHYLVALINE AND α-METHYLGLUTAMIC ACID
-
The synthesis of α-methyl substituted amino acids using Ni(II) complexes of the Schiff base obtained from alanine and (S)-2-N-(N'-benzylpropyl)aminobenzaldehyde is described.This complex was alkylated with isopropyl bromide, gramine iodomethylate, and methyl acrylate (in a Michael reaction).From the resulting mixtures of products, diastereomerically pure complexes were obtained by crystallization or silica gel chromatography.Both (S)- and (R)-enantiomers of the optically active amino acids α-Me-Val and α-MeGlu were obtained after decomposing the diastereomerically pure complexes.
- Belokon, Yu. N.,Motsishkite, S. M.,Tararov, V. I.,Maleev, V. I.
-
p. 1355 - 1360
(2007/10/02)
-
- Asymmetric Synthesis of Threonine and Partial Resolution and Retroracemization of α-Amino Acids via Copper(II) Complexes of Their Schiff Bases with (S)-2-N-(N'-Benzylprolyl)aminobenzaldehyde and (S)-2-N-(N'-Benzylprolyl)aminoacetophenone. Crystal and Molecular Structure of a ...
-
The work described here is concerned with the search for universal chiral reagent for the asymmetric synthesis, resolution, and retroracemization of amino acids.Reaction of N-benzyl-(S)-proline with o-aminobenzaldehyde or o-aminoacetophenone has given (S)-2-N-(N'-benzylprolyl)aminobenzaldehyde ((S)-BPAB) or (S)-2-N-(N'-benzylprolyl)aminoacetophenone ((S)-BPAAPh).These chiral reagents have interacted with α-amino acids (aa) and Cu(II) ions to form complexes CuII and CuII in which Schiff bases (S)-BPAB-aa or (S)-BPAAPh-aa act as tetradentate ligands and coordinate the copper ion by the nitrogen atoms of the pyrrolidine fragment, the deprotonated amide group, and the amino acid fragment and by the oxygen atom of the carboxylate.Such a structure was supported by data on elemental analysis, the molecular weight measurements, and electron, IR, and CD spectra.It was finally confirmed by an X-ray diffraction analysis of CuII.One equivalent of (S)-BPAB has reacted with 2 equiv of (R,S)-aa and 2 equiv of Cu(II), having given preferential formation of copper complexes of Schiff bases with (S)-aa.After their extraction with chloroform the amino acid enriched with the R enantiomer remained in the aqueous solution.In this manner partial resolution of racemic amino acids (Ala, Nva, Phe, Val, Thr) has been carried out with enantiomeric purity 4-50percent. (S)-BPAB or (S)-BPAAPh treatment of a racemic amino acid in the presence of Cu(II) ions (reagents ratio 1:1:1) and CH3O- ions permits enantiomeric enrichment via conversion of the R into S enantiomer (retroracemization).Thus (S)-Ala, (S)-Nva, (S)-Leu, (S)-Val, (S)Phe, and (S)-PhGly of enantiomeric purity 36, 12, 22, 54, 42, and 35percent, respectively, were obtained from racemic samples.CH3O--catalyzed reaction of CuII or CuII with acetaldehyde has given rise to a mixture of diastereomeric complexes, which upon removal of Cu(II) by H2S gave (R)-threonine of 60percent or 97-100percent enantiomeric purity and the threo/allo ratio 6:1 or 19:1, respectively, and permitted recovery of an unchanged initial chiral reagent (S)-BPAB or (S)-BPAAPh.
- Belokon', Yu. N.,Zel'tzer, I. E.,Bakhmutov, V. I.,Saporovskaya, M. B.,Ryzhov, M. G.,et al.
-
p. 2010 - 2017
(2007/10/02)
-
- (S)-o-N-(N-Benzylprolyl)aminobenzaldehyde and (S)-o-N-(N-Benzylprolyl)aminoacetophenone as Reagents for Asymmetric Synthesis of Threonine
-
Chiral aldehydes and ketones, derivatives of proline and piperidine-2-carboxylic acid have been synthesized and their Schiff bases with glycine form copper complexes which were hydroxyethylated with acetaldehyde; decomposition of the complexes obtained gave threonine with an optical purity of up to 97-100percent and with threo/allo ratios of up to 19 : 1, and the chiral reagents can be recovered and reused with no loss of optical purity of the threonine.
- Belokon, Yuuri N.,Zeltzer, Irina E.,Ryzhov, Michail G.,Saporovskaya, Marina B.,Bakhmutov, Vladimir I.,Belikov, Vasili M.
-
p. 180 - 181
(2007/10/02)
-