T. F. Savel'eva

A simple stereochemical model of pyridoxal-dependent aldolase: Asymmetric conversions of the amino acid fragment in chiral complexes of potassium a and Δ bis-/n-salicylideneaminoacidato/cobaltate(III)

Abstract Several chiral Co 3+ complexes with Schiff bases of amino acids glycine ( 1 ), valine ( 3 ), threonine ( 6 ), and salicylaldehyde or 3-methylsalicylaldehyde of the same amino acids ( 2 , 4 and 5 ) have been synthesized. Diastereomers ( a and b ) of compounds 3 – 6 were separated on Al 2 O 3 and enantiomers ( a and b ) of compounds 1 and 2 were resolved with brucine and strychnine. The structures of the obtained compounds were determined by elemental analysis, UV, PMR and ORD spectra. The Δ-absolute configuration of 5a was established by X-ray structural analysis. On this basis the Δ-absolute configuration was assigned to all a isomers and the Δ-absolute configuration to all b isomers. Kinetics and stereochemistry of α-proton exchange of the amino acid fragment in 1 – 4 was studied. Exchange of both protons of the glycine fragment in 1 proceeds with approximately the same rate, while the exchange of the α-protons in 2 proceed with different rates. The k R ex /k S ex ratio was experimentally established to be approximately 10.

ON THE MECHANISM OF THE FE(CO)5-CATALYZED KHARASCH REACTION. 2. REINVESTIGATION OF STEREOCHEMISTRY OF BRCCL3 ADDITION TO METHYL N-ACRYLOYL-(S)-PROLINA TE

Addition of BrCCl3 to methylN-acryloyl-(S)-prolinate (1) catalyzed by Fe(CO)5 or Fe(CO)5-PPh3 at 75–80 °C in benzene solution affords in good total yield methylN-((S)-2-bromo-3,3,3-trichlorobutyryl)-(S)-prolinate (2) and methylN-((R)-2-bromo-3,3,3-trichlorobutyryl)-(S)-prolinate (3) in an ∼1.5 : 1 ratio, which does not depend on the catalytic system employed or its concentration. Catalysis by the Fe(CO)5-PPh3 system substantially increases the adducts yield.

Preparative asymmetric synthesis of (R)- and (S)-α-methylserine Ni(II) complex with a Schiff base of α-alanine and (S)-2-[(N-benzylprolyl)amino]benzophenone

The kinetic and thermodynamic diastereoselectivity of the hydroxymethylation of the alanine fragment in the Ni(II) complex of the Schiff base of alanine and (S)-2-[(N-benzylprolyl)amino]benzophenone (BBP) was studied. Optically pure (R)- and (S)-α-methylserines were synthesized.

Asymmetric synthesis of threonine and allo-threonine via stereochemically inert dissymmetric complexes of cobalt(III)

The glycine fragments of the optically active cobalt(III) complexes (Ia and b), and (IIIa and b) condense with acetaldehyde in water at pH 11, and decomposition of the resulting complexes gives a mixture of asymmetric theorine and allo-threonine

Stereospecific radical addition of isopropanol andn-butanal to (5R)-(l-menthyloxy)furan-2(5H)-one

The radical addition of PriOH andn-butanal to (5R)-5-(l-menthyloxy)furan-2(5H)-one occurs regio- and diastereospecifically at position 4 of the furanone ring.

Convenient preparative method for synthesis of methyl (Z)-3-aryl-2-(carbobenzoxyamino)acrylates by Wittig—Horner reaction with the use of Et3N as a base

The Wittig—Horner reaction of CbzNHCH(CO2Me)P(O)(OMe)2 (1) with ArCHO (2) in the presence of Et3N as a base affords methyl (Z)-3-aryl-2-(carbobenzoxyamino)acrylates (3) with high degrees of diastereoselectivity (Z)/(E) > 10∶∶1. One recrystallization of the crude product is sufficient to obtain isomerically and chemically pure (Z)-3.

Asymmetric synthesis of aspartic and α-methylaspartic acids via Ni(II) complexes with schiff bases of glycine and alanine and chiral carbonyl-containing reagents

We propose a method for the synthesis of aspartic and α-methylaspartic acids by alkylation with ethyl bromoacetate of the α-carbon atom of the amino acid moiety in Ni(II) complexes of Schiff bases of glycine with (S)-2-[(N-benzylprolyl)amino]benzophenone and alanine with (S)-2-[(N-benzylprolyl)amino]-benzaldehyde, respectively. Attempts to synthesize α-methylaspartic acid by oxidative cleavage of the C=C bond to a COOH group in the complex of the Schiff base of α-allylalanine with (S)-2-[(N-benzylprolyl)amino]benzophenone were unsuccessful.

Synthesis of optically active amino acids during asymmetric phase-transfer catalysis

ConclusionsAsymmetric alkylation of the amino acid fragment of Ni2+ complexes of the Schiff bases of glycine with N-(2-pyridinecarbonyl)-o-aminobenzophenone and of alanine with N-(2-pyridinecarbonyl)-o-aminobenzaldehyde has been carried out under phase-transfer conditions using N-benzylcinchonidinium chloride as the chiral phase-transfer catalyst.

Asymmetric synthesis of glutamic acid from sodium bis[N-salicylideneglycinato]cobaltate(III) and sodium bis[N-3-methylsalicylideneglycinato]cobaltate(III)

The reaction of potassium Δ-bis[N-salicylideneglycinato]cobaltate (III) and potassium Λ-bis[N-3-methylsalicylideneglycinato]cobaltate (III) with methyl acrylate in water at pH 11.4 gives a mixture of diastereomeric complexes, and electrochemical reduction of which gives S-glutamic acid in asymmetric yields ranging from 10 to 46%, and a chemical yield that is close to 100% when based on reacted glycine.

Amino acids as CH acids. 15. The effect of a second asymmetric amino-acid center in potassium λ- and δ-[N-salicylideneglycinato-N-salicylidene-S-valinato] cobaltates(III) on the kinetic and thermodynamic stereoselectivity in asymmetric threonine synthesis

1. The presence of a neighboring valine fragment in the potassium Λ- and Δ-[N-salicylideneglycinato-N-salicylidene-S-valinato] cobaltates (III), compounds (I) and (II), reduces the CH-acidity of the glycine fragment, and the rate of C-C bond formation, as compared with sodium bis[N-salicylideneglycinato]cobaltate(III). 2. The chiral center of the valine fragments of (I) and (II) exerts a stereochemical effect on the kinetics and thermodynamic steroselectivity of C-C bond formation between the complexes valine fragments and the acetaldehyde.