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) > 101. One recrystallization of the crude product is sufficient to obtain isomerically and chemically pure (Z)-3.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2218-2220, November, 1995.The authors are grateful to the Dupont company (USA) for financing this study     

Mechanistic studies on the asymmetric alkylation of amino ester enolates using a copper(II)salen catalyst

Hammett data indicate that the asymmetric alkylation of enolates catalysed by copper(II)salen complex 1, proceeds by an asynchronous S(N)2 reaction and that the role of the catalyst is to enhance the nucleophilicity of the enolate.     

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 -methyl substituted amino acids using Ni(II) complexes of the Schiff base obtained from alanine and (S)-2-N-(N'-benzylpropyl)amino-benzaldehyde 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 -Me-Val and -Me-Glu were obtained after decomposing the diastereomerically pure complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1536–1542, July, 1991.     

Asymmetric synthesis of heteroorganic analogs of natural products. 6. (S)-α-amino-ω-phosphonocarboxylic acids

Alkylation, by -haloalkylphosphonates, of the Ni(II) complex of the Schiff base formed from glycine and (S)-2-N-(N¹-benzylprolyl)-o-aminobenzophenone has been used for the asymmetric synthesis of (S)-2-amino-4-phosphonobutyric and (S)-2-amino-5-phosphonovaleric acids.Institute of Bioorganic Chemistry and Oil Chemistry, Ukrainian Academy of Sciences, 250800 Kiev. A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 397–402, February, 1992.     

Asymmetric synthesis of (R)-S-(1,2,4-triazol-3-yl)cysteines by nucleophilic addition of triazolethiols to a NiII complex with a chiral dehydroalanine Schiff base

An efficient method was developed for the asymmetric synthesis of (R)-S-(1,2,4-triazol-3-yl)cysteines by the addition of 3,4-disubstituted 1,2,4-triazole-5-thiols at the electrophilic C=C bond in a Ni^II complex of a Schiff base of dehydroalanine with (S)-N-(N-benzylprolyl)aminobenzophenone. The stereoselectivity of the formation of diastereomeric complexes with the (S,R) configuration under conditions of thermodynamic control of the nucleophilic addition exceeds 94%. Acid treatment of the reaction mixtures afforded enantiomerically pure (R)-S-hetarylcysteines (ee >98%).     

Asymmetric synthesis of heteroorganic analogs of natural compounds. 3. General preparative method of diastereo- and enantioselective synthesis of fluorine-containing 2(R), 3(S)-Β-phenylserines

The diastereo- and enantioselective synthesis of the previously unknown 2(R), 3(S)--phenylserines containing fluorine atoms, the O-CHF₂-, O-CF₃-, and CF₃ groups in the benzene ring, was carried out by alkylation of a Ni(II) complex of a Schiff base of glycine with (S)-2-N-(N'-benzylprolyl)aminobenzophenone by fluorine-substituted benzaldehydes. The factors influencing the stereochemical result of the reactions studied are not the steric characteristics of the substituents in benzaldehydes, but their electronic nature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1166–1175, May, 1991.