Yuri T. Struchkov

General method of diastereo- and enantioselective synthesis of β-hydroxy-α-amino acids by condensation of aldehydes and ketones with glycine

Synthese en particulier de serine, hydroxy-3 valine, hydroxy-2 phenylserine, phenylserine et methylenedioxy-3,4 phenylserine

Novel class of transition metal coordination compounds with macrocyclic organosiloxanolate ligands; their synthesis and crystal structure

Abstract Interaction of sodium organosiloxanolates with transition metal chlorides leads to the formation of a novel class of coordination compounds, polymetallaorganosiloxanolates (PMOS) {SiPh(O)-O} n− n M 1 2 n−x 2+ Na n (M = Mn, Co, Ni, Cu), whose structure is elucidated by an X-ray diffraction study.

Asymmetric aldol reactions of chiral Ni(II)-complex of glycine with aliphatic aldehydes. Stereodivergent synthesis of syn-(2S)- and syn-(2R)-β-alkylserines

Abstract Stereoselectivity of aldol reactions between aliphatic aldehydes and Ni(II)-complex of chiral non-racemic Schiff base of glycine with ( S )- o -[ N -( N -benzylprolyl)amino]benzophenone (BPB) in the presence of excess of MeONa, has been studied as a function of time, reaction conditions and nature of an aldehyde. Two salient features of the reaction, very high pseudokinetic syn -(2 S )-diastereoselectivity, and dependence of thermodynamic syn -(2 R )-diastereoselectivity on the steric bulk of an aldehyde side chain, were disclosed and used for efficient (more than 90% de and ee) asymmetric synthesis of both syn -(2 S ) and syn -(2 R )-3-alkyl substituted serines. Synthetic potential and reliability of this asymmetric method are demonstrated with the large scale (2–20 g) preparation of enantiomerically pure amino acids.

General method for the synthesis of enantiomerically pure β-hydroxy-α-amino acids, containing fluorine atoms in the side chains. Case of stereochemical distinction between methyl and trifluoromethyl groups. X-Ray crystal and molecular structure of the nickel(II) complex of (2S,3S)-2(trifluoromethyl)threonine

The chiral NiII complex 1 of a Schiffs base derived from (S)-o-[N-(N-benzylprolyl)amino] benzophenone (BPB) and glycine was treated with fluoro-substituted aldehydes (aliphatic and aromatic)in MeOH or CHCl3. The addition proceeds with high diastereoselectivity to give, if catalysed by MeONa in MeOH, the corresponding complexes of syn-(2R)-3-fluorophenylserines (84–100% d.e.) and syn-(2S)-fluoroalkylserines (90% d.e.), and, if catalysed by NEt3 or DABCO (MeOH or CHCl3), the corresponding complexes of syn-(2S)-, and anti-(2S)-3-fluorophenylserines and fluoroalkylserines. The second-order asymmetric transformation may be successfully employed to obtain diastereoisomerically pure complexes of anti-(2R)-3-fluorophenylserines. Condensation of trifluoroacetone with complex 1, catalysed by MeONa, gave predominantly (at least >95% d.e.) the diastereoisomeric complex, containing (2S,3S)-β-(trifluoromethyl)threonine, as shown by an X-ray diffraction structural study. Diastereoisomerically and enantiomerically pure fluorine-containing 3-phenyl- and 3-alkyl-serines were obtained from the corresponding diastereoisomerically pure complexes, separated by chromatography or crystallization. The initial chiral auxiliary BPS was recovered (80–98%). The influence of the reactions conditions and the nature of the corresponding fluoro-substituted aldehydes on the diastereoselectivity of the reactions is discussed.

Synthesis and crystal structure of a hexanuclear rhenium cluster complex Cs3K[Re6(μ3-S)6 (μ3-Te0.66S0.34)2(CN)6]. Cationic control over orientation of the cluster anion

Abstract The hexanuclear complex rhenium salt Cs3K[Re6(μ3-S)6(μ3-Te0.66S0.34)2(CN)6] ({Bd1}) has been prepared by the reaction of Re6Te15 with molten KSCN and subsequent treatment with an aqueous solution of CsCl. Its crystal structure has been determined by X-ray structural analysis. The anion has the site symmetry 3 . The Re6 octahedron is coordinated to six μ3-S and two trans mixed μ3-X ligands of the refined composition 66(3)%Te+34(3)%S. In addition there are six almost linear terminal CN ligands in its environment. The Reue5f8Re distances [2.630(2) A] in the Re3 faces capped by the μ3-X ligands are significantly longer than those in the faces capped by the μ3-S ligands [2.615(2) A].

The synthesis and X-ray crystal structure of molybdenum oxomethoxide [MoO(OMe)4]2

MoO(OMe) 4 has been prepared by anodic oxidation of molybdenum metal in anhydrous methanol containing LiCl as an electrolyte. The X-ray single crystal study showed the complex to consist of pseudo-centrosymmetric dimeric molecules, [MoO(OMe) 3 (μ-OMe)] 2 . The general effect of the M(μ-OR) 2 M ring upon the arrangement of bonds with increased multiplicity is discussed in this and related molecules.

Synthesis, resolution and absolute configuration determination of (S)- and (R)-4-formyl-5-hydroxy [2.2]paracyclophane and its application in the asymmetric synthesis of α-amino acids

Racemic (R,S)-4-formyl-5-hydroxy[2.2]paracyclophane (FHPC) was resolved into enantiomers via its Schiffs base with (S)- and (R)-α-phenylethylamine (α-PEAM) and its absolute configuration was determined by an X-ray diffraction structural study. Scalemic FHPC or its derivatives can be used as chiral auxiliaries for the asymmetric synthesis of β-hydroxy-α-amino acids and α-methylphenylalanine with ees ranging mostly from 45 to 98%.

Synthesis of enantio- and diastereo-isomerically pure β- and γ-substituted glutamic acids via glycine condensation with activated olefins

The glycine fragment in the nickel(II) complex formed from the Schiff base of glycine and (S)-o[(N-benzylprolyl)amino]benzophenone undergoes base-catalysed Michael addition in methanol in the presence of MeONa to the activated olefins methyl acrylate, acrylonitrile, methyl methacrylate, acrolein, and methyl trans-cinnamate. Complexes of substituted (S)-glutamic acid or its derivatives were formed in good chemical yields with almost complete diastereoselection at the α-carbon atom of the amino acid moiety. Diastereoselection at the β- and γ-atoms was not significant, but the isomeric complexes could be easily separated chromatographically. Cleavage of the pure diastereo-isomers with aqueous HCl gave, in good yields, optically pure glutamic acids and regenerated the original chiral reagent. The configurations of the amino acid β- and γ-carbon atoms were determined by 1H n.m.r. spectroscopy and crystal structure X-ray analysis of the corresponding original complexes. The addition to acrolein, catalysed by triethylamine in methanol, leads to the 1,4-adduct exclusively. The amino acid thus obtained could be converted into (S)-proline by reduction with NaBH4.

A novel route to the trisilacyclobutane moiety. A possible silene-disilene reaction

Abstract The reaction of (Me 3 Si) 3 SiC(ue5fbO)Ad with a two-fold excess of Et 3 GeLi in THF, gives a 1:2 mixture of: 1,1,2,2-tetra-(trimethylsilyl) -3-trimethylsilyl-3-triethylgermoxy, 4-(1-adamantyl)-trisilacyclobutane ( 4 ) and adamantoyladamantyl-carbinol ( 5 ). The crystal structure of 4 is described and discussed. It is suggested that the trisilacyclobutane skeleton is formed by a cycloaddition reaction between a silene and a disilene.

General method for the asymmetric synthesis of anti-diastereoisomers of β-substituted L-2-aminobutanoic acids via chiral nickel(II) Schiff's base complexes of dehydroaminobutanoic acid. X-Ray crystal and molecular structure of the nickel(II) complex of the Schiff's base from [(benzylprolyl)amino]benzophenone and dehydroaminobutanoic acid

An efficient approach to the asymmetric synthesis of (L)-allo-isomers of β-substituted α-aminobutanoic acid is described. The chiral NiII complex of a Schiffs base derived from (S)-o-[N-(N-benzylprolyl)amino]benzophenone (BBP) and glycine was treated with acetaldehyde in MeOH. The addition proceeds with high diastereoselectivity to give, if catalysed by MeONa, the corresponding complex of (R)-threonine, and, if catalysed by Et3N, the corresponding complex of (S)-allo-threonine. The (R)-threonine complex was converted into the chiral NiII complex of dehydroaminobutanoic acid, and a X-ray diffraction structural study of its major isomer showed that the dehydroaminobutanoic acid moiety was in the E-configuration. The complex, in turn, entered into Michael addition reactions with nucleophiles, including MeOH, EtOH, PhSH, and PhCH2SH. The reaction proceeded with high diastereoselectivity, producing predominantly complexes of the allo-threonine derivatives (d.e. > 90%). Diastereoisomerically and enantiomerically pure α-amino acids were obtained after chromatographic purification, decomposition of the complexes, and recovery of the initial chiral auxiliary, BBP. The thiol addition reaction is accompanied by a side reaction leading to the formation of sizeable amounts of the vinylglycine complex. An approach to the synthesis of optically active vinylglycine starting with racemic methionine is described.