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Chirality is a key factor in the safety and efficacy of many drug products and, thus, the production of single enantiomers of drug intermediates has become increasingly important in the pharmaceutical industry. There has been an increasing awareness of the enormous potential of microorganisms and enzymes derived therefrom for the transformation of synthetic chemicals with high chemo-, regio- and enantioselectivities. In this article, some selected enzymatic processes are described for the synthesis of chiral intermediates for pharmaceuticals.

Currently, much attention has been focused on the interaction of small molecules with biological macromolecules. The search for selective enzyme inhibitors and receptor agonists or antagonists is o...

Two systems were analyzed that make it possible to reuse enzymes and cofactors in the reductive amination of the lithium salt of 6-(1′,3′-dioxolan-2′-yl)-2-keto-hexanoic acid (compound 1) to 6-(1′,3′-dioxolan-2′-yl)-2S-aminohexanoic acid, lithium salt (compound 2) catalyzed by phenylalanine dehydrogenase (PDH) with in situ NADH regeneration catalyzed by formate dehydrogenase (FDH). First, both enzymes and PEG-NADH, a mass-enlarged cofactor, were encapsulated within semipermeable microcapsules. These microcapsules catalyzed the biotransformation in the absence of external NAD. About 20 mg of compound 2 was formed per mL microcapsule per day. Substrate diffusion into the microcapsules was not rate-limiting. PEG(35,000)—NADH, but not PEG(20,000)—NADH, was retained within the microcapsules. The activity of the encapsulated enzyme was about 15–25% of the activity of the free enzyme. If saturating free NAD was added to microcapsules, the activity increased about threefold. The microcapsules could be reused, and...

Stepped spillways are provided to reduce the size of stilling basins with the view of reducing the overall cost of spillway and energy dissipation device. The characteristics of flow over stepped spillway are still not well known. This paper presents an equation for estimation of energy loss on stepped spillway for skimming flow regime, which is required for economic design of stilling basin. The equation for energy loss is derived by regression analysis utilising the available experimental data from various authors. Expressions for prediction of toe depth and coefficient of friction for stepped spillway are also developed. These would be useful in design of stepped spillways.

The compounds of the type [Cp2Ti(RCOCHCOR') (XCOO)] (where Cp = cyclopentad ieny 1; R = R' = CH3 or (CH3)3C; R = CH3, R' = C6H5; × = Cl2CH or Cl3C have been synthesised In aqueous medium by the reactions of [Cp2Ti (RCOCHCOR')]Cl with the sodium salts of dichloroacetic acid or trichloroacetic acid in 1:1 molar ratio. These products have been characterized on the basis of their elemental analyses, electrical conductance, magnetic measurements, and spectroscopic (IR, 1H NMR and electronic) studies.

Bis(cyclopentadienyl)titanium(IV)mercaptoacetamide derivatives of the type Cp2Ti(MA)Cl and Cp2Ti(MA)2 (Cp = cyclopentadienyl and MAH [dbnd] N-(aryl)-2-mercapto-acetamide; aryl = phenyl, o-tolyl, m-tolyl, p-tolyl or α-naphthyl) have been prepared from the reactions of dichlorobis(cyclopentadienyl)titanium(IV) (Cp2TiCl2) with various mercaptoacetamides in tetrahydrofuran (THF) at room temperature in the presence of triethylamine (Et3N). These new mercaptoacetamide derivatives have been characterized by their elemental analyses, electrical conductance, IR, 1H NMR and electronic spectral data.

The reactions of niobium and tantalum pentaethoxides and pentachlorides with 2-thiophenecarboxylic acid (HTCA) and 2-thiopheneacetic acid (HTAA) were carried out in different stoichiometric ratios. Complexes of the type M (OEt)5-n (L)n (n = 1–3 and M = Nb or Ta) and MC15-n Ln (n = 1 or 2 and M = Nb or Ta) were obtained and characterised on the basis of elemental analyses and spectral (i.r. and 1H n.m.r.) data.

Dichlorobis(cyclopentadienyl)titanium(IV) thio-Schiff base derivatives of the type Cp2Ti(TSB)Cl and Cp2Ti(TSB)2 have been obtained by the reaction of dichlorobis(cyclopentadienyl)titanium(IV), Cp2TiCl2, with bidentate thio-Schiff bases (TSBH) viz., S-methyl-β-N-(phenyl)methylenedithiocarbazate, S-methyl-β-N-(diphenyl)methylenedithiocarbazate, S-methyl-β-N-(phenyl)-ethylenedithiocarbazate, S-methyl-β-N-(cyclopentyl)dithiocarbazate, S-methyl-β-N-(cyclohexyl)dithiocarbazate and with tridentate thio-Schiff bases (TSBH2) viz., S-methyl-β-N-(2-hydroxyphenyl)methylenedithiocarbazate, S-methyl-β-N-(2-hydroxynaphthyl)methylenedithiocarbazate, S-methyl-β-N-(2-hydroxy-5-methylphenyl)ethylenedithiocarbazate, 2-hydroxy-4-methyl-5,6-diazo-7-thiono-8-thionona-2,4-diene and 2-hydroxy-4-phenyl-5,6-diazo-7-thiono-8-thionona-2,4-diene, derivatives of the type Cp2Ti(TSB′) were obtained. The anions of the corresponding bidentate and tridentate thio-Schiff bases are represented as [TSB]− and [TSB′]2-. These new thio-S...

Alkyl thioglycolates of the type Al(OR)G (R = Pri, But); M(OR)2G (M = Ti, Zr; R = Pri, But); MG2 (M = Ti, Zr), Al2G3 and Al(GH)G where GH2 is methyl or ethyl thioglycolate have been prepared. The isopropoxy derivatives were obtained by carrying out the reaction between the isopropoxide of the corresponding metal with methyl or ethyl thioglycolate in anhydrous benzene in different molar ratios, whereas the tertiary butoxy derivatives were prepared from the respective isopropoxy derivatives by alcohol interchange technique. Molecular weights of soluble titanium and zirconium derivatives show them to be dimeric in nature. Structures have been suggested on the basis of infrared spectral and molecular weight studies.

A novel series of complexes, of the type [M(DAPCH)X2(M=Zn(II), Cd(II) or Hg(II); DAPCH =planar pentadentate ligand derived from 2,6-diacetylpyridine and carbohydrazide, X=Cl, Br, I, NO3, CH3COO) have been synthesized and characterized by elemental analyses, conductance measurements and infrared spectral data. The ligand DAPCH appears to behave as a pentadentate ligand, having coordination sites at one pyridine nitrogen, two azomethine nitrogen and two amide oxygen atoms. Possible structures are proposed for these complexes. All the complexes contain terminal hydrazinic nitrogen atoms with an unshared electron pair and may take part in nucleophilic condensations. Therefore, the reactions of these complexes (X=Cl, Br, NO3) with 2,6-diacetylpyridine have also been studied viz., ring closure and formation of macrocyclic ligand complexes. Two types of cyclic products viz., mononuclear [M(L′)X2] and binuclear [M2(L′)X4] (M=Zn(II), Cd(II) or Hg(II); L=macrocyclic ligand derived from DAPCH and 2,6-diacet...

The zirconyl(IV) complex of 2,6-dipicolinoyl dihydrazine (DPH2), [ZrO(DP)(H2O)2] or [Zr(DP)(OH)2(H2O)], and its reactions with β-diketones have been described. The complexes so obtained have been characterised on the basis of elemental analyses, electrical conductance and spectral (infrared and electronic) data. The parent complex [ZrO(DP)(H2O)2] or [Zr(DP)(OH)2(H2O)] reacts with β-diketones to form complexes of the type [ZrO(DPM)(H2O)2] or [ZrO(DPM)(H2O)], where DPM is a macrocyclic ligand derived by the condensation of DPH2 and a β-diketone in the presence of the metal ion. All these complexes are six-coordinated.

The reactions of indium (III) chloride with some bidentate (SBH) and tridentate Schiff bases (SB'H2) such as, salicylideneaniline (SALAH), salicylidene-o-toluidine (o-SALTH), salicylidene-m-toluidine (m-SALTH), salicylidene-p-toluidine (p-SALTH), 2-hydroxyacetophenone-aniline (o-HyAcPhAH), 2-hydroxy-1-naphthylidene-aniline (o-HyNAH), acetylacetone-o-aminophenol (AcAcAmPH2) and benzoylacetone-o-aminophenol (BacAmPH2) have been carried out in 1:1 or 1:2 molar ratios in dry retrahydrofuran in the presence of tsisthylamine under anhydrous conditions. The compounds of the stoichiometry InC12L, InC1L2 and InC1L′ where L =a monobasic bidentate Schiff base and L′ =a dibasic tridentate Schiff base, have been synthesized and characterized by elemental analysis, molecular weight and spectral (infrared and 1Hn.m.r.) studies

Reactions of titanium isopropoxide with bidentate Schiff bases, such as salicylidene-o-toluidine, salicylidene-p-toluidine, 2-hydroxy-1-naphthylidene-o-toluidine, and 2-hydroxy-1-naphthylidene-p-toluidine in different stoichiometric ratios yield Ti(OPri)4-x (SB)x (where x = 1−3 and SB[sbnd] is the anion of the corresponding Schiff base, SBH) type products. These derivatives have been characterized by elemental analyses, and by infrared spectra and molecular weight determinations.

Niobium and tantalum pentaethoxides react with bifunctional tridentate benzoyl hydrazones (BH2) in refluxing benzene to give products of the type M(OEt)5–2n (B)n (where M - Nb or Ta and n = 1 or 2). The complexes have been characterised on the basis of elemental analysis and i.r. and 1Hn.m.r. spectra.

Complexes of ruthenium(III), platinum(IV), rhodium(III), palladium(II) and platinum(II) with 3-(o-hydroxyphenyl)-1,2, 4-triasoline-5-thione (pttH) and 3-(o-hydroxyphenyl)-4-(o-hydroxy-benzylidine)-1,2, 4-triasoline-5-thione (HO-bttH) have been Synthesised aad oharaoterised on the basis of elemental analyses and infrared and electronic spectra and magnetic susceptibility measurements. The pslladium(II) and platinum(II) Complexee are square planar, Whereas ruthenium(III), platinum(IV) and rhodium (III) Complexes possees pseudooctahedral stereo chemistry. Various ligand field and nephelauxetic parameters have been evaluated wherever possible.

Reactions of indium (III) isopropoxide with monobasic thio-Schiff bases, such as S-methyl-β-N-(furfurylmethylene)-dithiocarbazate (TSB1H), S-methyl-β-N-(phenylmethylene)dithio-carbazate (TSB2H), S-methyl-β-N-(phenylethylene)dithiocarbazate (TSB3H), S-methyl-β-N-(diphenylmethylene)dithiocarbazate (TSB4H), S-methyl-β-N-(cyclopentyl)dithiocarbazate (TSB5H), S-methyl-β-N-(cyclohexyl)dithiocarbazate (TSB6H), and dibasic thio-Schiff bases, such as S-methyl-β-N-(2-hydroxyphenylmethylene)dithiocarbazate (TSB1′H2) and S-methyl-β-N-(2-hydroxyphenylethylene)dithiocarbazate (TSB2′H2), have been studied in dry benzene in 1:1, 1:2 or 2:3 molar ratios under anhydrous conditions. The compounds of the type In(OPri)3-nLn, (OPri)InL′ and In2L3′, where L = monobasic thio-Schiff base, L′ = dibasic thio-Schiff base and n = 1, 2, have been synthesized and characterised by elemental analysis, molecular weight and spectral (infrared, 1H NMR and electronic) studies.

Reactions of tantalum pentaethoxide with p-haloarylsubstituted β-diketones as well as 2-thenoyltrifluoroacetone were carried out using different molar ratios. Compounds of the type [Ta(OEt)5-n(L)n], (where L = p-fluoro-, p-chloro-, p-bromobenzoylacetone and 2-thenoyltrifluoroacetone; n = 1, 2 or 3), have been isolated and characterised by elemental analysis, molecular weight determinations and spectral studies like i.r., and 1H n.m.r. Alcoholysis reactions with tertiary butanol were also carried out.

The reactions of hafnium isopropoxide isopropanolate with thio-Schiff bases (derived from the condensation of S-methyldithiocarbazate with aldehydes/ketones) in different molar ratios 1:n (n = 1 to 4) in refluxing benzene have been carried out. The products of the type, Hf(OPri)4-n(TSB)n (n = 1 to 4) and Hf(OPri)4–2n(TSB«)n (n = 1 or 2) ([TSB]− and [TSB«]2- are the anions of mono- and dibasic thio-Schiff bases, respectively) were obtained and characterized on the basis of elemental analyses, electrical conductance measurements and spectral (infrared, electronic and 1H n.m.r.) data.

Antimony trichloride when reacted with carbohydrazide and 1,5-bis(carbohydrazones), yields addition complexes of the type Sb(L)nCl3 (where n = 1,2) and Sb(L′)Cl3 as well as [Sb(L′)2Cl2] Cl (where L = carbohydrazide, L′ = 1,5-bis (carbohydrazones) of 2-hydroxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 2-hydroxyphenylmethylketone and 2,4-dihydroxyphenylmethylketone). These complexes are characterised on the basis of infra-red spectra, electronic spectra and conductivity measurements in addition to elemental analysis. These indicate that the ligands are coordinated to antimony(III) in a bidentate manner.

The mixed ligand uranyl(VI) complexes of pyridine-2,6-dicarboxylic acid (H2PDC) of the type [UO2(PDC) (N-N)], where N-N stands for a bidentate ligand, such as ethylenediamine, 2,2′-bipyridyl, 1,10-phenanthroline, o- and m-phenylenediamines, have been described. The complexes have been characterised on the basis of elemental analysis, electrical conductance and spectral (infrared and electronic) data.

The new chelating ditertiary phosphine (pptpf) forms low spin, diamagnetic, square-planar complexes of the type [M(pptpf)X2] (where M=Ni(II), Pd(II) or Pt(II); X=Cl, Br, I or NCS) when treated with corresponding metal salts. Group VI metal hexacarbonyls also react with the ligand (pptpf) to yield diamagnetic, octahedral complexes of type [M(CO)4(pptpf)] (where M=Cr, Mo or W). These complexes have been characterised on the basis of their elemental analysis, 1H n.m.r., electronic, infrared spectral measurements, electrical conductance and magnetic susceptibilities data. In all the complexes the ligand (pptpf) acts as a chelating ditertiary phosphine.

Interrelations were established, in a limited range of shear rate γ, among the non-Newtonian shear stress relaxation following cessation of steady-state flow σ(γ, t), the steady-flow viscosity η(γ), and the dynamic viscosity η(ω) or the storage modulus G′(ω) for three linear polyethylene melts (190°C). The data for these melts were obtained using the Weissenberg rheogoniometer and the Instron rheometer. Agreement between the experimental σ(γ, t) and those calculated from the relaxation spectrum H(ln τ) was good and involved no coordinate shift. The calculated values were obtained through the relation where θ = γτ/2, τ is the relaxation time, ω is the radian frequency, h(θ) = (2/π)[cot−1 θ + θ(1 - θ2)/(1 + θ2)2], andg(θ) = (2/π) [cot−1 θ + θ)/(1 + θ2)]. The relaxation spectrum was obtained either from the linear viscoelastic data [η(ω)] using the iterative method of Roesler and Twyman or from the nonlinear steady-flow viscosity using the iterative procedure based on the equation