Combinatorial solid-phase synthesis of 6-hydroxy-1,2,3,4-tetrahydro-beta-carbolines from l-5-hydroxytryptophan

A library of biologically relevant 6-hydroxy-tetrahydro-beta-carbolines (6-OH-THBCs) based on the L-5-OH-tryptophan scaffold was prepared. A solid-phase synthesis was developed, utilizing aminomethyl polystyrene resin and solid-phase-optimized reactions, such as Pictet-Spengler condensation. The library was designed such that three points of diversity would be readily introduced, making the strategy potentially suitable for generation of a large number of compounds.     

Amperometric Glucose Determination by Means of Glucose Oxidase Immobilized on a Cellulose Acetate Film: Dependence on the Immobilization Procedures

Glucose microelectrodes were prepared by immobilizing glucose oxidase onto a cellulose acetate film coating a platinum wire. Hexamethylenediamine (HMDA) and Glutaraldehyde (GA) were employed as spacer and coupling agent, respectively. Sensitivities and linear response ranges were studied as a function of the relative amounts of HMDA and GA. The best sensitivity was found when HMDA and GA were 5% and 2.5% in aqueous solutions, respectively. Taking as a reference the functioning of this biosensor, the roles of HMDA and GA percentages appear to be opposed when the extension of the linear response range is considered. Indeed, an increase of one unit in HMDA percentage (from 5 to 6 %) induces an increase in the extension of the linear response range equal to that obtained with a decrease of one unit of GA percentage (from 2.5 to 1.5%).     

Notiz über mikrobiologische Umsetzungen mit Halobacterium halobium: Reduktion von 3-Oxobutansäure-ethylester und Hydrolyse von 3-Hydroxybutansäure-ethylester. Cooperative Effekte von Reduktase und Hydrolase

Note on Biotransformations with Halobacterium halobium: Reduction of Ethyl 3-Oxobutanoate and Hydrolysis of Ethyl 3-Hydroxybutanoate. Cooperative Effects of Reductase and Hydrolase The archaebacterium Halobacterium halobium, growing in saturated NaCl solution, is tested for its ability to achieve biotransformations. We found that this microorganism does accept only a small variety of compounds as substrates. Ethyl acetoacetate ( 1 ) is reduced to ethyl (S)-3-hydroxybutanoate ( 2 ) of optical purity of 40–76%, but in low chemical yields. The reduction is accompanied by hydrolysis of the hydroxy-ester to 3-hydroxybutanoic acid ( 3 ). Hydrolysis of rac-ester 2 by Halobacterium halobium gives (R)- 2 of optical purity of up to 88%, depending upon reaction time, together with the almost racemic hydroxy-acid 3 , both in low chemical yields. Hopes that the ‘extremist’ Halobacterium halobium would be able to effect unique conversions were not fulfilled.     

Interconversion of the thiazine and thiazolidine system of β-lactam antibiotics,electrochemical cleavage of kamiya's disulphide promoted by bromide ion

A new transformation of Kamiya's disulphide ($\text{1}$) into the bromopenam derivative ($\text{4}$) has been carried out by electrolyzing the disulphide ($\text{1}$) in protic solvents in the presence of Me₄NBr. The transformation occurs through an intermediate episulphonium-bromide ion pair in which the bromide appears to tightly linked to the sulphur.     

Photochemical reactions. 145th Communication. Carbonyl vs. epoxyketone photochemistry: Photolysis of 1,2;3,4-diepoxy-2,6,6-trimethyl-1-cyclohexyl methyl ketone

The synthesis and photolysis of the title compound 3 is described. Irradiation (λ > 280 nm, MeCN) of the di-epoxyketone 3 leads predominantly to γ–H abstraction. Cyclization furnishes the cyclobutanols 22 – 24 , while cleavage gives compound 25 , presumably via the allene-oxide intermediate 36 . Further, products 27 and 28 are formed by Norrish fragmentation and by initial cleavage of the C(α)? O bond of the oxirane, respectively. The structures of the products 22 – 25 , 27 , and 28 were assigned on the basis of the spectral data of the photolysis products of the ¹³C-labelled diepoxyketone[6,6-dimethyl-¹³C₂]- 3 and by X-ray analysis of the compounds 24 and 35 , the latter being the p-nitrobenzoate of 22 .     

First-transition-metal complexes containing the ligands 6-amino-6-methylperhydro-1,4-diazepine (AAZ) and a new functionalized derivative: can AAZ act as a mimetic ligand for 1,4,7-triazacyclononane?

The structure and physicochemistry of the [Ni(II)(AAZ)(2)](ClO(4))(2) (1) complex (AAZ = 6-amino-6-methylperhydro-1,4-diazepine), as a system that is able to mimic some important chelate properties of 1,4,7-triazacyclononane, are reported. The syntheses of a new unsymmetric AAZ-functionalized ligand and the structure of its first heterodinuclear Fe(III)Zn(II) complex are also presented.     

Polarographische Untersuchungen an symmetrischen Triazacarbocyaninen in Methanol

Polarographic Investigations on Symmetrical Triazacarbocyanine Dyes in Methanol The reduction mechanism of eleven symmetrical triazacarbocyanine dyes with different heterocycles in methanol (containing lithium chloride or lithium acetate/acetic acid) has been investigated by means of polarography, cyclic oscillopolarography and coulometry. The reduction occurs in a reversible to irreversible two electron transfer step, followed by an irreversible chemical step. Reduction potentials, transfer coefficients and specific currents have been measured and compared with properties measured in acetonitrile. The effect of substituents X has been studied on the compounds 1-ethyl-2-[3-(1-ethyl-6-X-1,2-dihydroquinolin-2-ylidene)-1-triazeno]-6-X-quinolinium tetrafluoroborate 1f(X) and 3-ethyl-2-[3-(3-ethyl-5-X-Δ⁴-1, 3-thiazolin-2-ylidene)-1-triazeno]-5-X-1, 3-thiazolium tetrafluoroborate 1g(X) , and ρ-values of 0.20 and 0.40 V, respectively, have been found.     

Recent advances in characterization of CaCu3Ti4O12 thin films by spectroscopic ellipsometric metrology

CaCu3Ti4O12 (CCTO) thin films were successfully grown on LaAlO3(100) and Pt/TiO2/SiO2/Si(100) substrates by a novel MOCVD approach. Epitaxial CCTO(001) thin films have been obtained on LaAlO3(100) substrates, while polycrystalline CCTO films have been grown on Pt/TiO2/SiO2/Si(100) substrates. Surface morphology and grain size of the different nanostructured deposited films were examined by AFM, and spectroscopic ellipsometry has been used to investigate the electronic part of the dielectric constant (epsilon2). Looking at the epsilon2 curves, it can be seen that by increasing the film structural order, a greater dielectric response has been obtained. The measured dielectric properties accounted for the ratio between grain volumes and grain boundary areas, which is very different in the different structured films.     

Total synthesis of human insulin under directed formation of the disulfide bonds

A preliminary account is given of a total synthesis of human insulin involving directed formation of the three disulfide bonds at different stages of the fragment-condensation approach. The synthesis was facilitated by the application of two new methods for the selective removal of protecting groups. In the first, two S-Trt-protected cysteine residues are converted to the disulfide without affecting S-Acm-protected cysteine residues. The second new method consists in a very mild, pH-controlled, acidolysis of N(α)-Trt, leaving intact N(α)-Bpoc and other acid-labile protecting groups. The last step of the synthesis was the formation of the disulfide bridge between the Acm-protected cysteine residues A7 and B7 by iodine. Extensive counter-current distribution yielded the synthetic hormone in pure form. It was compared and found to be identical with natural human insulin. Identification was achieved by means of thinlayer chromatography and electrophoretic procedures, as well as by comparing the pattern of break-down by enzymes (finger-printing). The natural and synthetic hormones were crystallized under identical conditions. The synthetic human insulin was found to possess full biological activity in an in vitro system.     

Schwache Teilbarkeitshalbgruppen

In this paper we continue the study of Tbk-semigroups [1]. We define a weak Tbk-semigroup as an algebra (s,·,) which satisfies (A1) a(bc) = (ab)c, (A2) (S, ) is a semilattice, (A3) × (a b) y = xay xby, (A4) a (a b) S S (a b) . We shall prove that every weak Tbk-semigroup can be embedded into a Tbk-semigroup with 1, and we shall show that the theory of [1] can be developed already in weak Tbk-semigroups.

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Über den Inhalt dieser Note berichtete der Autor verschiedene Male , zuletzt im Juni 1974 an der T.U. München.