Chiral ferrocene cyanohydrin derivatives—access to novel intermolecularly linked and intramolecularly bridged ferrocene derivatives

By reduction of the cyano group in (R)-(cyanohydroxymethyl)ferrocene and (R,R)-1,1′-bis(cyanohydroxymethyl)ferrocene, amines were obtained giving access to several new diamine and diamide bridged chiral ferrocene derivatives. As a representative for an intramolecularly bridged ferrocene compound bearing two chiral centres (R,R)-8 was obtained with excellent optical purity.     

Über Verbrennungswärmen des Perylens und einiger seiner Derivate

Ohne ZusammenfassungDem Vorstand des Institutes für theoretische und physikalische Chemie Herrn Professor Dr. R. Kremann möchten wir für das rege Interesse, das er an unserer Arbeit durch freundlichste Überlassung der Apparaturen und Meßgeräte bewies, sowie für die tatkräftige Förderung an dieser Stelle herzlichst danken.     

Stereochemie und Mechanismus derPrins-Reaktion bei ausgeprägter Ladungsdelokalisierung im intermediären Carbeniumion

A detailed investigation of the reaction of 2.6-dimethyl-4-propenylphenol with formaldehyde showed thatPrins reactions of hydroxystyrenes in alkaline medium in most cases are kinetically controlled. By attack of formaldehyde, the same intermediate is generated from eithercis ortrans olefin. On further reaction by two independent pathways a 1.3-diol is formed by attack of a hydroxyl ion, or a 1.3-dioxane by reaction with additional formaldehyde via a hemiacetal. The steric course of the reaction is deduced from a discussion of the conformations of transition states.Prins reactions of arylolefins carrying strong +M-substituents proceed analogously under acylating conditions (e.g. in acetic acid) in weak acidic medium.

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Synthesis of γ-halogenated and long-chain β-hydroxy-α-amino acids and 2-amino-1,3-diols using threonine aldolases

The l- and d-threonine aldolase catalyzed formation of γ-halogenated and long-chain l- and d-3-alkylserine-derivatives 1-12, respectively, was shown starting from glycine and halogenated C₂- or C₄-C₁₂ aldehydes. lTA from Pseudomonas putida accepted all tested aldehydes with strongly varying diastereoselectivity (de up to 93%). Only aldehydes smaller than decanal were converted by dTA from Alcaligenes xylosoxidans with good selectivities (de up to 73%). Utilizing isobutanal enantio- and diastereopure d-syn-2-amino-3-hydroxy-4-methylpentanoic acid was obtained (ee>99%, de>95%), which was converted to the corresponding 2-amino-1,3-diol.     

N-(Arylaminosulfonyl)benzamide

N-(Arylaminosulfonyl)benzamides3 were prepared by reaction of N-chlorosulfonylbenzamide or 4-chloro-N-chlorosulfonylbenzamide, resp., with isocyclic and heterocyclic amines.

     

Electronic structure and conformational equilibria of phenyl-propylcarbocations

Modified CNDO calculations were performed on different conformations of various phenyl propyl cations and related compounds. Molecular energies and electronic structures are presented and discussed. A substituted secondary benzyl cation, the 1-phenyl-1-propyl carbocation (12) is found to be the most stable isomer. The open chain 1-phenyl-2-propyl carbocation (11b) has a lower energy than the propylene benzenium cation (11d). In contrary, previous calculations of 2-phenyl-1-ethyl cation lead to the result that in this case the ethylene benzenium cation is the most stable structure. Rotational barriers for different substituted 1-propyl and 2-propyl cations were calculated. The results are explained by hyperconjugative stabilization.     

Quantum chemical calculations on the interaction of diazomethane with proton acids

Diazoalkanes may form H-bonded associates with weak proton acids, whereas with strong acids proton transfer leads to the diazonium ion. In order to get information about protonation and association at and N, the corresponding energy balances, electron charge distributions and bond strengths have been calculated by means of quantum chemical ab initio methods with diazomethane as substrate and HF,NH₄⁺, OH₃⁺ as acids.     

The ring opening of cyclopentene oxides by pyrimidines and purines as a pathway to carbocyclic nucleoside analogues

Summary Various carbocyclic nucleosides withxylo-configuration have been synthesized using ring opening of 5-O-acetyl-1,2-anhydro-3-O-benzylcarba--DL-xylo-pentofuranose (6) by thymine, uracil, 4-N-benzoylcytosine, adenine, 6-N-benzoyladenine, and 2-amino-6-chloropurine in alkaline medium. For this purpose, the use of triethylaluminum is introduced into carbanucleoside chemistry. The new method proved to be superior over the application of sodium hydride and potassium or caesium carbonate.

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Ringöffnung von Cyclopentenoxiden mit Pyrimidinen und Purinen als Syntheseweg zu carbocyclischen Nucleosidanalogen

Zusammenfassung Ringöffnung von 5-O-Acetyl-1,2-anhydro-3-O-benzylcarba--DL-xylo-pentofuranose (6) mit Thymin, Uracil, 4-N-Benzoylcytosin, Adenin, 6-N-Benzoyladenin und 2-Amino-6-chlorpurin in alkalischem Medium ergab die entsprechendenxylo-konfigurierten carbocyclischen Nucleoside. Als Hilfsbase wurde Triethylaluminium verwendet, was deutliche Vorteile gegenüber der Verwendung von Natriumhydrid und Kalium- oder Cäsiumcarbonat bezüglich Produktreinheit und Ausbeute bietet.