Exploiting the regioselectivity of pyroglutamate alkylations for the synthesis of 6-azabicyclo[3.2.1]octanes and 4-azabicyclo[3.3.0]octanes

Depending on the N-protecting group of pyroglutamates, the reactivity can be directed to the formation of 6-azabicyclo[3.2.1]octanes or 4-azabicyclo[3.3.0]octanes, which are conformationally restricted glutamate analogues.     

α,ω-Diisocyanatocarbodiimides, -Polycarbodiimides,and Their Derivatives

Research in the field of low-molecular weight, oligomeric and polymeric α,ω-diisocyanatocarbodiimides and -polycarbodiimides has been fruitful, not only in connection with these compounds themselves, but also—as so often happens in chemistry—with quite different problems. Novel synthetic methods, discoveries concerning the properties of low-molecular weight carbodiimides and phosphane imide derivatives, as well as results on the fragmentation reactions of four-membered heterocyclic compounds containing oxygen, phosphorus, and nitrogen, and a better understanding of the diisocyanate polyaddition process are among the many by-products of this research. The “high- and low-temperature formation” of polycarbodiimides and the homogeneous and heterogeneous catalysis of this process are described, and the fundamental importance of four-membered ring fragmentation mechanisms resulting in the formation of phosphane imide derivatives is outlined. Interesting building blocks for the diisocyanate polyaddition and polycondensation processes can be synthesized by many derivatization reactions of oligomeric and high-molecular weight polycarbodiimides and polyuretonimines. The in situ production of polycarbodiimides via matrix reactions in flexible polyurethane foams leads to a cellular arrangement of the material due to the pronounced symmetrical growth processes. Combination-foams with increased carbonation tendencies are formed in this way. Attention is drawn to several industrial applications of α,ω-diisocyanatopolycarbodiimides, of high-molecular weight cross-linked polyuretonimines, and of polycarbodiimide foams.     

[(Mes3Sn)2MoO4], ein monomeres Triorganozinnmolybdat

[(Mes₃Sn)₂MoO₄], a Monomeric Triorganotin Molybdate Mes₃SnBr (Mes = 1, 3, 5‐trimethylphenyl) reacts with (NBu₄)₂[Mo₆O₁₉] in the presence of (NBu₄)OH (in CH₃CN as solvent) to form [(Mes₃Sn)₂MoO₄]. Alternatively the title compound can be obtained from the reaction of [MoO₂(acac)₂] (acac = 2, 4‐pentadionate) with Mes₃SnOH in isopropanol. [(Mes₃Sn)₂MoO₄] forms monoclinic crystals, space group C2/c, with a = 2271.6(3) pm, b = 825.2(1) pm, c = 2739.9(5) pm, β = 90.96(2)°. The crystal structure consists of isolated molecules in which a tetrahedral MoO₄ unit is connected to two terminal Mes₃Sn groups. The Mo‐O distances range from 169.6(4) to 181.1(3) pm and the Sn‐O distance is 204.8(3) pm.     

Ion-pair reversed-phase high-performance liquid chromatography analysis of oligonucleotides: retention prediction

An ion-pair reversed-phase HPLC method was evaluated for the separation of synthetic oligonucleotides. Mass transfer in the stationary phase was found to be a major factor contributing to peak broadening on porous C18 stationary phases. A small sorbent particle size (2.5 microm), elevated temperature and a relatively slow flow-rate were utilized to enhance mass transfer. A short 50 mm column allows for an efficient separation up to 30mer oligonucleotides. The separation strategy consists of a shallow linear gradient of organic modifier, optimal initial gradient strength, and the use of an ion-pairing buffer. The triethylammonium acetate ion-pairing mobile phases have been traditionally used for oligonucleotide separations with good result. However, the oligonucleotide retention is affected by its nucleotide composition. We developed a mathematical model for the prediction of oligonucleotide retention from sequence and length. We used the model successfully to select the optimal initial gradient strength for fast HPLC purification of synthetic oligonucleotides. We also utilized ion-pairing mobile phases comprised of triethylamine (TEA) buffered by hexafluoroisopropanol (HFIP). The TEA-HFIP aqueous buffers are useful for a highly efficient and less sequence-dependent separation of heterooligonucleotides.     

N(SCl)2 ⊕[MoCl5(NSCl)]⊖, ein Chlorthionitrenokomplex von Molybdän(VI)

N(SCl)₂^⊕ [MoCl₅(NSCl)]^?, a Chlorothionitrene Complex of Molybdenum (VI) . The title compound is formed together with MoCl₃(N₃S₂) by the reaction of MoCl₄ or MoCl₅ with (NSCl)₃ in CH₂Cl₂. The black, crystalline compound was characterized by its i.r. spectrum and an X-ray crystal structure determination. N(SCl)₂^⊕[MoCl₅(NSCl)]^? crystallizes in the monoclinic space group P2₁/n with four formula units per unit cell. The lattice constants are a = 716.3, b = 1627.4, c = 1178.9 pm and β = 100.90°. The [MoCl₅(NSCl)]^? ion posseses an almost linear Mo = N = S grouping with bond lengths that can be interpreted as double bonds. Crystal data for AsPh₄[MoCl₅(NSCl)] are reported.     

Synthesen von Heterocyclen, 62. Mitt.: Über Reaktionen mit Betain

Zusammenfassung Beim Erhitzen von Betain mit Phenylisocyanat (12) auf 140–160° entsteht Diphenylimidazolidin-dion-(2,4) (I).

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Diphenylimidazolidine-dion-2,4 (I) was obtained by the reaction of betaine with phenylisocyanate (12) at 140–160°.

     

Fluordiazadiphosphetidine, 11. Mitt.: Eine neue Methode zur Herstellung der doppelt zwitterionischen Verbindung (CH3N)6P4F8

A new synthetic route for the preparation of the betain-like compound (CH₃N)₆P₄F₈ from (CH₃NPF₃)₂,N-methyl-hexamethyldisilazane andN,N-dimethyl-urea has been found. The steps of this multi-stage reaction could be rationalized to a far extent.

10. Mitteilung:Kubjacek M., Utvary K., Mh. Chem.112, 305 (1981).     

Neue Reagentien zum papierchromatographischen Nachweis von Aminosäuren, 3. Mitt.: Reaktionen des 1,8-Trimethylenchinisatins mit primären Aminoverbindungen

Zusammenfassung 1,8-Trimethylenchinisatin-hydrat (TMCH) reagiert mit Aminosäuren zum farblosen Bis-(2-oxo-4-hydroxy-1,8-trimethylen-1,2-dihydro-3-chinolinyl)-amin (2). Da2 bei der Dehydrierung in das Farbsalz5 übergeht, welches eine dem Ruhemann-Purpur analoge Struktur aufweist, ergeben sich neuartige Aspekte zur Deutung des Mechanismus der Ninhydrin-Reaktion.

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1.8-Trimethylenequinisatin hydrate (TMCH) reacts with amino acids yielding the colorless bis-(2-oxo-4-hydroxy-1.8-trimethylene-1.2-dihydro-3-quinolyl)-amine (2). Upon dehydrogenation of2 the dye salt5 is obtained. Because of the close relationship between5 and Ruhemann's purple a re-interpretation of the mechanism of the ninhydrin reaction could be made.

     

Spaltungen mittels Diazonium verbindungen und Chinonimidchlorid, 9. Mitt.: Über 4-Hydroxystyryl-alkylketone

Zusammenfassung Die Weiterführung der Spaltungsversuche an methylsubstituierten 4-Hydroxystyryl-alkylketonen mit Chinonimidchlorid hat gezeigt, daß auch Systeme mit ungesättigter Kohlenstoffkette, die nur einen aromatischen Ring aufweisen, mittels Kupplungsreagentien unter Eliminierung der Seitenkette reagieren.

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The cleavage reaction of methyl 4-hydroxystyryl-alkylketones with p-benzoquinone-monochloroimine shows, that also compounds with an unsaturated carbon chain and with only one aromatic ring react under elimination of the side chain.

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Herrn Prof. Dr.A. Wacek, Vorstand des Institutes für Organische Chemie und Organisch-chemische Technologie der Technischen Hochschule Graz mit freundlichen Wünschen zum 70. Geburtstag gewidmet.