Synthese von Hydroxybenzylbenzimidazolen

Zusammenfassung Eine Reihe von Hydroxybenzylbenzimidazolen wurde durch Kondensation verschiedener aromatischer o-Diamine mit Brommandelsäuren unter Verwendung von 6n-HCl als Kondensationsmittel hergestellt. Für die Substituenten in der Benzolhälfte wurden die Stellungen 4(7)-, 5(6)-, 5,6- oder 4,6(5,7)- ge-wählt; der Phenylrest der Hydroxybenzylhälfte trägt ein Bromatom in der o- oder p-Stellung. Die Darstellung der o-Brom-mandelsäure wird beschrieben.

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A series of hydroxybenzylbenzimidazoles has been synthesized by condensing various aromatic o-diamines with bromomandelic acids using 6 N hydrochloric acid as condensing agent. o-Phenylene diamines to yield benzimidazoles substituted at positions 4(7)-, 5(6)- or 4,6(5,7)- were selected; the phenyl group of the hydroxybenzyl moiety carries a bromo substituent in the o- or p-position. The preparation of o-bromomandelic acid is described in some detail.

     

Synthese von Orellin

Synthesis of Orelline Orelline (1) , a metabolite of the toadstool Cortinarius Overllauns Fries with 2,2′-bipyridine structure, has been synthesized by the following method. The easily accessible 2-bromo-3-hydroxypyridine (3) was converted into the corresponding [2-(trimethylsilyl)ethoxy]methyl (SEM) ether 4 and coupled with Zn and NiCl₂/Ph₃P to form the bipyridine derivative 5 in 79% yield. Due to the chelating effect of the two SEM-ether groups in 5 , it was possible to from selectively the dilithium compound 6 by an exchange reaction with BuLi at ?50° in Et₂O. Reaction of 6 with electrophiles at ?20° afforded the 4- and 4,4′-substituted bipyridines 7–14 in excellent-to-reasonable yield. Oxidation of 6 with 2-(phenylsulfonyl)-3-phenyloxaziridin and with bis(trimethylsilyl)peroxide gave the 4,4′-diol 9 in 22 and 10% yield, respectively. Methanolysis of 9 directly afforded crystalline 1 in high yield, with properties identical with those of natural orelline. Formylation of 6 with N-formylmorpholine gave 45% of the dicarbaldehyde 13. Removal of the SEM groups in 13 by hydrolysis afforded the dihydroxydicarbaldehyde 15 that could be oxidized to 1 with alkaline H₂O₂. Attempts to oxidize 1 to orellanine (2) with 35% H₂O₂ according to a known procedure were unsuccessful (cf. Exper. Part). Compound 7 with two Me₃Si groups in 4,4′-position gave after methanolysis the fluorescence dye 16 with an appreciable Stokes shift in cyclohexane.     

Synthese von Cotarnin-Iodid

Summary Starting from 4-methoxy-1,3-benzodioxol-5-carbaldehyde (croweacin aldehyde,3) a six-step synthesis of cotarnin iodide (9, 67% total yield) is described.

     

Synthese von Nigrifactin

Zusammenfassung Es wird die Synthese des Nigrifactins, eines aus Streptomyces (Stamm FFD-101) gewonnenen Alkaloids, entsprechend nachfolgendem Formelschema beschrieben.

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Synthesis of nigrifactine

A synthesis of nigrifactine, an alcaloid of streptomyces (strain FFD-101), is described (see flow chart below).

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E. H. dankt Herrn Doz. Dr.E. Zbiral für wertvolle Diskussionen.     

Synthese von Phosphor-oxy-Halogeniden

Synthesis of phosphorus oxy halides A general method for the preparation of phosphorus oxy halides from thiophosphoric esters is described.     

Synthese von Indenothiophenen

The synthesis of 7.8-dihydro-6H-indeno[4.5-b]thiophene (3), 6.7-dihydro-5H-indeno[5.6-b]thiophene (6), and their 2-methyl- and 2-ethyl-homologues (4, 5, 7, 8) is described.     

Synthese von Visnagin

Ohne Zusammenfassung