Synthesis and Structure Elucidation of Pyrimidobenzimidazoles and Fused Derivatives II [1]. Dodecahydrobenzimidazo-[2,1-b]quinazolines and Decahydrobenzimidazo-[2,1-b]benzo[h]quinazolines [2]

Summary.  The cyclization reactions of trans-3a-hexahydro-2-benzimidazolamine with 2-alkylidene- and 2-benzylidenecyclohexanones and α-tetralones, respectively, yield mixtures of two isomeric condensates each. Thorough high resolution NMR analyses (¹H and ¹³C NMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, and 1D NOE difference spectra) revealed that the corresponding isomers are in all cases linearly fused diastereomeric 12α- and 12β-substituted trans-6aα-dodecahydrobenzimidazo[2,1-b]quinazolines and 7α-substituted trans-8aβ- and trans-8aα-decahydrobenzimidazo[2,1-b]benzo[h]quinazolines, respectively. The formation of corresponding angularly fused regioisomers was not observed so far. The stereochemistry and the tautomerism of some bases and their hydrochlorides as well as the regiospecific course of the cyclization reactions are discussed. Biological tests showed that the novel compounds don’t exert remarkable antibacterial and antimycotic effects. Received November 3, 1999. Accepted November 30, 1999     

Synthese und Strukturaufklärung von Pyrimidobenzimidazolen und kondensierten Derivaten, 3. Mitt. [1,2]. Decahydropyrimido[1,2-<Emphasis Type="Italic">a</Emphasis>]benzimidazol-2-ole und Octahydropyrimido[1,2-<Emphasis Type="Italic">a</Emphasis>]benzimidazole

Zusammenfassung.  Die Reaktion von racemischem trans-Hexahydrobenzimidazol-2-amin mit drei ausgew?hlten vinylogen Ketonen unter milden Bedingungen wurde untersucht. Nur im Fall der Umsetzung mit 4-Phenyl-3-buten-2-on konnten Cycloadditionsprodukte isoliert werden. Diese sind laut NMR-Analysen Gemische von zwei der acht m?glichen Diastereomeren, n?mlich von rac-2β-Methyl-4β-phenyl-trans-5aα- und trans-5aβ-decahydropyrimido[1,2-a]benzimidazol-2α-ol. Bei Umsetzungen des Amins mit Phenylbutenon bei erhoühten Temperatur sowie mit, 2-Methyl-1-phenyl-1-penten-3-on und 4^′-Chlorchalkon bildeten sich Gemische entsprechend substituierter rac-4α-Phenyl-trans-5aβ- und trans-5aα-octahydropyrimido[1,2-a]benzimidazole. Struktur und Stereochemie der Titelverbindungen und ihrer Hydrochloride wurden anhand NMR-spektroskopischer Untersuchungen aufgekl?rt. Die Ringschlu?reaktionen verlaufen in allen F?llen gleichgerichtet regio-, jedoch nicht diastereoselektiv. Versuche zur Beeinflussung der Regio- und/oder Diastereoselektivit?t der Cyclisierungsreaktion durch Variation der Reaktionsbedingungen hatten keinen Erfolg.

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Synthesis and Structure Elucidation of Pyrimidobenzimidazoles and Fused Derivatives III [1,2]. Decahydropyrimido[1,2- a ]benzimidazol-2-oles and Octahydropyrimido[1,2- a ]benzimidazoles

Summary.  The reaction of racemic trans-hexahydrobenzimidazol-2-amine with three vinylogous ketones under mild conditions was studied. Only in the case of 4-phenyl-3-buten-2-one cycloaddition products could be isolated. According to NMR spectroscopy they consist of mixtures of two of eight possible diastereomers: rac-2β-methyl-4β-phenyl-trans-5aα- and trans-5aβ-decahydropyrimido[1,2-a]benzimidazol-2α-ole. Reaction of the amine with the butenone at higher temperature and with, 2-methyl-1-phenyl-1-penten-3-one, and 4^′-chlorochalcone afforded mixtures of two diastereomers each, which turned out as rac-4α-phenyl-trans-5aβ- and trans-5aα-octahydropyrimido[1,2-a]benzimidazoles. Complete structural and stereochemical assignments of the title compounds and their hydrochlorides were established by NMR spectroscopic investigations. The results showed that all investigated cyclization reactions proceeded regioselectively with equal orientation of the components, but not diastereoselectively. Variation of the reaction conditions did influence neither regio- nor diastereoselectivity.

Received October 19, 2000. Accepted October 30, 2000     

Special Reactions of α,β-Unsaturated Ketones III [1]. Formation and Structure Elucidation of Dimers of 2-Aryl-methyleneketones: (5E)-5-Benzylidene-9β-phenyl-trans-4a-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthen-4aα-ol and 3β,5β-Bis-(4-methoxyphenyl)-2α,4β,6α-trimethyl-4α-propionyl-cyclohexanone [2]

Summary.  The reaction of 2-benzylidenecyclohexanone and 1-(4-methoxyphenyl)-2-methyl-1-penten-3-one with guanidine did not yield the expected 4-phenylhexahydro-2-quinazolinamine and 4-(p-methoxyphenyl)-dihydro-2-pyrimidinamine, respectively, but nitrogen-free products which turned out as [3+3]- and [4+2]-cycloadducts of two molecules of the applied vinylogous ketone each. According to elemental analyses, mass spectra, and, in particular, NMR analyses (¹H and ¹³CNMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, NOESY, and 1D NOE difference spectra), the prepared dimers were identified as racemic (5E)-5-benzylidene-9β-phenyl-trans-4a-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthen-4aα-ol and 3β,5β-bis-(4-methoxyphenyl)-2α,4β,6α-trimethyl-4α- propionylcyclohexanone, respectively. Structure and stereochemistry of the dimers are elucidated, and mechanisms for their formation are proposed. Received April 11, 2001. Accepted (revised) May 18, 2001     

Squares of characters and finite groups

Let G be a finite group and χ be an irreducible complex character. We study the character χ² in the case that χ(1) is a prime power.     

Pyrroloiminoquinone and related metabolites from marine sponges

This review presents the structure, biological activity, biosynthetic studies and, where applicable, references to syntheses of 81 marine alkaloids containing either tetra-, hexa- or octa-hydrogenated variants of pyrrolo[4,3,2-de]quinoline, pyrrolo[4,3,2-de]pyrrolo[2,3-h]quinoline and pyrido[2,3-h]pyrrolo[4,3,2-de]quinoline core skeletons. The literature describing the isolation of pyrroloiminoquinones, and related metabolites, from marine sponges is littered with taxonomic inconsistencies and recent efforts to clarify the taxonomy of the sponges that produce this group of metabolites are discussed.