A novel lumazine peptide, penilumamide (1), was isolated from the fermentation broth of a marine-derived fungal strain, identified as Penicillium sp. (strain CNL-338) and the structure of the new metabolite was determined by analysis of ESI-TOF MS data combined with 1D and 2D NMR experiments.
1,2-Dimethylindazolium-3-carboxylates are pseudocross-conjugated mesomeric betaines (PCCMB) and derivatives of the indazole alkaloid Nigellicin. They decarboxylate on heating to give intermediary N-heterocyclic carbenes of indazole that can be trapped with iso(thio)cyanates to amidates. Alternatively, 1,2-dimethylindazolium-3-amidates can be prepared starting from the corresponding 1H-indazol-3-carboxylic acid which is converted into its chloride, reacted with anilines and deprotonated on anion exchange resin. The heterocumulene moieties of these amidates, which are new representatives of pseudo-cross-conjugated mesomeric betaines, can be exchanged to 3,5-dichlorophenyl isocyanate via the N-heterocyclic carbene.
Nucleophilic substitution of 4-(dimethylamino)pyridine on pentachloropyridine yielded pentakis(pyridine-2,3,4,5,6-pentayl)pyridinium, tris-(3,5-dichloropyridine-2,4,6-triyl)pyridinium, or (tetrachloropyridin-4-yl)pyridinium depending on the reaction conditions. Nucleophilic substitution with water, hydroxides, and alcoholates resulted in new betaines and highly substituted pyridines. [structure: see text]
Spectroscopic investigations reveal that a hydroquinone pyridinium alkaloid isolated from the leaves of pomegranates Punica granatum L. (X-ray) exists as a mixture of a conjugated and a cross-conjugated heterocyclic mesomeric betaine in aqueous and DMSO-d6 solution. Twofold deprotonation yields an anionic tripole.
Nucleophilic substitution reactions on 4-(4-dimethylamino)-pyridinium-substituted tetrachloropyridine with oxygen nucleophiles such as alkoxides and phenolates resulted in the formation of 4-or 2,4-alkoxy-or -phenoxy-substituted chloropyridines depending on the reaction conditions. Substitution on 2,4,6-tris(4-dimethylamino)pyridinium-substituted 3,5-dichloropyridine gave the corresponding 2,4,6-tris-alkoxy-or -phenoxy-substituted pyridines which are not available by other routes.
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