1,3-Dimethyllumazine Derivatives from Limnatis nilotica

Abstract

Two previously unknown lumazine derivatives, 1 and 2, have been isolated from the parasitic freshwater leech Limnatis nilotica. The structures of the compounds have been elucidated by NMR and unambiguously corroborated by chemical synthesis.

Lumazine Peptides from the Marine-Derived Fungus Aspergillus terreus

“…The neighboring positions of this methyl group were occupied by the quaternary carbons at δ C 151.1 and 150.0 deduced from the HMBC data. Taken together, both the chemical shifts of the protons and carbons and the HMBC correlations among them revealed the presence of a 1-methyllumazine moiety, which was confirmed by comparing of the spectroscopic data with those of lumazine analogs in the literature ( Figure 4 ) [ 14 , 15 ]. Based on the combined HMBC data, the N -methyl group was placed at the N-1 position.…”

“…Simple lumazine-containing compounds from marine animals include those from the sponges Leucetta microraphis [ 18 ], Corallistes fulvodesmus [ 19 ], Corallistes undulates [ 14 ], and Clathria sp. [ 20 ], the polychaete Odontosyllis undecimdonta [ 21 , 22 , 23 ], and the ascidian Leptoclinides durust [ 24 ], whereas those containing the lumazine-6-carboxylic acid moiety were also found in the freshwater leech Limnatis nilotica [ 15 ]. Unlike the alkylated lumazines of animal origin, the recently reported penilumamides A–D from marine-derived Penicillium sp.…”

Secondary metabolites of fungi from marine habitats

“…414 The 1,3-dimethyllumazine-6-carboxamide moiety within a natural product had previously only been reported from the freshwater leech Limnatis nilotica. 415 The structure elucidation of 627 was severely hampered by the lack of protons in the lumazine part, but was achieved by a combination of 1,1-ADEQUATE and 1 H, 15 N HMBC experiments, use of the NMR-based structure generator COCON, 416 and detailed analysis of the ESI-TOF MS fragmentations. Compound 627 was inactive when tested for cytotoxic and antimicrobial properties, and also did not affect cellular Ca 2+ signalling in neuroendocrine cells.…”

Penilumamide, a novel lumazine peptide isolated from the marine-derived fungus, Penicillium sp. CNL-338

“…The observed 13 C-NMR shifts were mostly in good agreement with those of commercially available lumazine (Aldrich) 9 or with other synthesized or isolated lumazine derivatives. 8,13 …”

“…A 1,3-dimethyllumazine-6-carboxamide moiety within a natural product was only published once 8 whereas the “monomers” 1,3-dimethyllumazine-6-carboxylic acid and 1,3-dimethyllumazine-6-carboxamide are unknown as natural products.…”