ABSTRACT
Lyngbyabellin B (1) was isolated from a marine cyanobacterium, Lyngbya majuscula, collected near the Dry Tortugas National Park, Florida. This new cyclic depsipeptide displayed potent toxicity toward brine shrimp and the fungus Candida albicans. The planar structure was deduced using 1D and 2D NMR spectroscopic methods, and the stereochemistry is proposed through a combination of NMR and chiral GC/MS analysis.
Subject(s)
Antifungal Agents/isolation & purification , Bacterial Toxins/isolation & purification , Cyanobacteria/chemistry , Depsipeptides , Lyngbya Toxins/isolation & purification , Thiazoles/isolation & purification , Animals , Anti-Bacterial Agents , Anti-Infective Agents/pharmacology , Antifungal Agents/chemistry , Artemia/drug effects , Bacterial Toxins/chemistry , Bacterial Toxins/toxicity , Candida albicans/drug effects , Lyngbya Toxins/chemistry , Lyngbya Toxins/toxicity , Molecular Structure , Thiazoles/chemistryABSTRACT
The lipid extract of a Madagascan Lyngbya majuscula has yielded malyngamides Q and R, both amides of 7-methoxytetradec-4-enoic acid. The isolation of these metabolites was accomplished using preparative liquid chromatography, with final purification through repetitive reversed-phase HPLC. Structure elucidation was accomplished utilizing 1D and 2D NMR spectroscopic characterization of the natural products and comparisons with malyngamides A and B. DPFGSE 1D NOE data suggested a different geometrical stereochemistry at C-6 in malyngamides Q and R from that observed for malyngamide A, as well as the other known malyngamides. The Z stereochemistry was confirmed for malyngamide R by measurement of key diagnostic (3)J(CH) couplings utilizing the HSQMBC pulse sequence. The absolute stereochemistry of C-4' ' of the pyrrolidone ring was defined by chiral GCMS analysis of serine released by ozonolysis and acid hydrolysis.
Subject(s)
Amides/isolation & purification , Cyanobacteria/chemistry , Pyrroles/isolation & purification , Amides/chemistry , Molecular Structure , Pyrroles/chemistry , Spectrum AnalysisABSTRACT
A new brine-shrimp toxic and antifungal compound, tanikolide 1, has been isolated from the lipid extract of a Madagascan collection of the marine cyanobacterium Lyngbya majuscula. The structure of tanikolide was determined by spectroscopic methods, relying heavily on 2D NMR spectroscopy. The absolute configuration at C-5 of tanikolide was established as R by oxidizing the primary alcohol to an acid and analyzing the corresponding (R)- and (S)-PGME amide derivatives by (1)H NMR.
