ABSTRACT
Using an established CRISPR-Cas mediated genome editing technique for streptomycetes, we explored the combinatorial biosynthesis potential of the auroramycin biosynthetic gene cluster in Streptomyces roseosporous. Auroramycin is a potent anti-MRSA polyene macrolactam. In addition, auroramycin has antifungal activities, which is unique among structurally similar polyene macrolactams, such as incednine and silvalactam. In this work, we employed different engineering strategies to target glycosylation and acylation biosynthetic machineries within its recently elucidated biosynthetic pathway. Auroramycin analogs with variations in C-, N- methylation, hydroxylation and extender units incorporation were produced and characterized. By comparing the bioactivity profiles of five of these analogs, we determined that unique disaccharide motif of auroramycin is essential for its antimicrobial bioactivity. We further demonstrated that C-methylation of the 3, 5-epi-lemonose unit, which is unique among structurally similar polyene macrolactams, is key to its antifungal activity.
Subject(s)
Anti-Bacterial Agents/biosynthesis , Antifungal Agents/chemistry , Biosynthetic Pathways/genetics , Metabolic Engineering/methods , Streptomyces/genetics , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Antifungal Agents/pharmacology , CRISPR-Cas Systems , Gene Editing/methods , Methicillin-Resistant Staphylococcus aureus/drug effects , Microbial Sensitivity Tests , Polyenes/chemistry , Streptomyces/metabolismABSTRACT
A new highly efficient three-component reaction of alkyl acrylate, aldehyde and dialkyl malonate using ethyl diphenylphosphine as organocatalyst has been described. Various highly functional compounds bearing hydroxyl groups and the ester functions can be easily prepared in moderate to good yields according to our one-step procedure. The reactions are believed to proceed via Morita-Baylis-Hillman reactions of alkyl acrylate and aldehydes, followed by the Michael addition reactions of dialkyl malonates. Our reactions indicated that the intermediate species formed in the phosphine-catalyzed MBH reaction are an effective organic base to catalyze the Michael addition reactions of dialkyl malonates to the preformed MBH adducts.
Subject(s)
Acrylates/chemistry , Aldehydes/chemistry , Malonates/chemistry , Phosphines/chemistry , Catalysis , Molecular Structure , StereoisomerismABSTRACT
Series of N-substituted carbazole analogues bearing an indole ring were synthesized as anti-methicillin-resistant Staphylococcus aureus (MRSA) agents from a molecular hybridization approach. The representative compound 19 showed an MIC = 1 µg/mL against a panel of MRSA clinical isolates as it possessed comparable in vitro activities to that of vancomycin. Moreover, compound 19 also exhibited MIC = 1 µg/mL activities against a recent identified Z172 MRSA strain (vancomycin-intermediate and daptomycin-nonsusceptible phenotype) and the vancomycin-resistant Enterococcus faecalis (VRE) strain. In a mouse model with lethal infection of MRSA (4N216), a 75% survival rate was observed after a single dose of compound 19 was intravenously administered at 20 mg/kg. In light of their equipotent activities against different MRSA isolates and VRE strain, the data underscore the importance of designed hybrid series for the development of new N-substituted carbazoles as potential anti-MRSA agents.
ABSTRACT
Novel preparation of tetrasubstituted furans, starting from the Michael acceptors, tributylphosphine, and acyl chlorides, is realized. A broad range of highly functional furans can be efficiently generated in one step at room temperature within 10 min to 21 h in moderate to high yields (60-99%). The reaction was proposed to proceed via intramolecular Wittig-type reactions, using phosphorus ylides as intermediates.