Chemical Constituents of a Marine Bacterium Microbacterium sp. HN-3-14 and Their Antimicrobial Activities

One novel mevalonolactone-pyrimidine hybrid (microbacterin A, 1), two undescribed acetylglucosamine derivatives, N-((2S,5R)-5-((R)-1,2-dihydroxyethyl)-2-methoxy-2,5-dihydrofuran-3-yl)acetamide (2), N-((2R,5R)-5-((R)-1,2-dihydroxyethyl)-2-methoxy-2,5-dihydrofuran-3-yl)acetamide (3) along with five known compounds (4-8), namely, niacinamide (4), 7,8-dimethylalloxazine (5), adenine (6), adenosine (7), and deoxyadenosine (8), were isolated from the fermentation broth of a marine bacterium, Microbacterium sp. HN-3-14. Their structures and absolute configurations were elucidated through comprehensive spectroscopic analyses, including HR-ESI-MS, 1D and 2D NMR, theoretical ECD and NMR calculations, and dimolybdenum tetraacetate-induced CD (ICD) measurements. Antimicrobial experiments showed that 5 exhibited a weak inhibitory effect on Saccharomyces cerevisiae at the dose of 80 µg/mL.