Although soil-derived bacteria have proven to be the major source for commercial antibiotics and related bioactive metabolites, similar microorganisms found in marine habitats have been almost totally ignored, partly due to the diversity of unique bacteria in marine habitats and the difficulty in culturing many of them. As part of a continuing program to explore the nutritional requirements, distributions, and secondary metabolites of marine bacteria, we studied bacteria from bay and estuarine environments. A filamentous bacterium (isolate CNB-253, an unknown Streptomyces sp.) was isolated from shallow sediments in Bodega Bay, CA, which produces compounds with broad-screen antibacterial activity. Subsequent fermentation in saltwater-based media, EtOAc extraction of the whole broth, vacuum flash chromatographic purification, and HPLC purification led to the isolation of four new alkaloid esters of the rare phenazine class (1-4) and minor quantities of the known compounds 6-acetylphenazine-1-carboxylic acid (7) and saphenic acid (8). All four phenazine alkaloid esters (1-4) showed an identical molecular ion at m/z 414 amu (LREIMS) corresponding to C21H22N2O7. 1H NMR spectra revealed six aromatic protons and a hexose sugar pyranose functionality. Through 1H NMR coupling analyses, COSY experiments, acid hydrolysis, and NMR correlations (e.g., COLOC), the compounds were identified as regioisomeric quinovose esters of saphenic acid (8). The structures of 1 and 2 were confirmed as 3'-O-quinovosyl saphenate and 2'-O-quinovosyl saphenate, respectively, with 1 and 2 being α anomers that slowly equilibrated to their β anomers (3 and 4) upon standing. The CD spectrum of quinovose isolated from 1 and 2 indicated the rare L configuration. Comprehensive antibacterial testing showed that 1 and 2 exhibit modest broad-spectrum activity against numerous Gram-positive and Gram-negative bacteria: 1 is most potent against Hemophilus influenzae (MIC = 1 μg/mL) and Clostridium perfringens (MIC = 4 μg/mL), while 2 is more active against E. coli, Salmonella enteritidis, and Clostridium perfringens (all MIC = 4 μg/mL). The compounds were not appreciably cytotoxic against murine and human cancer cells in vitro.