The Australian plant pasture-derived Streptomyces sp. CMB-PB042 yielded the unprecedented polycyclic C-aminoglycoside-pyranonaphthoquinone polyketides glenthamine A (1) and glenthimine A (2), the latter being a rare example of a naturally occurring imine, along with the spiropolyketide glenthol A (3), its hydrolysis artifact glenthol B (4), and the highly rearranged C-aminoglycoside-pyranonaphthoquinone glenthamide A (5). Structures including absolute configurations of 1-5 were assigned by spectroscopic analysis, chemical interconversion, and biosynthetic considerations.