Cyclic Bipyridine Glycosides from the Marine-Derived Actinomycete <i>Actinoalloteichus cyanogriseus</i> WH1-2216-6

Cyanogrisides A–D (1–4), four new glycosidic derivatives of bipyridine featuring a novel cyclic glycoside generated by vicinal hydroxyl groups of an aglycone with both the anomeric center and the adjacent carbonyl of a keto sugar, were isolated from the marine-derived actinomycete Actinoalloteichus cyanogriseus WH1-2216-6. The structures of 1–4 were elucidated by spectroscopic analysis, X-ray single crystal diffraction, CD spectra, and chemical methods.