Lyngbyaloside B, a new glycoside macrolide from a Palauan marine cyanobacterium, Lyngbya sp.

A Palauan collection of the marine cyanobacterium Lyngbya sp., which had already afforded diverse peptide-based cytotoxins, also yielded a new glycoside macrolide exhibiting slight cytotoxicity. The compound was termed lyngbyaloside B (1) due to its structural analogy to the previously isolated lyngbyaloside (2). Lyngbyaloside B (1) appears to be only the third glycoside macrolide and second brominated compound of its kind from a marine cyanobacterium. Its gross structure was determined by a combination of NMR spectroscopy and mass spectrometric techniques. The relative stereochemistry for the 12 stereocenters is proposed on the basis of proton-proton spin-coupling constants and ROESY data.