Caylobolide A, a unique 36-membered macrolactone from a Bahamian Lyngbya majuscula.

[structure: see text]. A new 36-membered macrolactone, (25S,27S,29S,33S)-caylobolide A, was isolated from the Bahamian cyanobacterium Lyngbya majuscula. The structure of caylobolide contains an unprecedented repeated unit-a contiguous pentad of 1,5 diols-and a 1,3,5-triol. The relative steroechemistry of the 1,3,5-triol was determined using Kishi's Universal NMR database, and absolute stereochemistry at C25,27,29 and C33 were determined by Mosher's analysis. Caylobolide A exhibited in vitro cytotoxicity against human colon tumor cells (IC50 HCT 116, 9.9 microM).