2 FOR ONE - STRUCTURE REVISION OF THE MARINE SESTERTERPENE TETRONIC ACID STROBILININ TO (8Z,13E,20Z)-STROBILININ AND (8E,13Z,20Z)-STROBILININ

A reinvestigation of the known marine natural product strobilinin has revealed it not to be a single compound (2), but to consist of two naturally occurring geometric isomers, neither of which corresponds to the structure originally assigned. These isomers, (8E,13Z,20Z)-strobilinin (10) and (8Z,13E,20Z)-strobilinin (11), were resolved, characterized and identified as their respective acetate derivatives (6) and (7), and their structures assigned by spectroscopic analysis. It would appear that the absolute stereochemistry of the strobilinins is very likely opposite to that of co-occurring variabilin (1).