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).
A new approach was developed to construct quaternary stereogenic centers bearing nitrogen substituents in an enantioselective manner. The strategy takes advantage of [1,3]-chirality transfer from a chiral primary alcohol equivalent through an allyl cyanate-to-isocyanate rearrangement. This approach was employed in an efficient eight-step synthesis of the marine natural product, (+)-geranyllinaloisocyanide, in 43% overall yield.
Synthesis, Structure Revision, and Absolute Configuration of (+)-Didemniserinolipid B, a Serinol Marine Natural Product from a Tunicate Didemnum sp.