Total synthesis of the spirocyclic imine marine toxin (-)-gymnodimine and an unnatural C4-epimer

Stability of cyclic imine toxins: interconversion of pinnatoxin amino ketone and pinnatoxin A in aqueous media

Pinnatoxins belong to the cyclic imine (CI) group of marine toxins with a unique toxicological profile. The need for structural integrity of the aliphatic 7-membered cyclic imine for the potent bioactivity of pinnatoxins has been experimentally demonstrated. In this study, we probe interconversion of the natural cyclic imine and its open form, pinnatoxin A amino ketone (PnTX AK), under physiologically relevant aqueous conditions. Our studies demonstrate the high stability of PnTX A. The unusual stability of the imine ring in PnTX A has implications for its oral toxicity and detoxification. These studies, as well the access to PnTX amino ketone, were enabled by the total synthesis of (+)-pinnatoxin A completed previously in our laboratory.

Iron-catalyzed chemo- and stereoselective hydromagnesiation of diarylalkynes and diynes

Diarylalkynes are chemo- and stereoselectively hydromagnesiated in high yields at room temperature with an iron species generated in situ from FeCl(2)and EtMgBr. Functional groups such as bromide, iodide, amine, phenoxide, and alkene are well tolerated. Under similar conditions, diynes are chemo-, regio-, and stereoselectively hydromagnesiated. The resulting alkenylmagnesium compounds are a platform for further functionalization as a one-pot reaction.

Studies toward the synthesis of spirolide C: exploration into the formation of the 23-membered all-carbon macrocyclic framework

The synthesis of two complex subunits en route to spirolide C is described. A key alkyllithium addition to an aldehyde joins the fragments, which are advanced in order to investigate a ring-closing metathesis to form the 23-membered all-carbon macrocyclic framework.