Total synthesis of siphonarin B and dihydrosiphonarin B.
The spirocyclic core of the siphonarins was constructed by a directed cyclization of a linear triketone, prepared using a Sn(II)-mediated aldol coupling and Swern oxidation at C9 and C13. To circumvent a facile retro-Claisen pathway generating a baconipyrone-type ester, a Ni(II)/ Cr(II)-mediated coupling reaction with vinyl iodide was used to complete the first synthesis of siphonarin B and dihydrosiphonarin B. A stable isomeric spiroacetal was also prepared which could not be equilibrated to the siphonarin skeleton.
Paterson
Ian
I
University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, UK. ip100@cus.cam.ac.uk
Chen
David Yu-Kai
DY
Franklin
Alison S
AS
D007659:Ketones / Q000138:chemical synthesis*; D015394:Molecular Structure; D013141:Spiro Compounds / Q000138:chemical synthesis*
D007659:Ketones; D013141:Spiro Compounds; C448330:siphonarin B