General strategy for the synthesis of B1 phytoprostanes, dinor isoprostanes, and analogs.

The synthesis of the phytoprostane B1 types I and II is achieved in high overall yield (35-53%) by only two principal transformations starting from 1,3-cyclopentanedione. The first side chain is attached via O-acylation of the 1,3-dione followed by rearrangement and reduction to give the 2-alkyl-1,3-diones 4a-c. After conversion into the corresponding vinylic iodides 5a-c, the second side chain is introduced by transition metal catalysis following Heck- or Sonogashira-type protocols. The whole spectrum of the phytoprostane B1 types I, II, and the dinor isoprostane B1 type III and some structural analogs are rapidly accessible along the same general protocol.