SYNTHESES OF ISOCARBACYCLIN BY HIGHLY REGIOSELECTIVE ALKYLATION OF ALLYLIC ALCOHOLS

Syntheses of isocarbacyclin (20) using highly regioselective alkylation of the new allylic alcohol intermediate 6 having an exocyclic double bond are described. The allylic alcohol 6 was prepared by (i) allylic rearrangement of the allylic alcohol 3 having an endocyclic double bond and (ii) reductive cyclization of γ-ethynyl aldehyde 11a which was synthesized from (R)-4-hydroxy-2- cyclopentenone derivative 1 in 5 steps. γ-Alkylation of the allylic alcohol 6 was achieved by the use of Murahashi's method to result in the highly regioselective formation of isocarbacyclin (regioselectivity 99%). α-Alkylation of the allylic alcohol 3 was also achieved to construct isocarbacyclin. © 1990.