A practical synthesis of chiral tricyclic cyclopenta[b]benzofuran, a key intermediate of BeraprostElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ob01346e

A novel formal synthesis of Beraprost ( 1 ) is described. The tricyclic cyclopent[ b ]benzofuran core is efficiently prepared from (−)-Corey lactone diol in 12 steps with an overall yield of 37.4%. Key features of the strategy include a ring-closing metathesis reaction and aromatization to form the tricyclic cyclopenta[ b ]benzofuran framework, and selective halogenation/formylation to install the butyrate side-chain. A novel formal synthesis of Beraprost ( 1 ) is described.