Ring A was synthesised starting from geraniol 1 and involved acylation (acetic anhydride, DMAP, EtN) to 2, epoxidation (N-bromosuccinimide, tBuOH/HO then triethylamine) to 3, radical cyclisation (titanocene dichloride, manganese, triethylborane, 2,6-lutidine) to 4, alcohol protection (ethyl vinyl ether, camphorsulfonic acid) to 5, alcohol deprotection (NaOH, MeOH/THF/HO) to alcohol 6, Parikh-Doering oxidation to aldehyde 7, isomerization (DBU) to enone 8, organic reduction (sodium borohydride) to alcohol 9, alcohol protection (TBSCl, EtN) to TBS ether 10, hydrazone formation (HNNHTs) to 11 and  finally vinyl bromide formation (tBuLi, 1,2-Dibromoethane) in 12.