Scalable synthesis of methyl ent-isocopalate and its derivatives

An efficient and convenient synthetic route was developed to prepare the tricycle diterpene intermediates 1–3 starting from commercially available (−)-sclareol. This improved approach involving four-step reactions provides large-scale (30–40 g) methyl ent-isocopalate in 61% overall yield, which could supply sufficient material for the synthesis of marine natural products containing tricyclic diterpenes.