The present invention relates to terpene synthases that are capable of synthesizing mono-, bi- and/or tri-cyclic sesquiterpenes having a C2-C7 or a C3-C7 bond, starting from an acyclic pyrophosphate terpene precursor, farnesyl- pyrophosphate. Accordingly, for the first time, sesquiterpene synthases catalyzing the cyclization to the santalene and bergamotene carbon skeleton are disclosed. The present invention further relates to nucleic acid sequences encoding the sesquiterpene synthases and to methods for making terpenoids.