Terpenes represent the largest and structurally most diverse group of natural products. Since ancient times, humans have used terpenes contained in essential oils as medicinal agents, preservatives, and fragrances in their everyday life. Nowadays they are used in many scientific, industrial, and medical fields for their diverse properties. In the perfume and food industries, for example, sesquiterpenes in particular are used for their characteristic fragrances and flavors.In the ongoing search for new terpenes with sensory properties and biological activity, enzyme catalyzed biotransformations represent an exciting and efficient approach. Synthetically accessed, non natural linear terpenoids can be used as precursors for terpene cyclases to obtain various cyclic products. By using different enzymes, it is also possible to obtain multiple different products starting from the same substrate.In this dissertation, the synthesis of nine non natural linear farnesyl pyrophosphate derivatives and their subsequent application as substrates in biotransformations with eight selected heterologously expressed sesquiterpene cyclases is presented. The generated novel cyclization products were isolated, purified, and their structure elucidated. The information obtained from these results was used to investigate the cyclization mechanisms and substrate flexibility of the enzymes used.