Syn-copalyl-diphosphate synthase (, OsCyc1, OsCPSsyn, syn-CPP synthase, syn-copalyl diphosphate synthase) is an enzyme with systematic name 9alpha-copalyl-diphosphate lyase (decyclizing). This enzyme catalyses the following chemical reaction
This enzyme requires a divalent metal ion, preferably Mg<sup>2+</sup>, for activity.