The biosynthesis of longifolene begins with farnesyl diphosphate (1) (also called farnesyl pyrophosphate) by means of a cationic polycyclization cascade.  Loss of the pyrophosphate group and cyclization by the distal alkene gives intermediate 3, which by means of a 1,3-hydride shift gives intermediate 4.  After two additional cyclizations, intermediate 6 produces longifolene by a 1,2-alkyl migration.