This compound is originated from mevalonic acid pathway which produce dimethylallyl diphosphate (DMAPP) from acetyl-CoA. Three DMAPPs, or one DMAPP and two isopentenyl diphosphate (IPP), are made into a　farnesyl diphosphate (FPP), which is the fundamental precursor of sesquiterpene, and then sesquiterpene cyclise enzymes cause it a cyclization. The synthesis up to here is well known, though process after the first cyclization was unclear.
Anislactone-type sesquiterpenes which merrilactone A belongs to has been thought to be biosynthesized from majucin since they have γ-lactone. However, this pathway has trouble to elucidate some configurations and other feature they have. The biosynthesis shown in the figure was newly proposed and solved these problems.
The point of this pathway is that seco-prezizaane, anislactone and tashironin group which are all found in Illicium are all derived from the same intermediate 6. This is expected to be able to give all characteristic sesquiterpenes in Illicium plants a reasonable explanation of biosynthesis.