Scabrosin,a member of epipolythiodiketopiperazines(ETPs),is the only compound with biological activity isolated from the lichen xanthoparmelia scabrosa(presumably the fungal partner)in 1978.The 6-5 membered moiety in scabrosin can be built by an intramolecular nucleophilic substitution,wherein the amino group attacks the chiral carbon with a good leaving triphenylphosphine group to form a 5-membered N-heterocycle(Figure 1).