DPP dyes are based on the bicyclic heterocyclic compound diketopyrrolopyrrole. Naphthalene is formally a polycyclic compound, but is more specifically named as a bicyclic compound. Borneol is a bicyclic organic compound and a terpene derivative. This bicyclic compound consists of the fusion of benzene and imidazole. Being unsaturated, the bicyclic molecule is planar. Verbenone is a monoterpene, to be specific a bicyclic ketone terpene. Tropane is a nitrogenous bicyclic organic compound. Vetivazulene and guaiazulene are aromatic bicyclic sesquiterpenoids. Phalloidin is a bicyclic heptapeptide containing an unusual cysteine-tryptophan linkage. With bicyclic products, the cis isomer was selected for to varying degrees. The biosynthesis prostaglandins proceeds via an endoperoxide, a class of bicyclic peroxides. The compound is a prototype of a class of strained bicyclic hydrocarbons. The rearrangement is commonly used to form strained bicyclic and ring-fused systems. Therefore, fused bicyclic compounds have a "0" included in the brackets. One demonstration of this principle is found in the two bicyclic compounds depicted below.