“Initially our efforts concentrated on the two allyl side chains attached to the heterocycle via a methylene group.”

“As mentioned in the introductory section, the nitrogen heterocycle pyrrole occurs in bone oil, in which it is formed by the decomposition of proteins upon strong heating.”

“Many other furan derivatives occur naturally, including vitamin C. The structures of furfural and vitamin C are: The sulfur heterocycle thiophene and related compounds are found in coal tar and crude petroleum.”