Prior to that discovery in 1909, another fungal metabolite called Ergothioneine (ERGO), a naturally occurring amino acid that contains a sulfur atom on the imidazole ring, was discovered in Ergot ...

The purine structure consists of a pyrimidine ring (positions 1 to 6) fused to an imidazole ring (positions 7 to 9). Adenine and guanine, the two most common purines in DNA and RNA, share this core ...