Pyrrolobenzodiazepines are a group of DNA-alkylating natural products. What is the exact meaning of the [2,1-c][1,4] part in the full descriptive name pyrrolo[2,1-c][1,4]benzodiazepine?
General structure of pyrrolo[2,1-c][1,4]benzodiazepines. The 2-3 double bond is not present in all natural products.
Thanks to Loong I may be able to figure it out.
1,4-Benzodiazepine is pretty trivial, as [1,4] defines the position of the nitrogens like this:
For clarification [1,5] could look like 1H-1,5-benzodiazepine:
According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), isomers of fused polycyclic ring systems are distinguished by lettering each peripheral side of the parent component using the italic letters a, b, c, etc., beginning with a for the side numbered ‘1,2’, b for ‘2,3’, etc.
So the letters would be:
So pyrrolo[2,1-c] would be attached to the c-side. I still need clarification in one point though:
Does the direction 2,1 (NOT 1,2) show the direction of the attachment?