Exams › JEE Advanced › Chemistry
Correct answer: 3
Penicillin G (benzylpenicillin) contains a bicyclic system consisting of a four-membered beta-lactam ring fused to a five-membered thiazolidine ring. The three chiral carbons are: C-3 (the carbon bearing the carboxylate group in the thiazolidine ring), C-5 (the carbon at the ring fusion bearing H and N), and C-6 (the carbon bearing the amide side chain on the beta-lactam ring). All three have four distinct substituents, making them stereocentres. The natural configuration is 2S,5R,6R (using IUPAC numbering).