Thanks to SAMJ (the SOUTH AFRICAN MEDICAL JOURNAL), we can learn of first published guess as to penicillin's chemical structure

SAMJ : the South African Medical Journal

So much has been written about the earliest days of trying to determine the chemical structure of pure penicillin, in such truly massive tomes like "THE CHEMISTRY OF PENICILLIN" and "ANTIBIOTICS,VOLUME II", and much more delightfully in John Sheehan's lucid-but-learned "THE ENCHANTED RING" , that there seems little more to add.

But that is not so, thanks to the South African medical journal SAMJ and its enterprise at putting all of its over 100 years of back issues online and free to access.