Final answer:
Ciprofloxacin is the potent broad-spectrum antibiotic that is entirely synthesized, as opposed to penicillin and azithromycin which are not entirely synthetic.
Step-by-step explanation:
The potent broad-spectrum antibiotic that is entirely synthesized is Ciprofloxacin. Penicillin and its derivatives, although they can be synthetic, are not entirely synthesized; they are typically produced through fermentation and subsequent chemical modification. Vancomycin is a glycopeptide and is produced by the fermentation of certain species of Actinobacteria. Azithromycin is a macrolide antibiotic that is semi-synthetic, derived from erythromycin. Chloramphenicol, while it is entirely synthesized and has broad-spectrum activity, is not listed among the choices provided.