| | Re: why is a peptide bond stronger than an ester bond?
Esters contain a carbonyl center, which gives rise to 120° C-C-O and O-C-O angles. Unlike amides, esters are structurally flexible functional groups because rotation about the C-O-C bonds has a low barrier. Their flexibility and low polarity is manifested in their physical properties; they tend to be less rigid (lower melting point) and more volatile (lower boiling point) than the corresponding amides.
P.S. a peptide bond is an example of amide bond
Hope you understood the reason