Fig. 4

¹H NMR spectra of amoxicillin (A) and its degradation product (D3) isolated from the co-suspension of AMX and MG (B). The spectra were measured in DMSO-d₆. The major signals due to (5R)-amoxicillin diketopiperazine were observed with the minor ones due to the (5S)-diastereomer. The numerical characters on the spectrum (B) show assignments of the signals to the positions of the chemical structure of amoxicillin diketopiperazine (see Fig. 3). The integral values are shown under the ¹H signals