Figure 6.

Predicted Raman spectra for molecules 2 and 3 (Figure 5), which mimic the Δ¹ or Δ²-acyl enzyme, respectively. The dominant features arise from the highly polarizable N1=C2 stretch around 1600 cm^-1 (solid line) or C2=C3 stretching motions around 1550 cm-1 (dashed line). Hydrolysis of meropenem shows that the Δ¹-pyrroline is strongly favored thermodynamically over the Δ² isomer under basic conditions, while approximately equal amounts of the Δ¹ and Δ² isomers are present under acidic conditions.