The spectrum of the enzymatically synthesized product was not the same as the laboratory synthesized (2S, 3S) standard; in particular, the coupling constant between the C 2 and C 3 protons (H a and H ...The spectrum of the enzymatically synthesized product was not the same as the laboratory synthesized (2S, 3S) standard; in particular, the coupling constant between the C 2 and C 3 protons (H a and H b in the above figure) was 4.3 Hz for the standard and 7.1 Hz for the enzymatic product.