Figure 3.

A) Partial HSQC spectrum showing the region of crosspeaks of C-2 with its directly connected hydrogens H’ and H’’ for compound (2-¹³C,2-²H)-1 obtained by enzymatic conversion of (2-¹³C)GPP in deuterium oxide. Deuterium was specifically incorporated into H’ position. The indicated chemical shift data are for unlabelled 1 (for full data cf. Table S1, Supporting Information File 1). Blue circles point to ¹³C-labelled carbons. B) Intramolecular proton transfer from the protonated hydroxy function in (S)-7 to C-2.