The 13C NMR spectrum of isoascorbyl palmitate showed
the carbonyl group at C-1 and double bonds between C-2
and C-3 in isoascorbic moiety were intact which indicated
that the enzymatic reaction happened in other position.
The C-6’ signal at 65.6 ppm in the synthesized isoascorbyl
ester had a down-field shift of 3.9 ppm in comparison with
that of isoascorbic acid (61.7 ppm). These results proved
the presence of an ester bond on C-6′of the isoascorbyl
moiety and correspond with the pattern of chemical shift
reported by Park et al. [8] and Stamatis et al. [19].