5 One pot synthesis towards pharmaceutical precursor
Ethyl
2-[(4-chlorophenyl)methyl]-3-oxobutanoate (3g ) is the
precursor of antituberculosis drugs[3] and can be
produced by tandem reaction optimized above. Motivated by the
pharmaceutical application, we tried to scale up the synthesis of3g . To avoid enzyme deactivation at high concentrations ofp -chlorobenzaldehyde, fed-batch was selected. 50 mM 1g ,
50 mM EAA and 50 mM glucose were added at 2 h, 4 h, 7 h, 10 h, 13 h, 17
h and 20 h, respectively. The reaction progress was monitored by GC and
the result was shown in Figure 5, the product was continuously
synthesized within 13 hours. Then, 1.5 mg mL-1 NerA
and 1 mg mL-1 GDH were compensated for the loss of
enzyme activity. At 20 hours, the rate of reaction slowed down again and
stopped feeding. The synthesis of 3g was completed at 28 hours,
and the yield of 1g was 91%. Isolation of most products was
simply extracted by ethyl acetate, resulting in 88% yield (880 mg). The
transformation could be applied in
preparative-scale synthesis
without sacrificing yield.