5-Dehydroquinic acid preparation

The same conclusions were also obtained in a study of the forward dehydration reaction . Chemical methods were used to prepare samples of 2(s)-2-[ H]-3-dehydroquinic acid (26) and 2(r)-2-[ H]-3-dehydroquinic acid (27) . These were treated with an enzyme preparation from Escherichia coli 83-24 and an enzyme system for the cyclic generation of NADPH to give samples of (—)-shikimic... 

An enzyme that converts dehydroquinic acid to dehydroshikimic acid was obtained from wild-type E. eoli or Aerdbactor cells and named 5-de-hydroquinase 21S). This enzyme was absent in auxotrophs that accumulated dehydroquinic acid. No evidence of a cofactor was observed, but the enzyme preparation was too crude for this to be conclusive. 

Further support for 3-deoxy-D-arofefno-heptulosonic acid 7-phosphate as an intermediate in aromatic biosynthesis was given by the isolation of a phosphorylated keto acid from filtrates of a mutant of E. cali, blocked before 5-dehydroquinate. This compound was shown to be identical with synthetic 3-deoxy-D-ara wno-heptulosonic acid 7-phosphate by its chromatographic behavior, chemical properties, and conversion to 5-dehydroquinate by a purified enzyme-preparation. ... 

The conversion of 3-deoxy-D-am6mo-heptulosonic acid 7-phosphate to 5-dehydroquinate was also abolished by the chelating agent (ethylenedi-nitrilo)tetracetate, and could be restored partially by Zn and completely by Co . Occasionally, carbon-treated preparations could not be reactivated by diphosphopyridine nucleotide alone only by the further addition of cobaltous salts was activity restored. Attempts to acciunulate an intermediate by omitting, from such extracts, either diphosphop dine nucleotide or Co were not successful, and, unless both of these were simultaneously present, the 3-deoxy-D-oroWno-heptulosonic acid 7-phosphate remained xmchanged. 

Similarly, the methylene analogue of 3-deoxy-D-arabinoheptulosonic acid 7-phosphate (DAHP) has been prepared from the C7 aldehyde derived from methyl (methyl 3-deoxy-D-arabinoheptulopy-ranosid)onate in 60% yield.The protected 3-dehydroquinate (DHQ) has also been used as starting material in the synthesis of phosphonic DHQ synthase inhibitors by the same methylenediphosphonate approach in 56% yield (Scheme 8.66). Preparation of the phosphonate analogue of porphobilinogen is another illustration of the advantages of this synthetic procedure. ... 

---