Conversion of 3-dehydroshikimic acid

The stenc course of this reaction has now been determined s using samples of 6r and 6s-6-[SH]-3-dehydroshikimic acid as substrates. The results of these experiments show that it is the 6-pro r hydrogen that is eliminated in this reaction which therefore involves the rather unusual syn elimination of the elements of water. In a parallel study of the chemical conversion of 3-dehydroshikimic acid to protocatechuic acid—a reaction which occurs upon pyrolysis or heating with concentrated acid—the results indicated a nonstereo-specific reaction mechanism which involved a large isotope effect... 

The question may be asked what deep chemical deliberations prompted the choice of brucine from among the many possible alkaloids The answer is simple I happened to find a supply of brucine in the small collection of chemicals in the laboratory, tried it, and saw that it worked beautifully. I never knew from what earlier research it was left, but am glad that it was. Removal of the brucine as the insoluble picrate, and further routine manipulations gave a residue which crystallized slowly on contact with ether. I vividly remember my delight when I inspected the small test tube a few days after putting it into the refrigerator, and found that it contained a lot of pretty crystals of 3-dehydroquinic acid. I also recall the day on which this happened February 29, 1952 1952 was a leap year. Proof of structure and stereochemistry of the compound rests essentially on its reduction to quinic acid, on the absence of the pair of cis-hydroxyls present in shikimic acid, and on the conversion into 3-dehydroshikimic acid on mild treatment with acid. 

Some biochemical processes involve alcohol dehydration as a key step. An example is the conversion of 3-dehydroquinic acid to 3-dehydroshikimic acid. 

Partial conversion of 3-dehydroquinic acid to 3-dehydroshikimic acid (38) can be achieved by mild acid or base treatment and in contrast to the parallel enzymic conversion, which forms an integral part of the shikimate pathway, the mechanism for this reaction has been shown to involve a tram elimination of Hjax and the hydroxyl at C-1. 

Incorporation with some loss of the C-4 deuterium, possibly by conversion of the shikimic acid to 3-dehydroshikimic acid and loss of the C-4 hydrogen by enol-ization. The results obtained with shikimic acid are consistent with the... 

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