224 KoNRAD Block 



DISCUSSION 



Bentley: I would like to describe very briefly another direct con- 

 version of glucose into a 6-membered ring compound, which Dr. 

 Arnstein and myself have observed, apparently without the inter- 

 mediates of the glycolysis cycle being involved. We have been investi- 

 gating the biosynthesis of a mould product, kojic acid, which has this 

 structure: — 



H0-C2 4CH 



-CHl 5C-CH,0H 

 \ / 



This compound is a y-pyrone, and contains the same number of carbon 

 atoms as glucose. It is formed by various Aspergilli, and we have, 

 rather similarly to Dr. Bloch, used [l-^^CJglucose. When we allowed 

 the organism to metabolize this glucose, isolated the kojic acid and 

 degraded it, we found that at least 80 per cent of the ^^C was located in 

 carbon atom 1. The degradation was an alkaline hydrolysis of the 

 dimethyl compound, which results in the formation of formic acid 

 from carbon atom 1, with the production of methoxyacetone and 

 methoxyacetic acid. We have also shown that this hydrolysis goes 

 through a symmetrical intermediate, and at the moment the only 

 carbon atoms on which we can really argue are 1 and 4. (The latter is 

 obtained as iodoform after treating the methoxyacetone with alkaline 

 hj^oiodite.) However, since 80 per cent of the activity is in carbon 

 atom 1, we believe that this represents a direct conversion of glucose 

 to this 6-membered carbon compound without the intermediary for- 

 mation of triose phosphate. 



It is interesting that this compound can also be formed using dihy- 

 droxyacetone as a sole carbon source, and we have been very interested 

 to know how it jarises in this case; whether the dihydroxyacetone is 

 first synthesized into glucose or whether there is a direct utilization. 

 For this purpose we have synthesized dihydroxyacetone containing 

 i*C. The synthesis involves the condensation of formaldehyde with 

 ["CJnitromethane, yielding "CN02(CH20H)3; this compound is treated 

 with sodium in methanol, when one hydroxymethyl group is lost with 

 formation of the sodium salt of nitropropanediol, (HOCH2)2^*C = N02Xa. 

 On treatment with acid the nitro group is split off and we get the ketone 

 formed. It is not possible to crystallize the dihydroxyacetone at this 

 stage, and we have to add carrier material in order to get it out. But 

 the activity is certainly there, as shown by constant activity on recry- 

 stallization and the preparation of derivatives. We are currently 

 studying the formation of kojic acid from this compound labelled in the 

 2 position. It may be that the 80 per cent of activity that we find in 



