EXAMINATION OF THE STRUCTURE OF AN UN-KNOWN GREEN FLUORESCENT COMPOUND, COMPOUND G₂, ACCUMULATED IN NON-GROWING CELLS OF EREMOTHECIUM ASHBYII BY THE ADDITION OF DIMERIC DIACETYL

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The addition of dimeric diacetyl to Eremothecium ashbyii caused simultaneous accumulation of two green fluorescent compounds with the inhibition of riboflavin formation in non-growing cells. One compound, referred to as Compound G₁, was identified as 6, 7-dimethyl-8-ribityllumazine as reported previously and the other is referred to as Compound G₂. The latter compound was considered to be 6-methyl-7-(2-hydroxy-2-methyl-3-oxobutyl)-8-ribityllumazine because a violet fluo-rescent compound, 6-methyl-7-hydroxy-8-ribityllumazine was derived from Compound G₂ in the presence of p-quinone and because the known action mechanism of dimeric diacetyl as a trapping agent of possible intermediates in the biosynthetic pathway.
The results indicate that an immediate intermediate to 6, 7-dimethyl-8-ribityllumazine in the biosynthetic pathway of riboflavin is 4-ribitylamino-5-amino-2, 6-dihydroxypyrimidine, whose pyrimidine portion is derived by the elimination of a dimeric diacetyl fragment from the molecule of the isolated lumazine.