Through NMR experiments of the reaction of barbituric acid with carbodiimide, a general synthetic procedure for the preparation of 5-diaminomethylenebarbiturates (DABA) was developed. This procedure is very simple and applicable to the preparation of large quantities of DABA derivatives. Through the X-ray structural study of one of the DABA derivatives it was established that these compounds have a ylide-type structure with strong charge separation inside the molecule. 5-Ylide-pyridinium-methyl barbituric acid derivatives were investigated with the isolation of 4-dimethylamino-1-(2,4,6-trioxohexahydro- pyrimidin-5-ylide-methyl)-pyridinium as well as its corresponding 1,3- dimethylbarbituric acid derivative with quantitative yields. An alternative approach was attempted in order to prepare chiral 5-ylide-pyridinium-methyl-barbituric acid derivatives thus containing a chiral center between the charge separation. The extreme instability of the derivatives under investigation afforded the unique isolation of 4-dimethylamino-1- [(1,3-dimethyl-2,4,6-trioxo-hexahydro-pyrimidin-5-yl)-phenyl-methyl]-pyridinium in quantitative yield.