The stereochemistry of the condensation product of salicylaldehyde and n-butylbarbituric acid by NMR techniques

Since the discovery of the 5-deazaflavin cofactor (coenzyme F420) as a naturally occurring compound, a great attention has been focused on several iso steric flavin analogues. One of the simplest approaches towards the synthesis of oxadeazaflavin, compound which the nitrogen at the N-10 position of 5-deazaflavin is replaced by oxygen, is the direct condensation between barbituric acid and salicylaldehyde. In this paper, the use of some NMR techniques so as to determine the stereochemistry of the preformed isomer has been described and a possible mechanism for this isomerization discussed