Biosynthesis of Riboflavin Preparation of Phosphorylated Pyrimidine Intermediates

Abstract

2-Amino-5-nitro-6-(1'-D -ribityl)amino-4(3H)-pyrim idinone (6a) was converted to the dimethoxytrityl derivative, which was subsequently acetylated. The trityl residue was then removed, and the com pound was phosphorylated by the cyanoethyl method. Removal of the protecting groups yielded 2-am ino-5-nitro-6-(1'-D -ribityl) aminopyrimidinone 5'-phosphate (11a). Catalytic hydrogenation yielded the labile 2,5-diam ino-6-(T -D -ribityl) amino-4(3H )-pyrimidinone 5'-phosphate (3a) which is the substrate for a deaminase from yeast. 5-Amino-6-(1'-D -ribityl) amino- 2,4(1 H ,3H )-pyrim idinedione 5'-phosphate (3b) was prepared by an analogous sequence of reactions. It was further converted to 6,7-dimethyl-8-(1'-D -ribityl) lumazine 5'-phosphate (12b). The phosphoric acid esters prepared by the present procedures contained about 20% of an undesired isomer as a consequence of insufficient selectivity of the tritylation reaction