... 2- amino-5-formylamino-6-ribosylamino-4(3H)-pyrimidinone 5¢-phosphate; 3, 2, 5-diamino-6-ribosyl-amino-4(3H)-pyrimidinone 5¢-phosphate; 4, 5-amino-6-ribosylamino -2 , 4(1H,3H)-pyrimidinedione 5¢-phosphate; 5, 2, 5-diamino-6-ribityl-amino-4(3H)-pyrimidinone ... convert 2, 5-diamino- 6- ribosylamino-4(3H)-pyrimidinone 5¢-phosphate into 2, 5-diamino-6-ribitylami-no-4(3H)-pyrimidinone 5¢-phosphate, as shown by13C-NMR spectroscopyusing [2, 1¢ ,2 ,3¢,4¢,5 - 13C6 ]2, 5-diamino-6-ribosylamino-4(3H)-pyrimidinone5¢-phosphate ... 1¢carbon of product 5. However, using 4(R)-NADP 2 HFig. 4. Time-resolved13C-NMR signals. A mixture of [2, 1¢ ,2 ,3¢,4¢,5 - 13C6 ]-3 a and [2, 1¢ ,2 ,3¢,4¢,5 - 13C6 ]-3 b was generated by incuba-tion...