Abstract 10-Alkyl-2-amino-2-deoxo-5-deazaflavins were prepared by the condensation of 2- amino-6-chloro-5-formylpyrimidin-4 (3H)-one with the corresponding N-alkylanilines. 2- Amino-10-p-tolyl-2-deoxo-5-deazaflavin was prepared by the condensation of 2-amino-6-p- toluidinopyrimidin-4 (3H)-one with o-chlorobenzaldehyde. Some reactivities of 2- aminopyrimidin-4 (3H)-ones are described.