Protection and deprotection of fused 2-amino-4(3H)-pyrimidinones: conversion of pterins and 5-deazapterins to 2,4-diamino derivatives

5-Deazapterins and pterins are readily converted to their 4-deoxy-4-amino derivatives (a lactam-to-amidine conversion) by reaction with 4-chlorophenyl phosphorodichloridate and 1,2,4-triazole to give intermediate 4-[1'-(1,2,4-triazolyl)] derivatives, followed by reaction with aqueous ammonia. Some anomalous results obtained by application of the Mitsunobu reaction (normally a lactam-to-lactim ether conversion) to 5-deazapterins are detailed