Synthesis by alternative routes of our chem. library containing guanidino substitutes led to the identification of a rearrangement involving bis-dihydrotriazines.For example 1,4-bis{[4,6-diamino-1-methoxyphenyl-1,2-dihydro-1,3,5-triazin-2-yl]-4-phenoxymethyl}benzene (4) undergoes rearrangement to the isomeric 1,4-bis{[4-amino-6-methoxyphenylamino-1,2-dihydro-1,3,5-triazin-2-yl]-4-phenoxymethyl}benzene (5).The products of rearrangement were identified to be potent neuropeptide Y Y1 receptor competitive antagonists.A plausible mechanism for the rearrangement of 4 to 5 will be presented.