2-Aminooxazole is generally considered to play a central role in the origin of informational polymers. In the current contribution we use density functional calculations to investigate the detailed mechanism of 2-aminooxazole formation from the prebiotic soup according to the scenario suggested by M. W. Powner, B. Gerland and J. D. Sutherland, Nature, 2009, 459, 239-242. Parallel to the phosphate-catalyzed reaction pathway we also describe its water-assisted variant. Our calculations show that phosphate-catalysis is indispensable not only in the cyclization and the subsequent water-elimination steps, as previously suggested, but also in the very first reaction step leading to the formation of the carbinolamine intermediate. In addition, we suggest concurrent reaction channels for the cyclization and water-elimination reaction steps, both involving catalytic phosphate ions.