What results in this case is a kind of ‘mixed acetal’ in which the carbon that was originally part of the aldehyde is bonded to one oxygen and one nitrogen. In the first step of purine base synthesis,...What results in this case is a kind of ‘mixed acetal’ in which the carbon that was originally part of the aldehyde is bonded to one oxygen and one nitrogen. In the first step of purine base synthesis, a molecule of ammonia attacks the anomeric carbon of PRPP, displacing the diphosphate group in a two-step (S N 1) mechanism with an oxonium ion intermediate.
