The following questions are related to N-mannich base prodrugs. Which of the following is true about N-mannich base prodrugs?
1) N-mannich base prodrugs are used in the synthesis of pharmaceuticals.
2) N-mannich base prodrugs are a type of organic compound.
3) N-mannich base prodrugs are highly unstable.
4) N-mannich base prodrugs do not have any pharmacological activity.