No, you can't. Actions cannot be "traded" for bonus actions.
This is a rather weird issue since one would think that it should be possible based on how you'd envision it, but the RAW don't allow it.
The Player's Handbook puts the following limitation on the number of bonus actions (emphasis mine):
Your Turn - Bonus Actions
You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available. (PHB, p. 189)
However, spells with a casting time of one bonus action are described as follows (emphasis mine):
Casting Time - Bonus Action
A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven't already taken a bonus action this turn. You can't cast another spell during the same turn, except for a cantrip with a casting time of 1 action. (PHB, p. 202)
Now, since spells with a casting time of a bonus action are described as "especially swift", one would think that using a regular action would suffice just as well. This view is further supported by the Sorcerer's Metamagic feature, Quickened Spell:
Metamagic - Quickened Spell
When you cast a spell that has a casting time of 1 action, you can spend 2 sorcery points to change the casting time to 1 bonus action for this casting. (PHB, p. 102)
Furthermore, there is a case to be made based on the wording of the casting time of one bonus action (emphasis, once more, mine):
You must use a bonus action on your turn to cast the spell, provided that you haven't already taken a bonus action this turn.
This can be taken to literally mean that you must use your bonus action only if you have not used it yet. However, the rules don't say what happens if you have already used your bonus action when you attempt to cast the spell. To me, the wording seems to imply that such a clause was supposed to be present, but it isn't.
So, while the rules technically don't allow for it, I don't see a reason, balance-wise, why you should not be able to use an action instead, provided that you have already used your bonus action for this turn and have yet to cast a spell. And I cannot think of a situation where you'd rather first spend your bonus action on something else in order to be able to cast a spell with a casting time of one bonus action with your action instead.