JAMES JACOB:
An alchemist CAN take item creation feats, in any event. When an item calls for a spell prerequisite, the alchemist simply substitutes his extract of the same name. This does mean that, other than potions, there’s a lot of specific items an alchemist won’t qualify for, so it might be a good idea to max out your Spellcraft skill for all the requirements you’ll be missing…
http://paizo.com/threads/rzs2mz2b?How-does-the-alchemist-use-discoveries-th at#4