Unstructured Text to Structured Data
If you are only working for cases like the example you cited, you are better off using some manual rule-based that is 100% predictable and covers 90% of the cases it might encounter production..  
You could enumerable lists of all possible brands and categories and detect which is which in an input string cos there's usually very little intersection in these two lists..  
The other two could easily be detected and extracted using regular expressions. (1-3 digit numbers are always sizes, etc) 
Your problem domain doesn't seem big enough to warrant a more heavy duty approach such as statistical learning.
I am looking for references (tutorials, books, academic literature) concerning structuring unstructured text in a manner similar to the google calendar quick add button.
I understand this may come under the NLP category, but I am interested only in the process of going from something like "Levi jeans size 32 A0b293"
to: Brand: Levi, Size: 32, Category: Jeans, code: A0b293
I imagine it would be some combination of lexical parsing and machine learning techniques.
I am rather language agnostic but if pushed would prefer python, Matlab or C++ references
Thanks