How can I unite some elems in the list?

[Mike Ru]

I have a list.

list_ = ['did', 'is', 'not', 'come', 'will', 'kill', 'are', 'not']

I need to unite the elems that stand in front of 'not'. As a result, I need to get ->

list_ = ['did', 'is not', 'come', 'will', 'kill', 'are not']

I realy cannot figure how to do it out.