I recently designed a product for a customer. After finishing the prototype, the customer informed me that he wanted to switch the ATTiny to the TI MSP430G2233 microcontroller in order to utilize a local fabrication house that he has a connection with... And he wants it done by Monday (I have no experience with TI chips). I told him that relearning C programming in 36 hours is a wee bit unrealistic. So my questions are: Is there a way to generate a .C file from a .PDE or .INO? Are there any shortcuts besides taking a refresher course in C then transposing the code? Anybody feel up to transposing some code? Might as well try, right 
Your code is already C.
Your problem is now porting libraries.
I hope you charged your client lots.
Converting the sketch to 'C' should be pretty straight forward - it is already more-or-less C++ and if you aren't deliberately using C++ features then relatively little work would be required to convert it back to 'C'. I'd be far more concerned by the fact that your sketch probably uses a runtime framework and perhaps additional interface libraries and any of these that do hardware-specific stuff will need to be ported to your new platform. Depending what features and libraries you use, that could be a huge job.
This could be really hard, or easy. I'd start by copying mysketch.ino to mysketch.c and compiling it. Deal with the first errors first (compilers get lost after errors). Make a .h file with extern declarations, then you'll know what you're faced with.
Good luck!
Since the MSP430 also is supported by gcc c++, you shouldn't have to do much conversion.
In fact, there is the Energia project designed to support Arduino code on the MSP430 cpus: Home · energia/Energia Wiki · GitHub