I changed a little the original core files to add support for te 4313 (on the 2313 base), and then i replaced the winavr in the arduino folder with the new one. (the old one says:4313 supported only for assebly)
after creating a board.txt entry for my tests, i've been able to compile the blink setch and it works 
now i have to do further tests but it looks promising 