Thanks for the further information, Al. Whitesmiths C is credited as the first commercial C compiler, and you're absolutely correct that it was also the first that wasn't derived from the Unix C.
Later, in 1980, Small C was first released. An interpreter version was done as well. It's not strictly a CP/M C compiler, but certainly came after Whitesmiths and BDS-C.
But as far as the original question, the answer is simply that yes, there were C compilers available in the window between the first C on Unix and the several on CP/M.
Incidentally, K&R wasn't published until 1978.