We extend Zirnbauer's color-flavor transformation in the bosonic sector to the color group SU(N-c). Because the flavor group U(N-b,N-b) is noncompact, the algebraic method by which the original color-flavor transformation was derived leads to a useful result only for 2N(b)<= N-c. Using the character expansion method, we obtain a different form of the transformation in the extended range N-b <= N-c. This result can also be used for the color group U(N-c). The integrals to which the transformation can be applied are of relevance for the recently proposed boson-induced lattice gauge theory. (C) 2005 American Institute of Physics.