Let K be a nonconstant ordinary differential field of characteristic zero with algebraically closed constants C that is finitely generated over C in the differential sense and let G be a connected linear algebraic group defined over C. Then G is the differential Galois group of a Picard-Vessiot extension of K.
This generalizes a result of Mitschi and myself where K is only assumed to be finitely generated in the algebraic sense over C and the proof follows in a similar manner. The complete paper can be found here . The appendix can be read independently of the rest of the paper.