Full Idea
Frege's approach provides no concept of analyticity (hence Quine's attack), so there is no notion of the analytic a priori under which to bring the metaphysician's synthetic a priori propositions.
Gist of Idea
Frege fails to give a concept of analyticity, so he fails to explain synthetic a priori truth that way
Source
comment on Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884]) by Jerrold J. Katz - Realistic Rationalism Int.xxi
Book Reference
Katz,Jerrold J.: 'Realistic Rationalism' [MIT 2000], p.-14
A Reaction
So Frege might have been a logical positivist, if only he had given himself the right tools for the job?
Related Idea
Idea 9370 A statement is analytic if substitution of synonyms can make it a logical truth [Frege, by Boghossian]