a defendant must make a "particularized showing that materials exist requiring disclosure" in order to sustain a motion to compel. United States v. Juliano, No. 99 Cr. 1197, 2000 WL 640644, at ■2 (S.D.N.Y. May 18, 2000); see United States v. Evanchik, 413 F.2d 950, 953 (2d Cir. 1969) ("[T]he assurance b