The present application describes novel barbituric acid derivatives of formula I: ##STR00001## or pharmaceutically acceptable salt or prodrug forms thereof, wherein A, B, L, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, n, W, U, X, Y, Z, U.sup.a, X.sup.a, Y.sup.a, and Z.sup.a are defined in the present specification, which are useful as TNF-.alpha. converting enzyme (TACE) and matrix metalloproteinases (MMP) inhibitors.