Abstract: New compounds for the inhibition of blood clotting proteins, and more particularly, to malonic acid derivatives of the formula I, wherein R(1), R(2), R(3), R(4), R(5), and R(6) have the meanings indicated in the claims. The compounds of formula I are inhibitors of the blood clotting enzyme factor Xa. Processes for the preparation of the compounds of formula I, methods of inhibiting factor Xa activity and of inhibiting blood clotting, use of the compounds of formula I in the treatment and prophylaxis of diseases, which can be treated or prevented by the inhibition of factor Xa activity such as thromboembolic diseases, and use of the compounds of formula I in the preparation of medicaments to be applied in such diseases. Compositions containing a compound of formula I in admixture or otherwise in association with an inert carrier, in particular pharmaceutical compositions containing a compound of formula I together with pharmaceutically acceptable carrier substances and auxiliary substances.