Dianhydrohexitole-based benzamidines were synthesised as potential factor Xa inhibitors. The key steps for the synthesis of a bis-benzamidine series were nucleophilic aromatic substitutions and Mitsunobu reactions to introduce substituted phenyl ether moieties. Mono-benzamidines with an ortho-substituted biphenyl group were prepared using a Negishi-type cross coupling procedure. The benzamidines showed high biological activity and selectivity for factor Xa inhibition.The serine protease factor Xa (fXa) plays a central role in the blood coagulation cascade. Forming the prothrombinase complex with factor Va in the presence of calcium ions and phospholipide, it converts inactive prothrombin to active thrombin, which finally leads to blood clotting. 1 FXa has emerged as a very attractive target to develop orally active antithrombotic agents. 2-4 Highly potent and specific inhibitors of fXa can effectively block both venous and arterial thrombosis formation. There are several advantages of direct fXa-inhibition compared with other concepts in the development of antithrombotic drugs, like thrombin inhibition, 2,5 e. g., (a) highly efficacious, orally active and selective fXa inhibitors result in smaller amounts of agent administered, (b) fXa has no known activity other than as a procoagulant, and (c) since fXa has slow activation kinetics, affecting its function should result in easier management of the balance between therapeutic and bleeding effects of a drug.Since the X-ray structure of fXa 6 is known, a rational inhibitor design is facilitated. Furthermore, several low-molecular weight ligands could be co-crystallised with fXa providing a precise insight into the enzyme-ligand interactions. 7-9 The active site consists of the catalytic triad (His57, Asp102, Ser195), identical to other serine proteases, with two adjacent specific S1 and S4 pockets 3 (Figure 1a). The primarily hydrophobic S1 pocket with the carboxylic acid side chain of Asp189 located at the bottom is able to recognize an arginine residue or its mimic motifs such as benzamidine. Aromatic residues Phe174, Tyr99, and Trp215 constitute the aryl binding S4 pocket. At the backside of S4 a cation-binding cluster is formed by amide carbonyls of several amino acids. A lead structure of fXa inhibitors should exhibit three parts: a S1 ligand, a S4 ligand and a linker connecting them. Nearly all synthetic, low-molecular weight fXa inhibitors described in the literature were developed according to this principle. Figure 2 shows a representative selection of highly active fXa inhibitors. Figure 1 a) Design of dianhydrohexitole-based fXa inhibitors 1 (n = 0, 1) with regard to relevant protein ligand interactions. b) Dianhydro-hexitoles isosorbide 2 and isomannide 3.Promising linker candidates are substituted dianhydrohexitoles of type 1 (Figure 1a). In particular, isosorbide 2 (one exo, one endo OH, Figure 1b) and isomannide 3 (two endo OH) could connect the S1 benzamidine group and the S4 moiety. Compounds of type 1 should have the advantage of combining high rig...

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Starting with isosorbide or isomannide several dianhydrohexitole-based benzamidines were synthesized as potential factor Xa inhibitors. The key steps for the synthesis of the bisbenzamidines were nucleophilic aromatic substitutions and Mitsunobu reactions to build up phenylethers. Another type of monobenzamidines had ortho-substituted biphenyl groups. Their synthesis necessitated an optimization of cross coupling procedures due to the great sterical hindrance of the ortho-substituent. The benzamidines showed biological activity against factor Xa and selectivity against other serine proteases.