Reports of a high-affinity ligand for E-selectin, sialyl di-Lewis(x) (sLe(x)Le(x), 1), motivated us to incorporate modifications to previously reported biphenyl-based inhibitors that would provide additional interactions with the protein. These compounds were assayed for the ability to inhibit the binding of sialyl Lewis(x) (sLe(x), 2) bearing HL-60 cells to E-, P-, and L-selectin fusion proteins. We report that dimeric or trimeric compounds containing multiple components of simple nonoligosaccharide selectin antagonists inhibit sLe(x)-dependent binding with significantly enhanced potency over the monomeric compound. The enhanced potency is consistent with additional binding interactions within a single selectin lectin domain; however, multivalent interaction with multiple lectin domains as a possible alternative cannot be ruled out. Compound 15e (TBC1269) showed optimal in vitro activity from this class of antagonists and is currently under development for use in the treatment of asthma.

The calcium dependent E-selectin/sialyl Lewisx (sLex) interaction plays a key role in inflammation where it mediates the rolling of leukocytes prior to firm adhesion and extravasation from the vasculature. A model of E-selectin/sLex binding, along with previously reported structure-activity relationships of sLex-related oligosaccharide, was used in the rational design of non-oligosaccharide inhibitors of this pivotal interaction. A palladium-mediated biaryl-coupling (Suzuki) reaction was used as the key step to prepare a number of substituted biphenyls which were assayed for their ability to inhibit the binding of E-, P-, and L-selectin-IgG fusion proteins to sLex expressed on the surface of HL60 cells. Some of the compounds developed had greater in vitro potency than the parent sLex tetrasaccharide and are currently being evaluated in in vivo models of inflammation to select a candidate for clinical development.

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We have previously disclosed the discovery of 2,4-disubstituted anilinothiophenesulfonamides with potent ET(A)-selective endothelin receptor antagonism and the subsequent identification of sitaxsentan (TBC11251, 1) as a clinical development compound (Wu et al. J. Med. Chem. 1997, 40, 1682 and 1690). The orally active 1 has demonstrated efficacy in a phase II clinical trial of congestive heart failure (Givertz et al. Circulation 1998, 98, Abstr. #3044) and was active in rat models of myocardial infarction (Podesser et al. Circulation 1998, 98, Abstr. #2896) and acute hypoxia-induced pulmonary hypertension (Chen et al. FASEB J. 1996, 10 (3), A104). We now report that an additional substituent at the 6-position of the anilino ring further increases the potency of this series of compounds. It was also found that a wide range of functionalities at the 3-position of the 2,4,6-trisubstituted ring increased ET(A) selectivity by approximately 10-fold while maintaining in vitro potency, therefore rendering the compounds amenable to fine-tuning of pharmacological and toxicological profiles with enhanced selectivity. The optimal compound in this series was found to be TBC2576 (7u), which has approximately 10-fold higher ET(A) binding affinity than 1, high ET(A)/ET(B) selectivity, and a serum half-life of 7.3 h in rats, as well as in vivo activity.

A highly convergent, enantioselective total synthesis of (+)-phyllanthocin (l), the aglycon of the novel antineoplastic agent phyllanthoside (2), has been accomplished. The key feature of the approach entailed the dipolar cycloaddition of the nitrile oxide 7 with the optically active, bicyclic lactone 6, a substance that presented a sterically and electronically biased framework to ensure that this reaction proceeded with reasonable levels of regio-and stereoselectivity to afford 11 as the major product. The dispensible oxygen function at C(1) was removed from 11 in three straightforward operations to afford 18, which underwent a directed aldol reaction with the protected aldehyde 8c to give a mixture (1.2:l) of the two adducts 21c and 22c. Treatment of 21c with hydrofluoric acid in methanol gave a mixture of methyl glycosides 23 and 24. Similar treatment of 22c afforded a single methyl glycoside 25, which was transformed into 24 by oxidation and reduction. Unveiling of the latent @-hydroxy ketone array at C(5) and C(7) was achieved by hydrogenolysis and hydrolysis of the isoxazoline ring of 23 and 24 to give intermediates that underwent smooth acid-catalyzed, kinetic spiroketalization to furnish 3 as the major product. The spiroketal3 was then converted into (+)-phyllanthocin (1) according to protocols previously developed by Williams. Brimble, M. A. J. Chem. SOC., Chem. Commun. 1985, 781. (n) Barrett, A. G. M.; Carr, R. A. E.; Attwood, S. V.; Richardson, G.; Walshe, N. D. A.

Abstract. Binding of the P-, L-, and E-selectins to sialyl Lewis (CI Ͻ1 is synergistic; CI ϭ 1 is additive; and CI Ͼ1 is antagonistic). Similarly, BIMO interacted synergistically with sirolimus (CI ϭ 0.64) and FTY720 (CI ϭ 0.22). While the mechanism of immunosuppression was being analyzed, decreased infiltration of CD4 ϩ , CD8 ϩ , and macrophages on day 7 after grafting was observed. Multiple cytokines were also expressed, including IL-1␣, IL-1␤, IL-2, IL-4, IL-6, IL-10, IL-12, IL-18, TNF-␣, and IFN-␥ in kidney allografts on days 3, 5, and 7 after grafting, as measured by a ribonuclease protection assay. Furthermore, at similar time points, BIMO treatment reduced intragraft expression of P-selectin glycoprotein ligand-1, CX 3 CL1, CCL19, CCL20, and CCL2. Thus, BIMO blocks allograft rejection by reduction of intragraft expression of cytokines and chemokines.Whereas nearly all cells in an adult human are sessile, the majority of leukocytes provide a mobile defense of the individual's integrity (1). Precursors of leukocytes continuously undergo differentiation in the bone marrow and the thymus, whereas mature leukocytes continuously traffic between the spleen and the lymph nodes. Efficient deployment to an inflammatory site requires polarization, mobilization, and migration of leukocytes during processes that are controlled by adhesion molecules and chemokines (2). These molecules participate in the process of ischemia/reperfusion (I/R), as well as in acute and chronic rejection responses toward organ allografts (3,4).Adhesive interactions with the vascular endothelium initiate the migration of leukocytes to sites of inflammation. In this cascade of events (rolling, attachment, spreading, and transendothelial migration), the selectin family (P-, E-, and L-selectins) is largely involved in rolling and attachment (5). Rolling is initiated by the interaction of selectins with sialyl Lewis x (sLe x ) ligand (6); all selectins have an NH 2 -terminal, lectinlike domain binding to sLe x and other related ligands in a Ca 2ϩ -dependent manner (7). Two selectins are expressed on endothelial cells, namely, P-selectins, which are stored in granules and rapidly translocated to the cell surface, and E-selectins, which are induced by inflammatory cytokines (8). Within minutes after reperfusion, endothelial cells express P-selectins that mediate leukocyte rolling over the vascular lining.The main ligand for P-selectin is P-selectin glycoprotein ligand-1 (PSGL-1), which is a disulfide-bonded homodimeric mucin-like glycoprotein expressed on leukocytes, platelets, and CD34 ϩ cells (9). Functional PSGL-1 is modified with sialylation and fucosylation of O-linked sugars, as well as sulfation of tyrosine residues on the N-terminus (10). Engagement of PSGL-1 by P-selectins slows the movement of leukocytes and sparks a cascade of signaling pathways, leading to the expression of multiple adhesion molecules (11). During rolling, the leukocytes start expressing integrins triggered by cytokines and

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