Systematic structure-based design and stereoselective synthesis of novel multisubstituted cyclopentane derivatives with potent antiinfluenza activity

The design and synthesis of novel, orally active, potent, and selective inhibitors of influenza neuraminidase differing structurally from existing neuraminidase inhibitors are described. X-ray crystal structures of complexes of neuraminidase with known five- and six-membered ring inhibitors revealed that potent inhibition of the enzyme is determined by the relative positions of the interacting inhibitor substituents (carboxylate, glycerol, acetamido, hydroxyl) rather than by the absolute position of the central ring. This led us to design potential neuraminidase inhibitors in which the cyclopentane ring served as a scaffold for substituents (carboxylate, guanidino, acetamido, alkyl) that would interact with the four binding pockets of the neuraminidase active site at least as effectively as those of the established six-membered ring inhibitors such as DANA (2), zanamivir (3), and oseltamivir (4). A mixture of the isomers was prepared initially. Protein crystallography of inhibitor-enzyme complexes was used to screen mixtures of isomers in order to identify the most active stereoisomer. A synthetic route to the identified candidate 50 was developed, which featured (3 + 2) cycloaddition of 2-ethylbutyronitrile oxide to methyl (1S,4R)-4[(tert-butoxycarbonyl)amino]cyclopent-2-ene-1-carboxylate (43). Structures of the synthetic compounds were verified by NMR spectroscopy using nuclear Overhauser effect methodology. Two new neuraminidase inhibitors discovered in this work, 50 and 54, have IC(50) values vs neuraminidase from influenza A and B of <1 and <10 nM, respectively. These IC(50) values are comparable or superior to those for zanamivir and oseltamivir, agents recently approved by the FDA for treatment of influenza. The synthetic route used to prepare 50 and 54 was refined so that synthesis of pure active isomer 54, which has five chiral centers, required only seven steps from readily available intermediates. Further manipulation was required to prepare deoxy derivative 50. Because the activities of the two compounds are comparable and 54 [RWJ-270201 (BCX-1812)] is the easier to synthesize, it was selected for further clinical evaluation.

Addition of lithiated 9-deazapurine derivatives to a carbohydrate cyclic imine: convergent synthesis of the aza-C-nucleoside immucillins

Means have been developed for the synthesis and addition of 9-deaza-9-lithiopurine derivatives to the carbohydrate-derived cyclic imine 6 in facile convergent syntheses of biologically active aza-C-nucleosides.

Purine nucleoside phosphorylase inhibitor BCX-1777 (Immucillin-H)--a novel potent and orally active immunosuppressive agent

Patients with purine nucleoside phosphorylase (PNP) deficiency present a selective T-cell immunodeficiency. Inhibitors of PNP are, therefore, of interest as potential T-cell selective immunosuppressive agents. BCX-1777 is a potent inhibitor of PNP from various species including human, mouse, rat, monkey and dog, with IC50 values ranging from 0.48 to 1.57 nM. BCX-1777, in the presence of 2'-deoxyguanosine (dGuo, 3-10 microM), inhibits human lymphocyte proliferation activated by various agents such as interleukin-2 (IL-2), mixed lymphocyte reaction (MLR) and phytohemagglutinin (PHA) (IC50 values < 0.1-0.38 microM). BCX-1777 is a 10-100-fold more potent inhibitor of human lymphocyte proliferation than other known PNP inhibitors like PD141955 and BCX-34. Nucleotide analysis of human lymphocytes indicate that inhibition of proliferation by BCX-1777 correlates with dGTP levels in the cells. BCX-1777 has excellent oral bioavailability (63%) in mice. At a single dose of 10 mg/kg in mice, BCX-1777 elevates dGuo to approximately 5 microM. BCX-1777 was not effective in mouse T-cell models such as delayed type hypersensitivity (DTH) and splenomegaly because mouse T-cells do not accumulate dGTP as do human T-cells. However, in the human peripheral blood lymphocyte severe combined immunodeficiency (hu-PBL-SCID) mouse model, BCX-1777 was effective in prolonging the life span 2-fold or more. This is the first known example of a PNP inhibitor that elevates dGuo in mice similar to the levels observed in PNP-deficient patients. Furthermore, these dGuo levels are also required for in vitro T-cell inhibition by BCX-1777. Thus, BCX-1777 represents a novel class of selective immunosuppressive agents that could have therapeutic utility in various T-cell disorders.

Comparison of the anti-influenza virus activity of RWJ-270201 with those of oseltamivir and zanamivir

We have recently reported an influenza virus neuraminidase inhibitor, RWJ-270201 (BCX-1812), a novel cyclopentane derivative discovered through structure-based drug design. In this paper, we compare the potency of three compounds, RWJ-270201, oseltamivir, and zanamivir, against neuraminidase enzymes from various subtypes of influenza. RWJ-270201 effectively inhibited all tested influenza A and influenza B neuraminidases in vitro, with 50% inhibitory concentrations of 0.09 to 1.4 nM for influenza A neuraminidases and 0.6 to 11 nM for influenza B neuraminidases. These values were comparable to or lower than those for oseltamivir carboxylate (GS4071) and zanamivir (GG167). RWJ-270201 demonstrated excellent selectivity (>10,000-fold) for influenza virus neuraminidase over mammalian, bacterial, or other viral neuraminidases. Oral administration of a dosage of 1 mg/kg of body weight/day of RWJ-270201 for 5 days (beginning 4 h preinfection) showed efficacy in the murine model of influenza virus infection as determined by lethality and weight loss protection. RWJ-270201 administered intranasally at 0.01 mg/kg/day in the murine influenza model demonstrated complete protection against lethality, whereas oseltamivir carboxylate and zanamivir at the same dose demonstrated only partial protection. In the delayed-treatment murine influenza model, oral administration of a 10-mg/kg/day dose of RWJ-270201 or oseltamivir (GS4104, a prodrug of GS4071) at 24 h postinfection showed significant protection against lethality (P < 0.001 versus control). However, when the treatment was delayed for 48 h, no significant protection was observed in either drug group. No drug-related toxicity was observed in mice receiving 100 mg/kg/day of RWJ-270201 for 5 days. These efficacy and safety profiles justify further consideration of RWJ-270201 for the treatment and prevention of human influenza.

Stereoselective synthesis of a conformationally defined cyclohexyl carnitine analogue that binds CPT-1 with high affinity

Carnitine (1, 3-hydroxy-4-trimethylammoniobutyrate) is important in mammalian tissue as a carrier of acyl groups. In order to explore the binding requirements of the carnitine acyltransferases for carnitine, we designed conformationally defined cyclohexyl carnitine analogues. These diastereomers contain the required gauche conformation between the trimethylammonium and hydroxy groups but vary the conformation between the hydroxy and carboxylic acid groups. Here we describe the synthesis and biological activity of the all-trans diastereomer (2), which was prepared by the ring opening of trans-methyl 2,3-epoxycylohexanecarboxylate with NaN3. Racemic 2 was a competitive inhibitor of neonatal rat cardiac myocyte CPT-1 (K(i) 0.5 mM for racemic 2; K(m) 0.2 mM for L-carnitine) and a noncompetitive inhibitor of neonatal rat cardiac myocyte CPT-2 (K(i) 0.67 mM). These results suggest that 2 represents the bound conformation of carnitine for CPT-1.

Synthesis of 2-[6-(2,4-dinitrophenoxy)hexyl]oxiranecarboxylic acid: a selective carnitine palmitoyltransferase-1 inhibitor

Carnitine palmitoyltransferases 1 and 2 (CPT-1 and CPT-2) catalyze the transfer of long chain fatty acids between carnitine and coenzyme A. Unlike CPT-2, CPT-1 exists in at least two isoforms with different physical and kinetic properties. Liver and skeletal muscle each contain a different isoform of CPT-1. Cardiac muscle contains both isoforms, and the minor component is identical to the isoform found in the liver. 2-[6-(2,4-Dinitrophenoxy)hexyl]oxiranecarboxylic acid (2) was reported to be a selective inhibitor for the liver isoform of CPT-1. A synthesis of 2 is described here which involves the reaction of diethyl malonate with 1-bromo-6-phenoxyhexane.