High-Load, ROMP-Generated Oligomeric Bis-acid Chlorides: Design of Soluble and Insoluble Nucleophile Scavengers

[reaction: see text] An efficient strategy for scavenging a host of nucleophiles utilizing an oligomeric bis-acid chloride (OBAC), generated from the ROM polymerization of trans-bicyclo[2.2.1]hept-5-ene-2,3-dicarbonyl dichloride, is described. The reactivity and high load of the OBAC reagent is exploited in the scavenging of amines, alcohols, and thiols that are present in excess following a common benzoylation event. Following the scavenging event, these oligomers can be precipitated with EtOAc and filtered (SiO(2)), leaving benzoylated nucleophiles in excellent yield and purity.

ROMP-generated oligomeric sulfonyl chlorides as versatile soluble scavenging agents

[reaction: see text] A new method for homogeneous nucleophilic scavenging employing oligomeric sulfonyl chloride (OSC) reagents is described. The method utilizes OSC to rapidly scavenge a variety of amines that are present in excess. The OSC reagents are generated from ROM polymerization of 2-chlorosulfonyl-5-norbornene utilizing the second generation Grubbs catalyst to produce oligomers of varying size as stable, free-flowing powders. Following the scavenging event, these oligomers are precipitated with ethyl acetate leaving products in excellent yield and purity.

Ring-opening metathesis phase-trafficking (ROMpt) synthesis: multistep synthesis on soluble ROM supports

The use of ring-opening metathesis (ROM) oligomers as soluble supports for a multistep reaction sequence is described. A Mitsunobu reaction followed by an in situ ROMP-mediated phase-trafficking purification is utilized to generate soluble ROM oligomers that are isolated via precipitation with methanol. Once formed, the ROM oligomers serve as soluble supports for further solution-phase reactions, including a ring-closing metathesis. After each step, the support-bound products are isolated by precipitation with a suitable solvent. [reaction--see text]

New developments in chemical library synthesis. Norbornenyl tags for use in phase-switching, sequestration, capture-release and soluble support applications

A new, general chemical library purification platform is reviewed. This platform makes broad use of (oxa)norbornenyl-tagged reactants, reagents, catalysts, sequestration-enabling reagents and scavengers, in combination with Grubbs catalyst-mediated ring-opening metathesis polymerization (ROMP) reactions as an in situ polymerization purification technique. Extensions of this platform involve the use of preformed ROMP supports in synthesis, and polystyrene-supported Grubbs catalysts, which perform in a boomerang fashion.

Recent advances in chemical library synthesis methodology

The first part of this review highlights recent advances in polymer-supported reagents, catalysts, reactants and sequestrants. Particular attention is given to recent advances in polymer-supported oxidants, transition metal catalysts and polymer-supported reactants, including acyl groups, guanidinyl groups, alkyl groups and various classes of nucleophiles. This second part of the review highlights recent advances made in the areas of chemical tagging and phase-trafficking techniques, all of which have enabled further advances in the methodology of solution-phase chemical library synthesis.

Scavenge-ROMP-filter: a facile strategy for soluble scavenging via norbornenyl tagging of electrophilic Reagents

[reaction: see text] A new "chemical tagging" method for homogeneous electrophilic scavenging is described. The method utilizes 5-norbornene-2-methanol to scavenge/tag a variety of electrophiles that are present in excess. Once tagging is complete, the crude reaction mixture is subjected to a rapid ROM polymerization event utilizing the second generation Grubbs catalyst. This process yields a polymer that can be precipitated with methanol or ether/hexane, leaving products in excellent yield and purity.

Phase-trafficking reagents and phase-switching strategies for parallel synthesis

Strategies for the parallel synthesis of small molecule arrays are reviewed with an emphasis on those approaches that integrate the sciences of organic synthesis and product purification. The use of phase-trafficking reagents (PTRs) and phase-switching strategies are highlighted, which allow the rapid, parallel synthesis of small molecule arrays with built-in purification determinants.

A mixed resin bed for the quenching and purification of tetrabutylammonium fluoride mediated desilylating reactions

A polymer-bound calcium sulfonate resin is prepared and used to sequester tetrabutylammonium fluoride. The simultaneous use of the calcium sulfonate resin with a sulfonic acid resin is used for the quenching and purification of desilylating reactions involving tetrabutylammonium fluoride as the reagent. Employment of this resin workup technique eliminates the need for a liquid-phase extractive protocol allowing the procedure to be easily automated.

Chemically-tagged Mitsunobu reagents for use in solution-phase chemical library synthesis

A general method for high-throughput product purification of Mitsunobu reactions is described. Tagged phosphine and azodicarboxylate reagents are used to synthesize individual library members in solution-phase. Workup and purification are easily accomplished by post-reaction sequestration of the tagged reagents and reagent byproducts by a complementary functionalized ion exchange resin. The reagents are utilized in a 3 step library synthesis.

Recent advances in antiviral research: identification of inhibitors of the herpesvirus proteases

Major advances have been reported in the last two years regarding the molecular biology and structural properties of the herpesvirus proteases. X-ray diffraction studies have enabled several groups to solve the structure of the human cytomegalovirus protease. Fluorescence-based substrate assays have also been recently reported. These substrates exhibit sufficient kinetic and sensitivity properties to enable high-throughput screening efforts dedicated toward the discovery of protease inhibitors. Three classes of inhibitors have been reported recently: nonpeptidic aryl trifluoromethylketones; alternate substrate inhibitors (benzoxazinones/azalactones); and thiol-modifying inhibitors. The thiol-modifying class offers a unique opportunity to discover inhibitors specific to the human cytomegalovirus protease, as this protease requires reduced cysteine residues for its enzymatic activity.

The herpesvirus protease: mechanistic studies and discovery of inhibitors of the human cytomegalovirus protease

The herpesvirus protease is a recently identified enzyme which is essential for viral replication. It is found in all herpesviruses and offers a new molecular target for therapeutic intervention. Its genomic structure has recently been described and consists of a large open reading frame which encodes a fusion protein containing an amino-terminal protease domain in-frame with a carboxyl-terminal "assembly protein-like" domain. Auto-processing releases the amino-terminal protease as a maturational enzyme. The herpesvirus protease has been characterized as a novel serine protease. Four surface accessible sulfhydryl groups have been identified in the human cytomegalovirus (HCMV) protease. Utilizing a fluorogenic DABCYL-EDANS substrate assay, directed screening has identified a class of sulfhydryl-modifying benzimidazolylmethyl sulfoxides which inhibits recombinant HCMV protease. Site-directed mutagenesis studies suggest oxidative modification of surface-accessible HCMV protease Cys138 (and possibly Cys161) by this class of inhibitors. The benzimidazolylmethyl sulfoxide 1 inhibits HCMV protease (IC50 = 1.9 microM), exhibits selectivity vs. mammalian serine proteases, and exhibits antiviral activity in an HCMV infected cell culture assay.

SC-53606, a potent and selective antagonist of 5-hydroxytryptamine4 receptors in isolated rat esophageal tunica muscularis mucosae

(1-S,8-S)-N-[(hexahydro-1H-pyrrolizin-1-yl)methyl]-6-chloroimi+ ++- dazo[1,2-a]pyridine-8-carboxamide hydrochloride (SC-53606) acts as an antagonist of 5-hydroxytryptamine4 (5-HT4) receptor-mediated relaxation of carbachol-induced contractions in rat esophageal tunica muscular mucosae, but does not possess 5-HT4 agonist activity. SC-53606 demonstrated a pA2 value against 5-HT in this tissue of 7.91 +/- 0.08 (Ki = 12.3 +/- 1.17 nM). Similar pA2 values of 7.68 +/- 0.06, 7.67 +/- 0.06 and 7.63 +/- 0.05 were determined for the synthetic 5-HT4 receptor agonists SC-53116, 5-methoxytryptamine and renzapride, respectively. In addition, slopes of Schild plots for antagonism of these four agonists by SC-53606 were 1.07 +/- 0.02, 0.98 +/- 0.03, 1.04 +/- 0.02 and 0.96 +/- 0.06, respectively, and did not deviate from unity. The pA2 values for 5-HT4 antagonism against 5-HT were determined to be 6.80 +/- 0.09 for tropisetron and 7.36 +/- 0.08 for 2-methoxy-4-amino-S- chlorobenzoic acid-2-(diethylamino)ethyl ester SDZ 205-557), indicating that SC-53606 is more a potent 5-HT4 antagonist than either of the reference antagonists. Radioligand binding studies also demonstrated that SC-53606 is a selective antagonist with more affinity for 5-HT4 than for other 5-HT receptors. Displacement of radioligand binding from 5-HT1 and 5-HT2 receptors by SC-53606 was less than 50% at a 10 microM concentration. Similarly, SC-53606 displayed little binding affinity at alpha 1, alpha 2 and beta adrenergic, dopamine1, dopamine2 and muscarinic cholinergic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

SC-49518 enhances gastric emptying of solid and liquid meals and stimulates gastrointestinal motility in dogs by a 5-hydroxytryptamine4 receptor mechanism

SC-49518 (N-[exo-(hexahydro-1H-pyrrolizine-1-yl)methyl]-2-methoxy-4- amino-5-chlorobenzamide HCl), a new benzamide gastrointestinal prokinetic compound, was investigated to determine its ability to stimulate gastrointestinal motility in vivo and whether these actions could be mediated by agonist activity at the putative 5-hydroxytryptamine (5-HT)4 receptor. In conscious fasted dogs with strain gauge transducers and myoelectrodes, SC-49518 disrupted gastric and small intestinal migrating motility complex cycling for more than 3.5 hr. It stimulated gastric antral contractile and intestinal myoelectric spike burst activities during the normally quiescent Phase I of the migrating motility complex at doses as low as 0.01 and 0.03 mg/kg i.v., respectively. In a canine model of gastroparesis, SC-49518 reversed completely alpha-2 adrenergically delayed gastric emptying of a solid meal with an ED50 value of 0.1 mg/kg intragastrically and partially reversed delayed emptying of a liquid meal. SC-49518, like 5-HT, cisapride and renzapride, acted as an agonist (EC50 = 6.6 +/- 1.1 x 10(-8) M) at the putative 5-HT4 receptor in rat esophageal tunica muscularis mucosae by relaxing carbachol-induced contractions. SC-49518 was a partial agonist at 5-HT4 receptors, but also blocked high affinity (5-HT4-mediated) responses to 5-HT (10(-9) M to 3 x 10(-7) M) in guinea pig ileum with a pA2 value of 8.39.(ABSTRACT TRUNCATED AT 250 WORDS)

Styrylpyrazoles, styrylisoxazoles, and styrylisothiazoles. Novel 5-lipoxygenase and cyclooxygenase inhibitors

A series of styrylpyrazoles, styrylisoxazoles, and styrylisothiazoles were prepared and found to be dual inhibitors of 5-lipoxygenase and cyclooxygenase in rat basophilic leukemia cells. Compounds from this series also were found to inhibit the in vivo production of LTB4 when dosed orally in rats. Among these compounds, di-tert-butylphenols 19 and 33 exhibit oral activity in various models of inflammation and, most importantly, are devoid of ulcerogenic potential.

Inhibition of human neutrophil 5-lipoxygenase activity by gingerdione, shogaol, capsaicin and related pungent compounds

A series of structurally related pungent natural products including capsaicin, gingerol, and gingerdione among others were evaluated and found to be potent inhibitors of 5-HETE biosynthesis in intact human leukocytes, with IC50 values of 100 and 15 microM for capsaicin and gingerdione, respectively. Several compounds within this series were also found to inhibit PGE2 formation, with the most potent being gingerdione (IC50 = 18 microM). These and other data indicate that members of the capsaicin/gingerol family of pungent compounds can act as dual inhibitors of arachidonic acid metabolism, which could account in part for the antiinflammatory and analgesic properties of compounds within this group.

Inhibition of 5-hydroxy-eicosatetraenoic acid (5-HETE) formation in intact human neutrophils by naturally-occurring diarylheptanoids: inhibitory activities of curcuminoids and yakuchinones

Various diarylheptanoids including curcumin, bis (3,4-dihydroxy-cinnamoyl) methane, and yakuchinones A & B were screened and found to be potent inhibitors of 5-HETE production by intact human neutrophils, with respective IC50 values of 8.0, 4.4, 5.4, and 4.0 microM. These diarylheptanoids were found to be more potent than BW-755C, Phenidone, and AA-861. We have confirmed a previous report that several of these diarylheptanoids inhibit cyclooxygenase. Thus, curcuminoids and yakuchinones are more accurately characterized as dual inhibitors of arachidonic acid metabolism.

Quinolone antimicrobial agents. 2. Methylenedioxy positional isomers of oxolinic acid

The synthesis and antimicrobial activity of the methylenedioxy positional isomers, 1-ethyl-1,4-dihydro-5,6-methylenedioxy-4-oxo-3-quinolinecarboxylic acid (9) and 1-ethyl-1,4-dihydro-7,8-methylenedioxy-4-oxo-3-quinolinecarboxylic acid (17), of oxolinic acid (18) have been accomplished. Isomer 9 was prepared by the reaction of N-ethyl-6,7-methylenedioxyisatoic anhydride with sodioethyl formylacetate [L. A. Mitscher, H. E. Gracey, G. W. Clark III, and T. Suzuki, J. Med. Chem., 21, 485 (1978)], while isomer 17 was prepared by thermal cyclization of diethyl 2-[(2,3-methylenedioxyanilino)methylene]malonate [D. Kaminsky and R. I. Meltzer, J. Med. Chem., 11, 160 (1968)]. Both of the new isomers are less active in vitro when compared to oxolinic acid (18) itself.