- The Utility of t-Butyldimethylsilane as an Effective Silylation Reagent for the Protection of Functional Groups
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Treatment of compounds containing functional groups, such as alcohols, amines, and carboxylic acids, with t-butyldimethylsilane in the presence of a catalytic amount of palladium on carbon is described to provide a new, convenient method for the introduction of a t-butyldimethylsilyl (TBDMS) group.
- Yamamoto, Keiji,Takemae, Makoto
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Read Online
- Enantioselective synthesis of α-phosphanyl ketones and 2-phosphanyl alcohols
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An efficient, highly enantioselective methodology for the synthesis of α-phosphanyl ketones 7 and 2-phosphanyl alcohols 12 and 13, important hemilable ligands for enantioselective homogeneous catalysis and chiral building blocks in general, has been developed. The key step of this first enantioselective synthesis of α-phosphanyl ketones is the diastereoselective phosphanylation of SAMP hydrazones 2 to produce α-phosphanyl hydrazones, isolated as the more stable borane adducts 6. Subsequent ozonolysis afforded α-phosphanyl ketones 7. The enantioselective synthesis of 2-phosphanyl alcohols 12 and 13 has been accomplished by two fundamentally different procedures: the phosphanylation of unsubstituted chiral aldehyde hydrazones 9 and the alkylation of α-diphenylphopshanyl acetaldehyde SAMP hydrazone 10. After separation of the minor diastereomer, the borane-protected α-phosphanyl aldehyde hydrazones 11 were converted to unprotected 2-phosphanyl alcohols 13 by ozonolysis, reduction and removal of the borane group. The absolute configuration of the functionalized phosphanes was determined by X-ray analysis, NOE experiments or polarimetry. VCH Verlagsgesellschaft mbH, 1997.
- Enders, Dieter,Berg, Thorsten,Raabe, Gerhard,Runsink, Jan
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Read Online
- Synthesis of 2-C-Methyl-D-erythritol 4-phosphate: The first pathway-specific intermediate in the methylerythritol phosphate route to isoprenoids
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(matrix presented) 2-C-Methyl-D-erythritol 4-phosphate (4), formed from 1-deoxy-D-xylulose 5-phosphate (3), is the first pathway-specific intermediate in the methylerythritol phosphate route for the biosynthesis of isoprenoid compounds in bacteria, algae, and plant chloroplasts. In this report, 4 was synthesized from 1,2-propanediol (7) in seven steps with an overall yield of 32% and in an enantiomeric excess of 78%.
- Koppisch, Andrew T.,Blagg, Brian S. J.,Poulter, C. Dale
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Read Online
- TAU-PROTEIN TARGETING COMPOUNDS AND ASSOCIATED METHODS OF USE
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The present disclosure relates to bifunctional compounds, which find utility as modulators of tan protein. In particular, the present disclosure is directed to bifunctional compounds, which contain on one end a VHL or cereblon ligand which binds to the E3 ubiquitin ligase and on the other end a moiety which binds tan protein, such that tan protein is placed in proximity to the ubiquitin ligase to effect degradation (and inhibition) of tan. The present disclosure exhibits a broad range of pharmacological activities associated with degradation/inhibition of tan protein. Diseases or disorders that result from aggregation or accumulation of tan protein are treated or prevented with compounds and compositions of the present disclosure.
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Paragraph 1547; 1548
(2021/02/12)
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- NAPHTHYRIDINE COMPOUNDS AS INHIBITORS OF MER TYROSINE KINASE AND AXL TYROSINE KINASE
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The present invention relates to compounds of Formula (I) that function as inhibitors of MerTK activity, to processes for the preparation of such compounds, to pharmaceutical compositions comprising them and to their use in the treatment of proliferative
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Paragraph 00395-00396
(2021/10/11)
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- Non-naturally Occurring Regio Isomer of Lysophosphatidylserine Exhibits Potent Agonistic Activity toward G Protein-Coupled Receptors
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Lysophosphatidylserine (LysoPS), an endogenous ligand of G protein-coupled receptors, consists of l-serine, glycerol, and fatty acid moieties connected by phosphodiester and ester linkages, respectively. An ester linkage of phosphatidylserine can be hydrolyzed at the 1-position or at the 2-position to give 2-acyl lysophospholipid or 1-acyl lysophospholipid, respectively. 2-Acyl lysophospholipid is in nonenzymatic equilibrium with 1-acyl lysophospholipid in vivo. On the other hand, 3-acyl lysophospholipid is not found, at least in mammals, raising the question of whether the reason for this might be that the 3-acyl isomer lacks the biological activities of the other isomers. Here, to test this idea, we designed and synthesized a series of new 3-acyl lysophospholipids. Structure-activity relationship studies of more than 100 "glycol surrogate"derivatives led to the identification of potent and selective agonists for LysoPS receptors GPR34 and P2Y10. Thus, the non-natural 3-acyl compounds are indeed active and appear to be biologically orthogonal with respect to the physiologically relevant 1-and 2-acyl lysophospholipids.
- Nakamura, Sho,Sayama, Misa,Uwamizu, Akiharu,Jung, Sejin,Ikubo, Masaya,Otani, Yuko,Kano, Kuniyuki,Omi, Jumpei,Inoue, Asuka,Aoki, Junken,Ohwada, Tomohiko
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p. 9990 - 10029
(2020/10/18)
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- Using DMF as Both a Catalyst and Cosolvent for the Regioselective Silylation of Polyols and Diols
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Highly regioselective silylation of primary hydroxyl groups of unprotected polyols and diols was obtained by the use of a mixed solvent of MeCN/DMF (10:1) in this study. DMF was discovered to be a good catalyst in this reaction, although the silylation us
- Lv, Jian,Luo, Tao,Zou, Dapeng,Dong, Hai
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p. 6383 - 6395
(2019/11/05)
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- INHIBITORS OF INDOLEAMINE 2,3-DIOXYGENASE AND METHODS OF THEIR USE
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The present invention provides a compound of formula (II): an inhibitor of indoleamine 2,3-dioxygenase (IDO), which may be used as medicaments for the treatment of proliferative disorders, such as cancer, viral infections and/or autoimmune diseases. Its prodrugs are disclosed.
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Page/Page column 97; 98
(2019/07/20)
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- A Cinchona Alkaloid Antibiotic That Appears to Target ATP Synthase in Streptococcus pneumoniae
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Optochin, a cinchona alkaloid derivative discovered over 100 years ago, possesses highly selective antibacterial activity toward Streptococcus pneumoniae. Pneumococcal disease remains the leading source of bacterial pneumonia and meningitis worldwide. The structure-activity relationships of optochin were examined through modification to both the quinoline and quinuclidine subunits, which led to the identification of analogue 48 with substantially improved activity. Resistance and molecular modeling studies indicate that 48 likely binds to the c-ring of ATP synthase near the conserved glutamate 52 ion-binding site, while mechanistic studies demonstrated that 48 causes cytoplasmic acidification. Initial pharmacokinetic and drug metabolism analyses of optochin and 48 revealed limitations of these quinine analogues, which were rapidly cleared, resulting in poor in vivo exposure through hydroxylation pendants to the quinuclidine and O-dealkylation of the quinoline. Collectively, the results provide a foundation to advance 48 and highlight ATP synthase as a promising target for antibiotic development.
- Wang, Xu,Zeng, Yuna,Sheng, Li,Larson, Peter,Liu, Xue,Zou, Xiaowen,Wang, Shufang,Guo, Kaijing,Ma, Chen,Zhang, Gang,Cui, Huaqing,Ferguson, David M.,Li, Yan,Zhang, Jingren,Aldrich, Courtney C.
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supporting information
p. 2305 - 2332
(2019/04/25)
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- Unconventional Fragment Usage Enables a Concise Total Synthesis of (-)-Callyspongiolide
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An asymmetric synthesis of (-)-callyspongiolide is described. The route builds the macrolide domain atypically from a disaccharide and a monoterpene without passing through a seco-acid. Chiral iridium catalysis selectively joins fragments. Subsequent degradation of an imbedded butyrolactone via perhemiketal fragmentation affords a stereo- and regio-defined homoallylic alcohol that is engaged directly in a carbonylative macrolactonization. Further elaboration of the polyunsaturated appendage provides the natural product in a particularly direct and flexible manner.
- Manoni, Francesco,Rumo, Corentin,Li, Liubo,Harran, Patrick G.
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supporting information
p. 1280 - 1284
(2018/02/09)
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- PRODRUGS OF KALLIKREIN INHIBITORS
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Disclosed are compounds of formula I, II, and III, and pharmaceutically acceptable salts thereof, which are inhibitors of kallikrein. Also provided are pharmaceutical compositions comprising such a compound, and methods involving use of the compounds and compositions in the treatment and prevention of acquired or hereditary angioedema, or other diseases and conditions characterized by aberrant kallikrein activity. (I) (II) (III)
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Page/Page column 227-228
(2018/05/24)
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- N-substituted imidazole carboxylate compound, preparation method and medical uses thereof
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The present invention relates to a compound represented by a general formula (I) or a stereoisomer, a solvate, a pharmaceutically acceptable salt or a eutectic, a composition, a preparation method and medical uses thereof, wherein the general formula (I) is defined in the specification, and each substituent is defined in the specification.
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Paragraph 0311
(2017/12/13)
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- Catalytic signal amplification for the discrimination of ATP and ADP using functionalised gold nanoparticles
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Diagnostic assays that incorporate a signal amplification mechanism permit the detection of analytes with enhanced selectivity. Herein, we report a gold nanoparticle-based chemical system able to differentiate ATP from ADP by means of catalytic signal amplification. The discrimination between ATP and ADP is of relevance for the development of universal assays for the detection of enzymes which consume ATP. For example, protein kinases are a class of enzymes critical for the regulation of cellular functions, and act to modulate the activity of other proteins by transphosphorylation, transferring a phosphate group from ATP to give ADP as a byproduct. The system described here exploits the ability of cooperative catalytic head groups on gold nanoparticles to very efficiently catalyze chromogenic reactions such as the transphosphorylation of 2-hydroxypropyl-4-nitrophenyl phosphate (HPNPP). A series of chromogenic substrates have been synthesized and evaluated by means of Michaelis-Menten kinetics (compounds 2, 4-6). 2-Hydroxypropyl-(3-trifluoromethyl-4-nitro)phenyl phosphate (5) was found to display higher reactivity (kcat) and higher binding affinity (KM) when compared to HPNPP. This higher binding affinity allows phosphate 5 to compete with ATP and ADP to different extents for binding on the monolayer surface, thus enabling a catalytically amplified signal only when ATP is absent. Overall, this represents a viable new approach for monitoring the conversion of ATP into ADP with high sensitivity.
- Pezzato, Cristian,Chen, Jack L.-Y.,Galzerano, Patrizia,Salvi, Michela,Prins, Leonard J.
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p. 6811 - 6820
(2016/07/21)
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- Prodrugs of neuraminidase inhibitors
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A new class of neuramidase inhibitor prodrugs is provided characterized by a prodrug moiety of a carboxyl group modified to form a carbonyl ethoxy amino acid, a carbonyl ethoxy dipeptide or a carbonyl ethoxy tripeptide, a guanidine group modified to form a carbonyl ethoxy amino acid, a carbonyl ethoxy dipeptide, a carbonyl ethoxy tripeptide; a primary alcohol modified to form an esterified single amino acid, dipeptide or tripeptide of zanavimir of the unaltered therapeutic agent. Exemplary therapeutic agents so modified to form prodrugs include zanavimir, oseltamivir and peramivir. The prodrug has increased oral bioavailability relative to the unaltered neuraminidase inhibitor and is effective in the inhibition of viral infections involving neuraminidase in the viral reproductive cycle.
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Page/Page column 25; 26
(2015/12/01)
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- Ruthenium-catalyzed oxidative kinetic resolution of unactivated and activated secondary alcohols with air as the hydrogen acceptor at room temperature
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Enantiopure alcohols are versatile building blocks for asymmetric synthesis and the kinetic resolution (KR) of racemic alcohols is a reliable method for preparing them. Although many KR methods have been developed, oxidative kinetic resolution (OKR), in which dioxygen is used as the hydrogen acceptor, is the most atom-efficient. Dioxygen is ubiquitous in air, which is abundant and safe to handle. Therefore, OKR with air has been intensively investigated and the OKR of benzylic alcohols was recently achieved by using an Ir catalyst without any adjuvant. However, the OKR of unactivated alcohols remains a challenge. An [(aqua)Ru(salen)] catalyzed OKR with air as the hydrogen acceptor was developed, in which the aqua ligand is exchanged with alcohol and the Ru complex undergoes single electron transfer to dioxygen and subsequent alcohol oxidation. This OKR can be applied without any adjuvant to activated and unactivated alcohols with good to high enantioselectivity. The unique influence of substrate inhibition on the enantioselectivity of the OKR is also described. Alcohol resolution: An (aqua)ruthenium salen complex catalyzes the efficient oxidative kinetic resolution of both activated and unactivated secondary alcohols with air as the hydrogen acceptor at room temperature. The reaction is compatible with various functional groups, including halogen, ether, silyl ether, and ester groups. The reaction rate is lower at higher substrate concentrations as a result of substrate inhibition.
- Mizoguchi, Hirotaka,Uchida, Tatsuya,Katsuki, Tsutomu
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supporting information
p. 3178 - 3182
(2014/04/03)
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- CYCLOALKYLNITRILE PYRAZOLE CARBOXAMIDES AS JANUS KINASE INHIBITORS
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Cycloalkylnitrile pyrazole carboxamides as JAK inhibitors useful for the treatment of JAK-mediated diseases such as rheumatoid arthritis, asthma, COPD and cancer are provided.
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Page/Page column 88
(2013/04/10)
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- 4-(N,N-dimethylamino)pyridine-embedded nanoporous conjugated polymer as a highly active heterogeneous organocatalyst
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We report herein for the first time the incorporation of a versatile organocatalyst, 4-(N,N-dimethylamino)pyridine (DMAP), into the network of a nanoporous conjugated polymer (NCP) by the "bottom-up" approach. The resulting DMAP-NCP material possesses highly concentrated and homogeneously distributed DMAP catalytic sites (2.02 mmol g-1). DMAP-NCP also exhibits enhanced stability and permanent porosity due to the strong covalent linkage and the rigidity of the "bottom-up" monomers. As a result, DMAP-NCP shows excellent catalytic activity in the acylation of alcohols with yields of 92-99 %. The DMAP-NCP catalyst could be easily recovered from the reaction mixture and reused in at least 14 consecutive cycles without measurable loss of activity. Moreover, the catalytic acylation reaction could be performed under neat and continuous-flow conditions for at least 536 h of continuous work with the same catalyst activity. Copyright
- Zhang, Yuan,Zhang, Yong,Sun, Ya Lei,Du, Xin,Shi, Jiao Yi,Wang, Wei,Wang, Wei David
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experimental part
p. 6328 - 6334
(2012/06/18)
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- An unexpected migration of O-silyl group under Mitsunobu reaction conditions
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A 1,4 O→O silyl migration followed by nucleophilic substitution with phthalimide was observed under Mitsunobu reaction conditions. This one step secondary alcohol protection and primary alcohol substitution with N-nucleophiles was extended to a variety of
- Perali, Ramu Sridhar,Mandava, Suresh,Chunduri, Venkata Rao
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supporting information; experimental part
p. 3045 - 3047
(2011/06/26)
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- Chiral phosphine-phosphite ligands with a substituted ethane backbone. influence of conformational effects in rhodium-catalyzed asymmetric olefin hydrogenation and hydroformylation reactions
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A family of chiral (3,3′-di-tert-butyl-5,5′,6,6′- tetramethyl-2,2′-biphenol-derived) phosphine-phosphite ligands (P-OP) with a substituted ethane backbone has been synthesized and the performance of these ligands in the Rh-catalyzed enantioselective hydrogenation and hydroformylation of several representative olefins analyzed. Corresponding cationic rhodium complexes provide highly enantioselective catalysts for the hydrogenation of methyl (Z)-α-acetamidocinnamate (MAC) and dimethyl itaconate. The catalyst comparison indicates that, for the two substrates, product configuration is determined by the configuration of the phosphite. Regarding matching and mismatching effects in these hydrogenations, small effects were observed in the reduction of MAC, while for the itaconate the bigger difference between the matched and mismatched cases was of 21% ee. On the other hand, Rh catalysts based on P-OP ligands showed good levels of activity and regioselectivity in the hydroformylation of styrene and allyl cyanide, while moderate enantioselectivities were obtained. Participation of the two stereogenic elements has been observed in these reactions, and their mismatched combination leads to cancellation of enantioselectivity. To further investigate the influence of the ligand backbone in the course of these reactions, structures of rhodium model complexes Rh(Cl)(CO)(P-OP) were analyzed by DFT methods. The results obtained indicate the existence of two types of preferred conformations, whose relative stability depend on the backbone nature. Comparison of structures of the more stable conformers for each ligand indicates that the orientation of the biaryl phosphite group with respect to the coordination plane does not vary substantially along the series. Differently, the position of the phenyl phosphine substituents greatly depends on the backbone. On the basis of these observations it has been concluded that chiral induction in the hydrogenation is very predominantly due to the phosphite part of the ligand. Alternatively, conformation of the phosphine group has a great influence on enantioselectivity in the hydroformylation reactions, and even reversal of product configuration was observed between catalysts with an opposite axial equatorial arrangement of Ph phosphine substituents.
- Arribas, Inmaculada,Vargas, Sergio,Rubio, Miguel,Suarez, Andres,Domene, Carmen,Alvarez, Eleuterio,Pizzano, Antonio
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experimental part
p. 5791 - 5804
(2011/02/23)
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- PIPERIDINE-CONTAINING COMPOUNDS AND USE THEREOF
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A method for preventing and/or treating a metabolic disease, cerebrovascular disease, etc. which comprises administering to a mammal an effective amount of the compound of the formula (I) wherein all symbols have the same meanings as defined in the specification; a salt thereof, an N-oxide thereof, a solvate thereof, or a prodrug thereof. And a novel compound of the formula (I-1): wherein all symbols have the same meanings as defined in the specification; a salt thereof, an N-oxide thereof, a solvate thereof, or a prodrug thereof has an anti-diabetic effect and a neuroprotective effect. Accordingly, the compound of the formula (I) and the compound of the formula (I-1) are useful in a method for preventing and/or treating for a metabolic disease such as diabetes, cerebrovascular disease such as stroke, etc.
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Page/Page column 209
(2010/08/04)
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- AZA-BENZOFURANYL COMPOUNDS AND METHODS OF USE
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The invention relates to azabenzofuranyl compounds of Formula (I) with anti-cancer and/or anti-inflammatory activity and more specifically to azabenzofuranyl compounds which inhibit MEK kinase activity. The invention provides compositions and methods useful for inhibiting abnormal cell growth or treating a hyperproliferative disorder, or treating an inflammatory disease in a mammal. The invention also relates to methods of using the compounds for in vitro, in situ, and in vivo diagnosis or treatment of mammalian cells, or associated pathological conditions.
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Page/Page column 118
(2008/06/13)
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- MACROCYCLIC GHRELIN RECEPTOR MODULATORS AND METHODS OF USING THE SAME
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The present invention provides novel conformationally-defined macrocyclic compounds that can function as selective modulators of the ghrelin receptor (growth hormone secretagogue receptor, GHS-R1a and subtypes, isoforms and variants thereof). Methods of synthesizing the novel compounds are also described herein. These compounds are useful as agonists of the ghrelin receptor and as medicaments for treatment and prevention of a range of medical conditions including, but not limited to, metabolic and/or endocrine disorders, gastrointestinal disorders, cardiovascular disorders, obesity and obesity-associated disorders, central nervous system disorders, bone disorders, genetic disorders, hyperproliferative disorders and inflammatory disorders.
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Page/Page column 42
(2008/12/07)
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- Carbamate-appended N-alkylsulfonamides as inhibitors of γ-secretase
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The synthesis and γ-secretase inhibition data for a series of carbamate-appended N-alkylsulfonamides are described. Carbamate 54 was found to significantly reduce brain Aβ in transgenic mice. 54 was also found to possess markedly improved brain levels in transgenic mice compared to previously disclosed 1 and 2.
- Bergstrom, Carl P.,Sloan, Charles P.,Lau, Wai-Yu,Smith, David W.,Zheng, Ming,Hansel, Steven B.,Polson, Craig T.,Corsa, Jason A.,Barten, Donna M.,Felsenstein, Kevin M.,Roberts, Susan B.
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p. 464 - 468
(2008/12/21)
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- Method for producing alcohols
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A method for producing alcohols which comprises reducing esters or lactones with hydrogen gas in the presence of a catalyst comprising (i) a ruthenium compound, (ii) a monodentate monophosphine or a bidentate bisphosphine, and (iii) an amine. Examples of the catalyst include a ruthenium (Ru) complex represented by the formula:RuX1X2(LP)m(LN)n [X1 and X2 each represent an anionic ligand, LP represents a phosphine ligand, m is 1 when LP is bidentate, while m is 2 when LP is monodentate, LN represents an amine ligand, and n is 1 when LN is bidentate, while n is 2 when LN is monodentate.] and a catalyst comprising an amine and a ruthenium (Ru) complex of the formula: RuX1X2 (LP1)r [LP1 represents a monophosphine ligand and r is 3 or 4.].
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Page/Page column 16-17
(2008/12/08)
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- Lipase-catalyzed alcoholysis of diol dibenzoates: Selective enzymatic access to the 2-benzoyl ester of 1,2-propanediol and preparation of the enantiomerically pure (R)-1-O-benzoyl-2-methylpropane-1,3-diol
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Enzymatic debenzoylation of 1,2-propanediol dibenzoate with 1-octanol has been studied in organic solvent using lipases from different sources. In general a slow, highly regioselective alcoholysis in diisopropyl ether affords exclusively a monoester benzoylated at the secondary hydroxy group although the reaction proceeds with low enantioselectivity. In the presence of Pseudomonas cepacia lipase absorbed onto celite, a faster reaction allows the preparation of the 2-benzoyl ester of (R)-1,2-propanediol (82% ee) and the enantiomerically pure (R)-1-O-benzoyl-2-methylpropane-1,3-diol (>98% ee).
- Santaniello, Enzo,Casati, Silvana,Ciuffreda, Pierangela,Gamberoni, Luca
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p. 1705 - 1708
(2007/10/03)
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- Sulfonamide compounds and uses thereof
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In accordance with the present invention, there is provided a novel class of sulfonamide compounds. Compounds of the invention contain a core sulfonamide group. Variable moieties connected to the sulfur atom and nitrogen atom of the sulfonamide group incl
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Page/Page column 21
(2010/02/14)
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- The prediction of the absolute stereochemistry of primary and secondary 1,2-diols by1H NMR spectroscopy: Principles and applications
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The absolute configuration of 1,2-diols formed by a primary and a secondary (chiral) hydroxyl group can be deduced by comparison of the 1H NMR spectra of the corresponding (R)- and bis-(S)-MPA esters (MPA = methoxyphenylacetic acid). This metho
- Freire, Felix,Seco, Jose M.,Quinoa, Emilio,Riguera, Ricardo
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p. 5509 - 5522
(2007/10/03)
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- PHENYLSULFONAMIDE DERIVATIVES FOR TREATING ALZHEIMER'S DISEASE
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The invention relates to phenylsulfonamide derivatives, to a method for their production and to their use for producing medicaments for the treatment and/or prophylaxis of diseases, in particular Alzheimer's disease.
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- Comparative studies of the deprotection of various acid sensitive protecting groups with pyridinium p-toluenesulphonate
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Selective deprotection of the various acid sensitive protecting groups c.g. ethoxyethyl (EE) I-butyl dimethylsiyl (TBDMS) and t-butoxycarbonyl (BOC) groups with the inexpensive reagent pyridinum p-toulenesulphonate (PPTS), under mild conditions is reported.
- Zaidi, Javid H.,Fauq, Abdul H.,Ahmed, Naseera
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p. 4137 - 4138
(2007/10/03)
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- Kinetically Controlled Regiospecific Silylation of Polyols via Dibutylstannanediyl Acetals
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A general procedure is described whereby the tert-butyldimethylsilylation of unsymmetrical 1,2- and 1,3-diols via their dibutylstannanediyl derivatives occurs regiospecifically at the primary hydroxy group under neutral conditions; six-membered ring aceta
- Leigh, David A.,Martin, Richard P.,Smart, John P.,Truscello, Ada M.
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p. 1373 - 1374
(2007/10/02)
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- Pd-catalyzed ScN′ reactions: Stereoselective formation of cyclic carbamates from tert-butyldimethylsilyl carbamates
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Stereo selective formation of cyclic carbamates was achieved by the intramolecular trapping of a tert-butyldimethylsilyloxycarbonyl group with allylic esters upon activation with fluoride and cat. Pd(O). The reactive conformation is proposed to be D. The
- Spears, Glen W.,Nakanishi, Koji,Ohfune, Yasufumi
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p. 5339 - 5342
(2007/10/02)
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- Synthesis and Morphology of New Discogenic Phthalocyanine Derivatives
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New discogens based on the octasubstituted phthalocyanines (Pc) were synthesized: 2,3,9,10,16,17,23,24-octakis-phthalocyanine (1a), 2,3,9,10,16,17,23,24-octakis-phthalocyanine (1b), 2,3,9,10,16,17,23,24-o
- Cho, Iwhan,Lim, Youngsoo
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- Chemoselective Benzoylations of 1,2-Diols. Reactivity Comparisons of Reagents. Triphenylphosphine-Benzoyl Peroxide and Triphenylphosphine-Diethyl Azodicarboxylate-Benzoic Acid
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The triphenylphosphine-benzoyl peroxide (TPP-BPO) reagent initiates stereospecific benzoylation of secondary carbinol stereocenters with essentially complete inversion of stereochemistry.Monobenzoylations of 1,2-propanediol and styrene glycol with TPP-BPO and triphenylphosphine-diethyl azodicarboxylate-benzoic acid reagents afford a predominance of the more sterically encumbered C-2 benzoate with complete inversion of stereochemistry.Formation of a quintessential 1,3,2λ5-dioxaphospholane intermediate, followed by proton-assisted and highly stereoselective ring opening of the phospholanes to isomeric oxyphosphonium ions, allows for Arbusov displacement of triphenylphosphine oxide by benzoate anion.This rationale adequately accounts for both the high chemoselectivity and the stereochemistry of the reactions.
- Pautard, Anne M.,Evans, Slayton A.
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p. 2300 - 2303
(2007/10/02)
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