cas 2051-96-9, Benzyl lactate | Articles data

Articles about 2051-96-9Total 44 be found

Article title
Article abstract
Author
Journal number and time
Download

A Short Synthesis of the Mould Metabolite (R)-(+)-Carolinic Acid from (S)-Lactic Acid
(R)-(+)-Carolinic acid was prepared in seven steps and 59% yield from inexpensive benzyl l-lactate, the configuration of which was inverted by a Mitsunobu reaction with trifluoroacetate. The resulting benzyl d-lactate was cyclised by a domino addition-Wittig alkenation reaction with Ph3PCCO. The product tetronic acid was acylated with a second equivalent of this ylide to give a 3-acylylidenetetronic acid, which was olefinated directly with tert-butyl glyoxylate. The product alkene was hydrogenated and deprotected to afford pure crystalline (R)-(+)-carolinic acid, which proved inactive against Staphylococcus aureus and Escherichia coli mutant D21f2.
Linder, David,Schobert, Rainer
p. 4564 - 4568
(2016)
Read Online

Synthesis of an ammonium ionophore and its application in a planar ion-selective electrode
A modular technique was used to synthesize an ammonium-selective ionophore based on a cyclic depsipeptide structure. The ionophore was incorporated into a planar ion-selective electrode sensor format and the selectivity tested versus a range of metal cations in a commercial clinical diagnostic "point-of-care" instrument. Four sensor membrane formulations were tested, all of which consisted of plasticized PVC. Formulations differed as to the type of plasticizer used and whether an ionic additive was present. It was found that the membrane containing the polar plasticizer nitrophenyl octyl ether in the absence of ionic additive exhibited near-Nernstian behavior (slope, 60.1 mV/decade at 37 °C) and possessed high selectivity for ammonium ion over lithium and the divalent cations, calcium and magnesium (log KNH4+jPOT= -7.3, -4.4, and -7.1 for lithium, calcium, and magnesium ions, respectively). The same membrane also exhibited sodium and potassium selectivity that was comparable to that reported for nonactin (log KNH4+jPOT= -2.1 and -0.6 for sodium and potassium, respectively, compared to -2.4 and -0.9 in the case of nonactin). Membranes containing the less polar plasticizer, dioctyl phthalate, showed sub-Nernstian behavior (slope, 50 mV/decade at 37 °C). In all cases, the presence of the ionic additive potassium tetrakis(4-chlorophenyl)borate substantially reduced the selectivity observed. The flexible modular synthetic technique developed and reported here will allow the cyclic depsipeptide structure to be tuned for optimum selectivity.
Benco, John S.,Nienaber, Hubert A.,McGimpsey, W. Grant
p. 152 - 156
(2003)
Read Online

Organocatalytic chain scission of poly(lactides): A general route to controlled molecular weight, functionality and macromolecular architecture
A facile, single-step transesterification approach to poly(lactides) with controlled molecular weights and end-group functionality, as well as block and star-shaped architectures is described using nucleophilic amine catalysts.
Nederberg,Connor,Glausser,Hedrick
p. 2066 - 2067
(2001)
Read Online

A NEW TEMPLATE of MITSUNOBU ACYLATE CLEAVABLE in NONALKALINE CONDITIONS
The Mitsunobu inversion is one of the reliable methods for stereospecific substitution of chiral alcohols, but its deacylation step has limited the substrate scope. Here, we propose a new template of the Mitsunobu acylate that can be deacylated in non-alkaline treatments. The 3,4-dihydroxy-2-methylenebutanoate was selected as a template structure, and its acetonide- or bisTBS derivatives were synthesized. The latter especially showed excellent inversion efficiency (up to >99% ee) and good elimination performance for a series of secondary alcohols in near-neutral conditions. The results demonstrated the applicability of the new template for the substrates labile in alkaline conditions, such as a-hydroxyesters.
Sai, Yusuke,Sakakibara, Yoshimichi,Shigetomi, Kengo,Ubukata, Makoto,Uraki, Yasumitsu
p. 140 - 158
(2022/01/08)

Ni-Catalyzed C(sp3)–O Arylation of α-Hydroxy Esters
A Negishi cross-coupling of α-hydroxy ester derivatives and arylzinc reagents has been developed. This reaction tolerates both primary and secondary C(sp3)–O alcohol precursors and achieves efficient cross-coupling under Ni catalysis without the need for added external metal reductant, photocatalyst, or additives. The arylation of readily accessible C(sp3)–O electrophiles in this operationally simple, rapid, and mild reaction provides a complementary way of accessing desirable α-aryl ester products.
Monteith, John J.,Rousseaux, Sophie A. L.
supporting information
p. 9485 - 9489
(2021/12/09)

Functional Models of the Nickel Pincer Nucleotide Cofactor of Lactate Racemase
A novel nickel pincer cofactor was recently discovered in lactate racemase. Reported here are three synthetic nickel pincer complexes that are both structural and functional models of the pincer cofactor in lactate racemase. DFT computations suggest the ipso-carbon atom of the pyridinium pincer ligands act as a hydride acceptor for lactate isomerization, whereas an organometallic pathway involving nickel-mediated β-hydride elimination is less favored.
Shi, Renyi,Wodrich, Matthew D.,Pan, Hui-Jie,Tirani, Farzaneh Fadaei,Hu, Xile
supporting information
p. 16869 - 16872
(2019/11/13)

Novel SO3H-functionalized polyoxometalate-based ionic liquids as highly efficient catalysts for esterification reaction
Three novel heteropolyanion-based Br?nsted acidic ionic liquids (BAILs), butane mono sulfoacid-functionalized 1,10-phenanthrolinum, butane mono and bis sulfoacid-functionalized 1,4-dimethylpiperazinium salts of phosphortungstate catalyst (PhBs1-PW, [PipBs1]3-PW and [PipBs2]3-(PW)2) were synthesized and well characterized with FTIR, 1H and 13C NMR, Electro-Spray Ionization Mass Spectrometry (ESI-MS), Elemental analysis (CHNS), EDX and TG analysis techniques. The esterification reactions of monocarboxylic acids with monohydric alcohols were carried out using these catalysts. The introduced catalysts present a self-separation performance after reaction, which can be easily recovered and quite steadily reused as confirmed by six-run recycling test. Moreover, bis sulfoacid-functionalized 1,4-dimethylpiperazinium salt of phosphortungstate showed the best catalytic performance among the prepared catalysts for the esterification reaction.
Keshavarz, Mosadegh,Iravani, Nasir,Parhami, Abolfath
p. 272 - 278
(2019/04/25)

Ni-Catalyzed Reductive C-O Bond Arylation of Oxalates Derived from α-Hydroxy Esters with Aryl Halides
A Ni-catalyzed reductive cross-coupling of α-hydroxycarbonyl compounds modified with oxalyl groups and aryl halides has been developed that furnishes α-aryl esters under mild conditions and tolerates a variety of functionalized aryl halides bearing electron-withdrawing and -donating groups. This work highlights C-O bond fragmentation on secondary alkyl carbon centers that generates α-carbonyl radicals.
Gao, Mengyu,Sun, Deli,Gong, Hegui
supporting information
p. 1645 - 1648
(2019/03/11)

Synthesis and Applications of Unquaternized C-Bound Boron Enolates
A general and facile method to prepare unquaternized C-bound boron enolates by a ligand-controlled O-to-C isomerization is reported. Using this protocol, C-bound pinacolboron enolates have been isolated in pure form for the first time, and have been fully characterized by NMR spectroscopy and X-ray crystallography. In contrast to the general perception, such C-boron enolates are stable without coordinative saturation at the boron. Moreover, C-boron enolates present reactivities that are distinct from the O-boron enolates, and their applications in C-O and C-C bond formations are demonstrated.
Ng, Elvis Wang Hei,Low, Kam-Hung,Chiu, Pauline
p. 3537 - 3541
(2018/03/21)

Synthesis and Self-Assembly of Discrete Dimethylsiloxane-Lactic Acid Diblock Co-oligomers: The Dononacontamer and Its Shorter Homologues
Most of the theoretical and computational descriptions of the phase behavior of block copolymers describe the chain ensembles of perfect and uniform polymers. In contrast, experimental studies on block copolymers always employ materials with disperse molecular makeup. Although most polymers are so-called monodisperse, they still have a molecular weight dispersity. Here, we describe the synthesis and properties of a series of discrete length diblock co-oligomers, based on oligo-dimethylsiloxane (oDMS) and oligo-lactic acid (oLA), diblock co-oligomers with highly noncompatible blocks. By utilizing an iterative synthetic protocol, co-oligomers with molar masses up to 6901 Da, ultralow molar mass dispersities (D ≤ 1.00002), and unique control over the co-oligomer composition are synthesized and characterized. This specific block co-oligomer required the development of a new divergent strategy for the oDMS structures by which both bis- and monosubstituted oDMS derivatives up to 59 Si-atoms became available. The incompatibility of the two blocks makes the final coupling more demanding the longer the blocks become. These optimized synthetic procedures granted access to multigram quantities of most of the block co-oligomers, useful to study the lower limits of block copolymer phase segregation in detail. Cylindrical, gyroid, and lamellar nanostructures, as revealed by DSC, SAXS, and AFM, were generated. The small oligomeric size of the block co-oligomers resulted in exceptionally small feature sizes (down to 3.4 nm) and long-range organization.
Van Genabeek, Bas,De Waal, Bas F. M.,Gosens, Mark M. J.,Pitet, Louis M.,Palmans, Anja R. A.,Meijer
supporting information
p. 4210 - 4218
(2016/05/02)

Reversible ketomethylene-based inhibitors of human neutrophil proteinase 3
Neutrophil serine proteases, proteinase 3 (PR3) and human neutrophil elastase (HNE), are considered as targets for chronic inflammatory diseases. Despite sharing high sequence similarity, the two enzymes have different substrate specificities and functions. While a plethora of HNE inhibitors exist, PR3 specific inhibitors are still in their infancy. We have designed ketomethylene-based inhibitors for PR3 that show low micromolar IC50 values. Their synthesis was made possible by amending a previously reported synthesis of ketomethylene dipeptide isosteres to allow for the preparation of derivatives suitable for solid phase peptide synthesis. The best inhibitor (Abz-VADnV[ψ](COCH2)ADYQ-EDDnp) was found to be selective for PR3 over HNE and to display a competitive and reversible inhibition mechanism. Molecular dynamics simulations show that the interactions between enzyme and ketomethylene-containing inhibitors are similar to those with the corresponding substrates. We also confirm that N- and C-terminal FRET groups are important for securing high inhibitory potency toward PR3.
Budnjo, Adnan,Narawane, Shailesh,Grauffel, Cédric,Schillinger, Anne-Sophie,Fossen, Torgils,Reuter, Nathalie,Haug, Bengt Erik
p. 9396 - 9408
(2015/02/02)

Synthesis and properties of alternating copolymers of 3-hydroxybutyrate and lactate units with different stereocompositions
Alternating copolymers of (R)-3-hydroxybutyrate ((R)-3HB) and lactate (2-hydroxypropionate: 2HP) units were synthesized by polycondensation reaction of preprepared dimeric monomers, (R)-3HB-(R)-2HP and (R)-3HB-(S)-2HP, in the presence of condensation agent. On the basis of the NMR analyses, it was confirmed that the obtained copolymers had an alternating sequence of (R)-3HB and 2HP units. In contrast to random copolymers of (R)-3HB and 2HP units, the repeating sequence of alternately connected (R)-3HB and 2HP units formed crystalline region. The copolymer with alternating sequence of (R)-3HB and (S)-2HP units had a melting temperature at 83 °C. On the other hands, the melting temperature of copolymer of (R)-3HB and (R)-2HP units was quite higher than those of the corresponding homopolymers (around 180°C) and reached to 233 °C. When the alternating copolymers were prepared from a mixture of stereoisomeric dimers, both the melting temperature and crystallinity varied in the wide ranges depending on the composition of stereoisomeric dimers.
Tabata, Yuta,Abe, Hideki
p. 7354 - 7361
(2015/01/08)

Chemoselective esterification of α-hydroxyacids catalyzed by salicylaldehyde through induced intramolecularity
A new, direct and chemoselective esterification of α-hydroxyacids was developed using a reversible covalent-binding strategy. By taking advantage of acetal chemistry, simple aldehydes can be used to efficiently catalyze the esterification of α-hydroxy carboxylic acids in the presence of β-hydroxyacid moieties or other carboxylic acids in amounts equal to or in excess of the alcohols. A diverse array of α-aryl, α-alkyl, α-heteroaryl, and functionalized α-hydroxyacids were smoothly esterified with 1° and 2° alcohols catalyzed by 10 mol% inexpensive and commercially available salicylaldehyde, furnishing the resultant esterification products in 83-95% yields after a simple basic aqueous workup to remove the unreacted hydroxyacids. In addition, the salicylaldehyde can be recovered through vacuum distillation or silica gel purification, thereby meeting the standards of green chemistry. A mechanistic study proved that the formation of covalent adduct III during our proposed catalytic cycle (Scheme 1A) is responsible for the real catalysis.
Weng, Shiue-Shien,Li, Hsin-Chun,Yang, Teng-Mao
p. 1976 - 1986
(2013/03/13)

TRANSESTERIFICATION PROCESS USING MIXED SALT ACETYLACETONATES CATALYSTS
This invention is directed to a general catalyst of high activity and selectivity for the production of a variety of esters, particularly acrylate and methacrylate-based esters, by a transesterification reaction. This objective is achieved by reaction of an ester of a carboxylic or a carbonic acid, in particular of a saturated or unsaturated, typically, a 3 to 4 carbon atom carboxylic acid; with an alcohol in the presence of a catalyst comprising the combination of a metal 1,3-dicarbonyl complex (pref. Zn or Fe acetylacetonate) and a salt, in particular an inorganic salt, pref. ZnCl2, LiCI, NaCI, NH4CI or Lil. These catalysts are prepared from readily available starting materials within the reaction medium without the need for isolation (in-situ preparation).
-
Paragraph 0085-0087

(2013/04/13)

Silylation-based kinetic resolution of α-hydroxy lactones and lactams
A silylation-based kinetic resolution has been developed for α-hydroxy lactones and lactams employing the chiral isothiourea catalyst (-)-benzotetramisole and triphenylsilyl chloride as the silyl source. The system is more selective for lactones than lactams, and selectivity factors up to 100 can be achieved utilizing commercially available reagents.
Clark, Robert W.,Deaton, T. Maxwell,Zhang, Yan,Moore, Maggie I.,Wiskur, Sheryl L.
supporting information
p. 6132 - 6135
(2014/01/17)

Synthesis, characterization and activity of new phosphonate dipeptides as potential inhibitors of VanX
VanX, a Zn(II)-dependent D-ala-D-ala dipeptidase, is essential for vancomycin resistance in Enterococcus faecium. The enzymatic activity of VanX was previously found to be inhibited competitively by 2-{[(1-aminoethyl) (hydroxy) phosphoryl]oxy} propanoic acid (1B). Here we report the synthesis and characterization of seven phosphonate dipeptide analogs of D-ala-D-ala with various substituent, the activity evaluation indicated that six of these phosphonate analogs inhibit VanX with IC50 of 0.48-8.21 mM. These data revealed a structure-activity relationship which is that the large substituent group on β-carbon resulted in low binding affinity of the phonphonate analog to VanX. This information will be helpful to guide the design and synthesis of the tightly-binding inhibitors for VanX.
Jia, Chao,Yang, Ke-Wu,Liu, Cheng-Cheng,Feng, Lei,Xiao, Jian-Min,Zhou, Li-Sheng,Zhang, Yi-Lin
supporting information; experimental part
p. 482 - 484
(2012/03/11)

Continuous multiple liquid-liquid separation: Diazotization of amino acids in flow
A second-generation laboratory-scale, modular liquid-liquid separation device based on computer-controlled high-pressure pumps and a high-resolution digital camera has been invented. The diazotization of amino acids to produce valuable chiral hydroxyacids is demonstrated in flow for the first time. The use of a triple-separator system in conjuction with the developed diazotization process allows the safe and efficient production and automated isolation of multigram quantities of valuable chiral hydroxyacids.
Hu, Dennis X.,O'Brien, Matthew,Ley, Steven V.
supporting information; experimental part
p. 4246 - 4249
(2012/10/08)

METHOD FOR PRODUCING OPTICALLY ACTIVE 2-HYDROXY ESTER AND NOVEL INTERMEDIATE COMPOUND
Disclosed is a method for producing an optically active 2-hydroxy ester, comprising selectively esterifying one enantiomer of a racemic 2-hydroxy ester in a solvent containing a catalyst such as tetramisole or benzotetramisole, and a carboxylic acid anhydride, or a carboxylic acid anhydride and a carboxylic acid. In particular, in the case where the solvent contains a carboxylic acid anhydride, but does not contain a carboxylic acid, as the carboxylic acid anhydride, a carboxylic acid anhydride containing a tertiary or quaternary carbon atom in the a-position is used. On the other hand, in the case where the solvent contains a carboxylic acid anhydride and a carboxylic acid, as the carboxylic acid, a carboxylic acid containing a tertiary or quaternary carbon atom in the a-position is used.
-
Page/Page column 4-5

(2012/01/13)

A convenient method for the kinetic resolution of racemic 2-hydroxyalkanoates using diphenylacetic anhydride (DPHAA) and a chiral acyl-transfer catalyst
Diphenylacetic anhydride (DPHAA) was found to be a useful reagent for the kinetic resolution of racemic 2-hydroxyalkanoates in the presence of a catalytic amount of (R)-benzotetramisole ((R)-BTM). The combined use of DPHAA and (R)-BTM effectively produced a variety of the optically active 2-hydroxyalkanoates and the corresponding 2-acyloxyalkanoates from racemic 2-hydroxyalkanoates (s-values = 42-177). A fairly broad substrate scope was demonstrated by this novel chiral induction system. We also revealed that the use of only 0.3 equiv of DPHAA is enough to provide the optically active 2-acyloxyalkanoates in good yields and with excellent ee's by the added use of 0.3 equiv of pivalic anhydride for the kinetic resolution of the racemic 2-hydroxyalkanoates. Copyright
Nakata, Kenya,Sekiguchi, Akihiro,Shiina, Isamu
experimental part
p. 1610 - 1619
(2012/01/03)

Transesterification catalyzed by iron(III) β-diketonate species
A practical and clean protocol for transesterification catalyzed by a 5 mol % cheap, non-toxic and moisture stable Fe(acac)3 or other iron(III) β-diketonate species in solvent, such as heptane under azeotropic condition is developed. A remarkable rate enhancement was observed upon the addition of 5 mol % of an inorganic base, such as Na2CO3, which suggests that faster formation of a dimeric μ-alkoxy-bridged iron(III) species under alkaline conditions facilitates catalytic turnover. This system provides smooth transesterification over a wide range of structurally diverse esters and alcohols without disturbing functional groups. In addition, the use of iron β-diketonate complexes as catalysts is more environmentally friendly, safer, and economical than other transition-metal catalysts. Preliminary mechanistic studies indicate that the active catalyst is likely a dimeric μ-alkoxy-bridged iron(III) species, as determined by X-ray crystallography of [Fe(dbm)2(O-n-Bu)]2 derived from the alcoholysis of Fe(dbm)3 under alkaline conditions.
Weng, Shiue-Shien,Ke, Chih-Shueh,Chen, Fong-Kuang,Lyu, You-Fu,Lin, Guan-Ying
supporting information; experimental part
p. 1640 - 1648
(2011/04/17)

Acyclic guanidines as organic catalysts for living polymerization of lactide
We describe a facile route to structurally diverse guanidinium organic catalysts by reaction of carbodiimides with secondary amines. The efficacy of these catalysts for the living ring-opening polymerization (ROP) of lactide was demonstrated including predictable molecular weights and end-group fidelity. Theoretical studies indicate that the acyclic guanidines are less basic than 1, 5, 7-triazabicyclo[4.4.0]dec-5-ene (TBD), but as for the more active TBD, they catalyze ring opening by activation of the alcohol and by stabilizing the resultant tetrahedral intermediates through hydrogen bonding. These results demonstrate that weak secondary interactions are an important concept for controlled polymerization.
Zhang, Lei,Pratt, Russell C.,Nederberg, Fredrik,Horn, Hans W.,Rice, Julia E.,Waymouth, Robert M.,Wade, Charles G.,Hedrick, James L.
scheme or table
p. 1660 - 1664
(2011/09/20)

Ultrasound-assisted solvent-free synthesis of lactic acid esters in novel SO3H-functionalized Br?nsted acidic ionic liquids
Mild and efficient Fischer esterification reactions of lactic acid with a variety of straight chain aliphatic alcohols, cyclohexanol and benzyl alcohol were successfully performed using two novel Br?nsted acidic ionic liquids that bear an aromatic sulfonic acid group on the imidazolium or pyridinium cation under ultrasound irradiation. These reactions carried out smoothly with good to excellent conversion rate (78-96%) and satisfactory yields (73-92%) in shorter reaction time (4-6 h) at room temperature when the amount of ionic liquids was 20 mol%. These ionic liquids could be recovered readily and recycled five times without any significant loss in their catalytic activity.
Li, Xinzhong,Lin, Qi,Ma, Liang
experimental part
p. 752 - 755
(2011/10/08)

New insights into poly(lactic- co -glycolic acid) microstructure: Using repeating sequence copolymers to decipher complex NMR and thermal behavior
Sequence, which Nature uses to spectacular advantage, has not been fully exploited in synthetic copolymers. To investigate the effect of sequence and stereosequence on the physical properties of copolymers, a family of complex isotactic, syndiotactic, and atactic repeating sequence poly(lactic-co-glycolic acid) copolymers (RSC PLGAs) were prepared and their NMR and thermal behavior was studied. The unique suitability of polymers prepared from the bioassimilable lactic and glycolic acid monomers for biomedical applications makes them ideal candidates for this type of sequence engineering. Polymers with repeating units of LG, GLG and LLG (L = lactic, G = glycolic) with controlled and varied tacticities were synthesized by assembly of sequence-specific, stereopure dimeric, trimeric, and hexameric segmer units. Specifically labeled deuterated lactic and glycolic acid segmers were likewise prepared and polymerized. Molecular weights for the copolymers were in the range Mn = 12-40 kDa by size exclusion chromatography in THF. Although the effects of sequence-influenced solution conformation were visible in all resonances of the 1H and 13C NMR spectra, the diastereotopic methylene resonances in the 1H NMR (CDCl3) for the glycolic units of the copolymers proved most sensitive. An octad level of resolution, which corresponds to an astounding 31-atom distance between the most separated stereocenters, was observed in some mixed sequence polymers. Importantly, the level of sensitivity of a particular NMR resonance to small differences in sequence was found to depend on the sequence itself. Thermal properties were also correlated with sequence.
Stayshich, Ryan M.,Meyer, Tara Y.
supporting information; experimental part
p. 10920 - 10934
(2010/09/17)

Enantioselective iron-catalysed O-H bond insertions
The ready availability, low price and environmentally benign character of iron mean that it is an ideal alternative to precious metals in catalysis. Recent growth in the number of iron-catalysed reactions reported reflects an increasing demand for sustainable chemistry. Only a limited number of chiral iron catalysts have been reported and these have, in general, proven less enantioselective than other transition-metal catalysts, thus limiting their appeal. Here, we report that iron complexes of spiro-bisoxazoline ligands are highly efficient catalysts for asymmetric O-H bond insertion reactions. These complexes catalyse insertions into the O-H bond of a wide variety of alcohols and even water, with exceptional enantioselectivities under mild reaction conditions. The selectivities surpass those obtained with other transition-metal catalysts. This study should inspire and encourage the use of iron instead of traditional precious metals in the development of greener catalysts for catalytic asymmetric synthesis.
Zhu, Shou-Fei,Cai, Yan,Mao, Hong-Xiang,Xie, Jian-Hua,Zhou, Qi-Lin
experimental part
p. 546 - 551
(2010/10/04)

Kinetic resolution of the racemic 2-hydroxyalkanoates using the enantioselective mixed-anhydride method with pivalic anhydride and a chiral acyl-transfer catalyst
A variety of optically active 2-hydroxyalkanoates and the corresponding 2-acyloxyalkanoates are produced by the kinetic resolution of racemic 2-hydroxyalkanoates by using achiral 2,2-diarylacetic acid with hindered carboxylic anhydrides as the coupling reagents. The combined use of diphenylacetic acid, pivalic anhydride, and (+)-(R)-benzotetramisole ((R)-BTM) effectively produces (S)-2-hydroxyalkanoates and (R)-2-acyloxyalkanoates from the racemic 2-hydroxyalkanoates (s-values = 47-202). This protocol directly provides the desired chiral 2-hydroxyalkanoate derivatives from achiral diarylacetic acid and racemic secondary alcohols that do not include the sec-phenethyl alcohol moiety by using the transacylation process to generate the mixed anhydrides from the acid components with bulky carboxylic anhydrides under the influence of the chiral acyl-transfer catalyst. The transition state that provides the desired (R)-2-acyloxyalkanoate from (R)-2-hydroxyalkanoate included in the racemic mixture is disclosed by DFT calculations, and the structural features of the transition form are also discussed.
Shiina, Isamu,Nakata, Kenya,Ono, Keisuke,Sugimoto, Masuhiro,Sekiguchi, Akihiro
supporting information; scheme or table
p. 167 - 172
(2010/03/26)

Glucose promoiety enables glucose transporter mediated brain uptake of ketoprofen and indomethacin prodrugs in rats
The brain uptake of solutes is efficiently governed by the blood-brain barrier (BBB). The BBB expresses a number of carrier-mediated transport mechanisms, and new knowledge of these BBB transporters can be used in the rational targeted delivery of drug molecules for active transport. One attractive approach is to conjugate an endogenous transporter substrate to the active drug molecule to utilize the prodrug approach. In the present study, ketoprofen and indomethacin were conjugated with glucose and the brain uptake mechanism of the prodrugs was determined with the in situ rat brain perfusion technique. Two of the prodrugs were able to significantly inhibit the uptake of glucose transporter (GluT1)-mediated uptake of glucose, thereby demonstrating affinity to the transporter. Furthermore, the prodrugs were able to cross the BBB in a temperature-dependent manner, suggesting that the brain uptake of the prodrugs is carrier-mediated.
Gynther, Mikko,Ropponen, Jarmo,Laine, Krista,Lepp?nen, Jukka,Haapakoski, Paula,Peura, Lauri,J?rvinen, Tomi,Rautio, Jarkko
supporting information; experimental part
p. 3348 - 3353
(2010/03/05)

Catalytic asymmetric reaction with water: Enantioselective synthesis of α-hydroxyesters by a copper-carbenoid O-H insertion reaction
(Chemical Equation Presented) Taking on water: A novel catalytic asymmetric metal-carbenoid insertion reaction with water has been developed with copper complexes of chiral spiro bisoxazoline ligands as catalysts. This reaction provides an efficient and practical procedure for preparing chiral α-hydroxyesters and acids starting from readily available materials in high yields and enantioselectivities. BArF- = [B{3,5-(CF3)2C6H3)} 4]-.
Zhu, Shou-Fei,Chen, Chao,Cai, Yan,Zhou, Qi-Lin
p. 932 - 934
(2008/09/20)

A new convenient method for the generation of alkoxy radicals from N-alkoxydithiocarbamates
N-Alkoxydithiocarbamates 2, which can be conveniently prepared from alkyl halides or alcohols using N-methylhydroxydithiocarbamate 1, are very useful precursors of alkoxy radicais.
Kim, Sunggak,Lim, Chae Jo,Song, Sang-Eun,Kang, Han-Young
p. 688 - 690
(2007/10/03)

Esterification of carboxylic acids catalyzed by in situ generated tetraalkylammonium fluorides
Esterification of carboxylic acids with alkyl halides can be efficiently catalyzed by tetrabutylammonium fluoride (TBAF) generated in situ from tetrabutylammonium hydrogensulfate (TBAHSO4) and KF·2H2O in THF. The general applicability and the characteristic feature of this approach has been amply demonstrated.
Ooi, Takashi,Sugimoto, Hayato,Doda, Kanae,Maruoka, Keiji
p. 9245 - 9248
(2007/10/03)

Polycationic oligomers
The present invention relates to improved methods for introducing nucleic acid into cells by first complexing the nucleic acid with a selected polycationic oligomer which neutralizes the negative charge of the nucleic acid, and then contacting the cell with the complex facilitating uptake of the nucleic acid into the cells as a complex with the oligomer. The methods are preferably applied to introduction of nucleic acid into eukaryotic cells, and more preferably into human cells. The invention also relates to methods of introducing antisense and triplex-forming oligonucleotides into prostate cancer cells to inhibit expression of proteins associated with (or that promote) malignancy and to inhibit cell growth or proliferation. More particularly, the invention relates to a method for inhibiting the expression of the HER-2/NEU protein in prostate cancer cells and to a method for inhibiting prostate cancer cell growth or proliferation.
-
(2008/06/13)

A compact chemical miniature of a holoenzyme, coenzyme NADH linked dehydrogenase. Design and synthesis of bridged NADH models and their highly enantioselective reduction
An L-lactate dehydrogenase that requires coenzyme NADH catalyzes the enantioselective reduction of pyruvate to L-lactate in anaerobic glycolysis. As the first homochiral ansa-type NADH models, we designed the bridged NADH models 10a-c having a parapyridinophane structure for strictly mimicking the stereospecificity of hydrogen transfer in the biological asymmetric reduction with NADH. These models were synthesized in several steps from the corresponding bridged nicotinate 5 prepared by our novel pyridine-formation reaction of formyl-substituted (vinylimino)phosphorane 4 with methyl propiolate. The bridged NADH models 10a-c effected excellent biomimetic reduction at various temperatures in the presence of magnesium ion to achieve both the enantioselective and stereospecific reduction of the pyruvate analogues 12u-z into chiral lactate analogues 13u-z with 88-99% ee. The high enantioselectivity was almost completely dependent on the planar chirality of 10a-c but not on the nature of the substituents of their carbamoyl groups. The biomimetic reduction proceeded with retention of the planar chirality, showing that the bridged NADH models are useful for being recycled. An isotope experiment with the deuterated model (±)-10d confirmed the stereospecific hydrogen transfer, which is in good accordance with natural coenzyme characteristics. The model (S)-10c also exhibited good enantioselectivity for the reduction of activated ketones 14k-n into the corresponding chiral alcohols 15k-n with 79-89% ee. The simple bridged NADH model (S)-10c having both a primary carbamoyl group and a shielding bridge feigning an enzyme wall suggests a compact chemical miniature of a holoenzyme, coenzyme NADH linked dehydrogenase, in terms of the unique structure, high enantioselectivity, and recyclability.
Kanomata, Nobuhiro,Nakata, Tadashi
p. 4563 - 4568
(2007/10/03)

Esterification of carboxylic acid salts
Mono- or polycarboxylic acid esters are prepared by reacting a salt of such carboxylic acid with an organic halocompound, e.g., a (cyclo)alkyl, (cyclo)alkenyl, aryl or aralkyl halide, in an aqueous reaction medium, in the presence of a catalytically effective amount of a phase transfer catalyst, for example an onium salt.
-
(2008/06/13)

Facile generation of alkoxy radicals from N-alkoxyphthalimides
N-Alkoxyphthalimides, stable and readily accessible from alcohols and alkyl halides, are found to be very efficient alkoxy radical precursors.
Kim, Sunggak,Lee, Tai Au,Song, Yukwan
p. 471 - 472
(2007/10/03)

Facile Generation of Alkyl, Aminyl, and Alkoxy Radicals from Se-Phenyl Benzoselenohydroximate Derivatives
Se-Phenyl benzoselenohydroximate derivatives, which are prepared from stable and readily available Se-phenyl benzoselenohydroximate, are useful radical precursors for the generation of alkyl, aminyl, and alkoxy radicals.
Kim, Sunggak,Lee, Tai Au
p. 950 - 952
(2007/10/03)

Production of optically active triazole compounds and their intermediates
A compound of the formula (V): STR1 wherein Ar' is a halogenated phenyl group, R is a hydrocarbon residue having a functional group at the α-carbon, R3' is an optionally substituted aliphatic or aromatic hydrocarbon residue or an optionally substituted aromatic heterocyclic group, Y and Z are, the same or different, a nitrogen atom or a methine group optionally substituted with a lower alkyl group, and (R) and (S) represent configurations, which is an optically active intermediate for production of optically active triazole compounds (I): STR2 wherein the symbols have the same meanings as defined above, and methods of preparing the compounds (V) and (I).
-
(2008/06/13)

Stereoselective Pseudomonas cepacia lipase mediated synthesis of α-hydroxyamides
A new method for the synthesis of α-hydroxyamides via the Pseudomonas cepacia lipase catalyzed amidation of α-hydroxyesters in non-aqueous media is described. Reactivities of α-hydroxy benzyl esters are excellent, resulting in rapid conversions to good yields of α-hydroxyamides, while ethyl and methyl esters react more slowly, and some hindered esters show no reactivity under the conditions studied. Some benzyl esters react stereoselectively, producing excellent yields of asymmetric α-hydroxyamides.
Adamczyk, Maciej,Grote, Jonathan,Rege, Sushil
p. 2509 - 2512
(2007/10/03)

Design, synthesis and evaluation of D,D-peptidase and beta-lactamase inhibitors: Azapeptides, oxapeptides and related heterocycles
Reactive molecules susceptible to form stable acyl enzyme intermediates with D,D-peptidases and β-lactamases were designed as potential irreversible inhibitors of Penicillin Sensitive Enzymes (PSEs). The structures examined were a series of azapeptides and oxapeptides, both analogs of the D-Ala-D-Ala substrate, and some heterocycles, such as imidazolidinones and oxazolidinones, both analogs of the β-lactam antibiotics. The various strategies investigated for their synthesis are described and discussed. Some biological results are reported.
Marchand-Brynaert,Mougenot,Combret,Belotti,Guillot,Ghosez
p. 455 - 469
(2007/10/02)

On the synthesis and analysis of R,S- and S,R-N-[1-(ethoxycarbonyl)-3-phenylpropyl]-alanine
-
Lehmann,Radwansky,Thomas
p. 739 - 742
(2007/10/02)

Non-peptide Renin Inhibitors Containing 2-(((3-Phenylpropyl)phosphoryl)oxy)alkanoic Acid Moieties as P2-P3 Replacements
A series of novel renin inhibitors containing 2-(((3-phenylpropyl)phosphoryl)oxy)alkanoic acid moieties as P2-P3 surrogates are presented.The P2-P3 mimetics were obtained from (ω-phenylalkyl)phosphinic acids 1a-c and 2-hydroxyalkanoic acid benzyl esters 2a-f by N,N'-dicyclohexylcarbodiimide-mediated coupling and subsequent oxidation with sodium metaperjodate.Ester cleavage of these derivatives and coupling with P1-P'1 transition-state mimetics I-VII provided highly selective compounds with inhibitory potencies in the lower nanomolar range.Small renin inhibitors, such as analogues 8c and 8h with molecular weights of 539 and 537, respectively, could be prepared.These compounds exhibited IC50 values of about 20 nM against human plasma renin.Compound 7i was examined in vivo for its hypotensive effect.In salt-depleted cynomolgus monkeys, 7i inhibited plasma renin activity almost completely and lowered blood pressure after oral adiministration of a dose of 30 mg/kg.
Raddatz, Peter,Minck, Klaus-Otto,Rippmann, Friedrich,Schmitges, Claus-Jochen
p. 486 - 497
(2007/10/02)

Amino acid terminated polyesters having predetermined monomeric sequence
A composition is provided comprising an amino acid terminated polyester having a predetermined monomeric sequence comprising at least one amine and at least three monomeric units derived from at least one hydroxyacid. Such a polyester can be prepared by the stepwise addition of at least three monomeric hydroxyacid units to an amino acid monomeric unit. A medical device is also provided which is made in whole or in part of an amino acid terminated polyester having a predetermined monomeric sequence.
-
(2008/06/13)

A New and Facile Method for the Direct Preparation of α-Hydroxycarboxylic Acid Esters from α,β-Unsaturated Carboxylic Acid Esters with Molecular Oxygen and Phenylsilane Catalyzed by Bis(dipivaloylmethanato)manganese(II) Complex
In the presence of a catalytic amount of bis(dipivaloylmethanato)manganese(II) complex, the oxygenation of benzyl crotonate with molecular oxygen and phenylsilane proceeds smoothly under a mild condition to give benzyl 2-hydroxybutyrate in high yield.The reaction provides a new and convenient method for the direct preparation of various α-hydroxycarboxylic acid esters starting from α,β-unsaturated carboxylic acid esters.The influence of substituents of olefins on regioselectivity is also studied.
Inoki, Satoshi,Kato, Koji,Isayama, Shigeru,Mukaiyama, Teruaki
p. 1869 - 1872
(2007/10/02)

Interconversion of (R) and (S)-α-hydroxy esters: precursors of (S) and (R)-O-benzyl-α-hydroxylamino acid esters of high optical purity.
(R)- and (S)-α-hydroxy esters 5 are interconverted via their triflates 6 in high chemical as well as optical yields by reaction with dimethylformamide.The same triflates are efficiently converted into N-hydroxy-α-amino acid derivatives 7 of high optical purity.
Feenstra, R. W.,Stokkingreef, E. H. M.,Nivard, R. J. F.,Ottenheijm, H. C. J.
p. 5583 - 5596
(2007/10/02)

Synthesis and Physical Evaluation of Novel Ferroelectric Materials with High Spontaneous Polarization
A large number of ferroelectric dopants incorporating a chiral lactate unit, -OC*H(CH3)CO2-, have been synthesized and extrapolated values of Ps as high as 160 nC cm-2 have been found, although many of these compounds did not show any liquid crystal behavior.Terphenyls and laterally fluoro-substitued terphenyls incorporating the chiral lactate unit have also been synthesized, and in one case, a ferroelectric host material with an S*C phase and a Ps value of 124 nC cm-2 was obtained.Compounds containing two chiral units (one of which was a chiral lactate unit) were also synthesized in which the two chiral units were either directly linked or separated by a phenyl ring; the latter compounds gave very high Ps values (199 nC cm-2).The effect of molecular structure on Ps, tilt angle and phase behavior is discussed for both the mono-lactates and the di-chiral compounds.An outline (with references) of the experimental procedures used to prepare these compounds is also given.
Bone, M. F.,Bradshaw, M. J.,Chan, L. K. M.,Coates, D.,Constant, J.,et al.
p. 117 - 134
(2007/10/02)

Peptide carbazates and pharmaceutical composition
Certain novel peptide carbazates, their preparation, pharmaceutical compositions and novel methods of treating pancreatitis.
-
(2008/06/13)