101-10-0Relevant articles and documents
Kinetics and mechanism of thermal gas-phase elimination of α-substituted carboxylic acids: Role of relative basicity of α-substituents and acidity of incipient proton
Al-Awadi, Nouria A.,Kaul, Kamini,El-Dusouqui, Osman M. E.
, p. 499 - 504 (2000)
2-Phenoxypropanoic acid together with five of its aryl derivatives, its phenylthio and its N-phenylamino analogues were pyrolyzed at 494-566 K. The reactions were homogeneous, polar and free from catalytic and radical pathways, and obeyed a first-order rate equation. The limits of the Arrhenius log A (s-1) and E (kJ mol-1) values obtained for these reactions averaged 11.98 ± 1.71 and 158.1 ± 17.4, respectively. Analysis of the pyrolysates showed the elimination products to be carbon monoxide, acetaldehyde and the corresponding phenol, thiophenol or aniline compounds. The pyrolysis of 2-phenoxy- and 2-(N-phenylamino)-1-propanol was also investigated over the temperature range 638-792 K. The kinetic results and products analysis lend support to a reaction pathway involving a five-membered cyclic polar transition state. Copyright
Access to Optically Enriched α-Aryloxycarboxylic Esters via Carbene-Catalyzed Dynamic Kinetic Resolution and Transesterification
Liu, Bin,Song, Runjiang,Xu, Jun,Majhi, Pankaj Kumar,Yang, Xing,Yang, Song,Jin, Zhichao,Chi, Yonggui Robin
supporting information, p. 3335 - 3338 (2020/04/30)
Optically active α-aryloxycarboxylic acids and their derivatives are important functional molecules. Disclosed here is a carbene-catalyzed dynamic kinetic resolution and transesterification reaction for access to this class of molecules with up to 99% yields and 99:1 er values. Addition of a chiral carbene catalyst to the ester substrate leads to two diastereomeric azolium ester intermediates that can quickly epimerize to each other and thus allows for effective dynamic kinetic resolution to be realized. The optically enriched ester products from our reaction can be quickly transformed to chiral herbicides and other bioactive molecules.
Optimization of benzoxazole-based inhibitors of Cryptosporidium parvum inosine 5′-monophosphate dehydrogenase
Gorla, Suresh Kumar,Kavitha, Mandapati,Zhang, Minjia,Chin, James En Wai,Liu, Xiaoping,Striepen, Boris,Makowska-Grzyska, Magdalena,Kim, Youngchang,Joachimiak, Andrzej,Hedstrom, Lizbeth,Cuny, Gregory D.
, p. 4028 - 4043 (2013/06/27)
Cryptosporidium parvum is an enteric protozoan parasite that has emerged as a major cause of diarrhea, malnutrition, and gastroenteritis and poses a potential bioterrorism threat. C. parvum synthesizes guanine nucleotides from host adenosine in a streamlined pathway that relies on inosine 5′-monophosphate dehydrogenase (IMPDH). We have previously identified several parasite-selective C. parvum IMPDH (CpIMPDH) inhibitors by high-throughput screening. In this paper, we report the structure-activity relationship (SAR) for a series of benzoxazole derivatives with many compounds demonstrating CpIMPDH IC50 values in the nanomolar range and >500-fold selectivity over human IMPDH (hIMPDH). Unlike previously reported CpIMPDH inhibitors, these compounds are competitive inhibitors versus NAD +. The SAR study reveals that pyridine and other small heteroaromatic substituents are required at the 2-position of the benzoxazole for potent inhibitory activity. In addition, several other SAR conclusions are highlighted with regard to the benzoxazole and the amide portion of the inhibitor, including preferred stereochemistry. An X-ray crystal structure of a representative E·IMP·inhibitor complex is also presented. Overall, the secondary amine derivative 15a demonstrated excellent CpIMPDH inhibitory activity (IC 50 = 0.5 ± 0.1 nM) and moderate stability (t1/2 = 44 min) in mouse liver microsomes. Compound 73, the racemic version of 15a, also displayed superb antiparasitic activity in a Toxoplasma gondii strain that relies on CpIMPDH (EC50 = 20 ± 20 nM), and selectivity versus a wild-type T. gondii strain (200-fold). No toxicity was observed (LD 50 > 50 μM) against a panel of four mammalian cells lines.
(R,S)-2-chlorophenoxyl pyrazolides as novel substrates for improving lipase-catalyzed hydrolytic resolution
Kao, Min-Fang,Lu, Pei-Yu,Kao, Jou-Yan,Wang, Pei-Yun,Wu, An-Chi,Tsai, Shau-Wei
, p. 60 - 66 (2012/05/04)
The best reaction condition of Candida antartica lipase B as biocatalyst, 3-(2-pyridyl)pyrazole as leaving azole, and water-saturated methyl t-butyl ether as reaction medium at 45°C were first selected for performing the hydrolytic resolution of (R,S)-2-(4-chlorophenoxyl) azolides (1-4). In comparison with the kinetic resolution of (R,S)-2-phenylpropionyl 3-(2-pyridyl)pyrazolide or (R,S)-α-methoxyphenylacetyl 3-(2-pyridyl)pyrazolide at the same reaction condition, excellent enantioselectivity with more than two order-of-magnitudes higher activity for each enantiomer was obtained. The resolution was then extended to other (R,S)-3-(2-pyridyl)pyrazolides (5-7) containing 2-chloro, 3-chloro, or 2,4-dichloro substituent, giving good (E > 48) to excellent (E > 100) enantioselectivity. The thermodynamic analysis for 1, 2, and 4-7 demonstrates profound effects of the acyl or leaving moiety on varying enthalpic and entropic contributions to the difference of Gibbs free energies. A thorough kinetic analysis further indicates that on the basis of 6, the excellent enantiomeric ratio for 4 and 7 is due to the higher reactivity of (S)-4 and lower reactivity of (R)-7, respectively.
A new method for production of chiral 2-aryloxypropanoic acids using effective kinetic resolution of racemic 2-aryloxycarboxylic acids
Tengeiji, Atsushi,Nakata, Kenya,Ono, Keisuke,Shiina, Isamu
, p. 1227 - 1252 (2013/08/23)
We report a novel method for the preparation of 2-aryloxypropanoic acids by kinetic resolution of racemic 2-aryloxypropanoic acids using enantioselective esterification. The usage of pivalic anhydride (Piv2O) as an activating agent, bis(a-naphthyl)methanol ((α-Np)2CHOH) as an achiral alcohol, and (+)-benzotetramisole ((+)-BTM) as a chiral acyl-transfer catalyst enables the effective separation of various racemic 2-aryloxypropanoic acids to afford optically active carboxylic acids and the corresponding esters with high enantioselectivities. Furthermore, theoretical calculations of the transition states required to form the chiral esters successfully proved the enantiomer recognition mechanism of the asymmetric esterification.
Chlorination of 2-phenoxypropanoic acid with NCP in aqueous acetic acid: Using a novel ortho-para relationship and the para/meta ratio of substituent effects for mechanism elucidation
Segurado, Manuel A. P.,Reis, Joao Carlos R.,De Oliveira, Jaime D. Gomes,Kabilan, Senthamaraikannan,Shanthi, Manohar
, p. 5327 - 5336 (2008/02/07)
(Graph Presented) Rate constants were measured for the oxidative chlorodehydrogenation of (R,S)-2-phenoxypropanoic acid and nine ortho-, ten para- and five meta-substituted derivatives using (R,S)-1-chloro-3-methyl-2,6- diphenylpiperidin-4-one (NCP) as chlorinating agent. The kinetics was run in 50% (v/v) aqueous acetic acid acidified with perchloric acid under pseudo-first-order conditions with respect to NCP at temperature intervals of 5 K between 298 and 318 K, except at the highest temperature for the meta derivatives. The dependence of rate constants on temperature was analyzed in terms of the isokinetic relationship (IKR). For the 20 reactions studied at five different temperatures, tne isokinetic temperature was estimated to be 382 K, which suggests the preferential involvement of water molecules in the rate-determining step. The dependence of rate constants on meta and para substitution was analyzed using the tetralinear extension of the Hammett equation. The parameter λ for the para/meta ratio of polar substituent effects was estimated to be 0.926, and its electrostatic modeling suggests the formation of an activated complex bearing an electric charge near the oxygen atom belonging to the phenoxy group. A new approach is introduced for examining the effect of ortho substituents on reaction rates. Using IKR-determined values of activation enthalpies for a set of nine pairs of substrates with a given substituent, a linear correlation is found between activation enthalpies of ortho and para derivatives. The correlation is interpreted in terms of the selectivity of the reactant toward para- or ortho-monosubstituted substrates, the slope of which being related to the ortho effect. This slope is thought to be approximated by the ratio of polar substituent effects from ortho and para positions in benzene derivatives. Using the electrostatic theory of through-space interactions and a dipole length of 0.153 nm, this ratio was calculated at various positions of a charged reaction center along the benzene C1-C4 axis, being about 2.5 near the ring and decreasing steeply with increasing distance until reaching a minimum value of -0.565 at 1.3 nm beyond the aromatic ring. Activation enthalpies and entropies were estimated for substrates bearing the isoselective substituent in either ortho and para positions, being demonstrated that they are much different from the values for the parent substrate. The electrophilic attack on the phenolic oxygen atom by the protonated chlorinating agent is proposed as the rate-determining step, this step being followed by the fast rearrangement of the intermediate thus formed, leading to products containing chlorine in the aromatic ring.
The synthesis of α,β-unsaturated carbonyl derivatives with the ability to inhibit both glutathione S-transferase P1-1 activity and the proliferation of leukemia cells
Zhao, Guisen,Liu, Chuan,Wang, Rui,Song, Dandan,Wang, Xiaobing,Lou, Hongxiang,Jing, Yongkui
, p. 2701 - 2707 (2008/02/07)
Ethacrynic acid (EA), an α,β-unsaturated carbonyl compound, is a glutathione S-transferase P1-1 (GSTP1-1) inhibitor. Twenty-one novel EA derivatives have been synthesized. The effects of these compounds on GSTP1-1 activity and on the proliferation of human leukemia HL-60 cells have been determined. Compounds with a halogen substitution at the 3′-position of the aromatic ring have greater inhibitory effects on GSTP1-1 activity than those of compounds with a methyl substitution there. Compounds with substitutions at both the 2′- and 3′-positions of the aromatic ring have more antiproliferative ability than those with one substitution at 3′-position. Esterification of the carboxyl group appears to increase the antiproliferative ability.
Resolution of (±)-mandelic- and (±)-2-(chlorophenoxy)propionic-acid derivatives by crystallization of their diastereomeric amides with (R)- or (S)-α-arylethylamines
Jourdain, Franck,Hirokawa, Takahiko,Kogane, Tamizo
, p. 2307 - 2310 (2007/10/03)
An alternative and cost effective route for the resolution in high ees (95-99%) of (±)-mandelic-and (±)-2-(chlorophenoxy)propionic- acid derivatives is reported. The key step involves the covalent derivatization and separation of their diastereomeric amides with (R)- or (S)-α- arylethylamines.
Presynaptic cholinergic modulators as potent cognition enhancers and analgesic drugs. 2. 2-Phenoxy-, 2-(phenylthio)-, and 2-(phenylamino)alkanoic acid esters
Gualtieri,Bottalico,Calandrella,Dei,Giovannoni,Mealli,Romanelli,Scapecchi,Teodori,Galeotti,Ghelardini,Giotti,Bartolini
, p. 1712 - 1719 (2007/10/02)
Further modifications of the leads ((R)-(+)-hyoscyamine and (p- chlorophenyl)propionic acid α-tropanyl ester), which show analgesic and nootropic activities as a consequence of increased central presynaptic ACh release, are reported. 2-Phenoxy- and 2-(phenylthio)alkanoic acid esters showed the best results. Several members of these classes possess analgesic properties which are comparable to that of morphine and at the same time are able to reverse dicyclomine-induced amnesia. Confirmation was found that the mechanism of action is due to an increase in ACh release at central muscarinic synapses and that both auto- and heteroreceptors controlling ACh release are very likely involved. According to the results obtained with (R)- (+)-hyoscyamine, analgesic activity is stereochemistry dependent, since the R-(+)-enantiomers are always more efficacious than the corresponding S-(-)- ones. On the basis of their potency and acute toxicity, compounds (±)-28 (SM21) and (±)-42 (SM32) were selected for further study.
