- Stereoselective concise total synthesis of leodomycin C and D
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Stereoselective concise total synthesis of leodomycin C and D from commercially available propylene oxide using Jacobsens hydrolytic kinetic resolution (HKR), base-promoted alkyne zipper reaction, TPP-promoted enyne ester (ynoate) to diene ester (dienoate
- Chinnababu,Reddy, S. Purushotham,Reddy, D. Kumar,Rao, D. Chandra,Venkateswarlu
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- In-Situ Monitoring of Enantiomeric Excess during a Catalytic Kinetic Resolution
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Vibrational Circular Dichroism combined with FTIR spectroscopy (VCD-IR) is demonstrated as a viable tool for the in situ measurement of enantiomeric excess during asymmetric catalytic transformations. Employing the Jacobsen (salen)Co-catalyzed hydrolytic kinetic resolution of racemic epoxides as a proof-of-concept case study, methodology is developed to monitor the enantiomeric excess of the epoxide substrate as a function of conversion of the limiting reactant, water. Comparison of results for monomeric and oligomeric catalysts probes the molecularity of the catalyst by investigating nonlinear effects in catalyst enantiopurity. These results are in excellent agreement with previous mechanistic investigations of this reaction based on kinetic measurements and computational studies.
- Mower, Matthew P.,Blackmond, Donna G.
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- A practical synthesis of both enantiomers of 1-amino-2-propanol and propylene oxide
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A practical large-scale synthesis of both enantiomers of 1-amino-2-propanol 1 from L- and D-threonine is described. Greater than 99% e.e. propylene oxide 2 is obtained from 1 through a diazotization under basic conditions.
- Rossen,Simpson,Wells
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- Alternating copolymerization of CO2 and propylene oxide catalyzed by CoIII(salen)/Lewis base
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The use of CoIII(salen)/Lewis base catalyst system for copolymerization of CO2 and propylene oxide was analyzed. The ratio of catalyst to Lewis base cocatalyst influenced the TOF. The use of Lewis base cocatalyst enables high catalytic activity at low CO2 pressure and affords superior enantioselectivity. The results show that the use of cocatalyst produced a highly alternating monodisperse polycarbonate product without concomitant cyclic carbonate production.
- Paddock, Robert L.,Nguyen, SonBinh T.
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- A Combined Microbial/Chemical Synthesis of (+)-(R)-Methyloxirane Having High Enantiomeric Excess
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Clostridium thermosaccharolyticum (ATCC 31960) converts glucose to (-)-(R)-propylene glycol; standard procedures transform this substance to (+)-(R)-methyloxirane ((+)-(R)-propylene oxide) with enantiomeric excess >99percent.This procedure is capable of generating this useful chiral synthon on a large scale.
- Simon, Ethan S.,Whitesides, George M.,Cameron, Douglas C.,Weitz, David J.,Cooney, Charles L.
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- Chiral catalysts for the asymmetric cycloaddition of carbon dioxide with epoxides
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Several chiral BINADCo(III)X (BINAD = Bis(1,1′-2-hydroxy-2′-alkoxy-3-naphthylidene)-1,2-cyclohexanediamine, X = OAc, CF3CO2, CCl3CO2, OTs, p-NO2PhCO2) complexes were synthesized and used to
- Jin, Lili,Huang, Yongzhong,Jing, Huanwang,Chang, Tao,Yan, Peng
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- Regioselective Cyclodehydration of Chiral Diols with Diethoxytriphenylphosphorane, Triphenylphosphine-Tetrachloromethane-Potassium Carbonate, and Triphenylphosphine-Diethyl Azodicarboxylate Reagents. A Comparative Study
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The regioselectivity of cyclodehydration of chiral diols has been examined with the reagents diethoxytriphenylphosphorane, triphenylphosphine-tetrachloromethane-potassium carbonate, and triphenylphosphine-diethyl azodicarboxylate. (S)-(+)-Propane-1,2-diol and (R)-(-)-pentane-1,4-diol afford 80-87percent retention of stereochemistry at the chiral carbon in the ether while (S)-(+)-phenylethane-1,2-diol affords essentially racemic styrene oxide with all three reagents.
- Robinson, Philip L.,Barry, Carey N.,Bass, S. Woody,Jarvis, Susan E.,Evans, Slayton A.
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- Total synthesis of the proposed structures of eushearilide
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Total synthesis of (3R,16Z,20E,23S)- and (3R,16Z,20E,23R)-eushearilide was accomplished in 15 steps, respectively. Using either enantiomer of one of the four building blocks to assemble the phosphonium salt for the latter Wittig reaction, two diastereomers of eushearilide were prepared. Shiina macrolactonization (2-methyl-6-nitrobenzoic anhydride) was a key step in production of the 24-membered lactone in high yield.
- Yamauchi, Takayasu,Takidaira, Jun-Ichi,Okamoto, Kenya,Sugiura, Takaya,Horikoshi, Hiroki,Kudo, Shintaro,Sasaki, Shigeru,Mizushima, Noriko,Higashiyama, Kimio
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- Enantioselective Resolution Copolymerization of Racemic Epoxides and Anhydrides: Efficient Approach for Stereoregular Polyesters and Chiral Epoxides
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Herein we report an efficient strategy for preparing isotactic polyesters and chiral epoxides via enantioselective resolution copolymerization of racemic terminal epoxides with anhydrides, mediated by enantiopure bimetallic complexes in conjunction with a nucleophilic cocatalyst. The chirality of both the axial linker and the diamine backbones of the ligand are responsible for the chiral induction of this kinetic resolution copolymerization process. The catalyst systems exhibit exceptional levels of enantioselectivity with a kinetic resolution coefficient exceeding 300 for various racemic epoxides, affording highly isotactic copolymers (selectivity factors of more than 300) with a completely alternating structure and low polydispersity index. Most of the produced isotactic polyesters are typical semicrystalline materials with melting temperatures in the range from 77 to 160 °C.
- Li, Jie,Ren, Bai-Hao,Wan, Zhao-Qian,Chen, Shi-Yu,Liu, Ye,Ren, Wei-Min,Lu, Xiao-Bing
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supporting information
p. 8937 - 8942
(2019/06/11)
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- Homochiral Metal-Organic Cage for Gas Chromatographic Separations
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Metal-organic cages (MOCs) as a new type of porous material with well-defined cavities were extensively pursued because of their relative ease of synthesis and their potential applications in host-guest chemistry, molecular recognition, separation, catalysis, gas storage, and drug delivery. Here, we first reported that a homochiral MOC [Zn3L2] is explored to fabricate [Zn3L2] coated capillary column for high-resolution gas chromatographic separation of a wide range of analytes, including n-alkanes, polycyclic aromatic hydrocarbons, and positional isomers, especially for racemates. Various kinds of racemates such as alcohols, diols, epoxides, ethers, halohydrocarbons, and esters were separated with good enantioselectivity and reproducibility on the [Zn3L2] coated capillary column. The fabricated [Zn3L2] coated capillary column exhibited significant chiral recognition complementary to that of a commercial β-DEX 120 column and our recently reported homochiral porous organic cage CC3-R coated column. The results show that the homochiral MOCs will be very attractive as a new type of chiral selector in separation science.
- Xie, Sheng-Ming,Fu, Nan,Li, Li,Yuan, Bao-Yan,Zhang, Jun-Hui,Li, Yan-Xia,Yuan, Li-Ming
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p. 9182 - 9188
(2018/07/21)
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- A (R)- single thio propylene carbonate preparation method (by machine translation)
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The invention relates to a (R)- single thio propylene carbonate preparation method, including: (1) epoxy propane, epoxy hydrolase ECU1040 is mixed with water, for 0 - 5 °C reaction 10 - 40 hours, stopping the reaction, normal pressure is distilled to produce (R)- propylene oxide; (2) the above the resulting (R)- propylene oxide is mixed with organic solvent, adding carbonylation and alkali and organic amine, in the 10 - 30 °C under stirring into the carbonyl sulfide gas, until the oxysulfide until the gas does not absorb, the total reaction time is 15 - 30 hours, to obtain the (R)- single thio propylene carbonate ester. Preparation method of the invention normal pressure operation, high yield, simple and practical, low risk, less equipment investment, optical purity of the product to achieve 99% e.e value or more, and has excellent industrial prospect. (by machine translation)
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Paragraph 0007-0008; 0028-0029; 0031-0032
(2018/03/28)
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- The Rickiols: 20-, 22-, and 24-membered Macrolides from the Ascomycete Hypoxylon rickii
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In preceding studies the neotropical ascomycete Hypoxylon rickii turned out to be a prolific source of new secondary metabolites, considering that we had obtained terpenoids with five different scaffolds along with a series of terphenyls. From the mycelial extracts of a 70 L scale fermentation of this strain we additionally isolated nine new macrolides (1–9) by RP-HPLC. The planar structures were elucidated by NMR spectroscopy complemented by HR-ESIMS. The relative configurations were assigned by J-based configuration analyses and confirmed by Kishi′s Universal Database. Subsequently, the absolute configurations were assigned by Mosher′s method using the shift analysis of a tetra-MTPA derivative. For rickiol A (1) and E (5) we observed transesterification of 20-membered ring structures to 22-membered isomers rickiol A2 (6) and E2 (7), and to 24-membered isomers rickiol A3 (8) and rickiol E3 (9), respectively. Cytotoxic effects and moderate antibiotic activity against Gram-positive bacteria were observed for 1–8 and 1–6 and 8, respectively. The total synthesis of rickiol E3 (9) established easier access to these compounds.
- Surup, Frank,Kuhnert, Eric,B?hm, Andreas,Pendzialek, Tim,Solga, Danny,Wiebach, Vincent,Engler, Hauke,Berkessel, Albrecht,Stadler, Marc,Kalesse, Markus
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p. 2200 - 2213
(2018/01/27)
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- Stereoselective synthesis of 5′-hydroxyzearalenone
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A first stereoselective total synthesis of 14-memebered β-resorcylic macrolactone 5′-hydroxyzearalenone (1) has been achieved. The key steps are Jocobsen hydrolytic kinetic resolution, Sharpless asymmetric dihydroxylation, Vilsmeier-Haack reaction, Mitsunobu esterification and ring-closing metathesis.
- Avuluri, Srilatha,Bujaranipalli, Sheshurao,Das, Saibal,Yadav
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p. 3547 - 3549
(2018/08/29)
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- Bimetallic Chromium Catalysts with Chain Transfer Agents: A Route to Isotactic Poly(propylene oxide)s with Narrow Dispersities
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Bimetallic chromium catalysts are investigated for the enantioselective polymerization of propylene oxide. The catalyst is composed of two salen chromium species linked by an alkyl chain, the length of which significantly impacts the rate of polymerization. While the use of a chloride initiator on the catalyst resulted in bimodal molecular weight distributions, switching to a trifluoroacetate initiating group and adding a diol chain transfer agent afforded polymers of controllable molecular weight with low, unimodal dispersities.
- Morris, Lilliana S.,Childers, M. Ian,Coates, Geoffrey W.
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supporting information
p. 5731 - 5734
(2018/05/14)
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- POLYESTER STEREOCOMPLEXES, COMPOSITIONS COMPRISING SAME, AND METHODS OF MAKING AND USING SAME
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Compositions comprising stereocomplexes of enantiomeric polymer chains having individual repeat units formed from the reaction of an epoxide and cyclic anhydride. The compositions can be made by mixing two types of enantiomeric polymer chains having opposite absolute stereochemistry. The compositions can be used in applications such as biomedical applications and drug delivery applications.
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Paragraph 0109; 0110
(2016/02/29)
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- SYNTHESIS OF INTERMEDIATES USED IN THE MANUFACTURE OF ANTI-HIV AGENTS
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The present invention relates to a process of preparing intermediates of Formula (I). The process comprises of reacting compound of Formula (III) with compound of Formula (V) in the presence of a solvent selected from an alcohol, ether or water to form compound of Formula (I) wherein, R1 is selected from –NH2, Cl, Br, NHCOR", wherein R" is alkyl, aryl, Schiff's base of formula N=CHR', wherein R' is alkyl or aryl; R2 is selected from H, alkyl; R3 and R4, each independently is H; R5 and R6, each independently is H, alkyl; R7 is H, alkyl; and R8 is H, alkyl.
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Page/Page column 18-19
(2016/11/21)
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- Total synthesis, biological evaluation of dendrodolides A–D and their analogues
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A concise total synthesis of dendrodolides A–D (1–4) has been accomplished in 10 steps from commercially available (R)-propylene oxide and 3-buten-1-ol as starting materials. The key steps involved in the synthesis are Jacobsen hydrolytic kinetic resolution, epoxide ring opening with 2-allyl-1, 3-dithiane, Yamaguchi esterification and ring-closing metathesis (RCM). In addition, a series of ester derivatives were prepared utilizing Yamaguchi esterification at the C-3 position of the dendrodolide core and screened for their efficacy against cancer cell lines.
- Poornima,Venkanna,Swetha,Kamireddy, Karthik reddy,Siva, Bandi,Phani Babu,Ummanni, Ramesh,Babu, K. Suresh
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p. 4789 - 4797
(2016/07/18)
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- Chiral oligomers of spiro-salencobalt(III)X for catalytic asymmetric cycloaddition of epoxides with CO2
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Several new chiral oligomers of spiro-salenCo(III)X (spiro = 1.1′-spirobiindane-7.7′-diol) complexes have been designed, synthesized, and characterized by nuclear magnetic resonance (NMR), infrared (IR), and elemental analyses, in which, the chiral spiro moieties are first introduced into a scaffold of chiral salenCo catalysts. They were used to catalyze the asymmetric cycloaddition of epoxides with carbon dioxide. Under very mild reaction conditions, a kinetic resolution of racemic epoxides with CO2 was smoothly initiated by these chiral oligomer catalysts with good enantioselectivities, which can be attributed to the match effect between chiral backbones of salen and spiro. High stability and easy recyclability are their major advantages.
- Zhu, Zhouhe,Zhang, Yuqian,Wang, Kai,Fu, Xiying,Chen, Fengjuan,Jing, Huanwang
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- First Stereoselective Synthesis of the Cytotoxic Polyketide (4R)-1-(3,5-Dihydroxyphenyl)-4-hydroxypentan-2-one
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The first stereoselective synthesis of the cytotoxic polyketide (4R)-1-(3,5-dihydroxyphenyl)-4-hydroxypentan-2-one (1) was achieved from readily available propylene oxide and 3,5-dimethoxybenzyl alcohol. The synthesis involves Jacobsen's hydrolytic kinetic resolution (HKR) and Grignard reaction as key steps.
- Rajendra Prasad, Kothakonda,Purushotham Reddy, Sudina,Suresh Babu, Katragadda,Madhusudana Rao, Janaswamy
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p. 143 - 147
(2015/10/19)
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- Dinuclear salen cobalt complex incorporating Y(OTf)3: enhanced enantioselectivity in the hydrolytic kinetic resolution of epoxides
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The activation of inactive Jacobsen's chiral salen Co(ii) (salen = N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine) compound is attained by dinuclear chiral salen Co(iii)-OTf complex formation with yttrium triflate. The yttrium metal not only displays a promoting effect on electron transfer, but also assists in forming two stereocentres of a Lewis acid complex with Co(iii)-OTf. We found that the binuclear Co-complex significantly enhanced reactivity and enantioselectivity in the hydrolytic kinetic resolution of terminal epoxides compared to its analogous monomer and kinetic data are also consistent with these results.
- Patel, Deepak,Kurrey, Ganesh Ram,Shinde, Sandip S.,Kumar, Pradeep,Kim, Geon-Joong,Thakur, Santosh Singh
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p. 82699 - 82703
(2015/10/19)
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- Asymmetric total synthesis of stagonolide F
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A highly convergent stereoselective total synthesis of stagonolide F is described starting from commercially available 5-hexen 1-ol using asymmetric dihydroxylation, Jacobsen's hydrolytic kinetic resolution (HKR), regioselective epoxide ring opening with vinyl Grignard reaction, esterification, and ring-closing metathesis (RCM) as key steps.
- Chinnababu,Reddy, S. Purushotham,Babu, K. Suresh,Venkateswarlu
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p. 2886 - 2891
(2014/09/29)
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- A broadly applicable and practical oligomeric (salen)Co catalyst for enantioselective epoxide ring-opening reactions
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The (salen)Co catalyst (4a) can be prepared as a mixture of cyclic oligomers in a short, chromatography-free synthesis from inexpensive, commercially available precursors. This catalyst displays remarkable enhancements in reactivity and enantioselectivity relative to monomeric and other multimeric (salen)Co catalysts in a wide variety of enantioselective epoxide ring-opening reactions. The application of catalyst 4a is illustrated in the kinetic resolution of terminal epoxides by nucleophilic ring-opening with water, phenols, and primary alcohols; the desymmetrization of meso epoxides by addition of water and carbamates; and the desymmetrization of oxetanes by intramolecular ring opening with alcohols and phenols. The favorable solubility properties of complex 4a under the catalytic conditions facilitated mechanistic studies, allowing elucidation of the basis for the beneficial effect of oligomerization. Finally, a catalyst selection guide is provided to delineate the specific advantages of oligomeric catalyst 4a relative to (salen)Co monomer 1 for each reaction class.
- White, David E.,Tadross, Pamela M.,Lu, Zhe,Jacobsen, Eric N.
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p. 4165 - 4180
(2014/06/09)
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- Stereoselective total synthesis of multiplolide A and of a diastereoisomer
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A stereoselective total synthesis of multiplolide A (1) and of its diastereoisomer 2 was described from easily accessible starting materials (Schemes 2-4). The synthetic strategy involves a Jacobsen resolution, Sharpless epoxidation, Swern oxidation, Yamaguchi reaction, and ring-closing metathesis (RCM). Copyright
- Reddy, Bandi Chennakesava,Bangade, Vikas Madhukar,Ramesh, Palakuri,Meshram, Harshadas Mitaram
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p. 266 - 274
(2013/03/28)
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- A convergent synthesis of the [4.4]-spiroacetal-γ-lactones cephalosporolides e and F
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A short convergent synthesis of the fungal metabolites cephalosporolides E and F is reported. The key step makes use of a chelation-controlled Mukaiyama aldol reaction to access the key acyclic spiroacetal precursor with the required syn stereochemistry.
- Brimble, Margaret A.,Finch, Orla C.,Heapy, Amanda M.,Fraser, John D.,Furkert, Daniel P.,O'Connor, Patrick D.
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experimental part
p. 995 - 1001
(2011/03/19)
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- A flexible and unified strategy for syntheses of cladospolides A, B, C, and iso-cladospolide B
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A simple, efficient and flexible strategy for the syntheses of cladospolides A-C and iso-cladospolide B is reported here. This strategy involves Julia-Kocienski olefination and Yamaguchi macrolactonization as key steps, starting from either d-ribose or suitable tartaric acid esters. Although our initial efforts towards cladospolide A involving a ring closing metathetic approach were not successful, changing the mode of ring closure and the use of Julia-Kocienski olefination for the construction of the key intermediate solved this issue and paved the way for the completion of total syntheses of this class of natural products.
- Si, Debjani,Sekar, Narayana M.,Kaliappan, Krishna P.
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body text
p. 6988 - 6997
(2011/11/05)
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- Asymmetric ring opening of terminal epoxides via kinetic resolution catalyzed by chiral (salen)Co mixture
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The highly enantioselective hydrolytic kinetic resolution (HKR) of racemic terminal epoxides by bimetallic chiral (salen)Co and (salen)Co(III)-OAc mixture provides a simple and effective method for the synthesis of enantiomerically enriched terminal epoxides (ee > 99%) and diols. At the equimolar amounts of bimetallic chiral (salen)Co and (salen)Co(II)-OAc, the catalytic activity increases more than two times in comparison with (salen)Co(III)-OAc used alone. The mixed catalytic system can be recycled and reused. No significant loss of catalytic activity was observed after three runs.
- Jiang, Chengjun
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experimental part
p. 691 - 696
(2011/11/30)
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- Stereoselective synthesis of ophiocerins A and C
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An efficient synthesis of ophiocerins A and C has been achieved via a common intermediate. The stereogenic centers were generated by means of Jacobsen's hydrolytic kinetic resolution and Sharpless kinetic resolution.
- Show, Krishanu,Gupta, Priti,Kumar, Pradeep
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experimental part
p. 1212 - 1217
(2011/10/30)
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- A concise stereoselective total synthesis of Botryolide B
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The first total synthesis of Botryolide B is described from easily accessible starting materials. The synthetic strategy involves Jacobsen resolution, Sharpless epoxidation, Swern oxidation, Yamaguchi reaction, and ring closing metathesis (RCM).
- Reddy, B. Chennakesava,Meshram
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scheme or table
p. 4020 - 4022
(2010/08/07)
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- Catalytic Asymmetric Cycloaddition of Carbon Dioxide and Propylene Oxide Using Novel Chiral Polymers of BINOL-SalenCobalt(III) Salts
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Four new chiral polymers of BINOLSalen-cobalt(III) salt complexes have been designed, synthesized and applied to the direct fabrication of chiral propylene carbonate from racemic propylene oxide. The (R/S)-polymer catalyst 2 and (S/R)-polymer catalyst 4 exhibit better enantioselectivity than the (R/R)-polymer catalyst 1 and the (S/S)-polymer catalyst 3 and have been recovered and reused more than ten times without loss of activity and enantioselectivity.
- Yan, Peng,Jing, Huanwang
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experimental part
p. 1325 - 1332
(2009/12/24)
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- First asymmetric total synthesis of aspinolide A
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The first total synthesis of aspinolide A has been achieved using ring-closing metathesis as a key step. The stereogenic centers were generated by means of hydrolytic kinetic resolution (HKR) of racemic epoxides.
- Chowdhury, Partha Sarathi,Gupta, Priti,Kumar, Pradeep
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scheme or table
p. 7018 - 7020
(2010/02/28)
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- Enantioselective synthesis of decarestrictine J
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An efficient total synthesis of decarestrictine J has been achieved using ring-closing metathesis and Yamaguchi esterification as key steps. The stereogenic centres were generated by means of iterative hydrolytic kinetic resolution (HKR) of racemic epoxides.
- Chowdhury, Partha Sarathi,Gupta, Priti,Kumar, Pradeep
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scheme or table
p. 7188 - 7190
(2010/02/28)
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- Concise synthesis of stagonolide-F by ring closing metathesis approach and its biological evaluation
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The first total synthesis of 9-membered macrolide, stagonolide-F (3), starting from commercially available 1,5-pentane diol is reported. A combination of Jacobsen's hydrolytic kinetic resolution (HKR) and Sharpless epoxidation is used for the creation of two stereogenic centers, while ring-closing metathesis (RCM) strategy was used for the construction of the lactone ring. The molecule synthesized exhibited potent antifungal, antibacterial and cytotoxic activities against all the tested strains.
- Perepogu, Arun Kumar,Raman,Murty,Rao, Vaidya Jayathirtha
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body text
p. 46 - 51
(2009/08/07)
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- ISOSELECTIVE POLYMERIZATION OF EPOXIDES
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The present invention provides novel bimetallic complexes and methods of using the same in the isoselective polymerization of epoxides. The invention also provides methods of kinetic resolution of epoxides. The invention further provides polyethers with high enantiomeric excess that are useful in applications ranging from consumer goods to materials.
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Page/Page column 68-69
(2009/04/25)
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- Stereoselective synthesis of (+)-sordidin, the male-produced aggregation pheromone of the banana weevil Cosmopolites sordidus
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Stereoselective synthesis of (1S,3R,5R,7S)-(+)-sordidin, the natural male-produced aggregation pheromone of the banana weevil Cosmopolites sordidus (Germar) starting from 5-benzyloxy-(2E)-pentene-1-ol is described. The key transformations employed in the synthesis are Sharpless asymmetric epoxidation, Ueno-Stork cyclization, and Jacobsen kinetic resolution.
- Yadav,Reddy, K. Bhaskar,Prasad,Rehman, H. Ur
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p. 2063 - 2070
(2008/09/17)
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- NEW CHIRAL SALEN CATALYSTS AND METHODS FOR THE PREPARATION OF CHIRAL COMPOUNDS FROM RACEMIC EPOXIDES BY USING THEM
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The present invention relates to new chiral salen catalysts and the preparation method of chiral compounds from racemic epoxides using the same. More specifically, it relates to new chiral salen catalysts that have high catalytic activity due to new molecular structures and have no or little racemization of the generated target chiral compounds even after the reaction is completed and can be also reused without catalyst regeneration treatment, and its economical preparation method to mass manufacture chiral compounds of high optical purity, which can be used as raw materials for chiral food additives, chiral drugs, or chiral crop protection agents, etc., using the new chiral salen catalysts.
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Page/Page column 39
(2009/01/24)
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- Facile stereoselective synthesis of the C12-C24 fragment of macrolactin-A
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A simple and efficient stereoselective synthesis of the C12-C24 fragment of the natural product macrolactin-A was achieved from D-glucose as the starting material and with use of the Wittig and modified Julia olefination reactions as key steps. Georg Thieme Verlag Stuttgart.
- Yadav, Jhillu S.,Gupta, Manoj K.,Prathap
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p. 1343 - 1348
(2008/02/12)
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- Asymmetric ring-opening of epoxides on chiral Co(Salen) catalyst synthesized in SBA-16 through the "ship in a bottle" strategy
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Chiral Co(Salen) complex was synthesized in the mesoporous cage of SBA-16 through the "ship in a bottle" method. The pore entrance size of SBA-16 was precisely tailored by varying the autoclaving time and silylation with phenyltrimethoxysilane to trap Co(Salen) complex in the cage of SBA-16. Chiral Co(Salen) trapped in SBA-16 shows enantioselectivity (up to 87-96% ee) as high as that of the homogeneous catalyst for the asymmetric ring opening of terminal epoxides and can be recycled at least 10 times with no apparent loss of activity. The activity for the catalyst trapped inside SBA-16 can be significantly increased when the surface is modified with organic groups. This work extends the "ship in a bottle" synthesis from microporous materials to mesoporous cage-like materials and develops an effective strategy to trap metal complex catalyst with large molecular size into the nanopores or cavities of mesoporous materials.
- Yang, Hengquan,Zhang, Lei,Su, Weiguang,Yang, Qihua,Li, Can
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p. 204 - 212
(2007/10/03)
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- Enhanced cooperative activation effect in the hydrolytic kinetic resolution of epoxides on [co(salen)] catalysts confined in nanocages
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(Chemical Equation Presented) Being cagey: More than two chiral [Co-(salen)] catalyst molecules can be confined in one nanocage of SBA-16 by reducing the pore entrance size by silylation. The [Co(salen)]/SBA-16 catalysts with more than two [Co(salen)] complexes in each cage show a significantly enhanced cooperative activation effect and exhibit much higher activity than the homogeneous [Co(salen)] catalyst in the hydrolytic kinetic resolution of epoxides (see scheme).
- Yang, Heng Quan,Zhang, Lei,Zhong, Lin,Yang, Qi Hua,Li, Can
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p. 6861 - 6865
(2008/09/18)
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- "Cassette" in situ enzymatic screening identifies complementary chiral scaffolds for hydrolytic kinetic resolution across a range of epoxides
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(Figure Presented) Put the cassette in: An in situ enzymatic screen can give real-time estimates of the sense and magnitude of enantioselectivity across more than one substrate. Screening identified CoIII-salen catalysts with β-pinene- and α-naphthylalanine-derived chiral scaffolds with broad, yet complementary, substrate specificities. ADH = alcohol dehydrogenase, HL = horse liver, LK = Lactobacillus kefir, salen = (salicylidene) ethylenediamine.
- Dey, Sangeeta,Powell, Douglas R.,Hu, Chunhua,Berkowitz, David B.
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p. 7010 - 7014
(2008/09/17)
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- The enantioselective synthesis of elecanacin through an intramolecular naphthoquinone-vinyl ether photochemical cycloaddition
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Elecanacin, an unusual cyclobuta-fused naphthalene-1,4-dione derivative isolated from the bulbs of Eleutherine Americana Merr. et Heyne (Iridaceae) has been obtained, together with its epimer isoelecanacin, by a 2 + 2 cycloaddition resulting from irradiation of 5-methoxy-2-(2-vinyloxypropyl)naphthalene-1,4- dione. The synthesis of enantiopure elecanacin starting with (R)-propylene oxide has established the absolute configuration of the natural product and has revealed that the sample isolated from the bulbs possessed an enantiomeric excess of only 14%. The Royal Society of Chemistry 2006.
- Nielsen, Linda B.,Wege, Dieter
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p. 868 - 876
(2007/10/03)
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- Catalytic asymmetric addition of carbon dioxide to propylene oxide with unprecedented enantioselectivity
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New chiral catalyst systems were developed for the reaction of carbon dioxide with propylene oxide (PO) at atmospheric pressure to generate enantiomerically enriched propylene carbonate (PC). The best selectivity was achieved with a CoIII(salen)-trifluoroacetyl complex and bis-(triphenylphosphoranylidene)ammonium fluoride (PPN+F-) as catalysts, affording PC in 40% yield and 83% ee (selectivity factor = 19). In addition, PC was prepared for the first time by kinetic resolution of PO with tetrabutylammonium methyl carbonate (TBAMC, nBu4N +-OOCOMe). With TBAMC as "activated CO2", up to 71% ee was obtained.
- Berkessel, Albrecht,Brandenburg, Marc
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p. 4401 - 4404
(2007/10/03)
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- A new dinuclear chiral salen complexes for asymmetric ring opening and closing reactions: Synthesis of valuable chiral intermediates
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A new dinuclear chiral Co(salen) complexes bearing group 13 metals have been synthesized and characterized. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of epoxides with H2O, chloride ions and carboxylic acids and consequently provide enantiomerically enriched terminal epoxides (>99% ee). It also catalyzes the asymmetric cyclization of ring opened product, to prepare optically pure terminal epoxides in one step. The homogeneous dinuclear chiral Co(salen) have been covalently immobilized on MCM-41. The potential benefits of heterogenization include facilitation of catalyst separation and recyclability requiring very simple techniques. The system described is very efficient.
- Thakur, Santosh Singh,Chen, Shu-Wei,Li, Wenji,Shin, Chang-Kyo,Kim, Seong-Jin,Koo, Yoon-Mo,Kim, Geon-Joong
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p. 1862 - 1872
(2007/10/03)
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- Synthesis of optically pure terminal epoxide and 1,2-diol via hydrolytic kinetic resolution catalyzed by new heterometallic salen complexes
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The inactive chiral (salen)Co complex is easily activated by InCl 3 and TlCl3 Lewis acids by forming heterometallic salen complexes. These complexes show very high catalytic activity for the synthesis of enantiomerically enriched terminal epoxides (>99% ee) and 1,2-diols simultaneously via hydrolytic kinetic resolution. Strong synergistic effects of different Lewis acids, Co-In and Co-Tl, were exhibited in the catalytic process. The system described is very simple and efficient. Copyright Taylor & Francis Group, LLC.
- Thakur, Santosh Singh,Chen, Shu-Wei,Li, Wenji,Shin, Chang-Kyo,Koo, Yoon-Mo,Kim, Geon-Joong
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p. 2371 - 2383
(2007/10/03)
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- Hydrolytic kinetic resolution of epoxides catalyzed by chromium(III)-endo, endo-2,5-diaminonorbornane-salen [Cr(III)-DIANANE-salen] complexes. Improved activity, low catalyst loading
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The hydrolytic kinetic resolution (HKR) of terminal epoxides, using chiral chromium(III)-salen catalysts based on DIANANE (endo,endo-2,5-diaminonorbornane) , was studied. A broad substrate scope was found for the chromium(III)-DIANANE catalysts, and very low loadings (down to 0.05 mol%) were needed to achieve high enantiomeric purities of both the remaining epoxides and the product diols (up to >99% ee). Besides monosubstituted epoxides, 2-methyl-2-n-pentyloxirane, which is an example for 2,2-disubstituted epoxides, could be ring-opened in an asymmetric fashion with water in the presence of an electronically tuned chromium-(III)-DIANANE complex.
- Berkessel, Albrecht,Ertuerk, Erkan
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p. 2619 - 2625
(2007/10/03)
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- Concise strategy to the core structure of the macrolide queenslandon
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(Diagram presented) The fully functionalized core structure of the macrolactone queenslandon was prepared using a novel strategy consisting of a glycolate aldol reaction and hydroboration of the derived enol ether 17 followed by Suzuki cross-coupling with an iodostyrene. After conversion of the cross-coupling product to the seco acid 22, Mitsunobu macrolactonization and protecting group manipulations led to the queenslandon model 5.
- Khartulyari, Anton S.,Kapur, Manmohan,Maier, Martin E.
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p. 5833 - 5836
(2007/10/03)
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- Asymmetric epoxidation of terminal alkenes with hydrogen peroxide catalyzed by pentafluorophenyl PtII complexes
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Easily accessible chiral PtII complexes 1 allow highly enantioselective and completely regioselective asymmetric epoxidation of terminal alkenes with hydrogen peroxide. Copyright
- Colladon, Marco,Scarso, Alessandro,Sgarbossa, Paolo,Michelin, Rino A.,Strukul, Giorgio
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p. 14006 - 14007
(2007/10/03)
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- Stereoselective synthesis of (+)-diplodialides-B, C and a formal synthesis of (+)-diplodialide-A by ring-closing metathesis approach
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Stereoselective synthesis of diplodialides-B and C and the formal synthesis of diplodialide-A are reported. A combination of Jacobsen's hydrolytic kinetic resolution and Sharpless epoxidation is used for the creation of two stereogenic centers, while a ring-closing metathesis strategy was used for the construction of the lactone ring.
- Sharma,Reddy, K. Laxmi
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p. 3197 - 3202
(2007/10/03)
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- Synthesis of optically active 2-hydroxy monoesters via-kinetic resolution and asymmetric cyclization catalyzed by heterometallic chiral (salen) Co complex
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The binuclear chiral (salen) Co complexes bearing Lewis acids of Al and Ga catalyze regio- and enantioselective ring opening of terminal epoxides with carboxylic acids. The ring opened product of epichlorohydrin with carboxylic acids followed by cyclization step in the presence of catalyst and base represent straightforward, efficient methods for the synthesis of enatiomerically enriched (>99% ee) valuable terminal epoxides. Strong synergistic effects of different Lewis acid of Co-Al and Co-Ga were exhibited in the catalytic process.
- Li, Wenji,Thakur, Santosh Singh,Chen, Shu-Wei,Shin, Chang-Kyo,Kawthekar, Rahul B.,Kim, Geon-Joong
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p. 3453 - 3457
(2007/10/03)
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- Highly reactive and enantioselective kinetic resolution of terminal epoxides with H2O and HCl catalyzed by new chiral (salen)Co complex linked with Al
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The asymmetric hydrolytic kinetic resolution (HKR) of racemic terminal epoxides by new easily synthesized dimeric chiral (salen)Co bearing Al, provides a practical and straightforward method for the synthesis of enantiomerically enriched terminal epoxides (>99% ee) and diols. An inorganic acid, HCl is applied first time for the asymmetric ring opening reaction of terminal epoxides. Reactions are conveniently carried out at room temperature under an air atmosphere.
- Thakur, Santosh Singh,Li, Wenji,Kim, Seong-Jin,Kim, Geon-Joong
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p. 2263 - 2266
(2007/10/03)
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- Enantioselective synthesis of tarchonanthuslactone via iterative hydrolytic kinetic resolution
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A short and practical enantioselective synthesis of tarchonanthuslactone has been achieved in high diastereomeric excess using iterative Jacobsen's hydrolytic kinetic resolution and ring closing metathesis as the key steps.
- Gupta, Priti,Naidu, S. Vasudeva,Kumar, Pradeep
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p. 6571 - 6573
(2007/10/03)
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- Efficient total synthesis of iso-cladospolide B and cladospolide B
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An efficient synthesis of iso-cladospolide B and cladospolide B has been achieved using Jacobsen's hydrolytic kinetic resolution (HKR), Sharpless asymmetric dihydroxylation and Yamaguchi macrolactonization as the key steps.
- Pandey, Satyendra Kumar,Kumar, Pradeep
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p. 6625 - 6627
(2007/10/03)
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- Direct catalytic synthesis of enantiopure 5-substituted oxazolidinones from racemic terminal epoxides
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(Chemical Equation Presented) A venerable scaffold for asymmetric synthesis and drug development, chiral 5-substituted oxazolidinones are obtained in almost enantiomerically pure form (up to 99.9% ee) starting from racemic terminal epoxides. The salient features of this process include the very simple and convenient experimental protocol and the employment of a readily accessible catalyst and inexpensive, easily handled starting materials. An enantioconvergent approach for the total conversion of racemic epoxide into a single stereoisomeric oxazolidinone is also described.
- Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Melchiorre, Paolo,Sambri, Letizia
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p. 1983 - 1985
(2007/10/03)
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