- The total synthesis of (+)-aspicilin using 2,3-butane diacetal protected butane tetrols via a chiral memory protocol
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The total syntheses of the polyhydroxylated macrolactone (+)-aspicilin and a diastereoisomer have been achieved via a concise route, starting from the spatially desymmetrized (R′,R′,R,S)-2,3-butanediacetal-protected butane tetrol 13. The key steps include a regioselective silyl protection of 13 and a stereoselective Lewis acid mediated addition of allyltributylstannane to the equatorially disposed aldehyde of 4. Macrocyclization is achieved using ring closing metathesis, after which selective hydrogenation and protecting group removal yields the natural product.
- Dixon, Darren J.,Foster, Alison C.,Ley, Steven V.
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- The synthesis of polyfunctionalized, cyclohexene-based chirons from tartaric acid
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Compound ent-1 as well as certain related homochiral and polyfunctionalized cyclohexenes have been prepared from the 1,2-diacetal 4 that is itself readily derived from L-tartaric acid (3). Grignard addition and ring-closing metathesis processes constitute the key steps associated with the reaction sequences involved. This work provides a method for obtaining a range of potentially useful cyclohexenone-containing chirons that are enantiomerically related to those that have been prepared from the homochiral cis-1,2-dihydrocatechol 2, the product of the microbial biotransformation of bromobenzene.
- Buckler, Joshua N.,Schwartz, Brett D.,Banwell, Martin G.
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- The continuous flow synthesis of butane-2,3-diacetal protected building blocks using microreactors
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The continuous flow synthesis of butane-2,3-diacetal protected derivatives has been achieved using commercially available flow chemistry microreactors in concert with solid supported reagents and scavengers to provide in-line purification systems. The BDA protected products are all obtained in superior yield to the corresponding batch processes.
- Carter, Catherine F.,Baxendale, Ian R.,Pavey, John B. J.,Ley, Steven V.
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- The alkylation of a novel acetal derived from (2R,3R)-(+)-tartaric acid: An unexpected rearrangement
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The novel chiral bis-acetal dioxane 2a derived from (2R,3R)-(+)-tartaric acid was shown to undergo an unexpected rearrangement upon treatment with lithium amide base to give the chiral dioxolane 3a in optically active form. Alkylation and aldol studies were performed on the diisopropyl ester of this dioxolane 3b.
- Barros, M. Teresa,Burke, Anthony J.,Maycock, Christopher D.
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- Synthesis of acetal protected building blocks using flow chemistry with flow I.R. analysis: Preparation of butane-2,3-diacetal tartrates
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The syntheses of butane-2,3-diacetal protected tartrate derivatives are described using continuous flow processing techniques with in-line purification and I.R. analytical protocols.
- Carter, Catherine F.,Baxendale, Ian R.,O'Brien, Matthew,Pavey, John B. J.,Ley, Steven V.
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- AMINOGLYCOSIDE ANTIBIOTICS
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Provided herein are aminoglycosides for the treatment of infections, and pharmaceutical compositions, methods, kits, and uses thereof. Also provided are a methods of making aminoglycosides that enables late-stage derivatization of the C6' and C3 " amino groups, thereby allowing facile access to previously inaccessible aminoglycosides.
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Paragraph 00356
(2019/05/10)
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- Synthesis of C2-symmetric bisphosphine ligands from tartaric acid, and their performance in the Pd-Catalyzed asymmetric o-allylation of a phenol
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Starting from tartaric acid derived chiral diols or dicarboxylic acid dichlorides with either a 2,2-dimethyl-1,3-dioxolane (Taddol) or a 2,3-dimethoxy-2,3-dimethyl-1,4-dioxane (Tatrol) core structure, and BH 3-protected ortho-phosphanyl phenols, a set of fourteen new C 2-symmetric diphosphine ligands was synthesized. In addition, three related ligands were obtained from ortho-diphenylphosphino-anilines. The fully characterized ligands were then tested in the Pd-catalyzed enantioselective O-allylation of 4-methoxyphenol using crotyl methyl carbonate as a reagent. In addition, a pseudo-intramolecular variant of the reaction, using crotyl 4-methoxyphenyl carbonate as a substrate, was studied. The so-called Trost ligand was used as a reference. Although the Trost ligand (3 mol-%) gave up to 84% ee, one of the new ligands showed higher activity (50% ee with 0.075 mol-%). Copyright
- Dindaroglu, Mehmet,Akyol Dincer, Sema,Schmalz, Hans-Guenther
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supporting information
p. 4315 - 4326
(2014/07/21)
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- TARTROL-derived chiral phosphine-phosphite ligands and their performance in enantioselective Cu-catalyzed 1,4-addition reactions
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By using (R,R,R,R)-2,3-dimethoxy-2,3-dimethyl-1,4-dioxane-5,6-bis- diphenylmethanol (TARTROL) as a chiral building block, a set of six modular phosphine-phosphite ligands (with a 1,2-phenylene backbone) were synthesized and evaluated in the Cu-catalyzed a
- Dindaroglu, Mehmet,Akyol, Sema,Simsir, Hamza,Neudoerfl, Joerg-Martin,Burke, Anthony,Schmalz, Hans-Guenther
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p. 657 - 662
(2013/07/11)
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- Modification of chiral dimethyl tartrate through transesterification: Immobilization on POSS and enantioselectivity reversal in sharpless asymmetric epoxidation
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Modification of dimethyl tartrate has been investigated through transesterification with aminoalcohols to provide reactive functionalities for the covalent bonding of chiral tartrate to polyhedral oligomeric silsesquioxanes. The transesterification of dimethyl tartrate has been widely studied using different catalytic systems and reaction conditions. Through the proper selection of both the catalytic system and the reaction conditions, it is possible to achieve monosubstituted or bis-substituted tartrate derivatives as sole products. All the intermediate chiral tartrate-derived ligands were successfully used in the homogeneous enantioselective epoxidation of allylic alcohols providing moderate enantiomeric excess over the products. Attached amine groups have been used to support the modified tartrate ligands on to a haloaryl-functionalized silsesquioxane moiety. This final chiral tartrate ligand displays reverse enantioselectivity in the asymmetric epoxidation of allylic alcohols with regard to the starting dimethyl tartrate ligand, both molecules having the same chiral sign. However, the POSS-containing ligand can be easily recovered in almost quantitative yield and reused in asymmetric epoxidation reactions. In addition, recovered silsesquioxane-pendant ligand, though displaying decreasing catalytic activity in recycling epoxidation tests, showed very stable enantioselective behavior.
- Garcia, Rafael A.,Van Grieken, Rafael,Iglesias, Jose,Sherrington, David C.,Gibson, Colin L.
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experimental part
p. 675 - 683
(2010/09/14)
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- CATALYSTS
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Catalysts suitable for asymmetric hydrogenation reactions is described comprising the reaction product of a group (8) transition metal compound a chiral phosphine and a chiral diamine of formula (1) in which R1, R 2 R 3 or R 4 are independently hydrogen, a saturated or unsaturated alkyl, or cycloalkyl group, an aryl group, a urethane or sulphonyl group and R 5 , R 6 , R 7 or R8 are independently hydrogen, a saturated or unsaturated alkyl or cycloalkyl group, or an aryl group, at least one of R1, R 2 , R3 or R 4 is hydrogen and A is a linking group comprising one or two substituted or unsubstituted carbon atoms.
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Page/Page column 13
(2008/06/13)
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- Dialkylation of various butane-2,3-diacetals using allylsilane and 1,8-bis(trimethylsilyl)-2,6-octadiene
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We report in this paper a greatly improved procedure for the formation of a range of 1-acetyl-1-methyl-2,5-divinylcyclopentanes from 1,8- bis(trimethylsilyl)octa-2,6-diene (BISTRO) and 1,2-diacetals prepared directly from biacetyl. These 1-acetyl-1-methyl
- Mariet, Natacha,Pellissier, Helene,Ibrahim-Ouali, Malika,Santelli, Maurice
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p. 2679 - 2691
(2007/10/03)
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- Chiral C2-symmetric ligands with 1,4-dioxane backbone derived from tartrates: Syntheses and applications in asymmetric hydrogenation
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Chiral 1,4-diphenylphosphines 5-7 as well as thioether 8 were synthesized from tartrates employing Ley's "BDA" and "Dispoke" methodologies as the key step. Rhodium(I) complexes with 5-7 are efficient catalysts for the asymmetric hydrogenation of β-substituted enamides and MOM-protected β-hydroxyl enamides, which furnished chiral amines or β-amino alcohols with 94-99% ee. These results indicated that the 1,4-dioxane backbone in the ligands having the general structure 2 played an important role in stabilizing metal-ligand chelate conformation. Higher enantioselectivities with ligand 2 were achieved compared with the analogous ligands having the general structure 1.
- Li, Wenge,Waldkirch, Jason P.,Zhang, Xumu
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p. 7618 - 7623
(2007/10/03)
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- Porphyrazinediols: Synthesis, characterization, and complexation to group IVB metallocenes
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The first metalated porphyrazinediols 11 have been prepared from (L)- (+)-dimethyl tartrate via conversion into the corresponding dispoke or 2,3- dimethoxy-2,3-butanediyl protected 2,3-dihydroxymaleonitrile, Linstead macrocyclization, transmetalation, and deprotection. Their stability is very dependent on the nature of the metal ion in the cavity of the porphyrazine. Reaction of these porphyrazinediols with metallocene dichlorides led to new solitaire porphyrazines 12 while DDQ oxidation followed by trapping with diaminomaleonitrile afforded new porphyrazine dinitriles 14.
- Bellec, Nathalie,Montalban, Antonio Garrido,Williams, D. Bradley G.,Cook, Andrew S.,Anderson, Mairin E.,Feng, Xidong,Barrett, Anthony G. M.,Hoffman, Brian M.
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p. 1774 - 1779
(2007/10/03)
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- New building blocks for efficient and highly diastereoselective polyol production-synthesis and utility of (R',R',S,S) and (S",S",R,R)-2,3-butane diacetal protected butane tetrol derivatives
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The efficient synthesis of aldehydes derived from 2,3butane diacetal protected butane tetrols (S1,S',R,R)-5 and (R',R',S,S)-6 and their utility in the controlled synthesis of polyhydroxylated materials through highly diastereoselective Lewis acid mediated addition reactions of allyltributylstannane and silyl enol ether nucleophiles is described.
- Barlow, Jaqueline S.,Dixon, Darren J.,Foster, Alison C.,Ley, Steven V.,Reynolds, Dominic J.
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p. 1627 - 1629
(2007/10/03)
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- Investigations of the asymmetric intramolecular [2 + 2] photocycloaddition and its application as a simple access to novel C2-symmetric chelating bisphosphanes bearing a cyclobutane backbone
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The asymmetric intramolecular [2 + 2] photocycloaddition of αβ-enoates was evaluated as a simple access to the novel C2-symmetric bisphosphanes 22 and 27 possessing a cyclobutane backbone. A source of different chiral auxiliaries for investigations of the photochemical key step was provided by the transacetalization of dialkyl tartrates 3 with the corresponding 3,3-dialkoxybutan-2-ones 4. An insight into the selection mechanism was gained by temperature dependent measurements on the irradiation of the dicinnamates 10a-d, since the corresponding Eyring diagram discloses strictly linear functions as well as an isoselective relationship. Diol 8a turned out to be a structurally optimized auxiliary in terms of chiral induction and product crystallization and was also successfully applied in the first asymmetric photodimerization of 2-indenecarboxylic acid esters. Indeed, in this case excellent diastereoselectivities were achieved, too, but head-to-tail dimers 16a and 16b were formed predominantly. Diesters 11a and 16a were converted by standard procedures into the desired enantiopure 1,4-diphosphane 22 and 1,5-diphosphane 27. Furthermore, the hitherto unknown absolute configuration of δ-truxinic acid was elucidated from a single crystal X-ray structure analysis of 11a.
- Haag, Dieter,Scharf, Hans-Dieter
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p. 6127 - 6135
(2007/10/03)
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