- Toward the stereoselective synthesis of zaragozic acid framework: A desilylation-aldol reaction approach
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A convergent synthesis of the C3-C8 fragment of zaragozic acids is described. The key reactions include desilylation-aldol reaction, rearrangement induced by regioselective reductive cleavage, BAIB/TEMPO-Pinnick oxidation, esterification, silylation, and hydrogenolysis.
- Castillón, Sergio,Kurniawan, Yudhi D.,Robinson, Andrea J.,Tuck, Kellie L.
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supporting information
(2021/11/08)
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- Doubly diastereoselective conjugate additions of the antipodes of lithium N-benzyl-N-(α-methylbenzyl)amide to enantiopure ε-O-protected α,β-unsaturated esters derived from d-ribose
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Enantiopure ε-O-silyloxy- and ε-O-benzyloxy-α,β- unsaturated esters derived from d-ribose, each containing a cis-dioxolane unit, display excellent (≥95:5 dr) levels of diastereofacial directing ability upon conjugate addition of achiral lithium N-benzyl-N-isopropylamide. In contrast to the corresponding enantiopure ε-O-silyloxy-α,β-unsaturated ester derived from l-tartaric acid, which contains a trans-dioxolane unit, the conjugate additions of the antipodes of lithium N-benzyl-N-(α- methylbenzyl)amide to its cis-configured counterpart result in doubly diastereoselective 'matched' and 'mismatched' reaction pairings in which the inherent reagent control serves to augment or oppose, respectively, the established substrate diastereocontrol.
- Davies, Stephen G.,Foster, Emma M.,Lee, James A.,Roberts, Paul M.,Thomson, James E.
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p. 534 - 546
(2014/05/06)
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- Synthetic studies towards an advanced precursor of the jatrophane diterpene Pl-4
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Jatrophane diterpenes, isolated from members of the Euphorbiaceae plant family, constitute a class of biologically and structurally intriguing natural products. Herein, different strategies for the preparation of an advanced intermediate towards the total synthesis of the jatrophane diterpene Pl-4 are described. Key strategies for the elaboration of the jatrophane precursors include hydrometalation and radical reactions. Georg Thieme Verlag KG Stuttgart · New York.
- Fürst, Rita,Lentsch, Christoph,Rinner, Uwe
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supporting information
p. 357 - 367
(2014/02/14)
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- An unexpectedly facile cyclization of polyhydric alcohols
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Image Presented Contrary to previous reports in the literature, the reaction of polyhydric alcohols such as sorbitol or mannitol gives good yields of the tetrahydroxyoxepane derivative in the presence of an acid catalyst, in refluxing toluene, with complete retention of stereochemistry.
- Pavlik, Christopher,Onorato, Amber,Castro, Steve,Morton, Martha,Peczuh, Mark,Smith, Michael B.
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supporting information; experimental part
p. 3722 - 3725
(2011/02/28)
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- Carbon-branched carbohydrate chirons: practical access to both enantiomers of 2-C-methyl-ribono-1,4-lactone and 2-C-methyl-arabinonolactone
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Readily crystallized 2-C-methyl-d-ribono-1,4-lactone is formed in a one-pot procedure from d-glucose without any protecting groups by treatment with dimethylamine to give an Amadori ketose and then with aqueous calcium hydroxide in yields of approximately 25%; 2-C-methyl-l-ribono-1,4-lactone is similarly produced from l-glucose. 3,4-O-Isopropylidene-2-C-methyl-d-arabinono-1,5-lactone and 2-C-methyl-d-arabinono-1,4-lactone were prepared in a combined 60% yield by the Kiliani reaction of sodium cyanide with a protected 1-deoxy-d-ribulose derived from d-erythronolactone; the enantiomeric arabinonolactones are similarly available from l-erythronolactone.
- Booth, Kathrine V.,da Cruz, Filipa P.,Hotchkiss, David J.,Jenkinson, Sarah F.,Jones, Nigel A.,Weymouth-Wilson, Alexander C.,Clarkson, Robert,Heinz, Thomas,Fleet, George W.J.
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scheme or table
p. 2417 - 2424
(2009/04/06)
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- Synthesis of screening substrates for the directed evolution of sialic acid aldolase: Towards tailored enzymes for the preparation of influenza a sialidase inhibitor analogues
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The stereoselective synthesis of two epimeric screening substrates, (4R, 5R, 6R)- and (4S, 5R, 6R)-6-dipropylcarbamoyl-2-oxo-4,5,6-trihydroxy-hexanoic acid, for the directed evolution of sialic acid aldolase is described. The complementary methods relied on stereoselective indium-mediated additions of ethyl α-bromomethyl acrylate to functionalised aldehydes. With an α-hydroxy aldehyde, (2R, 3R)-2,3-dihydroxy-4-oxo butanoic acid dipropylamide, the addition was chelation controlled, and the syn product, (6R, 5R, 4S)-6-dipropylcarbamoyl-2-methylidene-4,5,6-trihydroxy-hexanoic acid ethyl ester, was obtained. In contrast, the stereochemical outcome of the addition to (2R, 3A)-N, N-dipropyl-2,3-O-isopropylidene-4-oxobutyramide was consistent with Felkin-Anh control, and the anti adduct, (4R, 5R, 6R)-6-dipropylcarbamoyl-2- methylidene-4-hydroxy-5,6-O-isopropylidene-hexanoic acid ethyl ester, was the major product. Ozonolysis and deprotection gave the screening substrates as mixtures of furanose and pyranose forms, in good yields. The Royal Society of Chemistry 2005.
- Woodhall, Thomas,Williams, Gavin,Berry, Alan,Nelson, Adam
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p. 1795 - 1800
(2007/10/03)
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- Enantiomerically pure 4-amino-1,2,3-trihydroxybutylphosphonic acids
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(1S,2R,3S)-, (1R,2R,3S)- and (1S,2R,3R)-4-amino-1,2,3- trihydroxybutylphosphonic acids were synthesised. The synthetic strategy involved preparation of the respective 4-azido-2,3-O-isopropylidene-l-threose or -d-erythrose, addition of dialkyl phosphites, separation of C-1 epimeric O,O-dibenzyl phosphonates, the reduction of azides and the removal of the protecting groups. The (2R,3S) and (2R,3R) configurations in the final products were secured by employing diethyl l-tartrate and d-isoascorbic acid as starting materials. The stereochemical course of the addition to the carbonyl groups in 4-azido-2,3-O-isopropylidene-l-threose or -d-erythrose followed that established earlier for 2,3-O-isopropylidene-d-glyceraldehyde and similar (3:1-4:1) diastereoselectivities were achieved.
- Wróblewski, Andrzej E.,G?owacka, Iwona E.
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p. 11930 - 11938
(2007/10/03)
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- Selective inhibition of Trypanosoma brucei 6-phosphogluconate dehydrogenase by high-energy intermediate and transition-state analogues
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Two series of compounds were designed to mimic the transition state and high-energy intermediates (HEI) of the enzymatic reaction of 6-phosphogluconate dehydrogenase (6PGDH). Sulfoxide analogues (7-11) were designed to mimic the transition state during the oxidation of the substrate to 3-keto-6-phosphogluconate, an enzyme-bound intermediate of the enzyme. Hydroxamate and amide derivatives of D-erythronic acid were designed to mimic the 1,2-cis-enediol HEI of the 6PGDH reaction. These two series of compounds were assayed as competitive inhibitors of the Trypanosoma brucei and sheep liver enzymes, and their selectivity value (ratio sheep/parasite) was calculated. The sulfoxide transition-state analogues showed weak and selective inhibition of the T. brucei enzyme. The hydroxamic derivatives showed potent and selective inhibition of the T. brucei 6PGDH with a Ki in the nanomolar range.
- Dardonville, Christophe,Rinaldi, Eliana,Barrett, Michael P.,Brun, Reto,Gilbert, Ian H.,Hanau, Stefania
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p. 3427 - 3437
(2007/10/03)
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- Studies toward the synthesis of pinolidoxin, a phytotoxic nonenolide from the fungus Ascochyta pinodes. Determination of the configuration at the C-7, C-8, and C-9 chiral centers and stereoselective synthesis of the C6- C18 fragment
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The absolute stereochemistry at the C-7, C-8, and C-9 chiral centers of pinolidoxin (1) has been determined by chemical and spectral methods. First, the synthesis of four stereoisomeric fully benzoylated 2,3-erythro-1,2,3,4- heptanetetrols, corresponding to the C6-C18 portion of the natural substance, has been accomplished starting from meso-tartaric acid. As next step, the selection of the synthetic tetrabenzoate possessing 'natural' stereochemistry (10a') suitable for absolute configuration determination, has been carried out by correlation with its 'natural' homologue derived from degradation of pinolidoxin. Determination of the stereochemistry at the title chiral centers has been carried out by application of the Mosher's method both to 7a', a compound stereochemically related to 10a', and to pinolidoxin itself. The stereoselective synthesis of a protected form of the C6-C18 portion of pinolidoxin, to be used in its total synthesis, has also been accomplished starting from commercially available D-erythronolactone.
- De Napoli, Lorenzo,Messere, Anna,Palomba, Daniela,Piccialli, Vincenzo,Evidente, Antonio,Piccialli, Gennaro
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p. 3432 - 3442
(2007/10/03)
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- D-erythronolactone as a C4 building unit. Part 2.1 a short and efficient synthesis of both enantiomers of epi-muricatacin, a diastereoisomer of the native acetogenin from Annona muricata
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Both enantiomers of epi-muricatacin (+)- and (-)-2 have been prepared from 2,3-O-isopropylidene-D-erythrose 7. The enantiomers (+)- and (-)-2 are obtained in good yields and with high diastereoisomeric and enantiomeric purity. The aim of the synthesis is to obtain both enantiomers of the target molecule from one chiral precursor. This was made possible by the reaction sequence for the introduction of the two different side chains being exchangeable.
- Gypser, Andreas,Peterek, Marcus,Scharf, Hans-Dieter
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p. 1013 - 1016
(2007/10/03)
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- Enantiospecific syntheses of leukotrienes C4, D4 and E4 and [14,15-3H2]leukotriene E4 dimethyl ester
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A 'chiral-pool' approach was employed to synthesize various leukotrienes (slow-reacting substance of anaphylaxis, SRS-A) enantiospecifically. The pivotal (S,S)-trans-epoxy alcohol 9 was prepared by efficient and facile routes starting from erythorbic acid (D-araboascorbic acid, 13). This epoxide could also be produced starting from D-glucose. The epimeric (S,R)-cis-epoxide 38 was obtained utilizing L-tartaric acid as the chiral starting material. Elaboration of 9 into leukotriene A4 methyl ester (5) and the potassium salts of leukotrienes C4 (4a), D4 (4b), and E4 (4c) was accomplished by standard methods. These salts exhibited potent contractile activities in the in vitro guinea pig ileum assay. Reduction of 14,15-dehydroleukotriene A4 methyl ester (44) with tritium gas gave [14,15-3H2]-5 and subsequently the dimethyl ester of [14,15-3H2]leukotriene E4 having a high specific activity of 40 Ci/mmol.
- Cohen,Banner,Lopresti,et al.
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p. 3661 - 3672
(2007/10/02)
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- Synthesis of optically active leukotriene (SRS-A) intermediates
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In an approach to SRS-A and analogues thereof, the key (5S, 6S)-epoxy alcohol 9 and its 6-epimer 18 were prepared starting from D-araboascorbic acid and L-diethyl tartrate, respectively.
- Cohen, Noal,Banner, Bruce L.,Lopresti, Rocco J.
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p. 4163 - 4166
(2007/10/02)
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