- Enzyme-catalyzed asymmetric synthesis; 10. Pseudomonas cepacia lipase mediated synthesis of enantiomerically pure (2R,3S)- and (2S,3R)-2,3-O-cyclohexylideneerythritol monoacetate from 2,3-O-cyclohexylideneerythritol
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Pseudomonas cepacia lipase catalyzed hydrolysis of 2,3-O-cyclohexylideneerythritol diacetate in an emulsion of water and diisopropyl ether gives (2S,3R)-2,3-O-cyclohexylideneerythritol monoacetate [(2S,3R)-1-acetoxy-2,3-cyclohexylidenedioxy-4-hydroxybutane] with ≥ 99% ee in 91% yield by a preferential attack at the R-center CH2OAc group. The enantiomeric (2R,3S)-2,3-O-cyclohexylideneerythritol monoacetate is obtained by acetylation of 2,3-O-cyclohexylideneerythritol with vinyl acetate catalyzed by the same enzyme with ≥ 99% ee in 78% yield by a combined enantiotopos and enantiomer differentiation through a preferential attack at the R-center CH2OH groups.
- Gais,Hemmerle,Kossek
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Read Online
- Asymmetric induction in intramolecular [2 + 2]-photocycloadditions of 1,3-disubstituted allenes with enones and enoates
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Irradiation of optically active allenes (89-92% ee) appended to enones and enoates affords alkylidenecyclobutane photoadducts with high levels of asymmetric induction (83-100%) derived exclusively from the allene fragment. The substrates studied include allenes tethered to enones such as 1,3-cyclohexanedione and 1,3-cyclopentanedione, as well as allenes tethered to functionalized coumarins. The enantiomer ratios of the photoadducts were quantified by derivatization of the products as the corresponding Mosher MTPA esters and analysis by 1H NMR spectroscopy. The exo-methylenecyclobutanes obtained upon irradiation of allene-coumarins are isolated as single olefin diastereomers. Irradiation of a coumarin tethered at C(5) with an optically active allene affords an alkynyl-substituted oxepane with complete asymmetric induction.
- Carreira, Erick M.,Hastings, Curtis A.,Shepard, Mary S.,Yerkey, Lori A.,Millward, Dan B.
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Read Online
- 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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- General Synthetic Approach to Rotenoids via Stereospecific, Group-Selective 1,2-Rearrangement and Dual S N Ar Cyclizations of Aryl Fluorides
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A general synthetic approach to rotenoids is described, featuring 1) stereospecific, group-selective 1,2-rearrangements of epoxy alcohols, and 2) S N Ar oxy-cyclizations of aryl fluorides. The common intermediate epoxyketone, en route to (-)-rotenone and (-)-deguelin, was prepared from d -araboascorbic acid in five steps. Also described is the conversion of (-)-deguelin into oxidized congeners, (-)-tephrosin and (+)-12a- epi -tephrosin.
- Matsuoka, Seiya,Nakamura, Kayo,Ohmori, Ken,Suzuki, Keisuke
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p. 1139 - 1156
(2019/02/26)
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- Synthesis of threo- and erythro-configured trihydroxy open chain lipophilic ketones as possible anti-mycobacterial agents
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A series of threo- and erythro-configured open-chain trihydroxy ketones was synthesized starting from L- and D-ascorbic acid respectively as the starting material, through the use of Grignard reactions for the requisite C[sbnd]C bond formations. The lipophilic ketones were screened against Mycobacteriumtuberculosis for anti-proliferative activity. The lipophilic ketones with tetradecyl alkyl side chains were found to be moderately active against cell proliferation.
- Borkar, Santosh Ramdas,Bokolia, Naveen,Aidhen, Indrapal Singh,Khan, Inshad Ali
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p. 186 - 195
(2017/01/11)
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- Benzoxazol and oxazine ketone compounds and intermediates for the preparation of crystalline form and (by machine translation)
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A preparation method for a high-purity benzoxazoleoxazine ketone compound, a crystal form thereof, and an intermediate compound for preparing a compound of formula (I), and a preparation method therefor.
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Paragraph 0270; 0271; 0272; 0273
(2016/10/09)
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- A method for synthesizing tetranoic acid
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The invention discloses a synthetic method of tetronic acid. The synthetic method comprises the following steps: firstly oxidizing low-price easily-available natural sodium D-isoascorbate as a raw material through hydrogen peroxide, and acidifying through hydrochloric acid to prepare a key synthetic intermediate, namely erythronolactone; secondly, reacting erythronolactone with sulfonyl chloride to generate crude tetronic acid; finally, simply re-crystallizing obtained crude tetronic acid to obtain pure tetronic acid. The synthetic method has the characteristics of few synthetic steps, simple and convenient process, low synthetic cost, convenience for large-scale industrialized production and the like; finally obtained pure tetronic acid is high in yield and purity, the yield can reach more than 87%, and the purity can reach more than 99%.
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Paragraph 0029-0040
(2017/03/08)
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- Unexpected facile synthesis of tetronic acid during the research on stereospecific total synthesis of (+)-biotin starting from D-erythorbic acid as chiral pool
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The reaction of D-erythronolactone (8) with the methanesulfonyl chloride in the presence of triethylamine afforded, after unexpected elimination reaction, the tetronic acid is obtained in excellent yield and chemical purity, instead of the dimesylates (7)
- Li, Xiao-Kang,Xiong, Fei,Shen, Zhong-Yuan,Zhang, Shu-Ping,Zhou, Yi-Hao,Xu, Ming-Lu,Zhou, Zi-Qian
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p. 1957 - 1958
(2015/03/30)
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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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body text
p. 2417 - 2424
(2009/04/06)
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- MW-assisted Er(OTf)3-catalyzed mild cleavage of isopropylidene acetals in Tricky substrates
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Erbium(III) trifluoromethane sulfonate is proposed as a very gentle Lewis acid catalyst in a MW-assisted chemoselective method for the cleavage of isopropylidene acetals in awkward substrates by using pure water as the solvent.
- Procopio, Antonio,Gaspari, Marco,Nardi, Monica,Oliverio, Manuela,Romeo, Roberto
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p. 1961 - 1964
(2008/09/19)
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- An enantioselective synthesis of (2S,3R)-3-(N-Benzyloxycarbonyl)amino-1-chloro-4-phenylthiobutan-2-ol, a central intermediate of nelfinavir
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(2S,3R)-3-(N-Benzyloxycarbonyl)amino-1-chloro-4-phenylthiobutan-2-ol 1 is a central intermediate of nelfinavir 2, which, being a potent HIV protease inhibitor, represents one of the most clinically efficacious anti AIDS drugs. Thus, a practical enantioselective synthesis of 1 has been devised which employs sodium erythorbate 9 as a chiral starting material. Consisting of the total 14-step functional group manipulations that proceed via methyl (2S,3R)-4-hydroxy-2,3-epoxybutyrate 8, the synthetic processes can dispense with chromatographic purification and provide architecturally complex 1 in 17% overall yield under a strict control of stereochemistry.
- Ikunaka, Masaya,Matsumoto, Jun,Fujima, Yoshito,Hirayama, Yoshihiko
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- Hydroxynitrile lyase catalyzed enantioselective HCN addition to O-protected α-hydroxyaldehydes
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Various O-protected glycol- and racemic lactaldehydes 3 and 6 as well as O-allyl protected racemic α-hydroxyaldehydes 7 (R1=Et, Pr, Bu) have been prepared to investigate and perform a stereoselective Kiliani-Fischer synthesis by hydroxynitrile lyase (HNL) catalyzed addition of HCN. From all protecting groups investigated the allyl moiety was most suitable. (R)-PaHNL from bitter almonds (Prunus amygdalus), yielding the (2S)-cyanohydrins 8-10, was found to be a more stereoselective catalyst than (S)-MeHNL from maniok (Manihot esculenta). While (R)-PaHNL led to enantiomeric excesses ≥93%, with (S)-MeHNL the (2R)-cyanohydrins 8-10 were obtained with enantiomeric excesses ≤78%.
- Roos, Juergen,Effenberger, Franz
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p. 2817 - 2828
(2007/10/03)
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- A new efficient access to glycono-1,4-lactones by oxidation of unprotected itols by catalytic hydrogen transfer with RhH(PPh3)4-benzalacetone system
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Treatment of unprotected pentitols and hexitols with RhH(PPh3)4-benzalacetone system leads exclusively to glycono-1,4-lactones in 60-96% yield.
- Isaac,Aizel,Stasik,Wadouachi,Beaupère
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p. 475 - 476
(2007/10/03)
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- Autoxidation Reaction Mechanism for L-Ascorbic Acid-related Compounds in Methanol without Metal Ion Catalysis
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The autoxidation mechanism for L-ascorbic acid (ASA)-related compounds such as D-arabo-ascorbic acid (= erythorbic acid; ERA) and triose reductone (TR) in methanol without metal ion catalysis was studied.The oxidation reaction of these ASA-related compounds seems to proceed via the C(2) oxygen adduct of ERA (or TR) by a similar reaction mechanism to that of ASA. - Keywords: L-ascorbic acid; autoxidation; D-erythorbic acid; triose reductone; C(2) oxygen adduct
- Miyake, Noriko,Kurata, Tadao
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p. 811 - 813
(2007/10/03)
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- A two-step preparation of a new C4 chiral building block derivative of D-erythronic acid
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1,2;3,4-Di-O-isopropylidene-D-erythronic acid (2,2,2′,2′-Tetramethyl-[R,R-(4,4′-bi-1,3-dioxolan)]-5-one) 4, a new C4 chiral building block derivative of D-erythronic acid was prepared in two steps from D-glucono-δ-lactone.
- De Souza,Da Silva,Ferreira
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p. 1339 - 1340
(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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- Enantioselective synthesis of loracarbef from sodium erythorbate
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Sodium erythorbate (7) has been converted to loracarbef (1). Oxidation of sodium erythorbate to D erythronolactone (8) followed by selective monotosylation and treatment with sodium ethoxide provided ethyl (2S,3R) 4 hydroxy 2.3 epoxybutyrate (10). Swern oxidation of this epoxide into the aldehyde (11), imine formation with tert-butylglycinate and an enantioselective Staudinger reaction with phthalimidoacetyl chloride afforded the (3S,4S)-cis-β-lactam (13). Appropriate functional group manipulations followed by a Dieckmann condensation, chlorination, and protecting group removals gave the enantiomerically pure nucleus of loracarbef (24).
- Frazier, Jeffery W.,Staszak, Mike A.,Weigel, Leland O.
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p. 857 - 860
(2007/10/02)
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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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