- A Concise Synthesis of the Key Tetrahydrofuran Moieties of Caruifolin A and EBC-342
-
A common strategy for the concise synthesis of the key tetrahydrofuran moieties of caruifolin A and EBC-342 is presented. Asymmetric dihydroxylation and intramolecular SN2-cyclization are key strategic reactions for the synthesis of the furan f
- Fernandes, Rodney A.,Bethi, Venkati
-
p. 6922 - 6928
(2020/06/10)
-
- Diastereoselective synthesis of trifluoromethylated 1,3-dioxanes by intramolecular oxa-Michael reaction
-
A highly diastereoselective synthesis of trifluoromethylated 1,3-dioxanes is described. The reaction proceeds by an addition/oxa-Michael sequence and works efficiently under mild reaction conditions, with a good substrate scope and acceptable to good yiel
- Becerra-Figueroa, Liliana,Brun, Elodie,Mathieson, Michael,Farrugia, Louis J.,Wilson, Claire,Prunet, Jo?lle,Gamba-Sánchez, Diego
-
supporting information
p. 301 - 305
(2017/01/13)
-
- 2,3,6-Trideoxy sugar nucleotides: Synthesis and stability
-
The synthesis and characterization of highly challenging 2,3,6-trideoxy sugar nucleotides were described for the first time. The study of their hydrolysis kinetics in aqueous buffers provided insight into their application as glycosyl donors.
- Wu, Mingxuan,Meng, Qingqing,Ge, Min,Bai, Linquan,Zhou, Huchen
-
p. 5799 - 5801
(2011/12/14)
-
- Allylcopper intermediates with N-heterocyclic carbene ligands: Synthesis, structure, and catalysis
-
(Figure presented) Allylcopper Intermediates with N-heterocyclic carbene liganda are synthesized by transmetalation of allylsiloxane reagents, and the crystal structures of allylcopper compounds are reported. The allylcopper transmetalation is utilized fo
- Russo, Vlncenzo,Herron, Jessica R.,Ball, Zachary T.
-
supporting information; experimental part
p. 220 - 223
(2010/03/30)
-
- Glycosidation via conjugate addition of anomeric alkoxides to nitroalkenes and nitrosoalkenes
-
The conjugate addition reactions of protected pyranose alkoxides to both nitroalkenes and nitrosoalkenes, as a route to 2-nitroalkyl, 2-oximinoalkyl and 2-oxoalkyl glycosides, are described.
- Trewartha, Gary,Burrows, Jeremy N.,Barrett, Anthony G. M.
-
p. 3553 - 3556
(2007/10/03)
-
- Synthesis of chiral oxacyclic dienes via ruthenium-catalyzed enyne metathesis: Useful building blocks for chiral tricyclic oxygen derivatives
-
Various chiral oxacyclic dienes were synthesized via enyne metathesis using Grubbs catalyst (PCy3)2Cl2Ru=CHPh. A series of substrates bearing a 1,2-diol skeleton was prepared from (2S)-(benzyloxy)-propanal. The enyne metathesis proceeds smoothly in CH2Cl2 at 23°C with a low loading of catalyst (2.0mol%) under ethylene gas (1-2.5atm), giving good yields of products without epimerization at any stereogenic carbon. Heating compound 5 comprising a disubstituted alkyne in benzene (80°C) under nitrogen resulted in formation of two diastereomers via epimerization of the primary product. The epimerization occurs at the oxacyclic carbon rather than the benzyl carbon. Diels-Alder reactions of chiral oxacyclic dienes 19 and 22 with maleic anhydride, maleimide and benzoquinone proceeded with high diastereoselectivities, yielding a single cycloadduct efficiently at ambient conditions. The structures of Diels-Alder adducts were determined by 1H NOE NMR spectra. The cycloadducts were formed via the approach of dienophiles to the diene in endo mode and opposite the substituent of the stereogenic center. The cycloadducts 29 and 31 were transformed into enantiopure tricyclic furans 35 and 38 after transformation of the (2S)-(silyloxy)ethyl group into an acetate group.
- Guo, Hongyun,Madhushaw, Reniguntala J,Shen, Fwu-Ming,Liu, Rai-Shung
-
p. 5627 - 5637
(2007/10/03)
-
- Ligand effects in selective addition reactions of organoindium reagents with carbonyl compounds
-
The reaction of the allyl indium sesquibromide (CH2 =CHCH2)3In2Br3 with four equivalents of a bulky lithium alkoxide ((CH3)3COLi or (CH3)3CCH2OLi) results in modified reagents which show unusual degrees of chemo-and stereoselectivity in reactions with carbonyl compounds. For example, in reactions with cyclohexanone derivatives, 84-93% equatorial attack with preferential formation of the axial alcohols is observed. Chiral aldehydes react in a highly diastereoselective manner.
- Reetz, Manfred T.,Haning, Helmut
-
p. 117 - 120
(2007/10/03)
-
- Preparation of Monosilyl Acetals from Esters via iBu2AlH Reduction and Trapping with N-(Trimethylsilyl)imidazole. Addition of Allyltrimethylsilane To Yield Homoallylic Alcohols or Ethers
-
Alkyl esters were reduced with iBu2AlH or a 1:1 mixture of iBu2AlH and iBu3Al (iBu2AlH*iBu3Al or iBu5Al2H), followed by trapping of the resulting tetrahedral intermediate with TMS-imidazole to produce monosilyl acetals.Reaction of the mixed acetals with allyltrimethylsilane in the presence of Lewis acids (Hosomi-Sakurai reaction) generated homoallylic alcohols or ethers selectively, depending on the substitution of the monosilyl acetal.TMS methoxy acetals (MeO-CH-OTMS) and TMS ethoxy acetals bearing additional complexing groups such as MeO- or Ph2C=N- provided alcohols with 1.5:1 - 9:1 threoselectivity, while simple TMS ethoxy acetals provided only ethyl ethers as products.The monosilyl acetal configuration was easily epimerized or racemized, and the configuration of the Hosomi-Sakurai product was apparently independent of the initial monosilyl acetal reactant configuration.
- Sames, Dalibor,Liu, Yunqi,DeYoung, Lynn,Polt, Robin
-
p. 2153 - 2159
(2007/10/02)
-
- CHELATION CONTROLLED ALLYLATION OF ALDEHYDES WITH A CHIRAL ALLYLSILYLENE DERIVED FROM (-)-10-PHENYLPINANEDIOL
-
The chiral allylsilylene prepared from (-)-10-phenylpinanediol reacts with chiral α-alkoxy aldehydes in the presence of stannic chloride to afford homoallylic alcohols with diastereofacial selectivity ratios as high as 100:0.The results are consistent with attack of the allylsilylene on the less hindered face of the chelated intermediate.Our preliminary studies on several silylenes prepared from bicyclo systems revealed that substituent effects on the chiral auxiliary and the silicon atom play an important role in the selectivity of these unique compounds.
- Shanmuganathan, Kirupathevy,French, Larry G.,Jensen, Bruce L.
-
p. 797 - 800
(2007/10/02)
-
- Effective 1,5-asymmetric induction in tin(IV) chloride promoted reactions between aldehydes and (4-alkoxy-2-alkenyl)tributylstannanes
-
Transmetallation of (S)-4-benzyloxy-2-pentenyl(tributyl)stannane (1) using tin(IV) chloride generates an allyltin trichloride which reacts in situ with aldehydes to give 1-substituted syn-(3Z)-5-benzyloxyhexenols with excellent stereoselectivity. With chiral aldehydes, the stereoselectivity of the reaction is dominated by the reagent, except for 2-alkoxyaldehydes which show matching and mismatching consistent with preferred Felkin-Anh diastereofacial selectivity.
- McNeill,Thomas
-
p. 322 - 334
(2007/10/02)
-
- Chelation controlled addition of allylstannanes to aldehydes in lithium perchlorate-diethyl ether
-
α-Alkoxy aldehydes undergo chelation controlled addition of allylstannanes with high diastereoselectivity in the presence of 5.0 M lithium perchlorate in diethyl ether at ambient temperature and pressure.
- Henry Jr.,Grieco,Jagoe
-
p. 1817 - 1820
(2007/10/02)
-
- Synthesis and Pharmacological Investigation of the Enantiomers of Muscarone and Allomuscarone
-
A strategy based on the use of (R)- and (S)-lactic ester as starting materials allowed the synthesis of the two enantiomers of muscarone and allomuscarone in >98percent enantiomeric excess.The compounds were examined for their ability to bind to membranes from cerebral cortex (M1), heart (M2), and salivary glands (M3) and to recognize affinity agonist states of the muscarinic receptors.The two pairs of enantiomers were also tested in five functional assays, and their muscarinic potency was determined.In both binding and functional tests, (-)-1 (2S,5S) and (-)-5 (2R,5S) were the eutomers of muscarone and allomuscarone, respectively.The eudismic ratio of muscarone, evaluated in the functional tests, spanned a range of 280-400.These values are substantially different from ones (2.4-10.1) reported in the literature.From a stereochemical point of view, muscarone behaves as muscarine and all other major muscarinic agonists; as a consequence, the hypotheses advanced to account for the anomalies of muscarone no longer have reason to exist.
- Amici, Marco De,Dallanoce, Clelia,Micheli, Carlo De,Grana, Enzo,Barbieri, Annalisa,et al.
-
p. 1915 - 1920
(2007/10/02)
-
- Asymmetric Synthesis Using Tartrate Ester Modified Allylboronates. 2. Single and Double Asymmetric Reactions with Alkoxy-Substituted Aldehydes
-
The reactions of tartrate allylboronates 1a and 1b with a series of chiral and achiral alkoxy-substituted aldehydes are described.It is shown that conformationally unrestricted α- and β-alkoxy aldehyde substituents have a significant, negative impact on the stereoselectivity of the asymmetric allylborations.For example, α-alkoxy aldehydes 25-27 and β-alkoxy aldehydes 28-30 undergo asymmetric allylborations with 1 in only 56-59percent and 63-66percent ee, respectively, while the reactions of 1 and aliphatic aldehydes such as decanal or cyclohexane-carboxaldehyde proceed in 86-87percent ee under the same conditions.Evidence of reduced stereoselection is also apparent in the double diastereoselectivity data reported in Table I and Scheme I for the asymmetric allylborations of chiral β-alkoxy aldehydes 16 and 19 and chiral α-alkoxy aldehyde 22.In contrast, chiral aldehydes containing alkoxy groups that are conformationally constrained by incorporation in rings, as in glyceraldehyde acetonide 4,4-deoxythreose ketal 7, and α,β-epoxy aldehydes 10 and 13, are excellent allylboration substrates, with diastereoselection in the cases of 4 and 7 being significantly greater than that obtained with simpler achiral substrates.A model that rationalizes this "alkoxy effect" is presented.Specifically, it is inferred that the observed trends in stereoselection are not steric in origin, but rather that unfavorable lon pair/lone pair interactions occur between the tartrate ester carbonyl and alkoxy substituents particularly of conformationally unconstrained aldehyde substrates (e.g., 16, 19, 22, 25-30) that results in diminished reaction stereoselection (see transition structures 58 and 61).For substrates with conformationally constrained alkoxy substituents , e.g. 4 and 7, favorable lone pair/dipole interactions between the tartrate ester carbonyl and the backside of the β-alkoxy C-O bond leads to increased stabilization of the favored transition state (see transition structures 59 and 60) and hence to increased reaction diastereoselection.A simple method for the analysis of the average diastereofacial selectivity of a chiral reagent in a pair of double asymmetric reactions is also presented.This analysis, which is independent of the intrinsic diastereofacial bias of the chiral aldehyde, enables one to make direct comparisons of the relative diastereoselectivities of a range of chiral substrates with a given chiral reagent (or vice versa).In this way, double diastereoselcetivity data are easily analyzed to determine if the chiral reagent/chiral substrate pair is "well behaved" compared to typical achiral substrate reference systems, thereby providing insight into the structural features that influence reaction stereoselectivity.
- Roush, William R.,Hoong, Lee K.,Palmer, Michelle A. J.,Straub, Julie A.,Palkowitz, Alan D.
-
p. 4117 - 4126
(2007/10/02)
-
- Chiral Synthesis via Organoboranes. 21. Allyl- and Crotylboration of α-Chiral Aldehydes with Diisopinocampheylboron as the Chiral Auxiliary
-
B-Allyldiisopinocampheylboranes have been screened for diastereofacial selectivity in their reaction with α-substituted chiral aldehydes.Both syn and anti products have been obtained in very high diastereoselectivities.Further, (E)-crotyldiisopinocampheylboranes and (Z)-crotyldiisopinocampheylboranes have been used for diastereofacial selectivity in their reaction with α-substituted chiral aldehydes.These crotylboranes, 20-23, are highly diastereoselective reagents and the corresponding (3,4- and 4,5-)-anti,syn, -anti,anti, and -syn,anti products have been obtained in very high facial selectivities; even the syn,syn product has been obtained in moderately good facial selectivity.Finally, the relative efficiences of the various chiral auxiliaries utilized in the literature for the allyl- and crotylboration have been compared with those achieved by the diisopinocampheylboron moiety.
- Brown, Herbert C.,Bhat, Krishna S.,Randad, Ramnarayan S.
-
p. 1570 - 1576
(2007/10/02)
-
- B-Allyldiisopinocampheylborane: A Remarkable Reagent for the Diastereoselective Allylboration of α-Substituted Chiral Aldehydes
-
B-Allyldiisopinocampheylboranes were screened for diastereofacial selectivity in their reaction with α-substituted chiral aldehydes.These reagents are the most highly diastereoselective allylboranes reported to date and appear ideally suited for use in synthetic organic chemistry as enolate equivalents.
- Brown, Herbert C.,Bhat, Krishna S.,Randad, Ramnarayan S.
-
p. 319 - 320
(2007/10/02)
-
- Stereoselective Syntheses of Alcohols, XXIV. - Synthesis of 2,6-Dideoxy-L-hexoses
-
Addition of the Z- and E-γ-alkoxyallylboronates 3 and 6 to O-benzyllactaldehyde led to various 3,4,5-trioxygenated 1-hexenes of arabino, xylo, ribo and lyxo configuration.The extent of asymmetric induction amounted to 82:18 (arabino/xylo) in the addition
- Hoffmann, Reinhard W.,Metternich, Rainer,Lanz, Joachim W.
-
p. 881 - 888
(2007/10/02)
-
- STEREOCONTROLLED ONE-POT CONVERSIONS OF α-ALKOXY ESTERS TO SYN- AND ANTI-1,2-DIOL DERIVATIVES
-
Complementary one-pot methods for the sequential addition of carbon and hydride nucleophiles to α-alkoxy esters leading to syn or anti mono-protected vicinal glycol derivatives are described.
- Burke, Steven D.,Deaton, David N.,Olsen, Robert J.,Armistead, David M.,Blough, Bruce E.
-
p. 3905 - 3906
(2007/10/02)
-