- Application in asymmetric Morita-Baylis-Hillman reactions
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N-Substituted 2-exo-hydroxybornyl-10-sulfonamides, prepared as potential chiral auxiliaries for use in asymmetric Morita-Baylis-Hillman (MBH) reactions, have been treated with acryloyl chloride to afford the corresponding 2-exo-Acrylate esters as MBH subs
- McIteka, Lulama P.,Lobb, Kevin A.,Kaye, Perry T.
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p. 151 - 163
(2016/10/22)
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- General approach for the stereocontrolled construction of the beta-lactam ring in amino acid-derived 4-alkyl-4-carboxy-2-azetidinones.
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The first general approach toward the asymmetric synthesis of 4-alkyl-4-carboxy-2-azetidinones derived from amino acids is described. The stereoselective construction of the beta-lactam ring was achieved through base-mediated intramolecular cyclization of the corresponding N(alpha)-chloroacetyl derivatives bearing (+)- or (-)-10-(N,N-dicyclohexylsulfamoyl)isoborneol as chiral auxiliary (ee up to 82%).
- Gerona-Navarro, Guillermo,Garcia-Lopez, M Teresa,Gonzalez-Muniz, Rosario
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p. 3953 - 3956
(2007/10/03)
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- Synthesis of new fluorine-containing taxoids by means of β-lactam synthon method
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A series of new fluorine-containing analogs of paclitaxel and docetaxel are synthesized using the coupling of (3R,4S)-1-acyl-β-lactams with high enantiomeric purity with properly protected baccatin III, 10-deacetylbaccatin III, and 14β-hydroxy-10-deacetyl
- Ojima,Kuduk,Slater,Gimi,Sun
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p. 209 - 224
(2007/10/02)
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- Diastereoselectivity in the Preparation of β-Silyl Esters from αβ-Unsaturated Esters and Amides Attachhed to Chiral Auxiliaries
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The conjugate addition of the phenyldimethylsilyl-cuprate reagent to cinnamate and crotonate esters and amides 1 of various known chiral auxiliaries, a-e, is diastereoselective.The sense of diastereoselectivity of silyl-cuprate addition to the esters 1b-d, 8 and 9 is different from established precedent based on carbon-cuprates, but is normal for silyl-cuprate addition to the amide 1a, the imines 1e and 21, and the oxazolidine 6.The chiral auxiliary e gives the best results of those tested, and the silicon-containing group can be removed from the chiral auxiliary using alkoxide ion in aprotic media, making available β-silyl esters 27-29 of high enantiomeric excess, with recovery of the chiral auxiliary 30.
- Fleming, Ian,Kindon, Nicolas D.
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p. 303 - 316
(2007/10/02)
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- Chiral acrylates as substrates in Baylis-Hillman reaction
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DABCO induces diastereoselective (7-70%) coupling of chiral acrylates (1-3) with aldehydes to produce the corresponding 2-(1-hydroxyalkyl)acrylates.
- Basavaiah,Gowriswari,Sarma,Dharma Rao
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p. 1621 - 1624
(2007/10/02)
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- ENANTIOSELECTIVE SYNTHESES OF α-AMINO ACIDS FROM 10-SULFONAMIDO-ISOBORNYL ESTERS AND DI-t-BUTYL AZODICARBOXYLATE
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Successive treatment of chiral esters 7 with LDA/Me3SiCl and di-t-butyl azodicarboxylate/TiCl4 and Ti(OiPr)4 gave N,N-di-t-butoxycarbonylhydrazinoesters 11 which on deacylation, hydrogenolysis, transesterification and acidic hydrolysis furnished (2S)-α-amino acid hydrochlorides 13 in good overall yields, high enantiomeric purity and with efficient recovery of the alcohol auxiliary 4.Experimental evidence for the configuration and conformation of the intermediate O-silyl ketene acetals 1 is provided.
- Oppolzer, Wolfgang,Moretti, Robert
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p. 5541 - 5552
(2007/10/02)
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- NEW SYNTHESIS OF THE CALIFORNIA RED SCALE SEX PHEROMONE
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The target molecules 1 and 2 were synthesized from a common intermediate 6 prepared from (R)-Limonene.The first enantioselective synthesis of 2 is described.
- Becker, D.,Sahali, Y.
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p. 4541 - 4546
(2007/10/02)
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- Camphorsulfonamide-Shielded, Asymmetric 1,4-Additions and Enolate Alkylations; Synthesis of a Southern Corn Rootworm Pheromone
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Using readily accessible 10-sulfonamido-isoborneols as regenerable, chiral auxiliaries, highly face-selective C-C-bond formations at Cα and Cβ of carboxylates could be conveniently achieved.Thus, conjugated additions of RCu to enoates (1->2) furnished, after saponification, β-substituted carboxylic acids 3 in 94-98 percent e.e.Similarly, propionates 12 yielded after deprotonation, enolate alkylation, and reductive ester cleveage the (R)-alcohols 15 in 78-98 percent e.e.The acid (+)-3e was converted to the pheromone (-)-11.
- Oppolzer, Wolfgang,Dudfield, Philip,Stevenson, Thomas,Godel, Thierry
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p. 212 - 215
(2007/10/02)
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- Asymmetric α-Acetoxylation of Carboxylic Esters
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Using the readily accessible chiral auxiliaries 1-3 the sulfonamide-shielded O-silylated esters 5 underwent ?-face-selective α-acetoxylation on successive treatment with Pb(OAc)4 and NEt3*HF to give after recrystallization α-acetoxy ester 6 in 55-66percen
- Oppolzer, Wolfgang,Dudfield, Philip
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p. 216 - 219
(2007/10/02)
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- ASYMMETRIC HALOGENATION OF CAMPHOR-10-SULFONIC ACID DERIVED ESTERS: AN EFFICIENT NEW ROUTE TO ENANTIOMERICALLY PURE HALOHYDRINS AND EPOXIDES.
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Successive treatment of chiral esters 1 with LDA/Me3SiCl and NBS or NCS gave crystalline α-haloesters 3 which furnished halohydrins 4 and terminal epoxides 5 in high e.e..
- Oppolzer, Wolfgang,Dudfield, Philip
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p. 5037 - 5040
(2007/10/02)
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- ASYMMETRIC DIELS-ALDER REACTIONS: FACILE PREPARATION AND STRUCTURE OF SULFONAMIDO-ISOBORNYL ACRYLATES
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The crystalline chiral auxiliaries 2, 3 and 4 were prepared from champhor-10-sulfonyl chlorides in 2 steps.Their readily accessible acrylates underwent efficient asymmetric Diels-Alder additions to cyclopentadiene, the topicity of wich agrees with X-ray evidence.
- Oppolzer, Wolfgang,Chapuis, Christian,Bernardinelli, Gerald
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p. 5885 - 5888
(2007/10/02)
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