- Synthesis and application of N-3,5-dinitrobenzoyl and C3 symmetric diastereomeric chiral stationary phases
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Three diastereomeric chiral compounds, namely, (R,R)-(+)-2-amino-1,2-diphenylethanol, (1S,2R)-(+)-2-amino-1,2-diphenylethanol, and (1R,2R)-(+)-1,2-diphenylethylenediamine were used as starting materials for preparing three N-3,5-dinitrobenzoyl derivative
- Ryoo, Jae Jeong,Yu, Jeong Jae
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- Synthesis of new C3 symmetric amino acid- and aminoalcohol-containing chiral stationary phases and application to HPLC enantioseparations
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We recently reported a new C3-symmetric (R)-phenylglycinol N-1,3,5-benzenetricarboxylic acid-derived chiral high-performance liquid chromatography (HPLC) stationary phase (CSP 1) that demonstrated better results as compared to a previously described N-3,5-dintrobenzoyl (DNB) (R)-phenylglycinol-derived CSP. Over a decade ago, (S)-leucinol, (R)-phenylglycine, and (S)-leucine derivatives were used as the starting materials of 3,5-DNB-based Pirkle-type CSPs for chiral separation. In this study, three new C3-symmetric CSPs (CSP 2, 3, and 4) were prepared by combining the ideas and results mentioned above. Here we describe the synthetic procedures and applications of the new C3-symmetric CSPs (CSP 2–CSP 4).
- Yu, Jeongjae,Armstrong, Daniel W.,Ryoo, Jae Jeong
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- PROCESS FOR THE PREPARATION OF A FLUOROLACTON DERIVATIVE
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A novel process for the preparation of a fluorolactone derivative of the formula (I) and of its acylated derivative of formula (V) wherein R1 stands for a hydroxy protecting group is described. The acylated fluorolactones of formula (V), particularly the benzoyl derivative with R1 =benzyl are important precursors for the synthesis of prodrug compounds which have the potential to be potent inhibitors of the Hepatitis C Virus (HCV) NS5B polymerase.
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Page/Page column 10; 11
(2014/07/23)
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- METHOD FOR PRODUCING PYRROLIDINE COMPOUND
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Provided is a method capable of efficiently producing a compound having a superior HSD1 inhibitory action and a compound useful as a synthetic intermediate therefor, with superior achievability of asymmetric synthesis (i.e., superior selectivity), superior yield, superior safety and superior industrial workability at a low cost. A method of producing a compound represented by the following formula [8]: or a salt thereof, or a solvate thereof, from a compound represented by the following formula [2]: or a reactive derivative thereof, or a salt thereof, or a solvate thereof.
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Page/Page column 97
(2009/10/01)
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- Asymmetric zinc-Reformatsky reaction of Evans chiral imide with acetophenones and its application to the stereoselective synthesis of triazole antifungal agents
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The Ni(acac)2 catalytic ZnEt2-mediated asymmetric Reformatsky-type reaction of Evans chiral imide with various acetophenones was studied. The chiral imido zinc enolate, which was formed through the metal-halogen exchange reaction of
- Yu, Luo-Ting,Ho, Meng-Tsung,Chang, Ching-Yao,Yang, Teng-Kuei
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p. 949 - 962
(2008/02/03)
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- Conjugate addition of lithiated (S)-4-isopropyl-3-[(methylthio)methyl]-5,5-diphenyloxazolidin-2-one to cinnamoyl derivatives: Preparation of enantiomerically pure 1,4-diols
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The Li derivative of (S)-4-isopropyl-3-[(methylthlio)methyl]-5,5-diphenyloxazolidin-2-one (Li-2; synthetically equivalent to a chiral formyl anion) adds to enones and enoates in a 1,4-fashion. Best results are obtained with 1,3-diarylpropenones (chalcones
- Gaul, Christoph,Seebach, Dieter
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p. 772 - 787
(2007/10/03)
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- Highly effective and recyclable chiral auxiliaries: A study of the synthesis and use of three 4-isopropyl-5,5-diaryloxazolidin-2-ones
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A series of three 5,5-diaryl substituted oxazolidin-2-ones (diphenyl, dinaphthyl and ditolyl) have been synthesised. Studies on the benzylation of the lithium enolates of N-acyl derivatives reveal that the yields obtained were sensitive to the method of quenching the reaction. This was particularly acute for the 5,5-diphenyl system where effective yields (69%) and high diastereoselectivities (dr 98 : 2) are only observed when the reactions were quenched into aqueous buffer. Methylation studies on the N-acyl derivatives showed that the most advantageous results (58-69%, dr ≥ 91 : 9) were only observed using the sodium enolates. The 5,5-ditolyl-4-isopropyloxazolidin-2-one proved to be more efficacious in terms of efficiency and diastereoselectivity (dr ≥ 97 : 3). Subsequent, simple alkaline hydrolyses of the alkylation products allowed for the high recovery and recyclability of the 5,5-diaryl substituted oxazolidin-2-ones without any deleterious endocyclic cleavage. In addition, the acyl portions were recovered in high yield from the alkaline hydrolyses without any evidence of racemisation.
- Alexander,Cook,Gibson,Kennedy
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p. 1538 - 1549
(2007/10/03)
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- A Valine-Derived Lithiated 3-Methylthiomethyl-1,3-oxazolidin-2-one for Enantioselective Nucleophilic Hydroxymethylation, Formylation, and Alkoxycarbonylation of Aldehydes
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(Equation Presented) The 3-methylthiomethyl-4-isopropyl-5,5-diphenyl-1,3-oxazolidin-2-one (I, prepared in three steps from Boc-valine ester) is lithiated and added to aldehydes, with protecting in situ trapping of the primary adducts, to give the N,S-acet
- Gaul, Christoph,Seebach, Dieter
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p. 1501 - 1504
(2007/10/03)
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- A short synthesis of (S)-α-(diphenylmethyl)alkyl amines from amino acids
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A range of (S)-α-(diphenylmethyl)alkyl amines were prepared from the corresponding (S)-α-amino acid ester hydrochlorides. These amines were derived by direct hydrogenation of their precursor oxazolidinones.
- O'Hagan, David,Tavasli, Mustafa
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p. 1189 - 1192
(2007/10/03)
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- A useful modification of the Evans auxiliary: 4-Isopropyl-5,5- diphenyloxazolidin-2-one
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The 4-isopropyl-5,5-diphenyloxazolidinone (1) is readily prepared from (R)- or (S)-valine ester, PhMgBr, and ethyl chlorocarbonate. It has a melting point of ca. 250°, a low solubility in most organic solvents, and a C=O group which is sterically protected from nucleophilic attack. Thus, the soluble N-acyl-oxazolidinones (7-16) can be prepared from 1 with BuLi at temperatures around 0°instead of - 78°(Scheme 3), their Li enolates can be generated with BuLi, rather than with LDA, and deacylation in the final step of the procedure can be achieved with NaOH at ambient temperatures (Scheme 12), with facile recovery of the precipitating auxiliary 1 (filtering, washing, and drying). The following reactions of N-acyl-oxazolidinones from 1 have been investigated: alkylations (Scheme 4), aminomethylations and hydroxymethylations (Scheme 5), aldol additions (Schemes 6 and 7), Michael additions (Schemes 9 and 10), and a (4 + 2) cycloaddition (Scheme 11). The well-known features of reactions following the Evans methodology (yield, diastereoselectivity, dependence on conditions, counter ions, additives etc.) prevail in these transformations. Most products, however, have higher melting points and a much more pronounced crystallization tendency than those derived from conventional oxazolidinones, and can thus be purified by recrystallization, avoiding chromatography (Table 1). The disadvantage of 1 having a higher molecular weight (ca. 150 Da) than the non-phenyl-substituted auxiliary is more than compensated by the ease of its application, especially on large scale. A number of crystal structures of oxazolidinones derived from 1 and a TiCl4 complex of an oxazolidinone are described and discussed in view of the diastereoselective-reaction mechanisms.
- Hintermann, Tobias,Seebach, Dieter
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p. 2093 - 2126
(2007/10/03)
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- A study of 4-substituted 5,5-diaryl oxazolidin-2-ones as efficacious chiral auxiliaries
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A series of three 5,5-diaryl substituted oxazolidin-2-ones (diphenyl, dinaphthyl and ditolyl) have been prepared and shown to be particularly effective chiral auxiliaries to afford high yields and diastereoselectivities for alkylation and azidations of their N-acyl derivatives. The 5,5-ditolyl oxazolidin-2-one proved to be particularly efficacious in terms of diastereoselectivity, yield and solubility.
- Gibson, Colin L.,Gillon, Karen,Cook, Stuart
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p. 6733 - 6736
(2007/10/03)
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- 1-magnesiotetrahydroisoquinolyloxazolines as chiral nucleophiles in stereoselective additions to aldehydes: Auxiliary optimization, asymmetric synthesis of (+)-corlumine, (+)-bicuculline, (+)-egenine, and (+)-corytensine, and preliminary 13C NMR studies of 1-lithio- and 1-magnesiotetrahydroisoquinolyloxazolines
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Transmetalation of 1-lithiotetrahydroisoquinolyloxazolines with magnesium halides affords Grignard reagents that add to aldehydes with up to 80% selectivity for one of the four possible diastereomeric products. An oxazoline chiral auxiliary derived from camphor provides an optimal blend of diastereoselectivity and isomer separability. Synthetic applications of the optimal auxiliary, patterned after a literature approach in the racemic series, comprise an improved (formal) synthesis of bicuculline, egenine, and corytensine, as well as an efficient synthesis of corlumine. Preliminary NMR studies show that both 1-lithio- and 1-magnesiotetrahydroisoquinolyloxazolines are dynamic mixtures in THF solution at low temperatures. The barrier to pyramidal inversion of the secondary Grignard reagent is in the 9.8-10.1 kcal/mol range, while an upper limit of about 8.2 kcal/mol can be assigned to the barrier to the organolithium inversion.
- Gawley, Robert E.,Zhang, Pingsheng
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p. 8103 - 8112
(2007/10/03)
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