- Staudinger/aza-Wittig reaction to access Nβ-protected amino alkyl isothiocyanates
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A unified approach to access Nβ-protected amino alkyl isothiocyanates using Nβ-protected amino alkyl azides through a general strategy of Staudinger/aza-Wittig reaction is described. The type of protocol used to access isothiocyanates depends on the availability of precursors and also, especially in the amino acid chemistry, on the behavior of other labile groups towards the reagents used in the protocols; fortunately, we were not concerned about both these factors as precursor-azides were prepared easily by standard protocols, and the present protocol can pave the way for accessing title compounds without affecting Boc, Cbz and Fmoc protecting groups, and benzyl and tertiary butyl groups in the side chains. The present strategy eliminates the need for the use of amines to obtain title compounds and thus, this method is step-economical; additional advantages include retention of chirality, convenient handling and easy purification. A few hitherto unreported compounds were also prepared, and all final compounds were completely characterized by IR, mass, optical rotation, and 1H and 13C NMR studies.
- Santhosh,Durgamma,Shekharappa,Sureshbabu, Vommina V.
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p. 4874 - 4880
(2018/07/15)
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- An efficient and facile synthesis of N-Cbz-β-aminoalkanesulfonamides
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An efficient method for the synthesis of N-Cbz-β- aminoalkanesulfonamides was described. N-Cbz-β-aminoalkanesulfona-mides were readily prepared in good yields from a variety of amino alcohols, including optically active ones, via N-Cbz protection with ben
- Meng, Fanhua,Chen, Ning,Xu, Jiaxi
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p. 2548 - 2553
(2013/06/27)
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- Cinchona alkaloid ester derivatives as ligands in the asymmetric dihydroxylation and aminohydroxylation of alkenes
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Cinchona alkaloid ester derivatives were adopted to asymmetric dihydroxylation and asymmetric aminohydroxylation reactions in excellent yields and enantiomeric excesses.
- Chen, Hui,Wang, Qiao Feng,Sun, Xiao Li,Luo, Jing,Jiang, Ru
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experimental part
p. 104 - 105
(2010/06/21)
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- A simple synthesis of N β-Fmoc/Z-amino alkyl thiols and their use in the synthesis of N β-Fmoc/Z-amino alkyl sulfonic acids
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A simple and efficient protocol for the synthesis of Nβ- Fmoc/Z-amino alkyl thiols is described. The approach uses sodium pyrosulfite-mediated hydrolysis of isothiouronium salts resulting from the reaction between N-protected aminoalkyl iodides and thiourea. N-Protected taurines were prepared through performic acid oxidation of the thiols and the products were further utilized for the synthesis of dipeptidosulfonamides. Georg Thieme Verlag Stuttgart - New York.
- Sureshbabu,Vishwanatha,Vasantha
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body text
p. 1037 - 1042
(2010/07/06)
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- Enantioselective synthesis of cyclic sulfamidates via Pd-catalyzed hydrogenation
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Using Pd(CF3;CO2)2/(S,S)-f-binaphane as the catalyst, an efficient enantioselective synthesis of cyclic sulfamidates was developed via asymmetric hydrogenation of the corresponding cyclic imines in 2,2,2-trifluoroethanol at room temperature with high enantioselectivities (up to 99% ee).
- Wang, You-Qing,Yu, Chang-Bin,Wang, Da-Wei,Wang, Xiao-Bing,Zhou, Yong-Gui
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supporting information; experimental part
p. 2071 - 2074
(2009/04/18)
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- A mild, efficient, and inexpensive protocol for the selective deprotection of TBDMS ethers using KHSO4
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Potassium hydrogensulfate in 30% aq. methanol deprotects a variety of tert-butyldimethylsilyl ethers at room temperature in excellent yields.
- Arumugam, Pandurangan,Karthikeyan, Ganesan,Perumal, Paramasivan T.
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p. 1146 - 1147
(2007/10/03)
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- Highly Enantioselective Synthesis of 1,2-Amino Alcohol Derivatives via Proline-Catalyzed Mannich Reaction
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Here we report a new catalytic asymmetric synthesis of oxazolidin-2-ones 4 and Cbz-protected 1,2-amino alcohols 5. Our sequence is based on the chemistry of previously unknown 5-acyloxy-oxazolidin-2-ones, which are obtained via proline-catalyzed direct asymmetric three-component Mannich reaction and Baeyer-Villiger oxidation.
- Pojarliev, Peter,Biller, William T.,Martin, Harry J.,List, Benjamin
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p. 1903 - 1905
(2007/10/03)
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- The use of pH to influence regio- and chemoselectivity in the asymmetric aminohydroxylation of styrenes
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(Matrix presented) The pH-controlled Sharpless asymmetric aminohydroxylation (AA) of styrenes provides 1-aryl-2-amino ethanols (regioisomer E enantio-, chemo-, and regioselectivity. As existing AA protocols typically give regioisomer A as the major reaction product when usin nitrogen sources, this method is a convenient alternative for the selective production of regioisomer B.
- Nesterenko, Vitaliy,Byers, Joshua T.,Hergenrother, Paul J.
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p. 281 - 284
(2007/10/03)
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- Synthesis of the kappa-agonist CJ-15,161 via a palladium-catalyzed cross-coupling reaction.
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Syntheses of CJ-15,161 (1) involving intermolecular N-arylation of an appropriately functionalized diamine, obtained from the precursor alpha-amino acids or, more conveniently, from the corresponding 1,2-amino alcohols via 1,2,3-oxathiazolidine-2,2-dioxide 22, are reported.
- Ghosh, Arun,Sieser, Janice E,Caron, Stephane,Watson, Timothy J N
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p. 1644 - 1645
(2007/10/03)
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- Asymmetric synthesis of α-arylglycinols via additions of lithium methyl p-tolyl sulfoxide to N-(PMP)arylaldimines followed by 'non oxidative' Pummerer reaction
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The results presented in this paper demonstrate that the stereochemical outcome of the reversible additions of lithium (R)-methyl p-tolyl sulfoxide to N-arylidene-p-anisidines (N-PMP imines) is a function of a) the reaction conditions used and b) the electronic properties of the arylidene moiety on the starting imine. High kinetically controlled (2S,R(S)) diastereoselectivity (-70 °C) was achieved for additions of imines bearing relatively electron-rich N-arylidene groups, while an electron-deficient nature of this group was found to favor the opposite stereochemical outcome. On the other hand, the reactions run under thermodynamically controlled conditions (0 °C) afforded equimolar mixtures of the diastereomeric products regardless of the pattern of substitution on the starting imines. Enantiopure α-arylglycinols were readily synthesized by 'non-oxidative' Pummerer rearrangement of diastereomerically pure β-aryl-β-N-(acyl)aminoalkyl sulfoxides, prepared from the corresponding N-PMP derivatives.
- Bravo, Pierfrancesco,Capelli, Silvia,Crucianelli, Marcello,Guidetti, Maurizia,Markovsky, Andrey L.,Meille, Stefano V.,Soloshonok, Vadim A.,Sorochinsky, Alexander E.,Viani, Fiorenza,Zanda, Matteo
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p. 3025 - 3040
(2007/10/03)
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- From styrenes to enantiopure α-arylglycines in two steps
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Direct enantioselective synthesis of (R)- and (S)-N-Cbz- or N- BOC-protected α-arylglycinols from styrenes via catalytic asymmetric aminohydroxylation, with enantioselective up to 99% and isolated yields up to 80%, is described. In a subsequent oxidation step, these glycinols yield the corresponding carbamate-protected α-arylglycines.
- Laxma Reddy,Barry Sharpless
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p. 1207 - 1217
(2007/10/03)
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- New synthesis of Evans chiral oxazolidinones by using Sharpless AA reaction
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Optically pure new Evans auxiliary analogs, (4R)- and (4S)-4-(2-naphthyl)oxazolidin-2-one, have been synthesized by using the Sharpless catalytic asymmetric aminohydroxylation reaction (Sharpless AA). The concise two-step synthesis involves a unique solution-to-solid Sharpless AA process and new neat cyclization conditions.
- Li, Guigen,Lenington, Robert,Willis, Steven,Kim, Sun Hee
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p. 1753 - 1754
(2007/10/03)
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- Synthesis of optically active imidazolines, azapenams, dioxocyclams, and bis-dioxocyclams
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Optically active 4-methyl-4-carbomethoxy-Δ2-imidazoline was efficiently synthesized on a multigram scale. Photolysis with (methoxymethylcarbene)chromium complex produced the optically active azapenam in good yield and with high stereoselectivity. Acid-catalyzed dimerization followed by reduction produced the corresponding optically active dioxocyclam in good yield. Using a bis-carbene complex, an optically active bis-dioxocyclam was produced in excellent yield.
- Hsiao, Yi,Hegedus, Louis S.
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p. 3586 - 3591
(2007/10/03)
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- Erhoehung der Effizienz der katalytischen asymmetrischen Aminohydroxylierung durch N-Halogencarbamat-Salze
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Keywords: Aminoalkohole; Asymmetrische Aminohydroxylierung; Carbamate; Katalyse
- Li, Guigen,Angert, Hubert H.,Sharpless, K. Barry
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p. 2995 - 2999
(2007/10/03)
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- Rationally Designed "Dipeptoid" Analogues of CCK. α-Methyltryptophan Derivatives as Highly Selective and Orally Active Gastrin and CCK-B Antagonists with Potent Anxiolytic Properties
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This paper describes the synthesis and structure-activity relationships (SAR) leading to the first rational design of "dipeptoid" analogues of the neuropeptide cholecystokinin (CCK).Compounds *,S*)>-4-2-3-(1H-indol-3-yl)-2-m
- Horwell, David C.,Hughes, John,Hunter, John C.,Pritchard, Martyn C.,Richardson, Reginald S.,at al.
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p. 404 - 414
(2007/10/02)
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