2528-15-6Relevant articles and documents
Total synthesis of micromide: A marine natural product
Han, Jianrong,Lian, Jingtang,Tian, Xia,Zhou, Shengwei,Zhen, Xiaoli,Liu, Shouxin
, p. 7232 - 7238 (2015/02/19)
This paper describes an efficient procedure for the synthesis of micromide, a natural product that shows anti-solid-tumor activity. Our strategy involved the synthesis of N-nosyl-protected amino acids and their N-methylation with iodo-methane. The hindered oligopeptides containing N-methyl amino acids were synthesized in excellent yields and high purities.[ampi]]
Organocatalytic synthesis of optically active β-branched α-amino esters via asymmetric biomimetic transamination
Su, Cunxiang,Xie, Ying,Pan, Hongjie,Liu, Mao,Tian, Hua,Shi, Yian
, p. 5856 - 5860 (2014/08/05)
This paper describes an efficient asymmetric biomimetic transamination of α-keto esters with a quinine-derived chiral base as the catalyst, giving a variety of β-branched α-amino esters in 50-96% yield and 87-95% ee. This journal is the Partner Organisations 2014.
Catalytic asymmetric amination of N-nonsubstituted α-alkoxycarbonyl amides: Concise enantioselective synthesis of mycestericina F and G
Berhal, Farouk,Takechi, Sho,Kumagai, Naoya,Shibasaki, Masakatsu
supporting information; experimental part, p. 1915 - 1921 (2011/03/22)
In an attempt to explore the synthetic utility of a ternary asymmetric catalyst comprising La(NO3)3·6H2O, amide-based ligand (R)-L1, and D-valine tert-butyl ester H-D-Val-OtBu, we investigated a catalytic, asymmetric amination of functionalized N-nonsubstituted α-alkoxycarbonyl amides using di-tert-butyl azodicarboxylate as an electrophilic aminating reagent. A highly functionalized, cyclic N-nonsubstituted α-alkoxycarbonyl amide delivered the desired amination product in up to 96% enantiometric excess, with the requisite functionalities of the polar heads of sphingosines with the appropriate stereochemical arrangement. The rapid asymmetric assembly of these functional groups allowed a concise enantioselective synthetic route to sphingosines to be established with a broad flexibility towards derivative synthesis. These studies have culminated in an efficient catalytic enantioselective total synthesis of immunosuppressive fungal metabolites mycestericina F (3a) and G (3b).
A bismuth(III)-catalyzed friedel-crafts cyclization and stereocontrolled organocatalytic approach to (-)-platensimycin
Eey, Stanley T.-C.,Lear, Martin J.
, p. 5510 - 5513 (2011/03/18)
A high yielding route to the (-)-platensimycin core is communicated. This entailed the discovery of Bi(OTf)3 to catalyze a Friedel-Crafts cyclization of a free lactol, supplemented by LiClO4 to suppress the Lewis basicity of the sulfonate group. After TBAF-promoted cyclodearomatization, a diastereoselective conjugate reduction of a dienone was achieved by adopting amine-based organocatalytic rationales to reverse the inherent steric control of the substrate.
Managing highly coordinative substrates in asymmetric catalysis: A catalytic asymmetric amination with a lanthanum-based ternary catalyst
Mashiko, Tomoyuki,Kumagai, Naoya,Shibasaki, Masakatsu
supporting information; experimental part, p. 14990 - 14999 (2010/01/30)
Full details of a catalytic asymmetric amination with a lanthanum/amide-based ligand catalyst system are described. A catalyst comprising La(NO3)3·6H2O, (R)-3a and H-D-Val-OtBu was identified to promote the catalytic asymmetric amination of nonprotected succinimide derivative 1 with as little as 1 mol % catalyst loading. Mechanistic studies by various spectroscopic analyses and several control and kinetic experiments suggested that the catalyst components were in equilibrium between the associated and dissociated forms, and that the reaction likely proceeded through a La(NO3)3· 6H2O/(R)-3a/H-D-Val-OtBu ternary complex. This catalyst system was also effective for asymmetric amination of N-nonsubstituted α-alkoxycarbonyl amides 7, hitherto unprecedented substrates in asymmetric catalysis, probably due to their attenuated reactivity and difficult stereocontrol, affording the amination products in up to >99% yield and >99% ee. The high catalytic performance and enantiocontrol of the reaction with highly coordinative substrates were achieved by the activation/recognition of the substrates exerted by coordination to lanthanum and hydrogen bonding cooperatively in the transition state.
An improved lanthanum catalyst system for asymmetric amination: Toward a practical asymmetric synthesis of AS-3201 (ranirestat)
Mashiko, Tomoyuki,Kumagai, Naoya,Shibasaki, Masakatsu
supporting information; body text, p. 2725 - 2728 (2009/05/27)
(Chemical Equation Presented) A catalytic asymmetric amination with a lanthanum/amide complex was significantly improved. The use of lanthanum nitrate hydrate in place of lanthanum triisopropoxide made the process reproducible, scalable, and cost-effective. The development of a ternary catalytic system of La/ligand/amine was a key to high ee and catalytic turnover. A 100 g scale reaction was performed to showcase a practical synthesis of a key intermediate for AS-3201, a highly potent aldose reductase inhibitor.
Efficient large (ca. 40 g) laboratory scale preparation of (S)- and (R)-valine tert-butyl esters
Krasnov, Victor P.,Levit, Galina L.,Bukrina, Iraida M.,Demin, Alexander M.,Chupakhin, Oleg N.,Yoo, Ji Uk
, p. 1911 - 1914 (2007/10/03)
A large laboratory scale (ca. 40 g) method for the preparation of enantiomerically pure (S)- and (R)-valine tert-butyl esters has been developed. The method involves three steps: preparation of N-TFA-valines, preparation of valine tert-butyl esters using 2-methylpropene in dioxane in the presence of sulfuric acid, and isolation of the target compounds as the acetate derivative. The overall yield is up to 70% relative to the starting valine, ee being more than 98% (by HPLC).
Preparation of (R)-2-azidoesters from 2-((p-nitrobenzene)sulfonyl)oxy esters and their use as protected amino acid equivalents for the synthesis of di- and tripeptides containing D-amino acid constituents
Hoffman,Kim
, p. 3007 - 3020 (2007/10/02)
(R)-2-Azidoesters and their derived (R)-2-azido acids are readily prepared from common amino acids by an inversion methodology that employs (S)-2-nosyloxyesters as key intermediates. The (R)-2-azidoesters can be used as protected amino acid equivalents in peptide synthesis. Basic hydrolysis frees the carboxyl group. Triphenylphosphine/water is used to free the amine group. By these reactions a variety of L-D and D-L dipeptides, L-D-L tripeptides, and depsipeptides can be prepared easily in good yields, and without detectable epimerization.
