1730-91-2Relevant academic research and scientific papers
Asymmetric hydrogenation of an α-unsaturated carboxylic acid catalyzed by intact chiral transition metal carbonyl clusters-diastereomeric control of enantioselectivity
Abdel-Magied, Ahmed F.,Doverbratt, Isa,Haukka, Matti,Nordlander, Ebbe,Raha, Arun K.,Rahaman, Ahibur,Richmond, Michael G.,Singh, Amrendra K.,Theibich, Yusuf
, p. 4244 - 4256 (2020)
Twenty clusters of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P?)] (P-P? = chiral diphosphine of the ferrocene-based Walphos or Josiphos families) have been synthesised and characterised. The clusters have be
Asymmetric [2,3]-Wittig rearrangements with chiral, phosphorus anion-stabilizing groups
Denmark, Scott E.
, p. 6631 - 6634 (1995)
The [2,3]-Wittig rearrangement of a chirally-modified phosphorus stabilized anion proceeds readily and with excellent diastereo- and enantioselectivity for alkyloxymethyl and (Z)-2-butenyloxymethyl derivatives.
Conformational study of poly(N-propargylamides) having bulky pendant groups
Tabei, Junichi,Nomura, Ryoji,Masuda, Toshio
, p. 5405 - 5409 (2002)
N-Propargylamides having chiral centers at the α-carbon of the amide groups, 1-3, were polymerized with (nbd)Rh+[η6-C6H5B-(C 6H5)3] to afford polymers with moderate molecular weights (Mn = 6000-32 000) in good yield. The 1H NMR spectra demonstrated that the polymers have stereoregular structures (cis = 100%). The polymers were proven to take a helical conformation with an excess of one- handed screw sense in CHCl3, which was supported by their intense CD effects and large optical rotations. It was confirmed that the helical structure was stabilized not only by the steric repulsion but also by the intramolecular hydrogen bonds between the pendant groups. CD spectroscopic study showed that the helical structure is more stable than that of the polymers without a branch at the α-position, which allowed the polymers to exist in the helical state in various solvents. The electronic absorption, CD effects, and optical rotations of the polymers closely correlated to the extent of the hydrogen bonding between the pendant amide groups.
Diastereomeric control of enantioselectivity: Evidence for metal cluster catalysis
Abdel-Magied, Ahmed F.,Singh, Amrendra K.,Haukka, Matti,Richmond, Michael G.,Nordlander, Ebbe
, p. 7705 - 7708 (2014)
Enantioselective hydrogenation of tiglic acid effected by diastereomers of the general formula [(μ-H)2Ru3(μ3-S)(CO) 7(μ-P-P*)] (P-P* = chiral Walphos diphosphine ligand) strongly supports catalysis by intact Ru
Palladium nanoparticle-graphene catalysts for asymmetric hydrogenation
Sz?ri, Korne?l,Puskás, Robert,Sz?ll?si, Gyo?rgy,Bertóti, Imre,Szépv?lgyi, János,Bartók, Mihály
, p. 539 - 546 (2013)
We report for the first time the application of palladium nanoparticle-graphene (Pd/Gn) catalysts in the asymmetric hydrogenation of aliphatic α,β-unsaturated carboxylic acids using cinchonidine as chiral modifier. Pd/Gns were prepared by deposition-preci
Chiral 2-alkylbranched acids, esters and alcohols. Preparation and stereospecific flavour evaluation
Rettinger,Burschka,Scheeben,Fuchs,Mosandl
, p. 965 - 968 (1991)
Racemic 2-alkylbranched acids are transformed to diastereomeric derivatives with (S)-2-hydroxy-3-phenylpropionic acid-N-methylamide of (S)-(-)-1-phenylethylamine and separated by liquid chromatography to pure diastereoisomers, which are subsequently hydrolyzed to yield optically pure acids. Enantiomeric alcohols are generated by LiAlH4-reduction of the corresponding acids, esters are synthesized by different methods. The odour impression of the enantiomeric compounds is investigated.
Toosendanin relatives, trypanocidal principles from Meliae Cortex
Mifundu, Michel N.,Murakami, Nobutoshi,Kawano, Tomikazu,Tamura, Satoru
, p. 702 - 709 (2020)
Africa Trypanosomiasis remains a serious health problem, but the approved drugs for this disease are so few that novel trypanocidal compounds are demanded. In search for trypanocidal principles from medicinal plants, we found MeOH extracts of Meliae Cortex with potent activity through the screening from about 300 kinds of methanolic extract. By bioassay-guided fractionation from this extract through the liquid–liquid partition and subsequent chromatographic technique using silica gel and ODS, finally we disclosed toosendanin (1) and its relatives as active principles. These active congeners showed not only potent trypanocidal activity but also little cytotoxicity to display the excellent selective index. Taking the isolated amount as well as trypanocidal activity into consideration, 1 was disclosed to be the responsible active principle in Meliae Cortex. Additionally, the derivatives of 1 were chemically prepared from 1 and bioactivity of them were also evaluated. Through the comparison with their trypanocidal activity among the isolated relatives and the synthesized derivatives of 1, the epoxide moiety was revealed to be essential for their potent trypanocidal activity. Furthermore, 3-O-acetyl group and 7-hydroxyl group were presumed to be important functional groups and introduction of methylpropionyl group into hemiacetal hydroxy moiety was clarified to enhance their typanocidal activity.
Achiral amine additives in the enantioselective hydrogenation of aliphatic α,β-unsaturated acids over cinchonidine-modified Pd/Al 2O3 catalyst
Makra, Zsolt,Sz?ll?si, Gy?rgy,Bartók, Mihály
, p. 56 - 61 (2012)
The effect of the achiral amine additive structure was studied on the enantioselective hydrogenation of (E)-2-methyl-2-butenoic acid and (E)-2-methyl-2-hexenoic acid over Pd/Al2O3 catalyst modified by cinchonidine. It was found that
Synthesis and evaluation of a new steroidal BINAP type phosphine
Enev,Harre,Nickisch,Schneider,Mohr
, p. 1767 - 1779 (2000)
The short and high yielding synthesis of a new cis-configured bissteroidal phosphine 7 is reported. The comparison of these new phosphines as ligands in ruthenium-based hydrogenation catalysts with the previously synthesized diastereomeric trans-configured phosphines 20 shows that the steroid backbone exerts only a minor influence on the enantioselection of the ruthenium catalysts and confirms that the bissteroidal phosphines behave as 'pseudo'-enantiomers in spite of their diastereomeric nature. Evidence is presented that the mode of catalyst preparation, i.e. catalyst structure, is the crucial reaction parameter which mainly determines the enantiomeric excess of the hydrogenation products. (C) 2000 Elsevier Science Ltd.
Eight new diterpenoids and two new nor-diterpenoids from the stems of Croton cascarilloides
Kawakami, Susumu,Toyoda, Hiroki,Harinantenaina, Liva,Matsunami, Katsuyoshi,Otsuka, Hideaki,Shinzato, Takakazu,Takeda, Yoshio,Kawahata, Masatoshi,Yamaguchi, Kentaro
, p. 411 - 418 (2013)
From the stems of Croton cascarilloides, eight new diterpenoids, named crotocascarins A-H (1-8), having a crotofolane skeleton were isolated along with two new nor-diterpenoids (9 and 10), named crotocascarins α and β, derived through rearrangement of the crotofolane skeleton. The structures of these compounds were elucidated by means of extensive one- and two-dimensional NMR spectroscopic analyses. The absolute structures of the diterpene moiety were determined by application of the circular dichroism (CD) rule for the γ-lactone ring. The relative structures of the two crotofolanes (1 and 2) and one rearranged compound (9) were confirmed by X-ray crystallographic analyses. Compounds 1, 2 and 9 possessed 2-methylbutyric acid in their molecules, the absolute configuration of which was found to be 2S by comparison of its HPLC behavior with that of an authentic sample. Therefore, the absolute structures of these crotocascarins (1, 2 and 9) were unambiguously determined. The absolute structures of crotofolanes are reported for the first time in this paper.
