- Isolation, characterization and antioxidant, tyrosinase inhibitory activities of constituents from the flowers of cercis glabra ‘spring-1’
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A phytochemical study on the flowers of Cercis glabra ‘Spring-1’ led to the isolation and identification of twelve compounds, including one new compound named as 1-O-α-L-rhamnosyl-(E)-phytol (1) and eleven known compounds. Their structures were elucidated based on physical data analysis, including HR-ESI-MS, NMR, UV, IR, and acid hydrolysis. All compounds were screened for in vitro antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl method. Compounds 4 and 5 exhibited obvious DPPH radical scavenging activities. All the isolates were tested for their inhibitory effects on mushroom tyrosinase, and compounds 6, 7, 10 and 11 showed moderate tyrosinase inhibitory activities.
- Shu, Penghua,Li, Yamin,Luo, Yuehui,Yu, Mengzhu,Fei, Yingying,Liu, Wanrong,Yang, Yuan,Wei, Xialan,Zhang, Yuhuan,Tu, Tieyao,Zhang, Lin
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p. 254 - 260
(2021/05/05)
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- New 29-nor-cycloartanes with a 3,4-seco- and a novel 2,3-seco-structure from the leaves of Sinocalycanthus chinensis
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Eight new triterpenoids, including sinocalycanchinensins A-E (1-5) with a 3,4-seco-29-nor-cycloartane skeleton, sinocalycanchinensin F (6) possessing a novel 2,3-seco-29-nor-cycloartane skeleton, and 29-nor-cycloartanes, sinocalycanchinensins G and H (7 and 8), have been isolated from the leaves of Sinocalycanthus chinensis. Their structures were elucidated on the basis of spectroscopic examinations. The cytotoxicities of the isolated new triterpenes against a panel of human cancer cell lines, including multi-drug resistant (MDR) cancer cell lines, were also evaluated. Compound 5 demonstrated enhanced cytotoxicity against MDR KB cells in the presence of colchicine, although all the compounds showed moderate or no cytotoxicities.
- Kashiwada, Yoshiki,Nishimura, Kazuya,Kurimoto, Shin-Ichiro,Takaishi, Yoshihisa
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experimental part
p. 2790 - 2796
(2011/06/19)
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- Stereocontrol of 1,5-related stereocentres using an intermediate silyl group-the diastereoselectivity of nucleophilic attack on a double bond adjacent to a stereogenic carrying a silyl group
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R-5-Methylcyclohex-2-enone 1 reacts successively with the phenyldimethylsilylzincate reagent and acetaldehyde to give with regiocontrol the aldols 7, dehydration of which creates the E-exocyclic double bond of the α-β-unsaturated ketone 2. Conjugate addition of the ethylcuprate reagent to this compound takes place with high (96 : 4) selectivity in favour of the R stereoisomer 12, hydrolysis of which gives (2R,3R,5S,2′ R)-2-(but-2′-yl)-3-dimethyl(phenyl)silyl-5-methylcyclohexanone 3. The oxime acetate of this ketone undergoes fragmentation in the presence of trimethylsilyl trifluoromethanesulfonate to give 3R,7R,5E-3,7-dimethylnon-5-enonitrile 4, in which an open-chain 1,5-stereo-chemical relationship is set up with a high level of stereocontrol. A similar sequence adding 4-methylpentylcuprate to the enone 2, and fragmentation gives 3R,7R,5E-3,7,11-trimethyldodec-5-enonitrile 20. Reduction and hydrogenation of this nitrile gives 3R,7R-3,7,11 -trimethyldodecanal 22, which can be converted into phytol 25. The ketoaldehyde 29 reacts with samarium iodide to give only the alcohol 30, in which the radical anion has attacked from the top surface, just like the cuprate reagents in their reactions with the ketone 2.
- Fleming, Ian,Maiti, Pranab,Ramarao, Chandrashekar
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p. 3989 - 4004
(2007/10/03)
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- A convenient and asymmetric protocol for the synthesis of natural products containing chiral alkyl chains via Zr-catalyzed asymmetric carboalumination of alkenes. Synthesis of phytol and vitamins E and K.
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[reaction: see text]. A convenient and asymmetric protocol for the synthesis of chiral oligoisoprenoids is described. Typically, a C14 vitamin E side chain 5 was synthesized in 47% yield over four steps. Isomeric purity of 5 was upgraded to >99% R at C-2 and 97% R at C-6 by the statistical formation of stereoisomeric p-phenylenebisurethanes and their diastereomeric separation. In addition, phytol and vitamin K were synthesized in 21% and 28% overall yields, respectively, over five steps from 1.
- Huo,Negishi
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p. 3253 - 3256
(2007/10/03)
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- Process for the preparation of tocopherol derivatives and catalyst
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A process is provided for the preparation of an α-tocopherol derivatives which are useful as antisterile vitamins, hypolipidemics, blood flow increasing agents, anti-cytosenility agents, antioxidants and the like. Catalysts are also provided. The α-tocopherol derivatives are represented by the following formula (VII): STR1 wherein n stands for 0 or an integer of from 1 to 5. The derivatives can be industrially prepared by employing as catalyst a metal ion-exchanged montmorillonite, metal ion-exchanged bentonite or metal ion-exchanged saponite which is substituted with one metal ion selected from the group consisting of scandium, yttrium, lanthanide element, aluminium, iron, tin, copper, titanium, zinc, nickel, gallium or zirconium.
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- Method of preparing C-18 ketones used in the manufacture of Vitamins E and K
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Methods of forming unsaturated C-18 ketones which can be used in the synthesis of Vitamins E and K1 are disclosed. One procedure involves coupling a C-9 primary allylic halide to a carbonyl-group-containing C-9 terminal alkyne. A second, two-step procedure employs a C-4 bis allylic halide (molar excess) and a carbonyl-group-containing C-9 terminal alkyne to form a C-13 primary allylic halide. The C-13 primary allylic halide can then be converted to the desired C-18 ketone by reaction with 2-methyl-3-butyn-2-ol. Novel C-18 ketones (e.g., 14-hydroxy-6,14-dimethyl-10-methylene-5-pentadecen-7,12-diyn-2-one), C-13 allylic halides (e.g., 10-chloromethyl-6-methyl-5,10-undecadien-7-yn-2-one) and C-9 allylic halides (e.g., 6-chloromethyl-2-methyl-6-hepten-3-yn-2-ol) are formed in the process.
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- 1,3,5-nonatriene derivatives, their preparation and their use
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1,3,5-Nonatriene derivatives of formula: STR1 in which R1 and R2, together with the carbon atom to which they are linked, form a carbonyl group, or each of R1 and R2 denotes alkoxy or R1 and R2 together form an alkylenedioxy radical, which may be made by reaction of a butadiene derivative of formula: STR2 in which R is alkyl or phenyl, with a butanal ketoacetal of 10 formula: STR3 followed by reaction of the product with a halomethyltriphenylphosphonium halide, are useful intermediates e.g. for the production of phytol.
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- STEREOSELECTIVE TOTAL SYNTHESIS OF NATURAL PHYTOL VIA DOUBLE BOND REDUCTIONS BY BAKER'S YEAST
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Natural (E)-(7R,11R)-phytol (1), a component of the chlorophyll molecule, vitamin K1 (2) and other natural compounds, was synthesized in enantiomerically and diastereomerically pure form by Li2CuCl4-induced coupling of two C10-inits (8,12).Both these units were prepared from geraniol (3) via enzymatic enantioselective hydrogenation of activated double bonds.
- Gramatica, Paola,Manitto, Paolo,Monti, Diego,Speranza, Giovanna
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p. 4481 - 4486
(2007/10/02)
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- A STEREOCONTROLLED TOTAL SYNTHESIS OF OPTICALLY ACTIVE (R,R)-PHYTOL
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A stereospecific synthesis of (R,R)-phytol with highly stereochemical purity in both absolute and geometrical configurations was achieved by utilizing the SN2 type ring-opening reaction of (R)-β-methyl-β-propiolactone, and the SN2' type ring-opening reaction of isopropenyl oxirane, from (R)-pulegone as a starting material.
- Fujisawa, Tamotsu,Sato, Toshio,Kawara, Tatsuo,Ohashi, Kazuo
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p. 4823 - 4826
(2007/10/02)
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