Search results for "Terpene"
showing 10 items of 816 documents
Acylated Triterpene Saponins from Atroxima libericaStapf
2011
The four new acylated triterpene saponins 1–4, isolated as two pairs of isomers and named libericosides A1/A2 and B1/B2, one pair of isomers 5/6, the (Z)-isomer libericoside C2 (5) being new, one new sucrose ester, atroximoside (7), and eight known compounds were isolated from the roots of Atroxima liberica by repeated MPLC and VLC on normal and reversed-phase silica gel. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR studies (1H- and 13C-NMR, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3-O-β-D-glucopyranosylpresenegenin 28-{O-α-L-arabinopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-4-O-[(E)-3,4-dimethoxycinnamoyl]-β-D-f…
Transformation of artemisin into artapshin and 8α-hydroxy-11β,13-dihydrobalchanin
1987
Abstract Partial syntheses of the sesquiterpene lactones artapshin ( 1 ) and 8α-hydroxy-11β, 13-dihydrobalchanin ( 2 ) from artemisin ( 3 ) are described.
Synthesis of (+)-Isoalantolactone and (+)-Isoalloalantolactone from (−)-Santonin
1992
Abstract This paper reports on the chemical conversion of (−)-santonin into (+)-isoalantolactone and (+)-isoalloalantolactone involving functionality transfer from C 6 to C 8 , refunctionalization of the ring A and the formation of the α-methylene-8 β,12-olide moiety.
Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides.
2014
The Michael addition of dibenzylamine to (+)-tert-butyl perillate (3) and to (+)-tert-butyl phellandrate (6), derived from (S)-(−)-perillaldehyde (1), resulted in diastereomeric β-amino esters 7A–D in a moderately stereospecific reaction in a ratio of 76:17:6:1. After separation of the diastereoisomers, the major product, cis isomer 7A, was quantitatively isomerized to the minor component, trans-amino ester 7D. All four isomers were transformed to the corresponding β-amino acids 10A–D, which are promising building blocks for the synthesis of β-peptides and 1,3-heterocycles in three steps. The steric effects of the isopropyl group at position 4 and of the α-methyl substituent of (R)-N-benzyl…
Omphalocarpoidone, a new lanostane-type furano-spiro-γ-lactone from the wood of Tridesmostemon omphalocarpoides Engl. (Sapotaceae)
2013
Abstract Phytochemical studies of the wood and the stem bark of Tridesmostemon omphalocarpoides Engl. (Sapotaceae) led to the isolation of omphalocarpoidone (1), a new lanostane-type furano-spiro-γ-lactone together with β-amyrin acetate (2), taraxerol (3), spinasterol (4), lichexanthone (5), epi-catechin (6), spinasterol 3-O-β- d -glucopyranoside (7), tormentic acid (8), and 1,2,3,4-tetrahydronorharman-1-one (9). Their structures were established on the basis of extensive NMR studies, mass spectrometry, and by comparison of the data with those previously reported in the literature. The structure of the new secondary metabolite was later confirmed by X-ray crystallography. Except for spinast…
Flavones, sesquiterpene lactones and glycosides isolated from Centaurea aspera var. Stenophylla
1984
Abstract From the alcoholic extract of Centaurea aspera var. stenophylla benzoic acid, p-hydroxybenzoic acid, apigenin, 6-methoxyluteolin, 11,13-dehydromelitensin, melitensin, stenophyliolide, ethyl-7-O-apigenin-glucuronate and the glucosides of sitosterol and stigmasterol were isolated and characterized. Stenophyllolide was shown to be 9,15-dihydroxygermacra-1(10),4,11-trien-12,6-olide.
A new dibenzofuran and other constituents from Ligularia caloxantha, a Chinese medicinal plant.
2008
A new dibenzofuran named 1,2,4-trimethyl-7,8-dimethoxy-dibenzofuran (1), together with seven known compounds, euparin (2), 2,5-diacetyl-6-hydroxy-benzofuran (3), 2-acetyl-5,6-dimethoxy-benzofuran (4), gummosogenin (5), lupeol (6), stigmasterol (7) and (E)-2,5-dihydroxy-cinnamic acid (8), were isolated from the roots of Ligularia caloxantha, a Chinese medicinal plant. The structures of the compounds were elucidated by spectroscopic methods.
Isomotiol, a new triterpene from strychnos potatorum
1978
Isomotiol (fern-8-en-3β-ol) was isolated from the leaves of Strychnos potatorum; it was not known previously as a natural product, but it has been obtained by acidic isomerization of compounds with a fern-7-ene or a fern-9(11)-ene skeleton. From the leaves and the bark mixtures of sitosterol, stigmasterol and campesterol were also isolated.
Carbohydrates as Stereodifferentiating Auxiliaries
2017
Carbohydrates are inexpensive natural products. Although they contain numerous functional groups and stereogenic centers in one molecule, carbohydrates were recognized as stereodifferentiating auxiliaries much later than other classes of natural products as for example amino acids or terpenes. Apart from their polyfunctional nature carbohydrates are characterized by the anomeric and exo-anomeric effects which have distinct influence of the spatial orientation of substituents linked to the anomeric position. Based on these stereochemical properties carbohydrates were used as stereodifferentiating auxiliaries in numerous diastereoselective reactions, such as aldol addition, alkylation reactio…
ChemInform Abstract: Stereoselective Synthesis of 8,12-Furanoeudesmanes from Santonin. Absolute Stereochemistry of Natural Furanoeudesma-1,3-diene an…
2010
Ketobutenolide 3, easily obtained from santonin (1), has been transformed into two natural furanoeudesmanes 4 and 5, isolated from Commiphora molmol and Tubipora musica, respectively. trans- And cis-decalin systems were obtained by stereoselective reduction of the C4−C5 double bond in 3 in the following way: hydrogenation of 3 over Pd/C followed by acidic treatment gave the cis isomer 10 as the major product; selective hydrogenation of the C1-C2 double bond with the Wilkinson’s catalyst followed by reduction with NaTeH yielded mainly the trans isomer 9. Compounds 9 and 10 were transformed into 4 and 5 in parallel sequences. Optical rotation and CD measurements of the synthetic products rev…