Elaeocarpus Alkaloids. V. The Alkaloids of Elaeocarpus kaniensis

1972 ◽  
Vol 25 (4) ◽  
pp. 817 ◽  
Author(s):  
N Hart ◽  
S Johns ◽  
J Lamberton
Keyword(s):  
Catalytic Hydrogenation ◽  
Complex Mixture ◽  
Platinum Oxide ◽  
Major Product ◽  
Spectroscopic Methods ◽  
Spectroscopic Evidence ◽  
D 12 ◽  
Absolute Stereochemistry ◽  
Leaf Alkaloids

The leaf alkaloids of Elaeocarpus kalziensis Schltr. are a complex mixture, from which eight new alkaloids have been separated. Spectroscopic evidence has shown that these alkaloids are a closely interrelated group of indolizidines and structures have been assigned to elaeokanine A (1), elaeokanine B (8), elaeokanine C (10), elaeokanine D (12), elaeokanine E (17), and elaeokanidine A (18), Elaeokanidine B and elaeokanidine C are stereoisomers of elaeokanidine A, but the spectroscopic evidence is insufficient for the structures of these alkaloids to be assigned unequivocally. The assigned structures in all cases indicate relative and not absolute stereochemistry. The structures established for elaeokanine A, elaeokanine B, and elaeokanine C by spectroscopic methods have been confirmed by synthesis. Catalytic hydrogenation of synthetic 8-n-butyryl-7-oxoindolizidine (22) over platinum oxide in ethanol afforded (�)elaeokanine C in 30% yield. Under these hydrogenation conditions a major product was 8-n-butyryl-7-oxo-8,9-dehydroindolizidine (23) formed by loss of hydrogen from (22).

scholarly journals The chemical behavior of terminally tert-butylated polyolefins

2015 ◽  
Vol 11 ◽  
pp. 1246-1258
Author(s):  
Dagmar Klein ◽  
Henning Hopf ◽  
Peter G Jones ◽  
Ina Dix ◽  
Ralf Hänel
Keyword(s):  
Catalytic Hydrogenation ◽  
Spectroscopic Data ◽  
Model Compound ◽  
Saturated Hydrocarbon ◽  
Complex Mixture ◽  
Diels Alder ◽  
Equivalent Amount ◽  
Chemical Behavior ◽  
Rearrangement Product ◽  
Olefinic Carbon

The chemical behavior of various oligoenes 2 has been studied. The catalytic hydrogenation of diene 3 yielded monoene 4. Triene 7 was hydrogenated to diene 8, monoene 9 and saturated hydrocarbon 10. Bromine addition to 3 and 7 yielded the dibromides 17 and 18, respectively, i.e., the oligoene system has been attacked at its terminal olefinic carbon atoms. Analogously, the higher vinylogs 19 and 20 yielded the 1,8- and 1,10-bromine adduts 23 and 24, respectively, when less than 1 equivalent of bromine was employed. Treatment of tetraene 19 with excess bromine provided tetrabromide 25. In epoxidation reactions, both with meta-chloroperbenzoic acid (MCPBA) and dimethyldioxirane (DMDO) two model oligoenes were studied: triene 7 and tetraene 19. Whereas 7 furnished the rearrangement product 31 with MCPBA, it yielded the symmetrical epoxide 32 with DMDO. Analogously, 19 was converted to mono-epoxide 33 with MCPBA and to 34 with DMDO. Diels–Alder addition of 7 with N-phenyltriazolinedione (PTAD) did not take place. Extension of the conjugated π-system to the next higher vinylog, 19, caused NPTD-addition to the symmetrical adduct 37 in good yield. Comparable results were observed on adding NPTD (equivalent amount) to pentaene 20 and hexaene 21. Using 36 in excess provided the 2:1-adduct 40 from 21 and led to a complex mixture of adducts from heptaene 22. With tetracyanoethylene (TCNE) as the dienophile, tetraolefin 19 yielded the symmetrical adduct 43, although the reaction temperature had to be increased. Pentaene 20 and hexaene 21 led to corresponding results, adducts 44 and 45 being produced in acceptable yields. With nonaene 42 and TCNE the 2:1-adduct 48 was generated according to its spectroscopic data. Exploratory photochemical studies were carried out with tetraene 19 as the model compound. On irradiation this reacted with oxygen to the stable endo-peroxide 52.

Antimicrobial and Antioxidant Isoflavonoid Derivatives from the Roots of Amphimas pterocarpoides

2013 ◽  
Vol 68 (8) ◽  
pp. 931-938 ◽  
Author(s):  
Edwige P. Fodja Saah ◽  
Valerie Tedjon Sielinou ◽  
Victor Kuete ◽  
Stephen T. Lacmata ◽  
Augustin E. Nkengfack
Keyword(s):  
Antioxidant Properties ◽  
2D Nmr ◽  
Antimicrobial Activities ◽  
Spectroscopic Methods ◽  
Chemical Transformations ◽  
Spectroscopic Evidence ◽  
Wide Range ◽  
Bacteria And Fungi

A new bis-isoflavone derivative, named amphiisoflavone (1), was isolated from the roots of Amphimas pterocarpoides, together with three known isoflavones, namely 8-methoxyisoformononetin (2), 6-methoxyisoformononetin (3) and isoformononetin (4). Chemical transformations carried out on compound 3 led to two new derivatives, 4´-acetoxy-6,7-dimethylisoflavone (3a) and 4´-O-prenyl- 6,7-dimethylisoflavone (3p), along with a known compound, 4´,6,7-trimethoxyisoflavone (3m). The structures of all compounds were elucidated from spectroscopic evidence, in particular by 1D and 2D NMR spectroscopic methods. These compounds were evaluated for their antioxidant properties and for their antimicrobial activities against a wide range of bacteria and fungi.

The chemical constituents of Australian Flindersia species. XIX. Triterpenoids from the leaves of F. bourjotiana F. Muell

1966 ◽  
Vol 19 (3) ◽  
pp. 455 ◽  
Author(s):  
GJW Breen ◽  
E Ritchie ◽  
WTL Sidwell ◽  
WC Taylor
Keyword(s):  
Chemical Constituents ◽  
Chemical Degradation ◽  
Spectroscopic Methods ◽  
The Absolute ◽  
Absolute Stereochemistry

From the leaves of Flindersia bourjotinna F. Muell. there were isolated sitosterol, triacontanol, lupeol, germanicol, germanicone, and four new triterpenoids, the bourjotinolones A, B, and C, and bourjotone. By chemical degradation and spectroscopic methods, the structures of these substances were shown to be 21,24-epoxy-23,25-dihydroxytirucall-7-en-3one, 23,24-dihydroxytirucalla-7,25-dien- 3-one, 25-chloro-23,24-dihydroxytirucall-7-en-3-one, and 25,26,27-trisnortirucall-7- ene-3,23-dione, respectively. Bourjotinolone C is almost certainly an artefact but bourjotinolone B and bourjotone are less likely to be. From biogenetic and N.M.R. spectral considerations, the absolute stereochemistry of the new triterpenes may be deduced.

A facile synthesis of methyl 3,6-dideoxy-α-L-xylo-hexopyranoside (colitose)

1978 ◽  
Vol 56 (20) ◽  
pp. 2686-2690 ◽  
Author(s):  
David R. Bundle ◽  
Staffan Josephson
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
Catalytic Hydrogenation ◽  
Major Product ◽  
Facile Synthesis ◽  
The Absolute

Methyl 3,6-dideoxy-α-L-xylo-hexopyranoside (7) bas been synthesised in four steps from methyl α-L-fucopyranoside. The intermediate methyl 3,4-O-benzylidene-α-L-fucopyranoside was separated into the S (1a) and R (1b) diastereoisomers and the absolute configuration established by proton and carbon-13 nmr spectroscopy. Under the conditions of the Hanessian–Hullar reaction methyl 4-O-benzoyl-3-bromo-3,6-dideoxy-α-L-gulopyranoside was the major product. Each diastereoisomer 1a or 1b gave identical products and product ratios; the stereochemistry and relative proportions of these products were determined by proton and carbon-13 nmr. The synthesis of ascarylose from methyl α-L-rhamnopyranoside by an analogous route is also reported. The bromo deoxy intermediates were reduced to the dideoxy sugars by catalytic hydrogenation with palladium.

Halogenated Metabolites of the Red Alga Plocamium cruciferum

1979 ◽  
Vol 32 (11) ◽  
pp. 2545 ◽  
Author(s):  
P Bates ◽  
JW Blunt ◽  
MP Hartshorn ◽  
AJ Jones ◽  
MHG Munro ◽  
...  
Keyword(s):  
Fatty Acid Methyl Esters ◽  
Methyl Esters ◽  
Complex Mixture ◽  
Red Alga ◽  
Organic Extract ◽  
X Ray ◽  
X Ray Crystallography ◽  
Halogenated Metabolites ◽  
Acid Methyl ◽  
Absolute Stereochemistry

The organic extract of Plocamium cruciferum gave a complex mixture of fatty acid methyl esters (26%), the tribromotrichloroalkene (12),(7%), n-heptadecane (0.4%), phytol(12%) and the unusual hydroxy bisnor-monoterpene (15) (43%). The absolute stereochemistry of the polyhalogenated alkene (12) was established by X-ray crystallography.

Photodecarbonylation of chiral cyclobutanones

1997 ◽  
Vol 75 (5) ◽  
pp. 518-522 ◽  
Author(s):  
Jailall Ramnauth ◽  
Edward Lee-Ruff
Keyword(s):  
Crystal Structure ◽  
Triplet State ◽  
Structure Determination ◽  
Major Product ◽  
X Ray ◽  
Principal Product ◽  
Independent Synthesis ◽  
Optically Pure ◽  
Absolute Stereochemistry

Triplet photosensitized irradiation of 2(S),3(R)-bis[(benzoyloxy)methyl]cyclobutanone gave optically pure (−)E-1(S),2(S)-bis(benzoyloxymethyl)cyclopropane as a major product in the nonpolar fraction along with its stereoisomer and cycloelimination products. The absolute stereochemistry of the chiral cyclopropane was established by independent synthesis and X-ray crystal structure determination of a synthetic precursor. The distribution of decarbonylation and cycloelimination products was inversely dependent on the concentration of the substrate. Irradiation of the same ketone in tetrahydrofuran or benzene gave mostly cycloelimination products. Addition of Michler's ketone increased the ratio of photodecarbonylation, suggesting a triplet state pathway for this process. This was corroborated by the addition of dicyanoethylene, which showed significant quenching of photodecarbonylation. Irradiation of 2(S)-[(benzoyloxy)methyl]cyclobutane in acetone gave the corresponding cyclopropane as the principal product. Keywords: photodecarbonylation, chiral cyclopropanes, cyclobutanones, triplet sensitization.

Time-resolved spectroscopic studies of the photochemistry of some diphenylgermylene (Ph2Ge:) precursors

2005 ◽  
Vol 83 (9) ◽  
pp. 1324-1338 ◽  
Author(s):  
Cameron R Harrington ◽  
William J Leigh ◽  
Bryan K Chan ◽  
Peter P Gaspar ◽  
Dong Zhou
Keyword(s):  
Steady State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Spectral Characteristics ◽  
Complex Mixture ◽  
Laser Flash ◽  
Spectroscopic Studies ◽  
Major Product ◽  
High Yield ◽  
Time Resolved

The photochemistry of diphenylbis(trimethylsilyl)germane (2a) and 1,4-dihydro-5-methyl-1,2,3,4,9,9-hexaphenyl-1,4-germanonaphthalene (11) has been studied in solution by steady-state and laser flash photolysis methods with a view to detecting the transient germylene derivative diphenylgermylene (Ph2Ge), which has previously been shown to be the major product of photolysis of 2a and a closely related derivative of 11. Steady-state trapping experiments confirm the formation of Ph2Ge as the major germanium containing primary product in both cases; with 2a, the results indicate that other transient species are also formed in minor yields, including phenyl(trimethylsilyl)germylene (Ph(TMS)Ge, ca. 6%) and diphenyl(trimethylsilyl)germyl radicals (Ph2(TMS)Ge, ≥15%). Laser flash photolysis of 2a in deoxy genated hexane solution yields a complex mixture of overlapping transient absorptions, which is shown to be comprised of Ph2Ge, tetraphenyldigermene (15) and its oligomerization products, and another species with spectral characteristics similar to the Ph2(TMS)Ge radical. The latter has been independently generated by hydrogen abstraction from diphenyl(trimethylsilyl)germane by tert-butoxyl radicals. Compound 11 extrudes Ph2Ge more cleanly and efficiently upon photolysis in solution, yet laser flash photolysis affords excited triplet and triplet-derived species as the only detectable transient products; interpretation of the results for this compound is made difficult by its slow thermal decomposition to 5-methyl-1,2,3,4-tetraphenylnaphthalene. It is concluded that in spite of the fact that both 2a and 11 afford Ph2Ge in high yield upon photolysis, they are poor precursors for study of the species in solution by time-resolved UV–vis methods, owing to the formation of other, more strongly absorbing transient products than Ph2Ge, whose lowest energy absorption is characteristically weak.Key words: germylene, germyl radical, flash photolysis, disilylgermane, photochemistry.

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