Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 46
Filter
Add more filters










Publication year range
1.
J Am Chem Soc ; 123(37): 9021-32, 2001 Sep 19.
Article in English | MEDLINE | ID: mdl-11552810

ABSTRACT

An enantioselective synthetic route to the thermodynamically most stable diastereomer of the structure assigned to sclerophytin A (5) has been realized. The required tricyclic ketone 33 was prepared by sequential Tebbe-Claisen rearrangement of lactones 29 and 30, which originated from the Diels-Alder cycloaddition of Danishefsky's diene to (5S)-5-(d-menthyloxy)-2(5H)-furanone (14). An allyl and a cyano group were introduced into the resulting adduct by means of stereocontrolled allylindation under aqueous Barbier-like conditions and by way of cyanotrimethylsilane, respectively. Following stereocontrolled nucleophilic addition of a methyl group to 33, ring A was elaborated by formation of the silyl enol ether, ytterbium triflate-catalyzed condensation with formaldehyde, O-silylation, and Cu(I)-promoted 1,4-addition of isopropylmagnesium chloride. The superfluous ketone carbonyl was subsequently removed and the second ether bridge introduced by means of oxymercuration chemistry. Only then was the exocyclic methylene group unmasked via elimination. An alternative approach to the alpha-carbinol diastereomer proceeds by initial alpha-oxygenation of 37 and ensuing 1,2-carbonyl transposition. Neither this series of steps nor the Wittig olefination to follow induced epimerization at C10. Through deployment of oxymercuration chemistry, it was again possible to elaborate the dual oxygen-bridge network of the target ring system. Oxidation of the organomercurial products with O(2) in the presence of sodium borohydride furnished 72, which was readily separated from its isomer 73 after oxidation to 61. Hydride attack on this ketone proceeded with high selectivity from the beta-direction to deliver (-)-60. Comparison of the high-field (1)H and (13)C NMR properties and polarity of synthetic 5 with natural material required that structural revision be made. Following a complete spectral reassessment of the structural assignments to many sclerophytin diterpenes, a general approach to sclerophytin A, three diastereomers thereof, and of sclerophytin B was devised. The presence of two oxygen bridges as originally formulated was thereby ruled out, and absolute configurations were properly determined. Key elements of the strategy include dihydroxylation of a medium-ring double bond, oxidation of the secondary hydroxyl in the two resulting diols, unmasking of an exocyclic methylene group at C-11, and stereocontrolled 1,2-reduction of the alpha-hydroxy ketone functionality made available earlier.


Subject(s)
Bridged-Ring Compounds/chemical synthesis , Furans/chemical synthesis , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/toxicity , Bridged-Ring Compounds/toxicity , Furans/toxicity , Molecular Conformation , Nuclear Magnetic Resonance, Biomolecular , Stereoisomerism
2.
Org Lett ; 2(13): 1879-82, 2000 Jun 29.
Article in English | MEDLINE | ID: mdl-10891181

ABSTRACT

[structure: see text] Spectroscopic reevaluation of sclerophytin B, the acetate of sclerophytin A, has demonstrated unequivocally that these coral metabolites are not composed of two ether bridges.


Subject(s)
Bridged-Ring Compounds/chemistry , Furans/chemistry , Molecular Structure , Magnetic Resonance Spectroscopy
3.
J Nat Prod ; 62(10): 1410-4, 1999 Oct.
Article in English | MEDLINE | ID: mdl-10543903

ABSTRACT

Two benzyltetrahydroisoquinoline-protoberberine dimers, longiberine (1) and O-methyllongiberine (2), were isolated from the roots of Thalictrum longistylum and represent a new class of dimeric alkaloids. The structure of longiberine (1) was established by spectral and chemical methods. Reductive cleavage of O-ethyllongiberine (4) with Na/liquid NH(3) yielded (+)-(S)-N-methylcoclaurine (5), which determined one-half of the dimer, and 1D and 2D NMR studies arranged the substituents on the protoberberine nucleus. Chemical conversion of thalidezine (6) to 1 via the O-acetyl N,N-didemethyl derivative 9, which was methylenated in the Mannich reaction and N-methylated by the Eschweiler-Clarke procedure, established the second asymmetric center as S and confirmed the ring size and the order of the substituents for 1. Methylation of 1 with diazomethane formed the O-methyl derivative 2, identical with the natural product.


Subject(s)
Alkaloids/isolation & purification , Plants/chemistry , Alkaloids/chemistry , Magnetic Resonance Spectroscopy , Mass Spectrometry/methods , Molecular Structure
4.
J Nat Prod ; 62(6): 803-10, 1999 Jun.
Article in English | MEDLINE | ID: mdl-10395492

ABSTRACT

Four dimeric alkaloids (1-4) containing an aporphine unit and representing unique structural features were obtained from Thalictrum fauriei and were characterized by spectral and chemical methods. Fauripavine (1), with a munitagine pavine unit, is the first such dimer with an aporphine C-1 diphenyl ether connection; although fauridine (2), also the first of its class, has codamine, a benzyl tetrahydroisoquinoline, linked at the same position. Faurithaline (3) and its 3-methoxy analogue 4, both with reticuline, a benzyl tetrahydroisoquinoline as the second unit, are the first dimers with the diphenyl ether linkage at C-8 of an aporphine oxygenated at C-10 and C-11. Oconovine (8) was converted to 8-hydroxy-O-methyloconovine (12) to determine the effect of oxygenation at C-8 on the proton chemical shift of the C-7 hydrogens in a study to support the C-8 ether linkage of alkaloids 3 and 4. All the alkaloids have the S-configuration at their asymmetric centers as established from their CD spectra when compared with those of model compounds.


Subject(s)
Alkaloids/chemistry , Aporphines/chemistry , Plants, Medicinal/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , Plant Extracts/chemistry , Spectrophotometry, Ultraviolet , Stereoisomerism
5.
J Nat Prod ; 59(8): 738-43, 1996 Aug.
Article in English | MEDLINE | ID: mdl-8792620

ABSTRACT

Two new benzyl-aporphine dimers, faurine (1) and its O-methyl ether (2), were obtained from Thalictrum fauriei and their structures determined by spectral and chemical methods. Faurine (1), the first dimer with the diphenyl ether connection at C-1 of the aporphine, did not undergo a Hofmann degradation, yet formed a chiral phenanthrene product (6) with cyanogen bromide. Two nondimeric chiral aporphine alkaloids, O-acetylisocorydine and O-methylisocorydine, gave the corresponding phenanthrene products 7 and 8, respectively, under the same conditions, but only compound 7 was optically active.


Subject(s)
Antioxidants/isolation & purification , Aporphines/isolation & purification , Lipoxygenase Inhibitors/isolation & purification , Antioxidants/chemistry , Aporphines/chemistry , Benzyl Alcohol , Benzyl Alcohols/chemistry , Chromatography, Gel , Cyanogen Bromide/chemistry , Lipoxygenase Inhibitors/chemistry , Magnetic Resonance Spectroscopy , Phenanthrenes/chemistry , Spectrophotometry, Ultraviolet , Stereoisomerism
6.
J Nat Prod ; 59(5): 463-8, 1996 May.
Article in English | MEDLINE | ID: mdl-8778236

ABSTRACT

Five cis-clerodane lactones, amphiacrolides J (1), K (2), L (3), M (4), and N (5), were isolated from the aerial parts of the composite Amphiachyris dracunculoides. The first four are new compounds, and the fifth was previously reported from another source. All compounds were assigned stereochemical structures based upon spectral and chemical data, including high-field 1D and 2D NMR for complete assignment of 1H- and 13C-NMR spectra. Amphiacrolide N (5) was converted to amphiacrolide J (1) by treatment with MeOH and TFA, and amphiacrolide L (3) was prepared from amphiacrolide B (9) by CrO3 oxidation to ketone 10 followed by its reduction with NaBH4.


Subject(s)
Diterpenes/isolation & purification , Lactones/isolation & purification , Plants/chemistry , Diterpenes/chemistry , Lactones/chemistry , Magnetic Resonance Spectroscopy , United States
7.
J Nat Prod ; 58(9): 1407-18, 1995 Sep.
Article in English | MEDLINE | ID: mdl-7494148

ABSTRACT

Two new 9,13-diepoxy labdane diterpenes, amoenolide K [1] and its 19-acetate [2], were isolated from the aerial parts of the composite Amphiachyris amoena and their structures were established by spectral methods, especially high-field nmr spectroscopy. Amoenolide K [1] was prepared from amoenolide A [3] by singlet oxygen addition via the ene reaction. A study was made of the ene reaction products with amoenolide K triacetate [5] which showed them to arise from stereospecific oxygen addition to the 8,9-double bond, with the exception of the sterically hindered beta-side at C-9, for which no products were isolated.


Subject(s)
4-Butyrolactone/analogs & derivatives , Diterpenes/isolation & purification , Naphthols/isolation & purification , Plants/chemistry , Spiro Compounds/isolation & purification , 4-Butyrolactone/chemistry , 4-Butyrolactone/isolation & purification , Diterpenes/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , Naphthols/chemistry , Oxidation-Reduction , Peroxides/chemistry , Peroxides/isolation & purification , Photochemistry , Spiro Compounds/chemistry
8.
J Nat Prod ; 58(2): 209-16, 1995 Feb.
Article in English | MEDLINE | ID: mdl-7769389

ABSTRACT

Two new modified labdane diterpenes, amoenolide L [1] and amoenolide M [2] with a 3-(p-hydroxyphenyl)propionate ester unit, were isolated from the above-ground parts of Amphiachyris amoena. Their stereochemical structures were assigned by spectral methods including uv, ir, fabms, and one- and two-dimensional high field 1H- and 13C-nmr. Properties of their acetate derivatives are also recorded.


Subject(s)
Diterpenes/chemistry , Naphthols/chemistry , Plants, Medicinal/chemistry , Diterpenes/isolation & purification , Magnetic Resonance Spectroscopy , Naphthols/isolation & purification , Spectrometry, Mass, Fast Atom Bombardment , Spectrophotometry, Infrared , Spectrophotometry, Ultraviolet
9.
J Nat Prod ; 58(1): 82-92, 1995 Jan.
Article in English | MEDLINE | ID: mdl-7760081

ABSTRACT

Five new labdane diterpene glycosides, amoenolide A 19-beta-D-glucopyranoside [1], and amoenolides E [3], F [4], G [6], and H [8] were isolated from the above-ground parts of Amphiachyris amoena. Amoenolide F is a 19-beta-D-glucopyranoside, while the others are 6-alpha-L-arabinopyranosides. Their structures were established by chemical and spectral methods, especially high-field nmr techniques, and complete 1H- and 13C-nmr assignments are given.


Subject(s)
Diterpenes/isolation & purification , Glycosides/isolation & purification , Plants/chemistry , Carbohydrate Sequence , Chromatography, Liquid , Diterpenes/chemistry , Glycosides/chemistry , Molecular Sequence Data , Spectrum Analysis
10.
J Nat Prod ; 57(10): 1382-90, 1994 Oct.
Article in English | MEDLINE | ID: mdl-7807123

ABSTRACT

Five new labdane diterpenes, amoenolide A 19-aldehyde [2], and amoenolides B [3], C [4], D [5], and J [6] were isolated from the above-ground parts of Amphiachyris amoena, and their structures determined by spectral methods, in particular high-field nmr, and selective chemical studies. Amoenolide J [6] had its carbon skeleton established by the INADEQUATE 13C-13C connectivity nmr experiment.


Subject(s)
Diterpenes/isolation & purification , Plants/chemistry , 4-Butyrolactone/analogs & derivatives , 4-Butyrolactone/chemistry , 4-Butyrolactone/isolation & purification , Diterpenes/chemistry , Magnetic Resonance Spectroscopy , Naphthols/chemistry , Naphthols/isolation & purification
11.
J Nat Prod ; 57(6): 767-75, 1994 Jun.
Article in English | MEDLINE | ID: mdl-7931365

ABSTRACT

Four new labdane diterpenes, amoenolide A [1] and its 19-acetate [2], 6-acetate [3], and 6,19-diacetate [4], were isolated from the above-ground parts of Amphiachyris amoena and their structures established by spectral and chemical methods. High-field 1H- and 13C-nmr assignments were made for each compound using 1D and 2D nmr techniques including 1H single-frequency spin-coupling and nOe difference experiments, one-bond and long-range carbon-hydrogen correlations, and the INADEQUATE carbon-carbon connectivity experiment. The absolute stereochemistry was established by the Horeau partial-resolution chemical method with amoenolide A and racemic 2-phenylbutyric anhydride, and by the cd exciton splitting physical method on the synthetic amoenolide A 2-acetate 6,19-dibenzoate [9].


Subject(s)
4-Butyrolactone/analogs & derivatives , Diterpenes/chemistry , Naphthols/chemistry , Plants, Medicinal/chemistry , 4-Butyrolactone/chemistry , 4-Butyrolactone/isolation & purification , Acetylation , Diterpenes/isolation & purification , Magnetic Resonance Spectroscopy , Molecular Conformation , Naphthols/isolation & purification
12.
J Nat Prod ; 57(6): 776-83, 1994 Jun.
Article in English | MEDLINE | ID: mdl-7931366

ABSTRACT

Two carterochaetols, chlorosilphanol A and silphanepoxol, isolated from the leaves of Silphium perfoliatum were assigned structures 1 and 3, respectively, from spectral studies and with absolute stereochemistry established by X-ray crystallography of 1. Complete 1H- and 13C-nmr assignments for the parent compounds and their acetates 2 and 4 were made at high-field using 1D and 2D methods, and chlorosilphanol A was chemically converted via its acetate to silphanepoxol. Revision of structure for related carterochaetols in the literature is required, in particular with respect to the stereochemistry at C-12 and that of the side-chain.


Subject(s)
Chlorohydrins/isolation & purification , Diterpenes/isolation & purification , Epoxy Compounds/isolation & purification , Furans/isolation & purification , Plants, Medicinal/chemistry , Chlorohydrins/chemistry , Crystallography, X-Ray , Diterpenes/chemistry , Epoxy Compounds/chemistry , Furans/chemistry , Magnetic Resonance Spectroscopy , Molecular Conformation
13.
J Nat Prod ; 53(5): 1312-26, 1990.
Article in English | MEDLINE | ID: mdl-2292688

ABSTRACT

Four cis-ent-neoclerodane lactones, amphiacrolide A [2], amphiacrolide B [3], amphiacrolide C [4] and amphiacrolide D [5] were isolated from the aerial parts of Amphiachyris dracunculoides, and their structures established by physical and chemical methods. High field 1H- and 13C-nmr assignments were made for each compound and some of their derivatives by using one- and two-dimensional nmr techniques including nOe difference, COSY, and CH-correlation of one-bond and multiple bond (COLOC) relationships. A chemical correlation of the amphiacrolides to gutierolide [1], a compound with absolute stereochemistry determined by X-ray analysis, established the stereochemistry for the group. Consequently, a compound having reported properties identical with amphiacrolide D [5] must have its structure revised to contain the beta-faced epoxide. Amphiacrolide A [2] had not been reported previously.


Subject(s)
Diterpenes/isolation & purification , Lactones/isolation & purification , Plants, Medicinal/analysis , Diterpenes/chemistry , Lactones/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure
14.
J Nat Prod ; 53(1): 131-7, 1990.
Article in English | MEDLINE | ID: mdl-2348198

ABSTRACT

Grayanotoxins I [2], IV [3], and XIV [4] were isolated from Kalmia angustifolia var. caroliniana, a North American member of the Ericaceae. Their structures were established from physical and spectral data (mp, ir, [alpha]D, uv, cd, ms, 1H and 13C nmr). High field 1H- and 13C-nmr assignments were made for each compound using 1D and 2D nmr techniques including extensive 1H single-frequency spin-decoupling and nOe difference experiments, one-bond and long-range (COLOC) carbon-hydrogen correlations, and the INADEQUATE carbon-carbon correlation experiment. This is the first report of the presence of grayanotoxins IV and XIV in this source, of complete high field (500 MHz) 1H-nmr assignments for any grayanoid, and of 13C-nmr assignments for grayanotoxins IV and XIV. For grayanotoxin I, ambiguities in the literature 13C-nmr assignments have been removed by definitive assignments made through the use of the INADEQUATE experiment.


Subject(s)
Diterpenes/isolation & purification , Plants/analysis , Toxins, Biological/isolation & purification , Diterpenes/toxicity , Magnetic Resonance Spectroscopy , Molecular Structure
15.
Inflammation ; 13(2): 175-84, 1989 Apr.
Article in English | MEDLINE | ID: mdl-2503443

ABSTRACT

Venom from the tropical ant, Pseudomyrmex triplarinus, has activity against rheumatoid arthritis. Since platelets are involved in inflammatory responses, they were employed to study the effects of venom on prostaglandin-dependent human platelet aggregation and secretion. The assay is very sensitive and uses microliter volumes, which makes it useful as a screen during isolation and characterization of venom components. Whole venom inhibited arachidonic acid- and U46619-induced platelet aggregation with IC50s of 45 and 39 micrograms/ml, respectively. This suggested that venom prevented the action of prostaglandins. Pure venom was fractionated by gel filtration and at least three materials with antiplatelet activity were detected. The smallest component (factor F) was most active and was purified by additional molecular filtration and characterized by UV absorbance, thin-layer chromatography, nuclear magnetic resonance spectra, and activity to platelets. Factor F was identified as adenosine, which is known to stimulate platelet adenylate cyclase and has not been previously reported to be a component of insect venom.


Subject(s)
Adenosine/pharmacology , Ant Venoms/pharmacology , Arthropod Venoms/pharmacology , Blood Platelets/physiology , Platelet Aggregation , 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid , Adenosine/isolation & purification , Animals , Ant Venoms/analysis , Arachidonic Acid , Arachidonic Acids/pharmacology , Blood Platelets/drug effects , Chromatography, Gel , Humans , Magnetic Resonance Spectroscopy , Platelet Aggregation/drug effects , Platelet Aggregation Inhibitors/analysis , Platelet Aggregation Inhibitors/pharmacology , Prostaglandin Endoperoxides, Synthetic/pharmacology , Serotonin/metabolism
17.
J Nat Prod ; 42(1): 126-128, 1979 Jan.
Article in English | MEDLINE | ID: mdl-27657655
18.
Lloydia ; 41(3): 257-70, 1978.
Article in English | MEDLINE | ID: mdl-672463

ABSTRACT

The roots of T. minus race B have yielded 9 alkaloids, thalirabine (1), thaliracebine (13), thalfine (19), thalfinine (20), thalrugosaminine (22), thalidasine (13), obaberine (24), thaliglucinone (25) and (S)-reticuline (26). The first two, possessing marked hypotensive activity, were assigned complete structures by physical and chemical methods. Thalfine (19) was given S-configuration at its one asymmetric center and was converted to thalfinine (20) and epithalfinine (21), thus the stereochemistry was established at one of the two optically active positions. The other alkaloids were identified by direct comparison with known samples. Antimicrobial testing showed thalirabine, thaliracebine, thalfine, and thalfinine to be active against Mycobacterium smegmatis.


Subject(s)
Alkaloids , Blood Pressure/drug effects , Plants, Medicinal , Alkaloids/isolation & purification , Alkaloids/pharmacology , Animals , Bacteria/drug effects , Chemical Phenomena , Chemistry , Dogs , Plants, Medicinal/analysis , Rabbits
19.
Lloydia ; 41(3): 271-6, 1978.
Article in English | MEDLINE | ID: mdl-672464

ABSTRACT

The roots of T. minus race B have yielded, in addition to adiantifoline (1) previously isolated from this source, two new related alkaloids, thaliadine (2) and thaliadanine (5). Both were assigned complete structures by spectral methods and by chemical interconversion to adiantifoline or its product. O-Desmethyladiantifoline should have structure 14, rather than the previously reported 5. All three isolated alkaloids show hypotensive activity in rabbits, and thaliadanine (5) has antimicrobial activity against Mycobacterium smegmatis.


Subject(s)
Alkaloids , Plants, Medicinal , Alkaloids/isolation & purification , Alkaloids/pharmacology , Animals , Aporphines/isolation & purification , Aporphines/pharmacology , Bacteria/drug effects , Blood Pressure/drug effects , Chemical Phenomena , Chemistry , Isoquinolines/isolation & purification , Isoquinolines/pharmacology , Plants, Medicinal/analysis , Rabbits
20.
Lloydia ; 40(5): 508-14, 1977.
Article in English | MEDLINE | ID: mdl-144834

ABSTRACT

Sixteen alkaloids were characterized from Thalictrum revolutum DC., namely; thalidasine, O-methylthalmethine, O-methylthalicberine, thalrugosaminine, thalicarpine, thalmelatine, pennsylvanine, palmatine, berberine, thalifendine, columbamine, jatrorrhizine, deoxythalidastine, thalphenine and magnoflorine. The structure of thairugosaminine (1) a bisbenzylisoquinoline type which was previously proposed on partial data was completely established, including the absolute configuration as S,S. Thalphenine, thalidasine, O-methylthalicberine, thalicarpine, thalrugosaminine and thaliglucinone were found to possess hypotensive activity in rabbits. Thalrugosaminine, thalicarpine, thalmelatine, O-methylthalmethine, pennsylvanine and thalphenine were found to be active against Mycobacterium smegmatis.


Subject(s)
Alkaloids/isolation & purification , Anti-Bacterial Agents , Antihypertensive Agents , Plants, Medicinal/analysis , Animals , Antifungal Agents , Aporphines/isolation & purification , Berberine/isolation & purification , Chemical Phenomena , Chemistry , Mycobacterium/drug effects , Rabbits
SELECTION OF CITATIONS
SEARCH DETAIL
...