- SEVERAL NEW CEMBRANOID DITERPENES FROM THREE SOFT CORALS OF THE RED SEA
-
Eight new diterpenoids have been isolated from three soft corals, Alcyonium utinomii, Lobophytum pauciflorum and Lobophytum crassum.The compounds were shown to be: 1,3,7,10-cembratetraen-12-ol (4); 1,3,6,11-cembratetraen-8-ol (5); 1,3,7,12(20)-cembratetraen-11-ol (6a); 2,7,11-cembratetraen-4,15-diol (8); 3,7,10-cembratrien-12,15-diol (9); and the lobolide related deacetyldeepoxy lobolide (15); deepoxy lobolide (16) and deacetyl-13-hydroxy lobolide (17), by spectral data and chemical studies (mainly ozonolysis).
- Kinamoni, Zvia,Groweiss, Amiram,Carmely, Shmuel,Kashman, Yoel,Loya, Yossi
-
-
Read Online
- Biotransformation of cycloalkanediones by Caragana chamlagu
-
The biotransformation of alkylcycloalkanediones using suspension plant cultured-cells of Caragana chamlagu gave oxo carboxylic acids by oxidative cleavage. 5,6-Dioxoheptanoic acid was obtained in high yield (95%) in a short time (7 h) from 2-methyl-1,3-cyclohexanedione. However, 1,2- and 1,4-cycloalkanediones were reduced stereoselectively and trans-1,2-cyclohexanediol and trans-1,4-cyclohexanediol were obtained, respectively. The mechanism of the oxidative cleavage of alkylcycloalkanediones is also discussed.
- Chai, Wen,Sakamaki, Hiroshi,Kitanaka, Susumu,Horiuchi, C. Akira
-
-
Read Online
- KRAS G12C Inhibitor and application thereof in medicine
-
The present invention relates to a novel compound having KRAS G12C modulating activity. The invention also relates to a preparation method of the compound and a pharmaceutical composition containing the compound.
- -
-
Paragraph 0186-0187; 0194-0195
(2021/02/24)
-
- Biogenesis-Guided Synthesis and Structural Revision of Sarocladione Enabled by Ruthenium-Catalyzed Endoperoxide Fragmentation
-
Sarocladione is the first 5,10:8,9-diseco-steroid with a 14-membered macrocyclic diketone framework to have been isolated from a natural source. Herein we report a biomimetic synthesis of sarocladione in only two or seven steps from inexpensive, commercially available ergosterol. The key feature of this synthesis was a novel ruthenium-catalyzed endoperoxide fragmentation, which transformed various saturated endoperoxides into olefinic diketones by cleavage of two C?C bonds. This synthesis allowed us to unambiguously determine the structure of sarocladione and provided experimental support for its revised biosynthetic origin. This work also vividly demonstrates that consideration of the biogenesis is a powerful tool for elucidating the structures of natural products.
- Ning, Yuhan,Tian, Hailong,Gui, Jinghan
-
supporting information
p. 11222 - 11226
(2021/04/19)
-
- Ozonolysis of bicyclic 1,2-dioxines: Initial scope and mechanistic insights
-
The ozonolysis of bicyclic 1,2-dioxines was investigated using a variety of 1,4-disubstituted 1,2-dioxines along with a 1,3-dialkyl and steroidal example, with yields ranging from moderate to excellent. Two different pathways were observed upon reaction of the 1,4-disubstituted 1,2-dioxines with ozone; one pathway saw the "expected" results, that is, cleavage of the olefinic moiety with generation of 1,4-dicarbonyl 1,2-dioxines, while the other pathway revealed a previously unobserved rearrangement involving cleavage of the peroxide linkage along with loss of either CO or CO2. Several unsymmetrical ozonolyses were also performed to further investigate the origins of this rearrangement, and initial mechanistic insights into the fragmentation pathways are discussed.
- Cain, Nicole M.,Tiekink, Edward R. T.,Taylor, Dennis K.
-
p. 3808 - 3819
(2012/06/29)
-
- Synthesis and chemistry of 2,3-dioxabicyclo[2.2.2]octane-5,6-diols
-
(Chemical Equation Presented) 1,4-Disubstituted 2,3-dioxabicyclo[2.2.2]oct- 5-enes were dihydroxylated with osmium tetroxide to yield diols anti to the peroxide linkage in a highly selective manner. Reduction of the peroxide bond furnished cyclohexane-1,2,3,4-tetraols with toxocarol relative stereochemistry in excellent yield. This new methodology was employed to synthesize the natural product (1S,2R,3S,4R,5R)-2-methyl-5-(propan-2-yl)cyclohexane-1,2,3,4-tetrol (1) in a short sequence from (R)-α-phellandrene. Moreover, during the study of the chemistry of 2,3-dioxabicyclo[2.2.2]octane-5,6-diols a hitherto unknown rearrangement was discovered which has wide applicability for the synthesis of 1,4-dicarbonyls, including optically enriched synthons. A broad range of mechanistic investigations applicable to this rearrangement are also reported.
- Valente, Peter,Avery, Thomas D.,Taylor, Dennis K.,Tiekink, Edward R. T.
-
experimental part
p. 274 - 282
(2009/04/10)
-
- Synthesis of furans, pyrroles and pyridazines by a ruthenium-catalysed isomerisation of alkynediols and in situ cyclisation
-
Alkyne-1,4-diols are readily available substrates which are isomerised to 1,4-diketones using Ru(PPh3)3(CO)H2/xantphos as a catalyst. In situ cyclisation into furans, pyrroles and pyridazines has been achieved under suitable conditions.
- Pridmore, Simon J.,Slatford, Paul A.,Taylor, James E.,Whittlesey, Michael K.,Williams, Jonathan M.J.
-
supporting information; experimental part
p. 8981 - 8986
(2009/12/27)
-
- 2,5-Disubstituted furans from 1,4-alkynediols
-
1,4-Alkynediols serve as readily available starting materials for isomerisation to 1,4-diketones, which can be converted in situ into the corresponding furans by acid-catalysed dehydration. A range of 2,5-disubstituted furans was prepared using the ruthenium-based catalyst Ru(PPh3)3(CO)H2 with Xantphos at 1 mol % loading.
- Pridmore, Simon J.,Slatford, Paul A.,Williams, Jonathan M.J.
-
p. 5111 - 5114
(2008/02/09)
-
- Ruthenium- and enzyme-catalyzed dynamic kinetic asymmetric transformation of 1,4-diols: Synthesis of γ-hydroxy ketones
-
Enzymatic kinetic resolution of unsymmetrical 1,4-diols in combination with a ruthenium-catalyzed hydrogen transfer process led to a dynamic kinetic asymmetric transformation (DYKAT) of the least hindered alcohol. Oxidation of the second hydroxy group tak
- Martin-Matute, Belen,Baeckvall, Jan-E.
-
p. 9191 - 9195
(2007/10/03)
-
- A short and efficient synthesis of (±)-trans-sabinene hydrate
-
A short synthesis of sabinene hydrate is reported. It uses cheap starting materials and affordable reagents. The main product of the synthesis is trans-sabinene hydrate.
- Galopin, Christophe C.
-
p. 5589 - 5591
(2007/10/03)
-
- Indenes via Fulvene Intermediates
-
Substituted indenes are prepared from 1,4-dicarbonyl compounds by treatment with base and cyclopentadiene.
- Coe, Jotham W.,Vetelino, Michael G.,Kemp, Daniel S.
-
p. 6627 - 6630
(2007/10/02)
-
- A General Preparative Method for Carbonyl-Protected γ-Lithioketones via Reductive Lithiation. Synthetic Uses of the Bishomoenolate Equivalents
-
The mixed cuprates, generated by reductive lithiation of bis(phenylthio)acetals using lithium 4,4'-di-tert-butylbiphenylide (LDBB), followed by addition of cuprous bromide-dimethyl sulfide complex, undergo conjugate addition to enones in the presence of t
- Cohen, Theodore,Zhang, Birong,Cherkauskas, John P.
-
p. 11569 - 11584
(2007/10/02)
-
- Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The synthesis of oxabicyclo[3.n.1]alkan-3-ones
-
Lewis acids are employed as catalysts in the annulation of 1,4- and 1,5-dicarbonyl dielectrophiles with bis(trimethylsilyl) end ethers of β-diketones and β-keto esters. A variety of 2-(alkoxycarbonyl)-m-oxabicyclo[3.n.1]alkan-3-ones can be constructed by this process in which two new carbon-carbon bonds are generated. Unusually high regiocontrol is observed, and good to excellent stereochemical control can be achieved at virtually every position on the new carbocycles. Intramolecular neighboring group participation is proposed to explain the unusually high selectivities attained in the annulation reaction.
- Molander, Gary A.,Camera, Kimberly O.
-
p. 830 - 846
(2007/10/02)
-
- Ozonolsysis of 1,4-disubstituted 1,3-cyclohexadienes and of related compounds in methanol
-
Ozonolysis of 1,4-dimethyl- (5a) and 1-methyl-4-isopropyl-1,3-cyclohexadiene (5b) in methanol occur stepwise by sequential cleavage of the two double bonds.Monoozonolysis products are the corresponding compounds 6 and 7, and diozonolysis products are the corresponding cyclic peroxides 19, 20, and 21.By contrast, ozonolysis of the non-conjugated diene 2,5-dimethyl-1,5-hexadiene (13) in methanol occurs by simultaneous mono- and diozonolysis to give 14, 16a, 18a, and 20a.
- Griesbaum, Karl,Mertens, Henri,Jung, In Chang
-
p. 1369 - 1375
(2007/10/02)
-
- Ruthenium(II)-Catalyzed Reactions of 1,4-Epiperoxides
-
The behavior of 1,4-epiperoxides in the presence of transition-metal complexes is highly dependent on the structures of the substrates and the nature of the metal catalysts.Reaction of saturated epiperoxides such as 1,3-epiperoxycyclopentane, 1,4-epiperoxycyclohexane, or dihydroascaridole catalyzed by RuCl2(PPh3)3 in dichloromethane gives a mixture of products arising from fragmentation, rearrangement, reduction, disproportionation, etc.Prostaglandin H2 methyl ester undergoes clean and stereospecific fragmentation to afford methyl(5Z,8E,10E,12S)-12-hydroxy-5,8,10-heptadecatrienoate and malonaldehyde.Bicyclic 2,3-didehydro 1,4-epiperoxides give the syn-1,2:3,4-diepoxides by the same catalyst.The monocyclic analogues are transformed to a mixture of diepoxides and furan products.The stereochemical outcome of the epoxide formation reflects unique differences in the ground-state geometry of the starting epiperoxide substrates.FeCl2(PPh3)2 serves as a useful catalyst for the skeletal change of sterically hindered bicyclic 2,3-didehydro 1,4-epiperoxides to the syn-diepoxides.In addition, the Fe complex best effects the conversion of 1,4-unsubstituted 2,3-didehydro epiperoxides to furans.The Ru-catalyzed reactions are interpreted in terms of the intermediacy of inner-sphere radicals formed by atom transfer of the Ru(II) species to peroxy substrates, in contrast to the Fe-catalyzed reactions proceeding via free, outer-sphere radicals generated by an electron-transfer mechanism.
- Suzuki, Masaaki,Ohtake, Hiroaki,Kameya, Yoshimi,Hamanaka, Nobuyuki,Noyori, Ryoji
-
p. 5292 - 5302
(2007/10/02)
-
- Competitive Reactions of Diene Cation Radicals Formed on Irradiated Metal Oxide Surfaces
-
The heterogeneous photochemical oxygenation of conjugated dienes induced by long wavelength UV irradiation of TiO2 powders suspended in oxygenated CH3CN was studied.In nearly all cases, products resulting from the oxidative cleavage of the double bonds were observed, in parallel to that previously reported for monoolefins.A mechanism is proposed which involves the intermediacy of a diene cation radical generated by transfer of an electron from the adsorbed diene to a photogenerated hole localized at the surface of the excited TiO2 particle.Non-oxidative cleavage products are also observed, and the effect of the semiconductor surface in controlling reactivity of the photogenerated cation radical is discussed.The first examples of aromatization and Diels-Alder dimerization mediated by irradiated semiconductor suspensions are presented.
- Fox, Marye Anne,Sackett, Debra D.,Younathan, Janet N.
-
p. 1643 - 1660
(2007/10/02)
-
- 2-Ethoxy-2-propenyl Diethyl Phosphate. An Efficient Halo Acetone Equivalent for the Pd-Catalyzed Cross-coupling with Tin Enolates
-
In the presence of Pd(0) complexes, 2-ethoxy-2-propenyl diethyl phosphate was found to react with organotins to give the corresponding coupling products, showing to be a more efficient halo acetone equivalent compared with the corresponding acetate or carbonate.Reaction with tin enolates gave the 1,4-diketone in moderate to good yields.
- Kosugi, Masanori,Ohashi, Kenji,Akuzawa, Kazuko,Kawazoe, Takashi,Sano, Hiroshi,Migita, Toshihoko
-
p. 1237 - 1238
(2007/10/02)
-
- UN ANION β-ACYLE MASQUE DANS LES REACTIONS D'ACYLATION: LE DERIVE LITHIE DU DIOXOLANNE DU LEVULATE DE TRIMETHYLSILYLE
-
An organolithium reagent derived form trimethylsilyl-4,4-ethylenedioxypentanoate reacts with mixed carboxylic-carbonic anhydrides as a homoenolate anion equivalent.Several monoethylene acetals of 1,4-diketones and the corresponding diketones are synthesized by this way.
- Moreau, Jean-Louis,Couffignal, Renee
-
p. 139 - 144
(2007/10/02)
-
- Thermal Reactions of Epoxyenones and Epoxydienes in the Ionone Series
-
On flash vacuum thermolysis at temperatures between 390 and 585 deg C, the epoxyenones 1-9 and the epoxydienes 10-12 undergo various types of reactions involving C-C and/or C-O bond cleavage in the oxirane ring.Thus, the compounds 1, 4-9, 11, and 12 were transformed to the divinyl ethers 13, 20, 21, 24, 25, 29, and 38 by a reversible homosigmatropic H-shift.On thermolysis of the epoxides 1-12, several products formed via carbonyl-ylide intermediates were also isolated.The extent of the formation of ylide products is clearly related to the conjugating ability of the functional groups neighboring the oxirane.Thus, the epoxides 3, 5, and 7-10 bearing a C(3)=C(4) bond, a 5-oxo function, a 3,4-epoxy or a 3,4-methano group, preferentially underwent reactions via a carbonyl-ylide intermediate.As a further reaction pathway, the epoxides 1-12 undergo cleavage of the C-O bonds of the oxirane, which, however, is presumably an acid-catalyzed rather than a thermal reacion.
- O'Sullivan, Anthony,Bischofberger, Norbert,Frei, Bruno,Jeger, Oskar
-
p. 1089 - 1106
(2007/10/02)
-
- Acid-catalysed Rearrangement of Trevoagenins A and B. The Acetal Function as Electron-donor Group in Heterolytic Fragmentations
-
The acid-catalysed rearrangement of trevoagenins A (1) and B (4) gave 3β-hydroxy-24-oxo-16,17-seco-5α-dammar-17(20)E-eno-16,30-lactone (5) (40percent), its 17(20)Z-ene isomer (7) (13percent), and (20R,24R)-3β,25-dihydroxy-15α,30-cyclo-20,24-epoxy-5α-dammaran-16-one (9) (2percent).Compounds (5) and (7) were produced through a heterolytic fragmentation mechanism.In order to study the scope of this rearrangement the C-20 epimeric hydroxy acetals (24) and (28) were synthesized starting from trevoagenin B and A, respectively.The reaction of the 20S-hydroxy acetal (24) with iodine led to the Z-olefin (29) while the 20R-hydroxy acetal (28) gave the E-olefin (30).The concerted nature of this heterolytic fragmentation, where acetals or hemiacetals are the electron-donor groups, is supported by the observed stereospecificity of the reaction.
- Francisco, Cosme G.,Freire, Raimundo,Hernandez, Rosendo,Salazar, Jose A.,Suarez, Ernesto,Cortes, Manuel
-
p. 2757 - 2763
(2007/10/02)
-
- α-Aminosaeuren als nucleophile Acylaequivalente, V. Sterisch gelenkte Michael-Addition von Oxazolin-5-on-Anionen an aktivierte Doppelbindungen; Synthese von 1,4-Dicarbonylverbindungen und γ-Oxonitrilen
-
Oxazolin-5-ones with bulky substituents like mesityl or 1-butylcyclohexyl at C-2 undergo triethylamine catalyzed addition to activated olefins exclusively at C-4.Hydrolysis of the derived 4,4-disubstituted 2-mesityl-2-oxazolin-5-ones 9 leads to N-mesitoyl
- Wegmann, Helmut,Steglich, Wolfgang
-
p. 2580 - 2594
(2007/10/02)
-