共查询到20条相似文献,搜索用时 15 毫秒
1.
Lokesh Chandra Pati 《Tetrahedron letters》2004,45(51):9451-9453
The stereoselective total synthesis of (±)-pisiferol (1) and (±)-pisiferal (2) has been successfully accomplished using the trans-octahydrophenanthrene derivative 20 as a key intermediate. Intramolecular cyclisation of the diazoketone 15 followed by catalytic hydrogenation provided, stereoselectively, the keto-ester 17 which was converted into the acetate 20 through the intermediates 18 and 19. 相似文献
2.
Tapas PaulDebabrata Mukherjee 《Tetrahedron letters》2003,44(27):4985-4988
Stereocontrolled total syntheses of the bridged tricyclic ketones (±)-clovan-3-one (5) and (±)-epi-clovan-3-one (6) and a facile total synthesis of the tricyclic sesquiterpene (±)-pseudoclovene-A (3) have been successfully accomplished involving participation of an aryl intramolecular cyclisation of the bromophenol 11 as a key step. 相似文献
3.
Christian R. Razafindrabe Sylvain Aubry Marta Andriantsiferana Marc Lemaire 《Tetrahedron》2010,66(46):9061-9066
A synthesis of functionalized phenolic α-amino-alcohol (±)-13 as synthetic precursor of the catechol tetrahydroisoquinoline structure of phthalascidin 650 is disclosed. Starting from 3-methylcatechol 5, eight steps of synthesis give rise to the synthesis of phenolic α-amino-alcohol (±)-13 in 27% overall yield. This synthetic strategy involves the elaboration of fully functionalized aromatic aldehyde 8 and its transformation into a phenolic α-amino-alcohol (±)-13, through a Knoevenagel condensation, simultaneous reduction of nitroketene and ester functions and hydrogenolysis of the benzyl protecting group. The pentacycle (±)-18 was obtained after four additional steps. The Pictet-Spengler cyclisation between the phenolic α-amino-alcohol (±)-13 and N-protected α-amino-aldehyde 4 allowed to obtain (1,3′)-bis-tetrahydroisoquinoline 14 with N-methylated and N-Fmoc removed. The last step was a Swern oxidation for allowing an intramolecular condensation. 相似文献
4.
Total synthesis of (±)-brazilin has been accomplished. m-CPBA epoxidation of allyl alcohol 10 and epoxy opening reaction mediated by m-chlorobenzoic acid, formed in situ as a byproduct, gave advanced intermediate diol 14. O-alkylation and cyclization gave phenol 6 which enabled the formal synthesis of (±)-brazilein and (±)-brazilide A. 相似文献
5.
Olena Affolter 《Tetrahedron》2009,65(33):6626-4417
Baeyer-Villiger oxidations of several tropane derivatives have been investigated. Whereas tropenones 15a-c underwent exclusive epoxidation to 21a-c, the corresponding 6-oxotropane derivative 28 yielded the desired lactone 29. Baeyer-Villiger oxidation was also possible for the O-isopropylidene-protected diols 32a,b. The resulting lactones 33a,b were employed in the total synthesis of (±)-7a-epi-hyacinthacine A1 (7a-epi-7) via an intramolecular nucleophilic alkyllithium addition to a carbamate as the key lactamization step. The target compound was prepared from tropenone 15b in 10 steps and 14% overall yield. Enzymatic resolution of pyrrolidine (±)-36 provided a formal total synthesis to both enantiomers of 7. 相似文献
6.
Rammohan DevulapallyYung-Son Hon 《Tetrahedron letters》2011,52(25):3183-3185
The first total synthesis of tetrahydrobenzo[a]anthraquinone natural product (±)-zenkequinone B (1) is reported. The key step involves the TiCl4-promoted intramolecular cyclization of 4-aryl-2-hydroxybutanal diethyl acetal 4 to give compound 3. The total synthesis of (±)-zenekequinone B (1) has been accomplished in five steps from readily available 2-(chloromethyl)-9,10-dimethoxyanthracene (5) in 40.3% overall yield. 相似文献
7.
A stereocontrolled total synthesis of methyl (±)-O-methyl podocarpate (4) has been successfully accomplished using the trans-fused diester 21 as a key intermediate. Intramolecular Michael reaction of the enone-diester 18 afforded the cis-fused keto-diester 19 in high yield which was stereoselectively converted into 21 via the enone 20. 相似文献
8.
A conceptually new total synthesis of oestrone, based on a novel cascade of radical cyclisations from the iodo aryl vinylcyclopropane 2, via 10, 15, 16 and 17, leading to the intermediate trans,anti,trans-oestradiol derivative 11 in one step, is described. Oxidation of 11, followed by demethylation of the resulting aryl methyl ether 18 then gives (±)-oestrone 1. 相似文献
9.
(±)-epi-Conocarpan 1 was synthesized via the key intermediate 5-bromo-cis-2-(4-methoxyphenyl)-3-methyl-2,3-dihydrobenzofuran 6 which was synthesized by a ruthenium(II) porphyrin-catalyzed intramolecular C-H insertion reaction using aryl tosylhydrazone salt 5 as the carbene source, starting from the commercially available 5-bromo-2-hydroxyacetophenone. 相似文献
10.
Daniel Oehlrich 《Tetrahedron》2007,63(22):4703-4711
A 15-step synthesis of (±)-luminacin D from ethyl pent-2-ynoate is reported. The pivotal step involves the formation of the central C-2′/C-3′ bond of the natural product by condensation of the titanium enolate derived from aromatic ketone 1 with aldehyde 2a. A remote asymmetric centre in aldehyde 2a exerts control over the stereochemical course of this reaction, with the major adduct (3a, 54% yield) possessing the required (2′S∗,3′R∗,5′R∗)-stereochemistry. This assignment was unambiguously established by X-ray crystallography of late stage synthetic intermediate, 17. Further manipulation of 3a (six steps) yielded synthetic (±)-luminacin D spectroscopically identical to material isolated from Streptomyces sp. Mer-VD1207 by Naruse et al. 相似文献
11.
Completion of the total synthesis of (±)-nominine (1) is described in detail. Based on the results of the preceding two papers, total synthesis of (±)-nominine was accomplished diverging from the intermediate 7. Thus, following pyrrolidine ring formation through transformation from 7 to 8, the C-ring was constructed by radical cyclization to form 10 from the enyne precursor 9. Subsequent elaboration of the C-ring, followed by formation of the azabicyclic ring system, completed a total synthesis of (±)-1. Single-crystal X-ray analysis of (±)-1 unambiguously confirmed its molecular structure and racemic crystal structure. 相似文献
12.
A novel and concise synthesis of (±)-pseudodeflectusin (1), an antitumor isochroman derivative isolated from the culture broth of Aspergillus pseudodeflectus, was accomplished by starting from 4-(tert-butyldimethylsilyloxy)-1-pentyne (3) and diethyl 3-oxopentanedicarboxylate (5). 相似文献
13.
Megumi Saeki 《Tetrahedron letters》2010,51(35):4620-5875
Total syntheses of (±)-cis-195A (1) and (±)-trans-195A (16) have been accomplished by a combination of palladium-catalyzed oxidative cyclization and Beckmann rearrangement as key reactions. 相似文献
14.
Rachid Skouta 《Tetrahedron letters》2007,48(47):8343-8346
(±)-Pterocarpan and analogues (4a-c) have been synthesized efficiently via the annulation of salicylaldehydes (1a, 1b and 1c) and o-methoxymethoxylphenylacetylene (2a), followed by a one-pot reduction and acidic cyclization of the ketones (3a-c). In addition, isoflavone derivatives (5a-c) have been synthesized rapidly, in two steps, via the annulation of salicylaldehyde (1a) and arylacetylenes (2b, 2c and 2d), followed by IBX/DMSO oxidation of the isoflavanones (3d, 3e and 3f). 相似文献
15.
In this paper we report on a efficient and flexible synthetic route towards the total syntheses of the dihydrocoumarine derivatives hydrangenol (1), phyllodulcin (1a) and macrophyllol (6b). The syntheses started with a readily available phosphonium salt 2 and suitable modified benzaldehydes 3/3a/3b resulting in 46 to 61% overall yields in three to four-steps sequences. The racemic products could be separated by chiral HPLC. The evidence of the (R)-enantiomer for sweetness could be demonstrated for 1a. 相似文献
16.
Karen Anderson EvansKebede Beshah David H YoungTed T Fujimoto Colin M TiceEnrique L Michelotti 《Tetrahedron》2003,59(13):2223-2229
Colchicine mimetic (±)-4S,5R-4-nitro-5-(2,3,4-trimethoxyphenyl)cyclohexene (1) was epoxidized to afford a mixture of epoxides. The epoxides were separately converted in two steps, with high stereoselectivity, to two regioisomeric α-methoxyketones. One regioisomer, (±)-2R,4S,5R-2-methoxy-5-nitro-4-(2,3,4-trimethoxyphenyl)cyclohexanone (17), proved to be about 12-fold more potent than synthetic precursor 1 against HCT-116 tumor cells while the other regioisomer, (±)-2R,4R,5S-2-methoxy-4-nitro-5-(2,3,4-trimethoxyphenyl)cyclohexanone (16), and the synthetic intermediates tested showed no improvement in potency. 相似文献
17.
Efficient formal syntheses of (±)-Asterisca-3(15),6-diene, a natural product with a bicyclo[6.3.0]undecane skeleton, and (±)-Pentalenene, a natural product with a tricyclo[6.3.0.04,8]undecane skeleton, have been achieved by using Rh(I)-catalyzed [(5+2)+1] cycloaddition. The [(5+2)+1] reaction provides an expeditious approach to reach the bicyclic cyclooctenone 4, which was quickly transformed (via hydroboration then oxidation) to diketone 14, a key advanced intermediate for the total synthesis of (±)-Asterisca-3(15),6-diene. Through further transformations, 14 was converted to diene 18, an advanced intermediate for the total synthesis of (±)-Pentalenene. 相似文献
18.
A concise stereoselective route to (±)-pentenomycin 1 in 33% overall yield starting from the readily accessible Diels-Alder adduct 4 is reported. The key reaction involves decarbonylation of β-methoxy-α,β-unsaturated aldehyde 8 obtained from β-hydroxy-dimethylketal 6. 相似文献
19.
Takayuki Muramatsu 《Tetrahedron letters》2007,48(51):8956-8959
We have developed a practical synthesis of the chiral lactam as a new chiral building block for alkaloid synthesis. Lipase-catalyzed kinetic resolution of hydroxylactam 8, followed by isolation-racemization of the chiral acetoxylactam 9 provided the optically pure hydroxylactam 8 in 96.0% yield with >99% ee after five cycles of kinetic resolution-racemization process. Chemical transformation of (S)-hydroxylactam 8 furnished chiral (−)-2-epi-lentiginosine (1) in 20% yield in 10 steps with no loss of enantiomeric excess. 相似文献
20.
Kenji ArimitsuSayo Nomura Hiroki IwasakiMinoru Ozeki Masayuki Yamashita 《Tetrahedron letters》2011,52(52):7046-7048
The first total synthesis of (±)-adunctin B (1), a natural product isolated from Piper aduncum (Piperaceae) and having antibacterial activity, was achieved in 1.26% overall yield in 15 steps from 5,7-dimethoxycoumarin-3-carboxylate (8). 相似文献