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1.
A Buzas R Cavier F Cossais J P Finet J P Jacquet G Lavielle N Platzer 《Helvetica chimica acta》1977,60(7):2122-2134
Synthesis and amoebicid properties of emetin analogs. Analysis of the new compounds by 13C-NMR. B/C-cis or trans-fused (±) 1-alkyl-3-desethyl-emetin. New 1-alkyl-3-desethyl-emetines were prepared for pharmacological purposes. The usual emetine synthesis sequence applied to cis-1-alkylbenzo [a]quinolizidin-2-ones afforded new cis-1-alkyl-3-desethyl-emetines. The trans-fused isomers were also prepared. The relative configuration are determined by 1H- and 13C-NMR. spectra. 相似文献
2.
A conformationally directed Cyclization to the Octahydrophenanthridine System. The bicyclic precursors 5b and 8b are cyclized to the cis-fused phenanthridine derivative 6b without any detectable formation of the corresponding trans-derivative 7b . The conformational aspects of this stereoselective cyclization are discussed. 相似文献
3.
cis(1-H, 8a-H)-1-Methylperhydro-oxazolo[3,4-a]pyridine and cis(1-H, 8a-H)-1-methylperhydrothiazolo[3,4-a]pyridine both adopt exclusively the trans-fused conformation in carbon tetrachloride solution at room temperature. Both parent unsubstituted systems exist under similar conditions as equilibria containing c. 67% (oxazolo compound) and 64% (thiazolo compound) of the trans-fused conformation. In marked contrast to these similar positions of conformational equilibria in both systems the trans(1-H,8a-H)-1-methylperhydrooxazolo[3,4-a]pyridine exists as c. 73% trans-fused in equilibrium with a cis-fused conformation whereas the trans(1-H, 8a-H)-1-methylperhydrothiazolo[3,4-a]pyridine exists almost exclusively in a cis-fused ring conformation. These differences in conformational equilibria are explained in terms of changes in non-bonded interactions. 相似文献
4.
Reaction of 3-bromocyclohexene with (S,S)-hydrobenzoin and (S)-mandelic acid and subsequent intramolecular oxyselenenylation of the resulting allylic ethers followed by oxidation-elimination afforded the valuable cis-fused bicyclic olefins, (1S,3S,4S,6R)-3,4-diphenylbicyclo[4,4,0]-2,5-dioxa-7-decene and (1S,3S,4R)-3-phenyl-4a,7,8,8a-tetrahydro-benzo[1,4]dioxan-2-one, respectively. Further stereoselective transformation of these cis-fused bicyclic olefins afforded the enantiopure cyclohexitols, muco-quercitol, d-chiro-inocitol and allo-inocitol. 相似文献
5.
Dr. Ko Sato Dr. Hiroshi Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9422-9428
Lignans are a group of polyphenolic phytochemicals that possess a large spectrum of chemical structures and biological activities. Here the syntheses of lignans – anwulignan, burseran, dehydroxycubebin, ruburisandrin B, and sesamin – are achieved based on a borate-mediated one-pot sequential Suzuki-Miyaura coupling of cis- and trans-fused bicyclic boranes, which were prepared by diastereoselective cyclic hydroboration of exo-cyclic diene with cyclopentyl- and thexylboranes, respectively. A one-pot sequential Suzuki-Miyaura coupling of each cyclic borate with various aryl bromides initiated by activation of the cyclic borane with the carbon nucleophile provided 2,3-dibenzylbutane derivatives with different aromatic substituents. Finally, the syntheses of naturally occurring lignans were accomplished in several steps from the products of Suzuki-Miyaura coupling. 相似文献
6.
A “Mannich-directed” 2-azonia-[3,3]-sigmatropic rearrangement is the key step in a new, completely stereoselective, method for preparing 9a-arylhydrolilolidines. Specifically, cis-fused bicyclic aminoalcohols 24 upon treatment with formaldehyde and acid afford hydrolilolidines 25 in a single step and in excellent yield. The complete stereoselectivity of this “ring-enlarging pyrrolidine annulation” reaction follows stereorationally from the trans-relationship of vinyl and amine functions in the bicyclic precursor 24 (eqn 6). 相似文献
7.
Substrates were designed to undergo tandem radical cyclizations to afford the cis, cis-fused hexahydrobenzofurobenzopyran ring system of the bisabosquals. Studies with these revealed that different initiating systems gave different yields and somewhat different diastereomeric ratios. A photocatalytic cyclization was also successful with the bisabosqual substrate. 相似文献
8.
Susanta Kumar Manna Arabinda Mandal Suresh Kumar Mondal Jayanta K. Ray Mahiuddin Baidya 《合成通讯》2013,43(5):625-634
A novel synthesis of 3,4-fused furans (both tricyclic and bicyclic) through platinum-catalyzed cyclization of 3-(2-formylcycloalkenyl)-acrylic amides 2 in methanol is described (up to 90% yield). Tricyclic 3,4-fused dihydrofuran derivatives were also obtained via reductive cyclization of 2. The substrates 2 were obtained from β- bromovinyl aldehydes by a Pd-catalyzed Heck reaction. 相似文献
9.
dl-Pumiliotoxin-C (4) was synthesized in a practical manner from trans-4-hexenal (9) . The key step 14 → 15 (Scheme 3) involves an intramolecular Diels-Alder reaction giving mainly the cis-fused indanols 15a , which were converted to the cis-fused ketone 16 . After Beckmann-rearrangement of 16 the octahydroquinolinone 7 was transformed to the lactim-ether 23 . (Scheme 7). Reaction of 23 with propylmagnesium bromide followed by hydrogenation furnished dl- 4 in a highly stereoselective fashion. 相似文献
10.
Fabrice Glarner Steven R. Thornton Daniel Schrer Grald Bernardinelli Ulrich Burger 《Helvetica chimica acta》1997,80(1):121-127
The title compounds 4 are obtained by photolysis of simple N-alkylpyridinium salts in H2O or alcohol. On reaction with [Fe2(CO)9] in THF, 4 gives bicyclic tricarbonyliron complexes 13a – d , which on oxidative decomplexation with ceric ammonium nitrate afford cis-fused cyclopenteno-β-lactams 15a – d . 相似文献
11.
Arpita Neogi 《Tetrahedron》2005,61(39):9368-9374
Tributyltin radical mediated cyclization of the glucose derived exo-methylene furanose derivatives 5a-c led to the highly functionalized cis-fused bicyclic ethers 6a-c. The product could subsequently be transformed to the optically active tricyclic nucleoside analogue 8 or oxepine derivative 9. 相似文献
12.
The regio- and stereocontrolled synthesis of -fused bicyclo[6.4.Oldodecane ring systems by the application of the Lewis acid-catalyzed intramolecular Diels-Alder reaction is described. 相似文献
13.
《Tetrahedron: Asymmetry》1999,10(5):869-875
By the adoption of a regio- and stereoselective intramolecular radical cyclisation reaction onto a chiron derived from diacetone glucose, the crucial cis-fused bicyclo[3.3.0]octane system was made and utilized for the first synthesis of discosiolide 1, thereby establishing the absolute stereochemistry of the natural product. 相似文献
14.
Trevor A. Crabb Roger F. Newton Janet Rouse 《Magnetic resonance in chemistry : MRC》1982,20(2):113-116
The 1H NMR parameters of the NCH2O protons in the spectrum of perhydropyrrolo[1,2-c][1,3]oxazine show its existence in solution at room temperature in the O-inside cis-fused conformation. rel-(3aS,6aS,6bR,10aS,11aS)-6a-Methylperhydroindolo[3,2,1-i,j]benzoxazine and rel-(3aS,6aS,6bS,10aR,11aS)-6a-methylperhydroindolo[3,2,1-i,j]benzoxazine are shown to adopt cis- and trans-fused conformations, respectively, for the corresponding bicyclic moiety. 相似文献
15.
《Tetrahedron: Asymmetry》2001,12(19):2649-2655
Pd(0)-catalyzed allylic amination of 3-bromocyclohexene with (1S,2S)-2-amino-1,2-diphenylethanol and subsequent intramolecular oxyselenenylation of the resulting allylic amine 6 followed by oxidation–elimination afforded the valuable cis-fused bicyclic olefin 10. Oxyselenenylation of cyclohexene with (1S,2S)-N-(benzyloxycarbonyl)-2-amino-1,2-diphenylethanol and subsequent oxidation–elimination gave the allylic ether 18. Intramolecular aminoselenenylation of 18 followed by oxidation–elimination provided the cis-fused bicyclic olefin 21, which is the regioisomer of 10. Further stereoselective transformation of 10 afforded enantiopure aminocyclohexitols. 相似文献
16.
Trevor A. Crabb Philip A. Jupp Yoshito Takeuchi 《Magnetic resonance in chemistry : MRC》1982,20(4):239-241
The 270 MHz NMR data on trans- and cis-(H-4a, H-7)-7-ethylperhydropyrido[1,2-c][1,3]thiazine show heavy conformational bias to the trans- and S-inside cis-fused conformations, respectively. Comparison of the 13C NMR spectra of these anancomeric systems with the 13C NMR spectrum of perhydropyrido[1,2-c][1,3]thiazine indicates a trans-?S-inside cis-conformational equilibrium for the latter compound in CDCl3 at 25°C, containing ca 75% trans-fused conformer. The 13C NMR spectrum of perhydropyrido[1,2-c][1,3]-thiazine at ?75°C showed 64% trans-fused conformer and 36% S-inside cis-conformer. 相似文献
17.
C. Richard Hutchinson Kenneth C. Mattes Masami Nakane John J. Partridge Milan R. Uskokovi 《Helvetica chimica acta》1978,61(4):1221-1225
A seven-step stereoselective synthesis of (±)-sweroside aglucone O-methyl ether ( 16a ) was achieved in 27% overall yield from 1, 4-cyclohexadiene ( 4 ) and methyl diformylacetate ( 5 ). Secologanin aglucone O-methyl ether ( 18a ) was then formed from 16a in 90% overall yield by a straightforward process. The key step in the synthesis was a [2+2]-enone-photoannelation of 4 and 5 to form the key intermediate 6 which possessed the desired cis-fused ring configuration, and all the caron atoms needed to complete the synthesis of 16a and 18a . 相似文献
18.
The novel styryl lactone analog (±)-3-deoxyisoaltholactone was synthesized in 5 steps from dihydrofuran. An intramolecular vinylsilane–oxocarbenium condensation thus afforded the central cis-fused bicyclic ether array in near quantitative yield as a single stereoisomer. 相似文献
19.
Samuel J. Plamondon Josephine M. Warnica Dainis Kaldre Prof. James L. Gleason 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):259-264
Polyene cyclizations offer rapid entry into terpenoid ring systems. Although enantioselective cyclizations of (E)-polyenes to form trans-decalin ring systems are well precedented, highly enantioselective cyclizations of (Z)-polyenes to form the corresponding cis-decalins have not been reported. Here, we describe the first application of iminium catalysis to the initiation of polyene cyclizations. Ethyl 1,2-diazepane-1-carboxylate catalyzes the cyclization of polyenes bearing enal initiators. Moreover, chiral bicyclic hydrazides catalyze the cyclizations of (Z)-polyene substrates to form cis-decalins with enantioselectivities of up to 97:3 er. DFT calculations suggest the catalysts promote the reaction by stabilizing positive charge as it develops during the bicyclization. 相似文献
20.
Xanthanolide‐type sesquiterpenoids are a diverse family of natural products isolated primarily from the genus Xanthium (Compositae). The intriguing molecular architectures and biological profiles of these natural products have rendered them attractive targets for total synthesis. This focus review aims to provide an up‐to‐date summary of progress in the chemical synthesis of xanthanolide‐type sesquiterpenoids. Different synthetic strategies to form 5/7‐cis‐ and 5/7‐trans‐bicyclic xanthanolides are presented in chronological order, with an emphasis on the key elements used to forge the characteristic 5/7‐bicyclic cores of the targets. Recent advances in the total syntheses of structurally more complicated polycyclic and dimeric xanthanolides are also discussed. 相似文献