共查询到20条相似文献,搜索用时 31 毫秒
1.
Michel Lebœuf Diego Cortes Reynald Hocquemiller André Cavé Angèle Chiaroni Claude Riche 《Tetrahedron》1982,38(19):2889-2896
The structure of guoregine, a new isoquinoline alkaloid from , Annonaceae, has been deduced by spectral analysis and confirmed by an X-ray structure determination. It is the first member of a new class of cularine-related alkaloids (α--dimetyltetradehydrocularines). 相似文献
2.
In contrast with the reaction of α-aminonitriles a, the corresponding -acylated α-aminonitriles b-f and oxalyl chloride do not yield pyrazinone derivatives, but 5-aminooxazoles - or 4(5)-imidazolones , the latter being converted in some cases into imidazo [2,1-]isoquinoline-2,5,6(3)-triones. Reactions of compounds b-f and ethyl chlorooxoacetate provide evidence for a 5(4)-iminooxazole intermediate , which aromatizes to yield 5-aminooxazoles -; however, unaromatizable īntermediates of type - isolable as 5(4)y-oxazolones after hydrolysis - undergo a catalyzed Dimroth-type rearrangement to give imidazolone derivatives . 相似文献
3.
For 12-- locked retinal analogues, thermal equilibria are established between 11-, 13--1c and 13--2c and between 9-, 11-, 13--1d and 9-, 13--2d; a photoisomerization occurs to transform 2c to --2a and 2d to 9--2b 相似文献
4.
Flow vacuum thermolysis (FVT) of thiophene-2,3-dicarboxylic anhydride () in the presence of 2,3-dimethylbutadiene () gives, in addition to 5,6-dimethylthianaphthene (). small quantities of a dihydrodimethylthianaphthene () and another dimethylthianaphthene () which is probably also formed by dehydrogenation of with chloranil. The partial structures of these minor products are consistent with their being formed by a [2+2]-cycloaddition between and an intermediate aryne, 2,3-didehydrothiophene (), followed by a rearrangement of the resulting adduct and dehydrogenation. FVT of in the presence of 2,5- () or 3,4-dimethylthiophene () also gave a mixture of the dimethylthianaphthenes (, ) which can be rationalized as arising by a [4+2]- and two [2+2]-cycloadditions of the aryne to the thiophenes with subsequent desulfurization. The lack of equilibration of the products , and , was demonstrated and their origin as a function of the structure and reactivity of the aryne discussed. 相似文献
5.
The - and -2-amino-4-cyclohexene-1-carboxylic acids and react with imidates to give the condensed-skeleton, bicyclic - and -pyrimidin-4-ones and . The amino acids and were reduced to the -and -1, 3-aminoalcohoIs and , which were cyclized by means of imidates to the bicyclic tetrahydro-4-3,1-benzoxazines and , or were converted, the corresponding carbamates and into the tetrahydro-4-3,1-benzoxazin-2(1)-ones and . The 2-thioxo analogues and were prepared by cyclization of the dithiocarbamates obtained from the aminoalcohols and by treatment with carbon disulphide. The -aminoalcohol and its saturated analogue reacted with -chlorobenzaldehyde to furnish the hexahydro and octahydro-4-3,1-benzoxazine , respectively. 1H and 13C NMR studies showed that, similarly to the earlier-investigated analogues containing oxygen or unsubstituted nitrogen at position 1, the synthesized isomrs , , and occurred as the preferred conformer in the heterocyclic twist inverse form of -inside type ( C6-N bond) (B). In the isomers containing a saturated C-2 atom ( and ), H-2 and H-6 are in relative positions. 相似文献
6.
The dimers & b) of dimethyl- and diethylcyclopentadienone ketals( & b) undergo a novel 1,3-alkoxy-rearrangement to (a & b). Mild hydrolysis of or gives the monoketones (a or b). On strong acid catalysed hydrolysis , or afford the cyclopentadienone-dimer(. 相似文献
7.
The synthesis of the 2,4,6-cycloheptatrienyl ketones – by two alternative routes is reported: Route 1): The adducts from the phenyl(trimethylsiloxy)-acetonitriles , known as “umpolung” reagents, and tropylium tetrafluoroborate are cleaved by triethylammonium fluoride to form the aromatic cycloheptatrienyl ketones –. Route 2): the phenyl, methyl, and cyclopropyl ketone (, , ) are prepared by treatment of the acid chloride with the corresponding organomanganese iodides RMnI (, , ). The Fe-catalyzed coupling reaction of the acid chloride with a Grignard reagent was also used for the preparation of ketone . 相似文献
8.
Ylures sans sel,evolution en phosphoranes et equilibre ylure ⇌ phosphorane : I Synthese et structure
Synthesis of new salt-free ylids , to , , , , and and phoiphoranes , , , , , to by addition of a trivalent phosphorus compound (phosphites and amino-phosphines ) to with dimethyl acetylencedicartboxylate in presence of a protic trapping reagent are described. The results are consistent with trapping of carbanionic species. In relation with the. cyclic of acyclic structure of the triivalent phosphorus compound and the protic trapping reagent ie : methanol, phenol, carboxylic acid, etc.., several pathways are involved. Clearly), three phenomena are shown : one can obtain an ylid via a phosphorane or conversely a phosphorane via an ylid or an equilibrium Phoiphorane ? ylid. Results are dealing with thermodynamic or kinetically controlled reactions. 相似文献
9.
- The corresponding - and -methyl- and -benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines were synthesized from - and -methyl and-benzyl-2- aminomethyl-1-cyclohexanols , from - and -methyl- and benzyl -2-hydroxymethyl-1-cyclohexylamines by reaction with formaldehyde. The aminoalcohols and were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of -benzyl--4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate . determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy. 相似文献
10.
o-Lithomethylphenyl isocyanide is reacted at ?78° with isocyanates and isothiocyanates to produce o-isocyanophenyl-acetamides and -acetothioamides . Isocyanides and are cyclized to indole-3-carboxamides and -3-thiocarboxamides via lithiathion, respectively. Isocyanides are also cyclized by Cu2O catalyst to produce 4,5-dihydro-1,3-benzodiazepin-4-ones with . 相似文献
11.
Condensation of 3-fluoro-2-butanone () with alkyl diethylphosphonoacetates () gave alkyl 4-fluoro-3-methyl-2-pentenoates (). Addition of bromine yielded alkyl-2,3-dibromo-4-fluoro-3-methylpentanoates () which were dehydrobrominated to alkyl 2-bromo-4-fluoro-3-methyl-2- pentenoates (). Since these compounds could not be hydrogenated to the desired alkyl 2-bromo-4-fluoro-3-methylpentanoates (), another route was taken. The esters were hydrogenated to alkyl 4-fluoro-3- methylpentanoates () which were converted to their carbanions. Treatment with bromine gave esters , and iodine gave alkyl 4-fluoro-2-iodo- 3-methylpentanoates (). Esters and were converted to alkyl 2-azido-4-fluoro-3-methylpentanoates () whose hydrogenation gave alkyl 2-amino-4-fluoro-3-methylpentanoates (). Hydrolysis afforded γ-fluoroisoleucine (). 相似文献
12.
Paul von Ragué Schleyer Peter Grubmüller Wilhelm F. Maier Otto Vostrowsky Lars Skattebøl Kjetil H. Holm 《Tetrahedron letters》1980,21(10):921-924
Tricyclo(4.2.2.o1,5)decane () in the presence of AlBr3 rearranges partly “forwards” to adamantane () and partly “backwards” to tetrahydrodicyclopentadiene (, largely the oxo isomer). Intermediate , characterizing the →exo-→→→ forward pathway, is found only in small amounts. The detection of a new intermediate, , also shows that a second major rearrangement route from to is being utilized (see dashed lines in Figure 1). 相似文献
13.
The biomimetic reactions of epoxygermacrene-D () with basic alumina afforded three new interesting compounds (, , and ), two of which ( and ) have the same carbon skeleton as that of periplanone-A (), a sexual stimulant for the American cockroach. The remaining one () is a bicyclo[3.1.0]hexane derivative, from whch an axisonitrile-3 type compound () has been produced. Finally, preisocalamendiol () was also converted into . 相似文献
14.
The reaction of tetracyclone with the cyclo-octatetraene-dimethyl acetylenedicarboxylate adduct at . 110° produces, in addition to the [4+2] Π cycloadduct (49%), 1,2,3,8-tetraphenylcyclo-octatraene (11%), together with the diketone (5%). In a similar reaction with the esterified cyclo-octatetraene-maleic anhydride adduct , the major product (82%) is accompanied by the cyclohexa-1,3-diene and the dihydrosemibullvalene derivative . Thermolysis of at . 145° leads to the cyclobutene ., which on catalytic hydrogonation followed by decarbonylation at 180°–190° gives 2,3,4,5-tetraphenylcyclo-octa-1,3,5-triene . Attempted thermal conversion of into a dihydrosemibullvalene failed. 相似文献
15.
Three quettamine type alkaloids, which incorporate either a benzofuran or a dihydrobenzofuran moiety within the molecular framework, have been obtained from . These are dihydrosecoquettamine (), secoquettamine (), and quettamine chloride (). Alkaloids and are racemates. Hofmann degradation of quettamine () provides secoquettamine () and the styrene which has a trans relationship between the hydrogens at C-1 and C-α, thus indicating the identical stereochemistry in quettamine. Emde reduction of quettamine leads to dihydrosecoquettamine () and the stilbene . Two other polar alkaloids in the plant are (+)-armepavine methochloride () and oblongine chloride (). An oblongine type alkaloid must be the biogenetic precursor for the quettamines. Arguments are presented favoring direct oxidative coupling in the biogenesis of the cularine alkaloids. 相似文献
16.
In order to elucidate the structure-activity relationships of the antifeeding diterpenes having a -clerodane skeleton, clerodin homolog was stereoselectively synthesized through 18 steps a key intermediate . Perhydrofuro[2,3-b]furan ring in the synthesized homolog was more unstable than that of the natural product, and gave a -MeOH adduct in a similar behavior to that of the model compounds and . 相似文献
17.
Terrence McCabe Jon Clardy L. Minale C. Pizza F. Zollo R. Riccio 《Tetrahedron letters》1982,23(33):3307-3310
The constitution and stereochemistry of , a yellow triterpenoid pigment isolated from a Somalian collection of the sponge ., has bben unequivocally established by spectral and x-ray crystallographic methods. The assignment of -- stereochemistry to the tricyclic nucleus of 1 suggests that the structures of several recently described tritepenoids from be reassigned. 相似文献
18.
Reaction of the cyclic 1, 3-dicarboxylic acid derivatives (), () and () with (R)- or (S)-citronellal (/) gives the enantiomeric tricyclic dihydropyrans (), (), () and (), probably via a 100% stereocontrolled intramolecular cycloaddition. 相似文献
19.
Felix H. Cano Concha Foces-Foces Manuel Bernabe Jesus Jimenez-Barbero Manuel Martin-Lomas Soledad Penades-Ullate 《Tetrahedron》1985,41(18):3875-3886
X-Ray and 1H N.M.R. studies on pyranoid rings 1,2--fused to dioxolane rings in acetylated -gluco- and --galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the -gluco but not in the -galactopyranose series. The crystal structure of 3,4,6-tri--acetyl-1,2--(R)--(l-cyano-ethylidene)-α--glucopyranose () and 3,4,6-tri--acetyl-1,2--()-(1-cyano-ethylidene)-α--galactopyranose ()have been determined by X-ray analysis. Lattice parameters for are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened 4C1 and that of the dioxolane ring as distorted E1. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The 1H N.M.R. spectra of and and 3,4,6-tri--acetyl-1,2-O-(S)- and (R)-ethylidene-α--glucopyranose ( and ), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ()-ethylidene-α--galactopyranose ( and ), and 3,4,6-tri--acetyl-1,2--()-and ()-benzylidene-α--glucopyranose ( and ) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the -gluco series , and may be described as flattened 4C1 and that of and as 25. The major solution conformation of the pyranoid ring in all compounds in the -galacto series (,,,) may be described as flattened 41. 相似文献
20.
Simon J. Edge W.David Ollis Julia Stephanidou Stephanatou J.Eraser Stoddart David J. Williams Kwamena A. Woode 《Tetrahedron letters》1981,22(23):2229-2232
The tri-3-methyltrianthranilide derivatives ()–() have been synthesised. Dynamic 1H n.m.r. spectroscopy indicates that the ,′,″-trimethyl derivative () exists in solution as slowly ring inverting ( ? *) enantiomeric helical conformations. X-Ray crystallography shows that the ,′-dimethyl-″-benzyl derivative () undergoes spontaneous resolution when it crystallises as a 1:1 adduct from toluene. The host molecules adopt a helical conformation (Figure 1) within a lattice structure that contains chiral channels (Figure 2) occupied by guest solvent molecules. 相似文献