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
An azaanalog of adamantene, 2-azaadamant-1-ene () and 4-azaprotoadamant-3-ene () were generated in the nonstatistical ratio via photolysis of 3-azidonoradamantane (). The highly strained and could not be isolable but were trapped by MeOH. Acidolysis of was also reported, and discussed in comparison with the photolysis. 相似文献
The crystal and molecular structures of the title isomeric compounds and , obtained by intramolecular N,S--dialkylation of 5,5-diphenyl-2-thiohydantoin with 1,2-dibro-moethane, have been determined from X-ray diffractometer data. 2,3-Dihydro-6,6-diphenylimidazo-[2,1-b]-thiazol-5(6H)-one crystallizes in space group P212121 with a=11.376(3), b=12,255(5), c=8.434(3) Å and Z=4. Crystals of , containing one molecule of benzene, are monoclinic,space group P21/c with a=11.539(6), b=10.242(3), c=16.353(5) Å, β=95.45(5)° and Z=4. In both cases a planar geometry of the two fused five-membered heterocyclic rings was found. The selected bond lengths in and , as well as those analogous imidazothiazinones and , were used to calculate EHOSE (Harmonic Oscillation Stabilization Energy). The problem of stability and chemical reactivity of compounds to is also discussed. 相似文献
The structures of three new prenylphenyl propanoids, wutaiensol (), wutaiensal (), and methyl demethoxywutaiensate () were established by correlating with S-rutaretin methyl ether () or S-marmesin () by chemical means. The structure of wutaialdehyde (), a related compound, was also established by total synthesis of the racemate and by correlating with . Preliminary piscicidal test on these compounds disclosed that and are weakly bu distinctly positive. 相似文献
A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines () from 3-(3-methylbut-1-enyl)-2-quinolones () is described. A neat synthesis of the alkaloids (±)-lunacrine (), (±)-lunasine () and (±)-demethoxylunacrine () is also reported. 相似文献
Compounds and prepared from eugenol () and safrole () respectively were submitted to ozonation in methanol at 0°C. The 3-alkyl muconic acid dimethyl esters were produced from (~ 45%), while starting from the 3-alkyl muconic acid monomethyl esters were obtained regiospecifically (~ 75%). These latter compounds were transformed (~ 85%) into the 4,4-dialkyl butenolides . 相似文献
The molecular structure of the cyclic dipeptide of dehydrophenylalanine [3,6-bis(phenylmethylene)-piperazine-2,5-dione] has been determined from three dimensional X-ray data. C18H14 N2O2 is monoclinic, space group C2/, with Z = 12 in a cell of dimensions =4Ø.774(1), =6.237(2), =17.731(3) Å, β=107.76(5)°. Molecules are approximately planar as far as the piperazinedione ring is concerned, and they are linked in two series of hydrogen-bonded ribbons. The vapour phase He(I) and He(II) photoelectron spectra are also presented. Their assignment is proposed by comparison with related molecules and supported by semiempirical quantum mechanical calculations. Analogies and differences with respect to the photoelectron results of the cyclic dipeptide of dehydroalanine and corresponding acyclic compounds are discussed. 相似文献
Several π-excessive heteropolyaromatic compounds, which contain furan and thiophen ring and are possible antifungal agents, have been synthesized in good yields according to two general methods. The first method has been used to prepare compounds possessing thiophens linked by their 2- and 5-positions, such as the ter-aryls , and . Two precursors of these compounds have been obtained either by the Glaser reaction, or using a novel Pd-mediated reaction. The second method,which consists of the Ni-or Pd-catalyzed heteroarylation of heteroarene halides via cross-coupling with heteroaryl Grignard reagents or zinc halides,has been used to prepare the bi-aryls , which contain two heteroaromatic units, and the ter-aryl . Compound has been also prepared starting from 2-(2-thienyl) furan () by selective lithiation, followed by bromination.The 13C NMR signals of and have been assigned on the basis of the literature data and by relaxation measurements. Relaxation data have been also used to obtain qualitative informations on the conformational equilibria of the bi-aryls , and the ter-aryls . 相似文献
(lS,5S)-exo-2(R)-Methylbicyclo[3.1.0]hexan-3-one () and (lS,5S)-endo-2(S)-methylbicyclo[3.1.0]hexan-3-one (2) were synthesized and their circular dichroism (CD) spectra run. Conformational analysis based on molecular mechanics calculations and Karplus equation analyses of vicinal H¦H NMR coupling constants indicate boat-like sofa conformations for both and , with very little ring distortion from the symmetry of the parent bicyclo[3.1.0]hexan-3-one. The lone dissymmetric ψ-axial and ψ-equatorial methyl groups of and , respectively, are both octant consignate. The natural product analogs of and , (?)-3-isothujone () and (+)-3-thujone () were prepared and examined similarly. Their α-methyl perturbers dominate the CD n-π★ Cotton effects. 相似文献
Natural (?)-botryodiplodin() has been synthesized from an antibiotic methylenomycin A (). The absolute configurations of (?)-botryodiplodin( and methylenomycin A () have also been established as shown in and respectively. 相似文献
Photoreactions of 2-(2′, 4′-dinitrobenzyl)-pyridine () and 2, 2′, 4, 4′-tetranitrodiphenylmethane () were investigated by means of ps-probe beam spectroscopy. It could be shown, that the electronic ground states of aci-nitro-forms and polymethine forms of flashed compounds were populated after 50 ps (compound ) and 30 ps (compound ) direct from excited states of compounds and . A possible reaction scheme will be given. 相似文献
Alkenes a–d interact at ?80°C in 15 min. with the Vilsmeier reagent (Me2N=CHCl)+PO2Cl2? in presence of 30% H2O2 to yield the corresponding epoxides a–d. The reaction could involve the formation of the highly reactive hydroperoxymethylenedimethylammonium salt (Me2N=CHOOH)+PO2Cl?2. 相似文献
Isomerization of -bicyclo[10.8.0]eicos-1(12)-ene () and -bicyclo[10.10.0]docos-1(12)-ene () to [10.8]- and [10.10]betweenanene ( and ) has been effected by sulfuric acid. In both cases, the betweenanene isomers were found to predominate at equilibrium (70/30 / and 95/5> /). 相似文献
(1,l-Dihydroperfluoroalkyl)phenyl- and --fluorophenyliodonium triflates and were synthesized by the reaction of l-bis(trifluoroacetoxy)iodo-1,l-dihydroperfluoroalkanes with triflic acid and benzene or fluorobenzene in 1,1,2-trichlorotrifluoroethane. The use of fluorosulfonic acid and sulfuric acid instead of triflic acid afforded (1,l-dihydroperfluoroalkyl) phenyliodonium fluorosulfonate and sulfate , respectively. Similarly, (1,1,ω-trihydroperfluoroalkyl)phenyliodonium triflate and 1,1,5,5-tetrahydroperfluoropentane-l,5-bisphenyliodonium triflate were synthesized. 相似文献
The model tripeptide Boc-Gly-S-Ala-Aib-OMe () and the two monothiated analogues Boc-Gly(1ψ2CSNH)-S-Ala-Aib-OMe () and Boc-Gly-S-Ala(2ψ3 CSNH)-Aib-OMe () were synthesized. Peptide was obtained by thiation of using 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide, Lawesson's Reagent (LR), followed by deprotection of the Boc group and coupling with Boc-Gly-OH. Thiation of with LR regiospecifically transformed the protected tripeptide to the monothiated analogue . X-Ray diffraction analysis showed that the type-III β-turn formed by the reference peptide is preserved in the monothiated analogue ; conversely,the structure of the isomeric tripeptide is partially extended. 相似文献
Methods were developed to prepare 1 -methyl-, 3-methyl- and 4-0-methyl-ψ-isocytidine by selective methylation.35O-Tetraisopropyldisiloxanyl-ψ isocytidine (8) was trimethylsilylated and then treated with MeI and, after deprotection, 1 -methyl-ψ isocytidine (6) was obtained. The 2deoxy analog (7) was also prepared in a similar manner from the 2deoxy analog (10) of 8. Treatment of 8 with CH2N2 afforded the 3-methyl-ψ-isocytidine derivative (19) as the major product. Methylation with diazomethane also occurred mainly on N3 of the 2deoxy analog 10 to form 20. Removal of the 3 5O-protecting group from 19 and 20 afforded 3-methyl-ψ-isocytidine (14) and its 2-deoxy analog (15), respectively. 2-N-Acetyl- 35O-tetraisopropyldisiloxanyl-ψ-isocytidine (24), on the other hand, gave the 4-O-methyl derivative (25) as the major product upon CH2N2 treatment. Subsequent deprotection of 25 afforded 4-O-methyl-ψ-isocytidine (29). aiv51b1p33b 相似文献
Aziridines and 2H-azirines are now very easy to prepare. These small rings are transformed in fluoroamine and fluoroketone by reaction with HF liquid or Olah reagent. Different compounds , or are obtained. A lot of examples will be described.a) Configuration of depends of the reagent (HF liquid or Olah reagent): Mechanism of this reaction will be discuss.b) Some aziridines give a mixture of fluoroaminoisomers. Example: With R = H, a mixture of (65 %) and (35 %) is obtained. It is possible to form quantitatively one regioisomer only, by using activating group on the nitrogen (R CO2tBu).c) From azirine , formation of or dépends of the nature of substituents at carbon C-2. If a carbocation can be easily formed at C-2 carbon, only fluoroketone is isolated.Difluoroamine are obtained if carbon C-2 is a secondary or primary one. By using a modified Olah's reagent, we improve the yield.Application of this results on synthesis of fluorosteroïd compound will be presented: 相似文献
The novel ylides (II) and (III) have been obtained treatment of perfluoro-1-azacyclohexene and perfluoro-2-azapropene, respectively, with -iminopyridinium ylide (I) generated from -aminopyridinium iodide and anhydrous potassium carbonate in methylene chloride. A mixture of the -triazolo[1,5-]pyridine (IV) and a compound thought to be its dihydro-analogue (V) were isolated following attack on perfluoroacetonitrile by the parent ylide (I); the former product was also prepared by heating 1,2-diamino-pyridinium iodide with trifluoroacetic anhydride. 相似文献
Three fungal metabolites with a common structural feature as prenylated phenols were synthesized in their naturally occurring and optically active forms: ascochlorin [(2',4',1',2',6')-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[5'-(1',2',6'-trimethyl-3'-oxo-cyclohexyl)-3'-methyl-2', 4'-pentadienyl] benzaldehyde], ascofuranone [(2',6',1')-(-)-5-chloro-2, 4-dihydroxy-6-methyl-3-[7'-(3',3'-dimethyl-4'-oxo-2'-oxacyclopentyl)-3',7'-dimethyl -2', 6'-heptadienyl] benzaldehyde] and ascofuranol [(2',6',1',4')-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[7'-(3', 3'-dimethyl-4'-hydroxy-2'-oxacyclopentyl)-3', 7'-dimethyl-2',6'-hepta-dienyl]benzaldehyde ]. (+)-Ascofuranone and (+)-ascofuranol were also synthesized. By the present synthesis the absolute configuration of the natural (-)-ascofuranol was established as (1',4'). 相似文献
2,4,6-Triphenylpyrylium with thiosemicarbazide and thiocarbohydrazide, gives 2-pyrazolines and which undergo cyclization yielding pyrazolo(1,5-c]pyrimidine 5 and pyrazolo [2,3-d]-1,2,4-triazepine derivatives, respectively. Reaction of with phenacyl bromides gave 1,3-thiazolo[3,2-b]pyrazolo [2,3-d]-1,2,4-triazepin-4-iums . Compound on treatment with phenacyl bromides gave 1-(4'-aryl-thiazol-2'-yl)-2-pyrazoline derivatives . Compound reacts with acyl chlorides to give pyrazolo[1,5-c]pyrimidine derivatives , and with aromatic aldehydes giving the 2-(Δ2'1 pyrazolin-1-yl)-5-aryl-1,3,4-Δ2-thiadiazolines which were easily converted to the corresponding 2-(Δ2-pyrazolin-1-yl)-5-aryl-1,3,4-thiadiazoles . 相似文献