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In previous work from our laboratory, we demonstrated that α-carbonyl radical cyclization reactions can serve efficiently as key steps in total synthesis of natural products.1 In this presentation,we report the total synthesis of (-)-α-pinguisene from enone 1 via α-carbonyl radical cyclization. 相似文献
3.
G. N. Molchanova P. V. Petrovskii T. M. Shcherbina A. P. Laretina L. S. Zakharov M. L. Kabachnik 《Russian Chemical Bulletin》1996,45(6):1445-1448
The synthesis of alkanols of the general formula R3Si(CH2)nCH(OH)RF (n = 1–3) is elaborated and their behavior under GC-MS is studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1516-1519, June, 1996. 相似文献
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Recently,three novel styryl-lactones,goniofufurone,goniopypyrone,and 8-acetylgo-niotriol,which are cytotoxic to human tumor cells,have been isolated from the stembark of Goniothalamus species.Amongst these lactones,goniopypyrone is the mostbioactive.Its unusual natural skeleton was revealed by X-rav structure analysis to be 相似文献
5.
《Tetrahedron: Asymmetry》2000,11(18):3665-3669
An efficient synthesis of the (S)-(−)- and (R)-(+)-enantiomers of 15-deoxyspergualin (15-DSG) is reported. The synthesis involves preparative HPLC separation and subsequent hydrogenolysis of two diastereoisomers 10a and 10b of fully protected 15-DSG penultimates. Alternatively, diastereomerically pure amide 10b (97% de) was also prepared from acid 8b (97% de), which was obtained via crystallization of a 1:1 diastereomeric mixture of 8a and 8b. 相似文献
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A very efficient and practical procedure for preparation of ( S)-( - )-ofloxacin has been developed (10 steps, overall yield ≥ 45 % ) . The key step of this approach is the regioselective nucleophilic substitution of 2-position fluorine atom of 2,3,4-tirfluoronitrobenzene by (S)-glycerol acetonide. 相似文献
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《Tetrahedron: Asymmetry》2004,15(17):2657-2660
In the presence of 10% NaOH in boiling MeOH enantiomerically enriched HPPH is racemized. This permits the deracemization of HPPH in the presence of brucine, giving enantiomerically pure (−)-(S)-HPPH [(−)-(S)-5-(4-hydroxyphenyl)-5-phenylhydandoin]. 相似文献
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A novel, efficient and protecting group free enantioselective synthetic approach of (?)-(R)-1 and (+)-(S)-rolipram 2 is described employing the organocatalyzed asymmetric Michael addition, Henry condensation, Wittig olefination and reductive lactamization reactions as key steps. 相似文献
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Kaerophyllin (1) ,hinokinin (2 )andtheiranalogue isohinokinin (3)belongtothedibenzylbutyrolactone lig nans .Kaerophyllin (1)wasisolatedfromtherootofspot tedcowparsley (ChaerophyllummaculatumWilld .) 1andhinokinin (2 )wasisolatedfromtheheartwoodofLiboce drusformosanaFlorin .2 AccordingtoMacRaeandTow ers ,3afivememberedlactoneringandamethylenedioxylgroupwereimportantstructuralcharacteristicswhichcon tributetotheactivityoflignansasantitumoragents .More over ,anunsaturateddoublebondbetweenC3—… 相似文献
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An efficient enantiospecific synthesis of a neuromodulator, antiepileplic and hypotensive drug (R)-(-)-γ-amino-β-hydroxybutyric acid (1) starting from (+) tartaric acid is described. 相似文献
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《中国化学快报》1997,(8)
ThenatieChenmanginclha,oneofthemoStbeandexpensivCherbaldrugSin~tionalChjnsemdednesisthewoodypartofAquIIarasinensisW.)Gilg.,whoseVofatileoilseforitaIUUnberofinterestinbiologicalandphannacologicalactivities,suchasanestheha,muscularrelaxationandanalgesta'.ReCentiyYanetaI2isolated(-)taim~cacid(1)frOmtheVOboleoilofChenAlang,anddeennineditSStIUCtUrbySpeCtrscoPicmethodandred~1toaknowncornPOunisobaimndnolCoInPOun1isthefirStcarboxylicacidwithdihydragarohanskeletonisolatedfromnisources.He… 相似文献
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A six step synthesis of (±)-7-hydroxylycopodine has been achieved in 5% overall yield. In the key step, a Prins cyclization of a bicyclic keto alkyne in 60% H(2)SO(4) forms a tricyclic dihydroxy amino ketone. 相似文献
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é. I. Ivanov A. A. Yavolovskii E. A. Kuklenko O. S. Timofeev 《Chemistry of Heterocyclic Compounds》1991,27(2):225-227
Depending on the base used, reaction of 3-(-hydroxyethyl)-8-thiaxanthine with p-toluenesulfonylchloride either stops at the stage of formation of the tosylate or gives 1,2,5-thiadiazolo[3,4-d]oxazolidino[2,3-b]pyrimidin-9(4H)-one. Upon treatment with ammonia or methylamine, both of these compounds react to give 3-(-hydroxyethyl)-8-thiaguanines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 272–274, February, 1991. 相似文献
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Po S. Poon Ng 《合成通讯》2013,43(13):2261-2268
A total synthesis of (±)-cis-5-hydroxycalamenene 1 has been achieved from tetralone 5, which in turn was prepared from 5-methoxy-α-tetralone 3. Grignard reaction of compound 5 with isopropylmagnesium chloride, followed by dehydration and aromatization, provided the substituted naphthalene 7 whose conversion to (±)-cis-5-hydroxycalamenene 1 was accomplished by demethylation, formylation, and hydrogenation. 相似文献
16.
《Tetrahedron: Asymmetry》2001,12(15):2205-2211
The enantiomerically pure (S)-5-(tosylmethyl)-2-pyrrolidinone 2, prepared from commercially available (S)-pyroglutaminol, is dialkylated at the nitrogen atom and the α-sulfonyl position using several dielectrophiles using sodium hydride as the base to diastereoselectively afford indolizidine derivatives 5 and the less common hexahydropyrrolo[1,2-a]azepin-3-one 6 in moderate to good yield. This domino process has been applied to the synthesis of (−)-δ-coniceine. 相似文献
17.
A seven-step synthesis of (±)-7-hydroxylycopodine that proceeds in 5% overall yield has been achieved. The key step is a Prins reaction in 60% sulfuric acid that gave the key tricyclic intermediate with complete control of the ring fusion stereochemistry. A one-pot procedure orthogonally protected the primary alcohol as an acetate and the tertiary alcohol as a methylthiomethyl ether. The resulting product was converted to 7-hydroxydehydrolycopodine by heating with KO-t-Bu and benzophenone in benzene followed by acidic workup. During unsuccessful attempts to make optically pure starting material, we observed the selective Pt-catalyzed hydrogenation of the 5-phenyl group of a 4,5-diphenyloxazolidine under acidic conditions and the Pt-catalyzed isomerization of the oxazolidine to an amide under neutral conditions. In attempts to hydroxylate the starting material so that we could adapt this synthesis to the preparation of (±)-7,8-dihydroxylycopodine (sauroine) we observed the novel oxidation of a bicyclic vinylogous amide to a keto pyridine with Mn(OAc)(3) and to an amino phenol with KHMDS and oxygen. 相似文献
18.
Abstract (R)-(?)-β-Cuparenone has been synthesized from (S)-(+)-acid-2 obtained via resolution of the racemic acid. Two of the noteworthy steps are (a) repeated methylation of ester (+)-8 with LDA/MeI to furnish (+)-10 and (b) the reaction of 12, having two neopentyl units with NaCN. 相似文献
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《Tetrahedron: Asymmetry》2000,11(23):4681-4686
A short and efficient synthesis of the title compounds is described. (S)-(−)-β-Cuparenone was prepared in 31% yield from p-tolualdehyde and mesityl oxide in eight steps. Absolute stereochemistry was established by means of a diastereoselective cyclopropanation using (R,R)-hydrobenzoin as a recoverable auxiliary. 相似文献
20.
《Journal of Structural Chemistry》2009,50(6):1166-1170
Compound I contains in its molecule pyridyl, monoxime and hydrazone functions. A non-merohedral twin crystal of the compound
with two reciprocal lattices differently oriented and giving rise to double diffraction spot sets with the 0.5:0.5 ratio of
the twin components was studied. The hydrazone and oxime units are approximately planar. The dihedral angles between this
plane and the planes of the pyridine and phenyl rings are 30.79(19)° and 18.43(13)°, respectively. Both the oxime and hydrazone
units in I have an E configuration. The molecules of I are linked via C-H⋯O and O-H⋯N hydrogen bonds forming a 3D framework. The compound was
also characterized by IR, 1H NMR and elemental analyses. 相似文献