Hydrolytic reactions of guanosyl-(3',3')-uridine and guanosyl-(3',3')-(2',5'-di-O-methyluridine)

Hydrolytic reactions of guanosyl-(3',3')-uridine and guanosyl-(3',3')-(2',5'-di-O-methyluridine) have been followed by RP HPLC over a wide pH range at 363.2 K in order to elucidate the role of the 2'-hydroxyl group as a hydrogen-bond donor upon departure of the 3'-uridine moiety. Under neutral and basic conditions, guanosyl-(3',3')-uridine undergoes hydroxide ion-catalyzed cleavage (first order in [OH(-)]) of the P-O3' bonds, giving uridine and guanosine 2',3'-cyclic monophosphates, which are subsequently hydrolyzed to a mixture of 2'- and 3'-monophosphates. This bond rupture is 23 times as fast as the corresponding cleavage of the P-O3' bond of guanosyl-(3',3')-(2',5'-di-O-methyluridine) to yield 2',5'-O-dimethyluridine and guanosine 2',3'-cyclic phosphate. Under acidic conditions, where the reactivity differences are smaller, depurination and isomerization compete with the cleavage. The effect of Zn(2+) on the cleavage of the P-O3' bonds of guanosyl-(3',3')-uridine is modest: about 6-fold acceleration was observed at [Zn(2+)] = 5 mmol L(-)(1) and pH 5.6. With guanosyl-(3',3')-(2',5'-di-O-methyluridine) the rate-acceleration effect is greater: a 37-fold acceleration was observed. The mechanisms of the partial reactions, in particular the effects of the 2'-hydroxyl group on the departure of the 3'-linked nucleoside, are discussed.     

X-ray Structure of 1- (3' -Phenyl-4' -morpholinyl-2' 5' - dithiole-1' - ylidene)-3, 4-biscarboethoxy-2-thionaphthalene

1INTR0DUCTIONa-Thiocarbonylthioformamideshavebeensynthesizedsince1980[l-23,however,thereisn0reP0rtofthesecomP0undsrelatedtheirpropertiesandreactivities(3).Ac-cordingtothepublishedpapers('-",adithioketone,adithioesterandadithioth-ioesteraresnitablefort4 2JcycloadditionwithalkenicandacetylenicdienophileS.Wewanttoknowwhethera-thiocarbonylthioformamideshavethesamecharacters,thereforethereactionofathiobenzoylthioformmorpholine(1)withdiethylacetylenedicarboxylate(2)wasexplored.Theredultsshowth…     

Practical designed syntheses of all stereoisomeric bis(2,2')- and tris(2,2',2' ')-tetrahydrofurans

A convenient synthetic entry to the entire group of bis(2,2')- and tris(2,2',2' ')-tetrahydrofurans has been developed. The method is concise and relies on chromatographic separation, decarbonylation, and annulation to arrive at a specific product of defined relative configuration. [reaction: see text]     

Solid-state synthesis of poly(3',4'-dimethoxy-2,2':5',2"- terthiophene): comparison with poly(terthiophene) and poly(3',4'-ethylenedioxy-2,2':5',2"- terthiophene)

A new terthiophene monomer: 3',4'-dimethoxy-2,2':5',2"-terthiophene (TMT) was synthesized and characterized by 1H-NMR, 13C-NMR and FTIR. The solid-state oxidative polymerizations of TMT were performed in various ratios of oxidant (FeCl?) to monomer (TMT). The resulting polymers were characterized by 1H-NMR, FTIR, UV-vis-NIR, GPC, X-ray diffraction, CV, as well as TGA and conductivity measurements. The structure and properties of poly (TMT) were compared with those of polyterthiophene [poly(TT)] and poly (3',4'-ethylenedioxy-2,2':5',2"-terthiophene) [poly(TET)] prepared under the same polymerization conditions. After comparative analysis with poly(TT) and poly(TET), the effects of the dimethoxy substituent and FeCl? on the structural and physicochemical properties of the poly(TMT)s were discussed in depth. The comparison suggested that the dimethoxy-substituted polymer did not display higher crystallinity, thermal stability, conductivity and electrochemical activity than ethylenedioxy substituted one. The results also showed that the effect of FeCl? on poly(TMT) was similar that seen with the poly(TT), in which the oxidation degree, electrochemical activity and conductivity increased steadily with increasing [FeCl?/[TT] ratio. Furthermore, the poly(TMT) and poly(TT) are mostly made up of dimers with a small amount of higher molecular weight components.     

3-(2-二唑啉基)-色酮类化合物的合成研究

报道了取代的邻羟基苯乙酮(1a～1e)经Vilsmeier-Haack反应一步制得3-醛基色酮(2a～2e),2a～2e与取代的芳酰肼(3a～3c)缩合制得15个酰腙类化合物(4a～4o),4a～4o在醋酸酐作用下关环得15个3-(2-苝二唑啉基)-色酮(5a～5o),并通过元素分析,IR,~1H NMR和MS诺数据确证了上述化合物的结构。     

N-(S)-(1’-氯甲基-2’-烷基)-2-乙基-2-(4S-烷基-4,5-二氢噁唑)丁酰胺的合成

由L-氨基酸不对称合成了4种新型手性化合物(6a,6b,7a,7b),其结构经IR,~1H NMR,~(13)C NMR及MS等证实。     

Synthesis of [ethylene-1-(eta(5)-4,5,6,7-tetrahydro-1-indenyl)-2- (eta(5)-4',5',6',7'-tetrahydro-2'-indenyl)]titanium dichloride, the elusive isomer of the Brintzinger-type ansa-titanocenes

We present a short synthesis of 1-(2-indenyl)-2-(3-indenyl)ethane (5) and a method for its conversion to the ansa-metallocene [ethylene(eta5-inden-1-yl)(eta5-inden-2-yl)]titanium dichloride (13). The synthetic strategy applied to prepare bisindene 5 relies on the efficient alkylation of 2-(phenylsulfonyl)indane followed by HMPA-assisted E1cB-elimination of phenylsulfinate. This tandem sequence circumvents the predisposition of indene to undergo C(1)-alkylation and enables access to C(2)-substituted indenes. The key step in the synthesis of the title ansa-titanocene (4) features a previously unreported equilibration step to generate the bis(indenide anion) of 5. Complexation with TiCl4.(THF)2 followed by hydrogenation of the product metallocene furnishes ansa-titanocene 4.     

Stereoselective Synthesis of (6R)-6-(5-Methyl-2-furyl)-2-oxocyclohexanecarboxyl-10', 2'-Sultam

PseudolaricacidA(l)whichexhibitsantifungalandantifertilityactivitieswasisolatedfromPeudolarl-xKaenlpjbriGord'.Theabsoluteconfigurationsofthesechiralcenterswereassignedtobe3S,4S,10RandIIRrespectively'.Accordingtotheretrosyfltheticanalysis.theskeletonofIcouldbeconstructedbyintramolecular[4- 31cycloadditiontyomaseven-memberedlactone2(Schemel)whichcouldbeobtainedfrom(6S)-6-Thesynthesisbeganwithbetalprotected0-ketoacid4,tbllowedbyamidationwith(-)-camphorsultamandDCCtoobtainapairofdiastereomer…     

1-(2'-苯基-1', 2', 3'-三唑-4'-甲酰基)-4-芳基氨基硫脲及其 环化产物的合 成

以2-苯基-1,2,3-三唑-4-甲酰肼为原料合成了几种新的1-(2'-苯基-1',2',3'-三唑-4'-甲酰基)-4-芳基氨基硫脲,在不同条件下环化,制得一系列新的1,3,4-噻二唑、1,3,4-恶二唑和1,2,4-均三唑衍生物。化合物的结构经元素分析、IR、^1HNMR和MS确证,并对其波谱性质进行了讨论。