Total Synthesis of (±)- Cis -5-Hydroxycalamenene

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.     

Synthesis of ( )-5α-Hydroxy-β-selinene and (-)-5β-Hydroxy-β-selinene

Eudesmanederivativeshavebeendrawingconsiderableattentionduetotheirwidespectrumofbiologicalproperties,particularlyantifeedant,cellgroWthinhibitoryandplantgroWthregulatingactivitiesl'2.Recently,twoepimericeudesmanederivatives( )-5a-hydroxy-6-selinene1and(-)-56-hydroxy-6-selinene2wereisolated3fromtheaerialpartsofCSubtraPicaFMell.,andtheirstructuresweredeterminedbyspectroscopicmethods.Herein,wereportafacilesynthesisofbothtwodiastereomers1and2from( )-dihydrocarvone3infivesteps,usingtheregioselect…     

1,3-Dipolar Cycloaddition of Substituted Benzonitrile Oxide to 5-(R)-(l-Menthyloxy)-2(5H)-furanone

Isoxazoline compounds as key intermediates for construction of natural products have been developed very fast as an hot area in organic synthesis1. 5-(R)-(l-menthyloxy)- 2(5H)-furanone as a valuable chiral synthon has been recently studied for its high stereoselectivity in many reactions2. In this paper, we focused on its reactivity and regioselectivity of the 1,3-dipolar cycloaddition with the substituted benzonitrile oxide3 and several isoxazoline compounds were obtained and characterized…     

Indole derivatives. 138. Synthesis of α-(5-indolyl)ethylamine and 5-(2-aminoethoxy)- and 5-(aminoethylthio)tryptamines

The reaction of 5-acetylindole with hydroxylamine with subsequent reduction of the resulting oxime gave -(5-indolyl)ethylamine. Coupling of 4-(2-phthalimidoethoxy)- and 4-(2-phthalimidoethylthio)phenyldiazonium chlorides with ethyl -acetyl--phthalimidovalerate, subsequent cyclization of the resulting hydrazones, hydrolysis, decarboxylation, and removal of the phthalyl protecting group led to the formation of 5-(2-aminoethoxy)- and 5-(2-aminoethylthio)tryptamines, respectively.For Communication 137, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 46–48, January, 1992.     

Asymmetric Conjugate Addition of Alcohols to (R)-(-)-5-[(1R,2S,5R)-Menthyloxy]-2-(5H)-Furanone

(R)-(-y5-[(IR,2S,5R)-menthyloxy](1)isausefulchiralsynthonreadilypreparedonatWo-stepprocedure-l']FindingsoffuranoneringsexistingascomponentSofsomenaturalproductSI'laswellastheiractivereactivityl']havestimu1atedeXtensiveresearchofitSasymmetricreactionswhichincludeDiels-Alderreactions,l']l,3-dipo1arcycloadditions,['1Michaelauditionsl5]andconjugateedditionsofaminesl']andmercaPtans.g4:,::7f:7':theseadductsledtovariousmultifunctionalhomochiralbuildingblockssuchas2-alkyl-l,4-butanediols,I'l2-aI…     

The mechanism of fluxionality of (1,2,7-η3-2-Me-benzyl)(η5-C5H5)Mo(CO)2

It is shown that (1,2,7-η³-2-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits in solution as one isomer which is fluxional, probably via (7-η¹-2-Me-benzyl)((η⁵-C₅H₅)Mo(CO)₂, with ΔG^≠₃₇₀ = 23.6 ± 1.0 kcal mol⁻¹. In contrast, (1,2,7-η³-3-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits as two isomers at −20°C, which undergo interconversion at room temperature with ΔG^≠ 15.7 kcal mol⁻¹. This dynamic process is an allyl rotation. It is probable that there is also a low energy [1,5]-sigmatropic shift.     

Total synthesis of (±)-cycloclavine and (±)-5-epi-cycloclavine

Novel routes to the naturally occurring indole alkaloid cycloclavine and its unnatural C(5)-epimer are described. Key features include the rapid construction of the heterocyclic core segments by two Diels-Alder reactions. An indole annulation was accomplished by a late-stage intramolecular Diels-Alder furan cycloaddition, and a methylenecyclopropane dienophile was used for a stereoselective intramolecular [4 + 2] cycloaddition to give the cyclopropa[c]indoline building block present in cycloclavine.     

Synthesis and structure of η6-(biphenyl)-η5- (cyclopentadienyl)iron(II) hexaflourophosphates

A series of η⁶-(biphenyl)-η⁵-(cyclopentadienyl)iron(II) hexafluorophosphates have been prepared. Demethylation occured during the synthesis of the 2′-OMe derivatives to yield the correspoding 2′-OH product. The mechanism of this process is discussed. In all cases the complexation involved the unsubstituted phenyl ring. From ¹³C NMR data, values of Hammett resonance parameters σ_R, were calculated which show that the [CpfeC₆H₅]⁺ group behaves as an electron-withdrawing substituent comparable in strength to the cyano group. Approximate values of the biphenyl interplanar angle (θ) were obtained. θ appeared to be significantly lower when electron-releasing substituents were present. ⁵⁷ Fe Mössbauer data support the strong electron acceptor properties of the [CpFe⁺C₆H₅] moiety. In particular the quadrupole splitting (QS) shows a marked increase for the 4-OMe derivative relative to the unsubstituted comples. This is in direct contrast to the aryl ferrocenes. Here, the ferrocenyl and OMe substituents are electronically and so there is no (QS) enhancement.     

2-Polyfluoroalkylchromones. 11. Synthesis and structures of 5-hydroxy-3-(2-hydroxyaryl)-5-polyfluoroalkyl-Δ2-pyrazolines and 3(5)-(2-hydroxyaryl)-5(3)-polyfluoroalkylpyrazoles

The reaction of 2-hydroxy-2-polyfluoroalkylchroman-4-ones with hydrazine affords 5-hydroxy-3-(2-hydroxyaryl)-5-polyfluoroalkyl-²-pyrazolines, whereas 2-polyfluoroalkylchromones under similar conditions produce 3(5)-(2-hydroxyaryl)-5(3)-polyfluoroalkylpyrazoles. 5-(2-Hydroxyaryl)-1-methyl-3-polyfluoroalkylpyrazoles were synthesized in the reaction with methylhydrazine, and the reaction with phenylhydrazine afforded regioisomeric 3(5)-(2-hydroxyphenyl)-1-phenyl-5(3)-polyfluoroalkylpyrazoles.     

Addition of boranes to (E)-(η5-C5H5)2Zr(CH=CHPh)Cl

In this study, the addition of boranes to (E)-(η⁵-C₅H₅)₂Zr(CH=CHPh)Cl (3) has been examined in order to investigate the regioselectivity of these ‘hydroboration’ reactions. We have found that these additions proceed with remarkable selectivity to give exclusive formation of a saturated organic molecule where one carbon atom has both the boron and the zirconium fragments. These reactions do not proceed via a conventional hydroboration reaction, but instead go through an initial transmetalation step to generate (E)-(η⁵-C₅H₅)₂Zr(H)Cl (1) and the corresponding alkenyl boron intermediate, whereupon subsequent hydrozirconation of this latter species gives the geminal products. An x-ray diffraction study has been conducted on gem-(η⁵-C₅H₅)₂Zr(CH(Bpin)CH₂Ph)Cl (pin = 1, 2-O₂C₂Me₄) (2). Crystals of 2 were orthorhombic with a = 18.545(3) Å, b = 15.713(3) Å, c = 16.157(3) Å in the space group Pccn. An x-ray diffraction study has also been conducted on the trinuclear zirconium oxide species (η⁵-C₅H₅)₂ZrO₂[ZrCl(η⁵-C₅H₅)₂]₂ (4). Crystals of 4 were orthorhombic with a = 13.6000(8) Å, b = 14.2252(8) Å, c = 17.6500(10) Å in the space group P2(1)2(1)2(1).      

Why are SiX5(-) and GeX5(-) (X = F, Cl) stable but not CF5(-) and CCl5(-)?

The possible existence of the CF(5)(-), CCl(5)(-), SiF(5)(-), SiCl(5)(-), GeF(5)(-), and GeCl(5)(-) anions has been investigated using ab initio methods. The species containing Si and Ge as central atoms were found to adopt the D(3h)-symmetry trigonal bipyramidal equilibrium structures whose thermodynamic stabilities were confirmed by examining the most probable fragmentation channels. The ab initio re-examination of the electronic stabilities of the SiF(5)(-), SiCl(5)(-), GeF(5)(-), and GeCl(5)(-) anions [using the OVGF(full) method with the 6-311+G(3df) basis set] led to the very large vertical electron detachment (VDE) energies of 9.316 eV (SiF(5)(-)) and 9.742 eV (GeF(5)(-)), whereas smaller VDEs of 6.196 and 6.452 eV were predicted for the SiCl(5)(-) and GeCl(5)(-) species, respectively. By contrast, the high-symmetry and structurally compact anionic CF(5)(-) and CCl(5)(-) systems cannot exist due to the strongly repulsive potential predicted for the X(-) (F(-) or Cl(-)) approaching the CX(4) (CF(4) or CCl(4)). The formation of weakly bound CX(4)···X(-) (CF(4)···F(-) and CCl(4)···Cl(-)) anionic complexes (consisting of pseudotetrahedral neutral CX(4) with the weakly tethered X(-)) might be expected at low temperatures (approaching 0 K), whereas neither CX(5)(-) (CF(5)(-), CCl(5)(-)) systems nor CX(4)···X(-) (CF(4)···F(-) and CCl(4)···Cl(-)) complexes can exist in the elevated temperatures (above 0K) due to their susceptibility to the fragmentation (leading to the X(-) loss).     

Photochemical Synthesis of 5-Ethynyl-5′-(1-Propynyl)-2.2′-Bithiophene

The synthesis of the title compound is described. The key-step is the photochemical coupling between 5-iodo-2-thienylcarbaldehyde and 2-bromothio-phene to give 5-bromo-2,2′-bithienyl-5′-carbaldehyde.     

Oxidation of theexo- andendo-phenylcyclohexadienyl iron complexes Fe(η5-6-PhC6H6) (η5- C5H5)

The roe of oxidatively induced homolyhc scission a the C(sp³)-H bonds in the iron phenykychhexadienyl complexes Fe(⁵-6-PhC₆H₆)(⁵-C₅H₅) (1) depends on the spatial orientation of the Ph substitutent. In the case of the (1 _endo ⁺) radical cation this process, resulting in the cationic biphenyl complex (Fe(⁶ -C₆H₅C₆H₅)(⁵-C₅H₅)]⁺ (2 ⁺), is fast and proceeds for several minutes. In the case of the more stable radical cation (1 _exo ⁺) the formation of 2⁺ is slow and takes tens minutes to complete.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1698–1700, July, 1996.     

Synthesis of cis-(±)-2-Hydroxymethyl-5-(Cytosine-1'-yl)-1,3-Oxathiolane (BCH-189)

cis-BCH-189 are potent anti-HIV agents and have been synthesized from mannose1 galactose2 or glucose3 etc. Owing to so many synthetic steps, it is difficult and expensive to obtain a few grams. In this paper, we have designed new route and promoted the reaction conditions for the synthesis of this nucleoside cis- (+)- BCH-189 from cheap starting material via a four step route as shown in Scheme 1. By this method, a series of derivatives of title compound can be synthesized conviniently for…     

Crystal Structure and Spectra Characters of 2-Benzoly-3-(4-(1,2,4-triazole)-5-anilino-thiophene and 2-(4-Methyl-benzoly)-3-(4- chlrolphenyl)-3-(1,2,4-triazole)-5-anilino-thiophene

Triazole derivatives are widely studied, because they represent the largest group of modern fungicides and are widely used both in human and veterinary therapy and in agriculture. We synthesized the title compound in which the thiophene ring was substituted by a 1,2,4-triazole group, a phenacyl group, a phenylaminol group and a benzene ring.     

Convergent asymmetric synthesis of indolizidines from (S)-5-(tosylmethyl)-2-pyrrolidinone: synthesis of (−)-δ-coniceine

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.     

A highly enantioselective synthesis of 5- (ι-menthyloxy) -4-substituted-3-chloro-2(5H) -furanones

In this paper, stereocontrolled tandem Michael addition-elimination reaction of the novel chiral source, S-(ι-menthyloxy)-3,4-dichloro-2(5H)-furanone, with various thiols and amines has been investigated. A series of new enantiomerically pure compounds, 5-(ι-menthyloxy)-4-substituted-3-cnloro-2(5H)-furanones, were obtained in good yields with d. e.(?)98% under mild conditions.     

Total synthesis of 5R,5-(1''''R-hydroxy-2''''-phenylethyl)-γ-lactone

The latest and highly efficient asymmetric dihydroxylation was employed to create the chiral vicinal dihydroxy group of the title compound 1, which has been synthesized from phenylacetaldehyde through 6 steps with a total yield of 61%.     

Synthesis of (3S,5R)-cis- and (3S,5S)-trans-3,5-Dimethylvalerolactones and Their Conversion to Biotransformation Products of (S)-5-Ethyl-5-(2′-pentyl)barbituric Acid

(R,S)-5-Ethyl-5-(2′-pentyl)barbituric acid (I)^1,2 is metabolized in vivo to give all four possible optical isomers of 5-ethyl-5-(3′-hydroxy-1′-methylbutyl)barbituric acid (II). ^3,4 From metabolism studies of pure (1′S)- I and (1′3)-I, Palmer and co-workers^4,5 were able to determine the relative amounts of each of the four isomers formed. These studies showed that (1′S)-I gave mainly one enantiomer of (1′S)-II, whereas (1′R)-I gave approximately equal amounts of both (1′R)-II enantiomers.