The synthesis of the potent anti-herpes virus agent, E-5(2-bromovinyl)-2′-deoxyuridine and related compounds

The synthesis of $\text{E}$-5(2-bromovinyl)-2′-deoxyuridine in good yield from deoxyuridine $\text{via}$ an intermediate organopalladium derivative is described. The corresponding chloro and iodo compounds have also been made as have the corresponding bromo and iodo 2′-deoxycytidines.     

Completely stereoselective synthesis of all four stereoisomeric 1-carbamoyloxy-1,3-alkadienes via anti-diastereoselective homoaldol reaction from aldehydes and a single carbon-three-unit

Lithiation of both ($\text{Z}$)- and ($\text{E}$)-3-trimethylsilyl-2-propenyl $\text{N}$,$\text{N}$-diisopropyl carbamate 2 affords the (2$\text{E}$) -lithium compound 3. Aluminium- or titanium-mediated addition to aldehydes, 4 gives (1$\text{E}$)-(3$\text{R}$*4$\text{S}$*)-enol carbamates 7. A stereospecific Peterson elimination (borontriflouride- or base-mediated) introduces the second double bond either with (3$\text{E}$)- or with (3$\text{Z}$)-configuration. So just by reagent selection for each of the two steps, (1$\text{E}$,3$\text{E}$)-, (1$\text{E}$,3$\text{Z}$)-, (1$\text{Z}$,3$\text{E}$)-, or (1$\text{Z}$,3$\text{Z}$)- dienes 8 - 11, respectively, are prepared with stereoselectivities up to > 99.7%     

Preparation and reactivity of 2,6—dimethoxy—4—allylidene—2,5—cyclohexadien—1—one (vinyl quinone methide) a novel synthesis of sinapyl alcohol

Title compound ($\text{3}$b), prepared in concentrated CHCl₃ or benzene solution and spectroscopically characterized, is shown to be an useful intermediate for the synthesis of sinapyl alcohol ($\text{1}$b) and its derivatives.     

A new pathway in the reactions of chromones and hydroxylamine in anhydrous solutions

In the nucleophilic reaction of chromone ($\text{1}$) with NH₂OH·HC1 in anhydrous methanol a new compound 2-methoxychromanone ($\text{6}$) appeared as an intermediate in the formation of chromone oxime ($\text{8}$) and 2-methoxychromanone oxine ($\text{7}$).     

Stereochemically controlled synthesis of unsaturated acids via diphenylphosphinoyl (Ph2PO) -ketoacids

Acylation of phosphine oxide anions with derivatives of cyclic anhydrides or oxidative cleavage of cyclic allyl phosphine oxides gives Ph₂PO-ketoacids: reduction, separation of diastereoisomers, and completion of the Horner-Wittig reaction gives single isomers ($\text{E}$) or ($\text{Z}$) of unsaturated acids.     

Reactions of sulfoxonium allylides with nitrile oxides and ring transformations of their reaction products

Reactions of allylides ($\text{1}$) with nitrile oxides ($\text{2}$) afforded furanylglyoxylate oxime ($\text{3}$) and 6H-l,2-oxazine ($\text{4}$). Ring transformations of $\text{3}$ and $\text{4}$ gave $\text{4}$ and pyrrolinone ($\text{6}$), respectively.     

A Wittig reaction on mucochloric and mucobromic acids. Preparation of ethyl (2E, 4Z -4,5-dihalo-2,4-pentadienoates and alkyl 2E -5-bromo-2-penten-4-ynoates

Reaction of mucochloric and mucobromic acid with (ethoxycarbonylmethylene) triphenyl-phosphorane affords the ethyl ester of (2$\text{E}$, 4$\text{Z}$ -4,5-dichloro- and (2$\text{E}$, 4$\text{Z}$) -4, 5-dibromo-2,4-pentadienoic acid respectively; in the latter case ethyl (2$\text{E}$ -5-bromo-2-penten-4-ynoate is formed concomittantly.     

Electrophile-mediated cyclizations in carbohydrate chemistry: synthesis of highly functionalized ribofuranose and ribopyranose compounds

Iodine-mediated cyclization of (Z)- and (E)-{=D}-ribohept-2-enonates $\text{1}$ and $\text{2}$ gave exclusively the β-ribofuranose and α-ribofuranose derivatives $\text{3}$ and $\text{4}$, respectively. Cyclization of the (Z)- and (E)-2-heptene-1-ol derivatives $\text{5}$ and $\text{6}$ gave ribofuranose products ($\text{7}$ and $\text{8}$) and a ribopyranose ($\text{9}$), respectively.     

A new synthetic method of 3-acyltetronic acid derivatives and its application to the synthesis of isoaspertetronin a (isogregatin A)

A new synthetic method of 3-acyltetronic acid derivatives from the corresponding 3-bromo compound via lithiation with n-BuLi followed either by acylation with acid chloride or better by first reacting with aldehyde and then subsequent oxidation with active MnO₂ is described. A revised structure $\text{10}$ for aspertetronin A(gregatin A) was presented based on the synthesis of the proposed structure $\text{8}$ and spectral comparison of a model compound $\text{12}$ with the natural product.     

Polymerization in liquid crystals—IV: The polymerization of cholesteryl-vinyl-succinate

The solid-, cholesteric- and liquid-state polymerizations of cholesteryl-vinyl-succinate (CVS) are studied. Only one of the three polymorphic modifications of CVS oligomerizes in the solid state into oligomers of degree $\text{P}\text{= 2}\text{to}\text{6}$ in a homogeneous topochemical reaction. The rate of polymerization in the cholesteric state is lower than that in the liquid state at the same temperature. Kinetic constants were measured at 85° using benzoyl peroxide as initiator and the Banfield radical, giving E_overall = 15.4, 36.4 kcal/mole^?1; $\text{f = 0.52, 0.19; k}{}_{\mathrm{p}}\text{/k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.0167, 0.0192}$, (1/mole sec)^{$\text{1}\text{2}$}, ($\text{E}{}_{\mathrm{p}}\text{?}\text{1}\text{2}\text{E}{}_{\mathrm{t}}\text{) = 0.40, 21.4}$ kcal mole^?1. The values refer to the liquid- and the cholesteric-state reactions, respectively. The average degree of polymerization is low in both cases ($\text{P}\text{= 20}\text{and}\text{22}$). It was concluded that the molecular weights are controlled by chain transfer and that the initiation reaction is mostly dependent on the phase where the reaction takes place.     

The synthesis of 3-vinylindoles and 11H-5-cyanobenzol[a]carbazole

The synthesis of 3-vinylindoles through Wadsworth Emmons reactions with 3-formyl and 3-acylindoles is described. Although 3-formylindoles react directly with phosphonate derivatives, 3-acylindoles need prior activation by N-sulphonation. 11$\text{H}$-5-Cyanobenzo[$\text{a}$]carbazole has been prepared by the oxidative cycloaddition of $\text{E}$-3-(indol-3′-yl) propenotrile and benzyne.     

Synthesis and properties of 4,6-Di-t-Butyl-Cyclopenta-1,2-Dithiole and its 3-aza-derivative

2,4-Di-t-butyl-cyclopentadiene-1-carbaldehyde ($\text{3}$) and 2,4-di-t-butyl-cyclopentadienone oxime ($\text{7}$) are easily converted into the title compounds $\text{6}$ and $\text{10}$, respectively. The spectroscopic and chemical properties of the new heterocyclic 10π-electron systems are described.     

Halogen cleavage reactions of cis-(threo-PhCHDCHD)Mn(CO)4PEt3

Halogen cleavage reactions of $\text{cis}$-($\text{threo}$-PhCHDCHD)Mn(CO)₄, PEt₃ ($\text{3}$) are studied in detail and are found to proceed either predominantly with retention or inversion, or non-stereospecifically, depending on reaction conditions. Reaction mechanisms involving S_E2 (inversion), S_E2 (retention) and S_E (oxidative) processes are proposed, demonstrating that halogen cleavage reactions of $\text{3}$ straddle the mechanistic borderline between electrophilic substitution and oxidation processes of transition metal alkyl compounds.     

New prostaglandin (PGF) derivatives from the soft coral Lobophyton depressum

Four PGF derivatives (15S)-PGF_2α-11-acetate methyl ester ($\text{1}$a), the 18-acetoxy derivative of compound $\text{1}$a ($\text{2}$a) as well as their two corresponding free carboxylic acids ($\text{1}$b) & $\text{2}$b) were isolated from a soft-coral and their structure elucidated, mainly on basis of their spectral data.     

Organophosphorus chemistry. Part 18. Possible intervention of a phospha-alkene in the reactions of a fluoroalkylphosphine with alkoxides

Thermal reactions of phenylphosphine with tetrafluoroethylene and 1,1-difluoroethylene give, respectively, a mixture of phenyl-1,1,2,2-tetrafluoroethylphosphine and 1,2-bis-(phenylphosphino)tetrafluoroethane, and phenyl-2,2-difluoroethylphosphine. The phenyltetrafluoroethylphosphine reacts with an excess of ethanolic or methanolic alkoxide to give the corresponding alkyl phenyl-($\text{E}$)-1-fluoro-2-alkoxyvinylphosphinite and minor amounts of the isomeric alkyl phenyl-($\text{Z}$)-2-fluoro-2-alkoxyvinylphosphinite. The use of an equimolar proportion of sodium methoxide enables the intermediate products methyl phenyl-1,2,2-trifluoroethylphosphinite and methyl phenyl-($\text{E}$)-1,2-difluorovinylphosphinite to be isolated: further reaction of these with methoxide yields the corresponding ($\text{E}$)-1-fluoro-2-methoxyvinylphosphinite. The reactions are discussed in terms of mechanisms which involve either an intermediate phospha-alkene or a hydride ion shift.     

Asymmetric allylsilane-mediated carbocyclization: A highly enantiospecific synthesis of (1S, 2S)-(+)-2-methyl-3-cyclopenten-1-ol

An enantiospecific synthesis of the title compound is described which involves the TiCl₄-promoted cyclization of the chiral allylic silane having formyl group, which was obtained via the Claisen rearrangement of ($\text{R}$, $\text{E}$)-1-trimethylsilyl-1-buten-3-ol.     

Synthesis of streptococci phosphatidyl-α-diglucosyldiglyceride and related glycolipids : Application of the tetraisopropyldisiloxane-1,3-diyl (tips) protecting group in sugar chemistry. Part V

A short and convenient synthesis of phosphatidyl-α-diglucosyldiglyceride (i.e. compound $\text{8d}$) and two related Streptococci glycolipids (i.e. compounds $\text{6a}$ and $\text{6b}$) will be presented. 4',6'-Tetraisopropyl-disiloxane-1,3-diyl (TIPS) protected α-glucosyl diglyceride (i.e. compound $\text{2}$) turned out to be a suitable protected precursor. Thus, compound $\text{2}$ was selectively condensed with glucosyl bromide $\text{3}$ to afford $\text{4}$. Removal of the protecting groups from $\text{4}$ gave glycolipid $\text{6a}$. The “dynamic” properties of the TIPS pro- tecting group were utilized to convert 4',6'-TIPS protected $\text{4}$ into 3',4'- TIPS protected derivative $\text{5a}$. Compound $\text{5a}$ could then be condensed with either a stearoyl fatty acid or a phosphatidyl moiety to give the fully protected derivatives $\text{5c}$ and $\text{8a}$, respectively. Finally, removal of all the protecting groups from $\text{5c}$ and $\text{8a}$ afforded the glycolipid $\text{6b}$ and glycophospholipid $\text{8d}$, respectively.     

Photochemistry of dienones—X: Photochemistry of (e)-β-ionone oxime ethyl ether

(E)-β-ionone oximc ethyl ether [(E, E)-4] upon direct irradiation with λ either254or 313 nm yields the geometrical isomer (E, Z)-4 and (Z)-retro-γ-ionone oxime ethyl ether (Z,E)-5 as the sole primary products, illustrating (E)-(Z) isomerization (φ₃₁₃ =0.49) and a 1, 5-hydrogen shift (φ313 =0.15) respectively. From studies with triplet photosensitizers and with ethyl iodide (to enhance the singlet-triplet intersystem crossing) it is concluded that these two products in the direct irradiation result only from the singlet excited state, and that the inter-system crossing quantum yield is relatively low. Upon prolonged irradiation of (E,E)-4 with λ 313 nm the eventual products are (Z,E)-5 and (Z,Z)-5, whereas with λ 254 nm they are (E,E)-5 and [(Z,E)-5 and/or (E,Z)-5]. Upon triplet photosensitization (E,E)-4 undergoes only (E)-(Z) isomerization, leading to a mixture of all the four geometrical isomers of4. From the dependence of the geometrical isomer distribution in the photostationary state on the triplet energy of the sensitizer the triplet energies of (E,E)-4, (E, Z)-4, (Z, E)-4, and (Z, Z)-4 have been determined to be ca 55, < 55,57, and 57 $\text{kcal}\text{mol}$ respectively.     

Etude expérimentale et théorique de la photolyse de dérivés du cycle pyrazolone

When irradiated in protic solvents such as water and primary alcohols, pyrazolinone derivatives undergo photocleavage between the two nitrogen atoms. Substituting the C-4 atom with an electronegative group stabilizes the open chain which is obtained but a thermal transposition takes place from the linear intermediate when C-4 carries a hydrogen atom or a methyl group. The $\text{STO}\text{3G}$abinitio scheme was used to study the photocleavage and the influence of the C-4 substituent, giving evidence of a mechanism which involves triplet excited states of the π, σ^* type.     

Stereospecific 2-vinylcyclohexanol formation via internal attack of an allylsilane moiety on an aldehyde group

Acid catalyzed cyclization of ($\text{E}$)-HCO-(CH₂)-₄-CH=C(Me)-CH(SPh)SiMe₃ affords $\text{cis}$-2-substituted cyclohexanol, while ($\text{Z}$) compound affords the $\text{trans}$ isomer. Those cyclized products are transformed to the corresponding α-methyl γ-lactones.