A new route to 7-deazaguanine derivatives

The Synthesis of 2-amino-4,6-dichloro-5-(2,2-diethoxyethyl) pyrimidine $\text{7}$ has been performed in four steps starting from guanidine and diethylallylmalonate. $\text{7}$ is a new key intermediate for the synthesis of 7-alkyl-2-amino-3,4-dihydro-7H-pyrrolo [2,3-d] pyrimidin-4-ones.     

Palladium-catalyzed cyclization reactions of 3-propargylthio 1,2,4-triazin-5(2h)-ones to thiazolo-1,2,4-triazinones

Selective transformation of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{1}$) to 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c][1,2,4]-triazin-4-ones ($\text{2}$) and 3-methylene-2,3-dihydro-7H-thiazolo[3,2-b]-[1,2,4]triazin-7-ones ($\text{3}$) is performed under the conditions of Pd(II) salt or sodium hydroxide catalysis, respectively.     

Acyclic stereocontrol via asymmetric [2,3]-Wittig rearrangement with high enantio- and erythro-selectivity and its use in the chiral synthesis of insect pheromones

Such an asymmetric [2,3]-Wittig variant that is both highly enantio- and erythro-selective is described within the context of the chiral synthesis of the insect pheromones, (3$\text{S}$, 4$\text{S}$)-4-methyl-3-heptanol and ($\text{S}$)-4-methyl-3-heptanone.     

Bridgehead nitrogen heterocycles from 2,4,6-triphenyl- pyrylium cation and thiosemicarbazide or thiocarbohydrazide

2,4,6-Triphenylpyrylium with thiosemicarbazide and thiocarbohydrazide, gives 2-pyrazolines $\text{3a}$ and $\text{3b}$ which undergo cyclization yielding pyrazolo(1,5-c]pyrimidine 5 and pyrazolo [2,3-d]-1,2,4-triazepine $\text{7}$ derivatives, respectively. Reaction of $\text{7}$ with phenacyl bromides gave 1,3-thiazolo[3,2-b]pyrazolo [2,3-d]-1,2,4-triazepin-4-iums $\text{10}$. Compound $\text{3a}$ on treatment with phenacyl bromides gave 1-(4'-aryl-thiazol-2'-yl)-2-pyrazoline derivatives $\text{6}$. Compound $\text{3b}$ reacts with acyl chlorides to give pyrazolo[1,5-c]pyrimidine derivatives $\text{14}$, and with aromatic aldehydes giving the 2-(Δ^2'1 pyrazolin-1-yl)-5-aryl-1,3,4-Δ²-thiadiazolines $\text{12}$ which were easily converted to the corresponding 2-(Δ²-pyrazolin-1-yl)-5-aryl-1,3,4-thiadiazoles $\text{13}$.     

Cycloaddition reactions of 2,3-didehydrothiophene generated by flow vacuum thermolysis of thiophene-2,3-dicarboxylic anhydride

Flow vacuum thermolysis (FVT) of thiophene-2,3-dicarboxylic anhydride ($\text{2}$) in the presence of 2,3-dimethylbutadiene ($\text{6}$) gives, in addition to 5,6-dimethylthianaphthene ($\text{9}$). small quantities of a dihydrodimethylthianaphthene ($\text{12}$) and another dimethylthianaphthene ($\text{13}$) which is probably also formed by dehydrogenation of $\text{12}$ with chloranil. The partial structures of these minor products are consistent with their being formed by a [2+2]-cycloaddition between $\text{6}$ and an intermediate aryne, 2,3-didehydrothiophene ($\text{1}$), followed by a rearrangement of the resulting adduct $\text{11}$ and dehydrogenation. FVT of $\text{2}$ in the presence of 2,5- ($\text{17b}$) or 3,4-dimethylthiophene ($\text{17c}$) also gave a mixture of the dimethylthianaphthenes ($\text{18}$$\text{22}$, $\text{23}$) which can be rationalized as arising by a [4+2]- and two [2+2]-cycloadditions of the aryne $\text{1}$ to the thiophenes $\text{17}$ with subsequent desulfurization. The lack of equilibration of the products $\text{18}$, $\text{22}$ and $\text{23}$, was demonstrated and their origin as a function of the structure and reactivity of the aryne $\text{1}$ discussed.     

Schlüsselreaktionen einer synthese des sibirosamins

[2,3]-Sigmatropic rearrangement and vic. $\text{cis}$-oxyamination of 3-$\text{C}$-methyl-ald-m-enopyranosides are the key steps for the synthesis of a sibirosamine precursor.     

The solution photochemistry of αβ-unsaturated sulphones

1-Phenyl-2-(benzenesulphonyl)-ethylene and 1-phenyl-2-(benzenesulphonyl)-prop-1-ene have been shown to undergo $\text{Z}$,$\text{E}$-photoisomerisation, whereas 2-benzenesulphonylindene readily forms [_π2 + _π2] photoadducts with 2,3-dimethylbut-2-ene, cyclopentene, and cyclohexene.     

Bioactive marine metabolites IX. Mycalisines A and B,novel nucleosides which inhibit cell division of fertilized starfish eggs,from the marine sponge mycale sp.

Two novel nucleosides, mycalisines A and B, have been isolated from a marine sponge and their structures elucidated as 4-amino-5-cyano-7-(3-$\text{O}$-methyl-5-deoxy-β-D-$\text{erythro}$-pent-4-enofuranosyl)-pyrrolo[2,3-$\text{d}$]pyrimidine and 5-cyano-7-(3-$\text{O}$-methyl-5-deoxy-β-D-$\text{erythro}$-pent-4-enofuranosyl)-pyrrolo[2,3-$\text{d}$]pyrimidine-4-one, respectively. Both compounds inhibit cell division of fertilized starfish eggs.     

Studies on Chirality Transfer in the [2,3] Sigmatropic Rearrangement of Anions Derived from Trialkylstannylmethyl Allylic Ethers. Stereospecific Synthesis of (2R)-3-Benzyloxy-2-methylpropanol.

Virtually complete chirality transfer is observed in the [2,3] sigmatropic rearrangement of the anion derived from trialkylstanylmethyl ($\text{E}$)- or ($\text{Z}$)-allylic ethers.     

The effect of alkene configuration on the partitioning between the carbenic reactions and the 1,7-electrocyclisation of α-)o-alkenylaryl)diazoalkanes

The 1,7-electroclyclisation of α-($\text{o}$-alkenylaryl)diazoalkenes to 1$\text{H}$-2,3-benzodiazepines is blocked by the $\text{cis}$ substituent in $\text{Z}$ alkenyl groups and the diazo-compounds then react via alternative routes including a new intramolecular carbene reaction to give naphtho[a]cycloheptenes.     

The synthesis of a 3-diazobicyclo[2.2.1]Heptan-2-one inhibitor of thromboxane a2 synthetase

The synthesis of a PGH₂ analog 5-$\text{endo}$(2(Z), 6-$\text{exo}$(1E)-3-diazo-5-(7-hydroxy-2-heptenyl)-6-(3-hydroxy-1-octenyl)bicyclo[2.2.1]heptan-2-one 2 is described.     

Novel intramolecular diels-alder reactions with alkynylthio derivatives of 1,2,4-triazines. New routes to thieno[2,3-b]pyridines and thieno[2,3-c]pyridines.

S-Alkylation of 1,2,4-triazine-6-thiones with 4-iodobutyne, followed by oxidation to the sulfoxide and intramolecular cycloaddition (at room temperature),gives 2,3-dihydrothieno[2,3-$\text{c}$]pyridines, which are readily dehydrated with acetic anhydride to thieno[2,3-$\text{c}$]pyridines. The same series of reactions carried out on 1,2,4-triazine-3-thiones leads to thieno[2,3-$\text{b}$]pyridines.     

A general synthesis of side chain derivatives of Δ9-thc

The synthesis of (6aR, 10aR)-trans-3-[1′,3′-dithian-2′-yl]-6a,7,8,10a-tetrahydro-6,6,9- trimethyl-6H-dibenzo[b,d]pyran-l-ol t-butyldimethylsilyl ether ($\text{4b}$) is reported. The use of this compound as a source of side chain derivatives of cannabinoids is illustrated by syntheses of 1′-,2′-,3′- and 4′-hydroxy-Δ⁹-THC, and 3-carboxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-o1 ($\text{6}$).     

A new approach to the [6]paracyclophane system: synthesis of 2,3-dicarbethoxy[6]paracyclophane

The reaction of the dibromide $\text{1}$ with McMurry's reagent gives 2,3-dicarbethoxy[6]paracyclophane ($\text{2}$) in about 40% yield.     

A facile synthesis of strained bridgehead olefins by a gas-phase elimination reaction

A synthesis of bicyclo[3.3.1]non-1-ene $\text{1}$ and of a 10:1 mixture of bicyclo[4.2.1]non-1(8)-ene $\text{2}$ and bicyclo[4.2.1]non-1(2)-ene $\text{3}$ by gas-phase pyrolysis of the corresponding bridgehead acetates and chlorides is reported.     

Stereocontrolled synthesis of either (22S)- or (22R)-hydroxy-23-acetylenic steroid side chains via [2,3]-Wittig sigmatropic rearrangement

A unified approach to either (22$\text{S}$)- or (22$\text{R}$)-hydroxy-23-acetylenic steroid side chains is described which relies on the concept of the stereochemical transmission via the [2,3]-Wittig sigmatropic rearrangement.     

Synthesis of 2-isopropylfuro(2,3-b)quinolines-a new synthesis of (±)-lunacrine, (±)-lunasine and (±)-demethoxylunacrine

A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines ($\text{4}$) from 3-(3-methylbut-1-enyl)-2-quinolones ($\text{2}$) is described. A neat synthesis of the alkaloids (±)-lunacrine ($\text{1a}$), (±)-lunasine ($\text{12a}$) and (±)-demethoxylunacrine ($\text{1b}$) is also reported.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

Structure elucidation and synthesis of (2s)-4-oxo-1-azabicyclo[3.3.0]octa-5,7-diehe-2-carboxylic acid,a new metabolite isolated ercm stheptomyces oliyacbjs

The structure of a new metabolite isolated from $\text{Streptomyces}$$\text{olivaceus}$ has been shown to be (2S)-4-oxo-1-azabicyclo[3.3.0]octa-5,7-diene-2-carboxylic acid by means of its spectroscopic properties and total synthesis.     

The 185-nm photochemistry of 2,3-diazabicyclo[2.2.1]heptene and of its denitrogenation products bicyclo[2.1.0]pentane and cyclopentene

The 185-nm denitrogenation of 2,3-diazabicyclo[2.2.1]heptene ($\text{1}$) afforded bicyclo[2.1.0]-pentane ($\text{2}$) and cyclopentene ($\text{3}$) presumably via a “hot” cyclopentane-1,3-diyl diradical ($\text{8}$); 1,4-pentadiene ($\text{4}$) and methylenecyclobutane ($\text{5}$) were secondary products of the 185-nm photolysis of ($\text{2}$) and ($\text{3}$).