Preparation and phosphorylation reactivity of n-nonacylated nucleoside phosphoramidites

$\text{N}$-nonacylated nucleoside phosphoramidites can be prepared in two steps from 2′-deoxynucleosides. Their use in phosphorylation reactions is exemplified.     

Use of 2-methylsulfonylethyl as a phosphorus protecting group in oligonucleotide synthesis via a phosphite triester approach

2-Methylsulfonylethoxy dichlorophosphine has been converted into the mono-N-morpholino derivative and applied for the preparation of 5′-O,N-protected d-nucleoside-3$\text{-}\text{?}$phosphoramidites. The latter intermediates could be used in the presence of 1-hydroxybenzotriazole for the formation of 3′-5′-phosphotriester linkages. The MSE protecting group can be removed selectively and fast under mild basic conditions.     

Eine einfache photochemische synthese von cyclopent[d][1,3]oxazinen aus 2,4-cyclohexadienimin-derivaten

A synthesis of cyclopent[d][1,3]oxazines $\text{8}$ is reported involving the photochemically induced transformation of 2,4-cyclohexadienimines $\text{4}$ via dienylketenimine intermediates $\text{6}$ and the dihydroderivatives $\text{7}$.     

The trapping of excitons by impurities and its dependence on the impurity concentration

When excitons migrate through molecular crystals containing impurities the relative probabilities of their decay at a site of the host lattice or at an impurity can often be deduced experimentally from the material's luminescence spectrum. Theoretically, the mean probability $\text{K}$ that an exciton will be captured by an impurity can be calculated by solving a diffusion equation with a term that takes account of the exciton-impurity interaction. The results of such calculations are reported, with particular emphasis on the dependence of $\text{K}$ on the impurity concentration c for small values of c. It is found that if the impurities behave as absorbing spheres $\text{K}$ is proportional to c, but if the interaction potential is of the multipole-multipole form then d(log$\text{K}$)/d(logc) depends on the exciton's mean free path and on c, and can be much less than unity. The physical reasons for these results are discussed.     

Complete enantiospecificity in the highly regioselective and stereoselective photo- and thermal rearrangements of some homoconjugated ketones

The oxa-di-π-methane (ODPM) photorearrangement of 2-(carbomethoxy)spiro [5.5]undeca-1,3-diene-7-one ($\text{1}$d) to $\text{2}$d and the latter's thermal rearrangement to $\text{3}$d were shown to be not only fully regio-and stereoselective but also to occur with complete enantiospecificity. An additional example, the 2-hydroxymethyl derivative ($\text{1}$f) was also studied and the two systems were chemically correlated.     

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 ($\text{6}$).     

12-S-CIS conformationally locked retinoids: Thermal and photochemical interconversions leading to new geometric isomers

For 12-$\text{s}$-$\text{cis}$ locked retinal analogues, thermal equilibria are established between 11-$\text{cis}$, 13-$\text{cis}$-1c and 13-$\text{cis}$-2c and between 9-$\text{cis}$, 11-$\text{cis}$, 13-$\text{cis}$-1d and 9-$\text{cis}$, 13-$\text{cis}$-2d; a photoisomerization occurs to transform 2c to $\text{all}$-$\text{trans}$-2a and 2d to 9-$\text{cis}$-2b     

Micellar diastereoselectivity - tripeptide substrates

Kinetic stereoselectivities are reported for the micelle-catalyzed basic esterolyses of the four diastereomeric ,$\text{Z}$-($\text{D}$ or $\text{L}$)-Phe-($\text{D}$ or $\text{L}$)-Phe-($\text{L}$)-Pro $\text{p}$-nitrophenyl esters.     

The use of differential scanning calorimetry to identify methaqualone samples: forensic applications.

The d.s.c. curves of commercial samples of methaqualone—Qu$\text{aa}$lude (U.S.A.), Qu$\text{aa}$lude (Mexico), Sopar, Mandrax and Parest — are presented. Similar d.s.c. curves were found for Qu$\text{aa}$lude (U.S.A.), Qu$\text{aa}$lude (Mexico), and Mandrax, while Sopar and Parest exhibited different types of curves. New and old formulations of the Qu$\text{aa}$lude (U.S.A.) brand could be differentiated by differences in the tablet filler and binder. Unfortunately, d.s.c. could not be used to determine the country of origin of the drug, although it was useful to characterize it. The technique can be used to identify samples of 0.15 mg or less.     

Asymmetric synthesis IV. Preparation of chiral α-aminonitriles from a new N-cyanomethyl-1,3-oxazolidine synthon

The synthesis of (?)-N-Cyanomethyl-4-phenyl-1,3-oxazolidine $\text{1}$ is reported. Good yields and moderate diastereomeric excesses (d.e.s.) of mono- and di-substituted α-aminonitriles were obtained from this simple chiral template.     

Pummerer rearrangements using chlorotrimethylsilane

Pummerer rearrangements of 3-carbomethoxythian-4-one $\text{S}$-oxide ($\text{1}$) have been investigated and chlorotrimethylsilane found to be the reagent of choice for preparing the corresponding α,β-unsaturated sulphides ($\text{2}$ and $\text{3}$). Related chlorotrimethylsilane-induced Pummerer rearrangements are also reported.     

Reaktion von trans-1-arylbutadienen und 1,1-diarylbutadienen mit tetracyanethylen (TCNE) und 2,2-bis(trifluormethyl)ethylen-1,1-dicarbonitril (BTF): kinetische studie

Kinetic data (substituent effects, solvent effects, activation parameter) are reported for the reactions of trans-l-arylbutadienes $\text{1}$ and 1,1-diarylbutadienes $\text{3}$ with TCNE $\text{4}$ and BTF $\text{5}$. (2+2)- and (4+2)-cycloadducts $\text{7}$ respectively $\text{9}$ can rearrange or undergo-cycloreversions with quite different reaction rates-depending on the substituent in the aryl-ring.     

The cybrodins: new seco-illudalanes from the bird's nest fungus cyathus bulleri brodie.

The structures of the $\text{seco}$-illudalane sesquiterpenoids cybrodol $\text{2}$), isocybrodol ($\text{3}$), cybrodic acid ($\text{6}$), cybrodal ($\text{4}$), and trisnorcybrodolide ($\text{5}$), are presented. These are the first $\text{seco}$-illudalanes to be reported.     

Synthesis of (+) dictyopterene a constituent of marine brown algae and (+) dictyopterene C′ by chirality transfer of optically active allylic benzoate with palladium (O) catalyst.

The first enantioselective syntheses of (+) dictyopterene A $\text{1}$ and (+)dictyopterene C′ were reported. The key reaction was based on palladium promoted cyclisation of chiral allylic benzoate $\text{5}$ with transfer of chirality (anti attack of the palladium with respect to the leaving group) to give optically active vinylcyclopropane $\text{7}$ with (R) configuration which contains proper functionality for further elaboration into $\text{1}$ and $\text{3}$     

Fluorinated chromenes 1: 2,2,2-trifluoroethoxy precocene analogs and their corresponding 3,4-epoxides

Preparation of potential insect antijuvenile hormone agents 2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2H-chromene ($\text{3a}$), 6-methoxy-2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2$\text{H}$-chromene ($\text{3b}$) and 7-methoxy-2,2-dimethyl-6--(2,2,2-trifluoroethoxy)-2$\text{H}$-chromene ($\text{3c}$) and the corresponding 3,4-epoxides $\text{5a}$ and $\text{5b}$ is reported.     

Synthesis of the n-benzoyl derivatives of L-arabino,L-xylo and L-lyxo (L-vancosamine) isomers of 2,3,6-trideoxy-3-C-methyl-3-aminohexose from a non-carbohydrate precursor

The synthesis of the N-benzoyl derivatives of $\text{L}$-$\text{arabino}$ (10),$\text{L}$-$\text{xylo}$ (13) and $\text{L}$-$\text{lyxo}$ ($\text{L}$-vancosamine) (12) 2,3,6-trideoxy-3-$\text{C}$-methyl-3-aminohexose from the (2$\text{S}$,3$\text{R}$) diol (1) prepared in fermenting bakers' yeast from α-methylcinnamaldehyde and acetaldehyde is reported     

Synthesis and physical properties of 6,12-diarylazuleno[1,2-b]azulenes

The structure of a minor dimer ($\text{2a}$) of 1-arylcycloheptatrienylidenethylene was determined by X-ray crystallography. Dehydration of $\text{2a}$ and $\text{2b}$ gave novel non-benzenoid aromatics---6,12-diarylazuleno[1,2-b]azulenes ($\text{3a}$ and $\text{3b}$), whose electronic and NMR spectral properties were reported.     

Synthesis of the dioxabicyclononane unit of tirandamycin

A seven-step synthesis of (±)-$\text{3b}$ an advanced, common intermediate for construction of the dioxabicyclononane units of both tirandamycin and streptolydigin from $\text{14}$ is described (Scheme 1). Conversion of $\text{3b}$ to the fully developed fragment of tirandamycin is also reported.     

Athrotaxis alkaloids. Part I. Alkaloids of A. Cupressoides

Eleven homoerythrina-type alkaloids ($\text{tilda1}$-$\text{tilda9}$, $\text{tilda11}$, $\text{tilda12}$) have been isolated from A. cupressoides (Taxodiaceae), of which six ($\text{tilda6}$-$\text{tilda9}$, $\text{tilda11}$,$\text{tilda12}$) had not previously been reported.