A new strategy for the protection of deoxyguanosine during oligonucleotide synthesis

The protection of the 6-oxo group of deoxyguanosine with the 2-trimethylsilylethyl ($\text{2}$), phenylthioethyl ($\text{3}$), 4-nitrophenylthioethyl ($\text{4}$), 4-nintrophenethyl ($\text{5}$), and cyanoethyl ($\text{6}$) groups is described. Each protecting group is introduced in good yield and is cleaved under mild conditions. Compatibility with the various approaches to oligonucleotide synthesis is discussed.     

Five new steroidal glycosides,pregnedioside-A, -B,and their three monoacetates,from an Okinawan soft coral of Alcyonium sp.

Five new pregnene-type steroidal glycosides, named pregnedioside -a ($\text{1}$), 4′-O-acetyl-pregnedioside-a ($\text{2}$), 3′-O-acetyl-pregnedioside-a ($\text{3}$), pregnedioside-b ($\text{5}$), and 4′-O-acetyl-pregnedioside-b ($\text{6}$), were isolated from an Okinawan soft coral of Alcyonium sp. and their structures were elucidated. These are rare examples of steroidal gylcosides from soft coral.     

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.     

A reinvestigation of the structures of acomonine,iliensine, 14-dehydroiliensine,and 14-benzoyliliensine

The novel structures assigned by Yunusov et al to the C₁₉-diterpenoid alkaloids, acomonine ($\text{1}$), iliensine ($\text{2}$), 14-dehydroiliensine ($\text{3}$), and 14-bensoyliliensine ($\text{4}$) have been found to be in error. We have demonstrated that these alkaloids are identical with the well-known alkaloids, delsoline ($\text{5}$), delcosine ($\text{6}$), 14-dehydrodeloosine ($\text{7}$), and 14-benzoyldelcosine ($\text{8}$), respectively.     

Syntheses of enantiomeric dihydropyrans through stereocontrolled intramolecular cycloaddition

Reaction of the cyclic 1, 3-dicarboxylic acid derivatives ($\text{1}$), ($\text{2}$) and ($\text{3}$) with (R)- or (S)-citronellal ($\text{4}$/$\text{5}$) gives the enantiomeric tricyclic dihydropyrans ($\text{10}$), ($\text{11}$), ($\text{12}$) and ($\text{13}$), probably via a 100% stereocontrolled intramolecular cycloaddition.     

The total synthesis of i-oxygenated eudesmanolides

A route towards I-oxygenated eudesmanolides, via a (2+2) photocycloaddition reaction for constructing the decalin framework is described. The following natural substances have been synthesized. (=)-dihydroreynosin ($\text{1}$), (±)-1- oxo-dihydronmagnolialide ($\text{2}$), (±)-maritimin ($\text{3}$), (±)-dihydromagnolialide ($\text{4}$), (±)-magnolialide ($\text{5}$), (±)-dihydrosantamarine ($\text{6}$). Also a synthesis of (±)--santonin ($\text{7}$) is presented.     

New Phenyl propanoids having weak piscicidal action and the related compound: wutaiensol,wutaiensal, wutaialdehyde,and methyl demethoxywutaiensate

The structures of three new prenylphenyl propanoids, wutaiensol ($\text{1}$), wutaiensal ($\text{2}$), and methyl demethoxywutaiensate ($\text{4}$) were established by correlating with S-rutaretin methyl ether ($\text{9}$) or S-marmesin ($\text{24}$) by chemical means. The structure of wutaialdehyde ($\text{3}$), a related compound, was also established by total synthesis of the racemate and by correlating with $\text{1}$. Preliminary piscicidal test on these compounds disclosed that $\text{2}$ and $\text{4}$ are weakly bu distinctly positive.     

Singlet oxygenation of cis,cis-1,5-cyclooctadiene: a convenient synthetic entry into 5,8-difunctionalized oxygen derivatives of 1,3-cyclooctadiene

The 6-hydroperoxy-1,4-cyclooctadiene ($\text{2}$), which is formed in the photosensitized oxygenation of 1,5-cyclooctadiene ($\text{1}$), affords on further singlet oxygenation 5,8-dihydroperoxy-1,3-cyclooctadiene ($\text{3}$), which via triphenylphosphine reduction leads to $\text{cis}$-5,8-dihydroxy-1,3-cyclooctadiene ($\text{4}$) and subsequent pyridinium chlorochromate oxidation to 1,3-cyclooctadien-5,8-dione ($\text{8}$).     

Pyrolysis of homoadamant-3-ene

Pyrolysis of homoadamant-3-ene ($\text{5}$), generated from 1-adamantylcarbene ($\text{7}$), leads to the same three olefins ($\text{2}$, $\text{3}$, and $\text{4}$) that are produced from pyrolysis of 3-homoadamantyl acetate ($\text{1}$).     

Peri-bridged naphthalenes. 4. chalcogen-bridged acenaphthylenes

Three new electron donors, acenaphtho[5,6-$\text{cd}$]-1,2-dithiole ($\text{1}$), acenaphtho[5,6-$\text{cd}$]-1,2-diselenole ($\text{2}$), and acenaphtho[5,6-$\text{cd}$]-1,2-ditellurole ($\text{3}$), can be prepared in 28%, 22%, and 14% yields respectively by reaction of the elemental chalcogens (S, Se, Te) with 5,6-dilithioacenaphthylene ($\text{4}$). Compound $\text{4}$ is generated by treatment of 5,6-dibromoacenaphthylen ($\text{5}$), for which a convenient preparation is described, with $\text{n}$-butyllithium (2 equiv.) in THF at ?78°C.     

Chemical synthesis of phosphorylated fundamental structure of lipid a

1-α-Monophosphate ($\text{2}$), 4′-monophosphate ($\text{3}$), and 1-α, 4′-diphosphate ($\text{4}$) of 6-0-(2-deoxy-2-tetradecanoylamino-6-0-tetradecanoyl-β-D-glucopyranosyl) -2-deoxy-2-tetradecanoylamino-3, 4-di -0-tetradecanoyl-D-glucopyranose were prepared in order to elucidate the role of phosphate moieties in endotoxic activity of lipid A.     

A short and efficient synthesis of 11-deoxyanthracyclinones: strong base-induced cycloaddition of the suitably substituted tetrahydrohomophthalic anhydride

The preparation and use of the suitably substituted tetrahydrohomophthalic anhydride ($\text{17}$) as a common intermediate for a short regiospecific synthesis of 11-deoxyanthracyclinones, 11-deoxydaunomycinone ($\text{11}$), 11-deoxy-carminomycinone ($\text{12}$), and 4-demethoxy-11-deoxydaunomycinone ($\text{13}$) is described.     

New antimicrobial diterpenes from the sponge spongia officinalis

The methanol extract of the sponge Spongia officinalis from Pt. Guimar, Tenerife (Canary Islands) contained new diterpenoids which inhibited the growth of microbes. The structures of the new diterpenes isolated were determined as; 11β-hydroxyspongi-12-en-16-one ($\text{2}$), 11β-acetoxyspongi-12-en-16-one ($\text{3}$), 7β,11β-dihydroxy8pongi-12-en-16-one ($\text{5}$), and 7β,11α-dihydroxy-spongi-12-en-16-one ($\text{6}$), by spectral and chemical degradation studies. The previously reported diterpenes isoagatholactone ($\text{1}$) and aplysillin ($\text{4}$) were also found in the extract.     

Structure and synthesis of gastrolactone

The novel cyclopentenoid monoterpene, gastrolactone ($\text{4}$), was synthesized from carvenolide ($\text{5}$), and the synthetic material was found to be identical to the natural product by direct comparison. This synthesis confirmed structure $\text{4}$ which had been suggested earlier on the basis of spectral data.     

Minor and trace sterols in marine invertebrates 30. Isolation,structure elucidation and partial synthesis of 26-methylstrongylosterol and 28-methylxestosterol - two marine sterols arising by a novel quadruple biomethylation sequence

Two new sterols, 26-methylstrongylosterol ($\text{4}$) and 28-methylxestosterol ($\text{5}$), arising from a hitherto unknown quadruple biomethylation sequence, together with the biogenetically important “missing link”, durissimasterol ($\text{6}$), were isolated from the Indo-Pacific sponge $\text{Strongylophora}$$\text{durissima}$.     

Stereoselective olefinic cyclization assisted by the selenyl group — biogenetic-type synthesis of caparrapi oxide

The acid catalysed cyclization of β-hydroxy selenide ($\text{4}$), which was prepared from nerolidol ($\text{1}$) $\text{via}$ the epoxide ($\text{3}$), was carried out to give bicyclic ether ($\text{5}$) directly which was further transformed into caparrapl oxide ($\text{6}$).     

Alicyclische verbindungen-v. darstellung diverser 1,3-butadienylcyclobutane

$\text{cis}$-($\text{3}$) and $\text{trans}$-1,3-Butadienylcyclobutane ($\text{4}$), all-$\text{trans}$-1-(1 ,3-butadieny1 )-2- vinylcyclobutane ($\text{10}$), and all-$\text{trans}$-1,2-bis(1,3-butadienyl)cyclobutane ($\text{15}$) have been prepared from readily available starting materials, and pyrolyzed to various cyclohexenes.     

Biomimetic reactions of germacrenes

The biomimetic reactions of epoxygermacrene-D ($\text{1}$) with basic alumina afforded three new interesting compounds ($\text{4}$, $\text{5}$, and $\text{6}$), two of which ($\text{4}$ and $\text{6}$) have the same carbon skeleton as that of periplanone-A ($\text{3}$), a sexual stimulant for the American cockroach. The remaining one ($\text{5}$) is a bicyclo[3.1.0]hexane derivative, from whch an axisonitrile-3 type compound ($\text{14}$) has been produced. Finally, preisocalamendiol ($\text{2}$) was also converted into $\text{6}$.     

Preparation of perfluoroalkylthiohydroximates from perfluoroalkyl nitriles

S-Methyl($\text{Z}$)-2,2,2-trifluorothioacetohydroximate ($\text{1}$), S-methyl($\text{Z}$)-2,2,3,3,3-pentafluorothiopropiohydroximate ($\text{2}$), and S-methyl($\text{Z}$)-2,2,3,3,4,4,4-heptafluorothiobutyrohydroximate ($\text{3}$) were prepared by reaction of the corresponding perfluoroalkyl nitriles $\text{4}$, $\text{5}$, and $\text{6}$ with methanethiol and hydroxylamine hydrochloride.     

Intramolecular silyl migration in the singlet oxygenation of 2-methyl-5-trimethylsilylfuran

Tetraphenylporphyrin-sensitized photooxygenation of 2-methyl-5-trimethylsilylfuran ($\text{4}$) affords quantitatively trimethylsilyl 2-oxo-4-pentenoate ($\text{5}$), presumably via intramolecular Baeyer-Villiger rearrangement of the intermediary dioxirane ($\text{3a}$).