Reactions of ketene acetals—IX: The synthesis of naphthoquinones from benzoquinones

Halogenobenzoquinones react with ketene acetals and give benzofurans, but in the presence of acetic acid, naphthoquinones are produced in variable yields. Some aspects of the reaction have been studied and the method has been applied to the synthesis of useful intermediates and of derivatives of some naturally occurring naphthoquinones such as tri-O-methylflaviolin 20 and tetra-O-methylspinochrome B23. Benzoquinones also react with conjugated ketene acetals without acid catalysis, providing convenient syntheses of ramentaceone 43, O-methylstypandrone 45 and 1,3,6,8-tetramethoxyanthraquinone 34.     

Retrodienic reactions XVI - flash thermolytic generation of reactive functional allenes

Butadienal 1, propadienol 2 and propadienamine 3 are synthesized by flash vacuum thermolysis of their anthracenic Diels-Alder adducts and characterized at low temperature.     

Apurinic DNA reactivity: Modelisation of apurinic DNA breakage with phenylhydrazine and formation of a pyrazole adduct

We have elucidated the exact mechanism of apurinic oligodeoxynucleotide d(Tp[AP]pT) cleavage by phenylhydrazine and shown that the final isolated product is in fact a 3-substituted derivative of 1-phenyl-pyrazole.     

Structure of absintholide a new guaianolide dimer of Artemisia absinthium L.

Absintholide $\text{1}$ is a new guaianolide dimer whose structure and stereochemistry has been elucidated on the basis of high resolution n.m.r.     

Synthesis of new allenic prostanoids

New allenic prostanoids 5c, d, 7,9c, and 15b have been prepared by total synthesis. In each case a cuprate-propargylic acetate reaction was used as the key step.     

Improved procedure for the preparation of deoxynucleoside phosphoramidites: Arylphosphoramidites as new convenient intermediates for oligodeoxynucleotide synthesis

A simplified procedure for the preparation of deoxynucleoside methyl- and arylphosphoramidites is described. Both types of phosphoramidites can be conveniently activated by N-methylaniline trifluoracetate for their use in oligodeoxynucleotide synthesis.     

Growth ofschizosaccharomyces pombe on glucose-malte mixtures in continuous cell-recycle cultures kinetics of substrate utilization

The aerobic growth ofSchizosaccharomyces pombe on mixtures of glucose and malate was investigated during continuous high cell density cultures with partial cell-recycle using a membrane bioreactor. Determination of the specific metabolic rates relative to substrates and products allowed the capacity of the yeast to metabolize malic acid under both oxidative metabolism (carbon limited cultures) and oxidofermentative metabolism (carbon sufficient cultures) situations to be characterized. Under carbon limiting conditions, the specific rate of malate utilization was dependent on the residual concentration and a limit for a purely oxidative breakdown without ethanol formation was observed for a characteristic ratio between the rates of substrate consumption qm/qg of 1.63 g.g^-1. In addition, the mass balance analysis revealed the incorporation of malic acid into biomass. In carbon excess environments, the specific rate of malate utilization was dependent on both the residual malate and the specific rate of glucose consumption indicating that in addition to its conversion into ethanol malate can be respiratively metabolized for qm/qg ratios higher than 0.4 g.g^-1.