Martial Thomas

Comparative oxidation of phenols with benzeneseleninic anhydride and with benzeneseleninic acid

Abstract Oxidation of phenols by benzeneseleninic acid 2 in methylene dichloride leads to the para -quinones, whereas oxidation by benzeneseleninic anhydride 1 is confirmed to afford the corresponding ortho -quinones. Addition of indole, as a phenylselenium (II) trapping agent, inhibits the formation of phenylselenoquinones in the oxidation with 1 or 2 .

Organotellurinic acid anhydrides as selective oxidants in organic synthesis

Abstract Several aryltellurinic acid anhydrides have been compared for their oxidising properties in acetic acid. Very high yields of quinones and disulphides can be obtained under conditions where phenols are not oxidised.

An expeditious route to carbocyclic nucleosides : (-)-Aristeromycin and (-)-carbodine

Abstract The readily available bicyclic lactone (−)-1 was transformed into diacetate (−)-2 which served in an expeditious route to (−)-aristeromycin (3a) and (−)-carbodine (3b) in acceptable yields.

Purification of immunosuppressive factors extracted from bovine spleen (lymphoid chalone).

A low molecular weight immunosuppressive factor FA which is able to reduce the blastic transformation capacity of lymphoid cells from treated mice has been characterized. It was prepared from a bovine spleen acetone powder and found to be associated partly with high molecular weight carriers in the form of an active complex characterized previously as part of a ‘lymphoid chalone’ fraction. FA may be obtained by selective ultrafiltration of F followed by P‐2 Biogel chromatography of the ultrafiltrate. Thymidine, deoxyinosine and deoxycytidine have been identified as the major constituents of FA by mass spectrometry, ultraviolet absorption data and thin layer chromatography. However, none of these nucleotides has the biological activity of FA.

Convenient chemical resolution of a bicyclic hydroxylactone of synthetic interest

The readily available bicyclic lactone 1 was resolved by treatment with (S)-O-acetyllactyl chloride to give a separable pair of diastereoisomers (−)-3 and (−)-4 the respective configuration of which was deduced from X-ray crystallography performed on the bromo derivative (−)-5.

The purification of an immunosuppressive factor extracted from bovine spleen—III: Purification process

A low mol. wt substance (PM < 2000) with immunosuppressive properties has been extracted from bovine spleen: when injected into mice, previously sensitized to sheep red blood cells, this factor reduced the hemolysin plaque forming capacity of spleen cells of treated animals measured vitro in the Jernes test. Different techniques of purification: column chromatographies (Biogel P-2, neutral alumina, Sephadex LH-20), thin layer chromatography, high pressure liquid chromatography (μ Bondapack-C18), have been applied. They allowed the separation of the immunosuppressor from a stimulating factor which increased the response in the Jernes test of the lymphocytes of the treated sensitized animals. Furthermore, those techniques led to a highly purified factor which is about 107 times more active than the starting material; the injection of a dose of approximately 2 × 10−7 mg is sufficient to induce a 50% response inhibition in the Jernes test.

Telluramine derivatives as selective oxidants

Abstract Tetravalent morpholino-tellurium derivatives 1 and 6 quickly oxidize hydroquinones to quinones and thiols to disulphide under neutral conditions. Bulky phenol 15 is slowly oxidized by 5 and 6 to the diphenoquinone 16 .

Facile synthesis of a cis-syn thymine dimer building block and its incorporation into oligodeoxynucleotides

Abstract The synthesis of a building block containing the photobiologically relevant cis – syn thymine cyclobutane photoproduct and its incorporation into oligonucleotides by the phosphoramidite-based solid-phase synthesis is reported. Compared to previous syntheses, this route is extremely short and allows such modified oligonucleotides to be easily available for biological studies.

Synthesis and incorporation of carbocyclic nucleosides into a hammerhead ribozyme domain–RNase resistance and catalytic activity

A hammerhead ribozyme domain incorporating (–)-carbodine 8a and (–)-aristeromycin 8b at selected positions, manifests increased RNase resistance and exhibits significant catalytic activity.