A highly diastereoselective approach for the synthesis of protected a,b-dioxyaldehydes derived from (Z)tris(trimethylsilyl)silyl “super silyl” enol ethers is described. A general and highly syn-stereoselective aldol reaction directed by the “super silyl” group catalyzed by triflimide (HNTf2) is developed providing a,bdioxyaldehydes and 1,2,3-triol fragments which can be a useful platform for th...

The efficient organocatalytic synthesis of heterocyclic systems of biological relevance is a subject of growing interest. We have found that the pyrrolidine/benzoic acid-catalyzed reaction of α-substituted propenals such as methacrolein, 2-benzylpropenal and 2-(n-hexyl)propenal with activated hydrazines takes place in very good yields (83%-99.6%) under very mild conditions to afford 4-substitut...

Lewis base catalysed 1,3-dipolar cycloaddition between α,β-unsaturated acyl fluorides and N-[(trimethylsilyl)methyl]amino ethers has been achieved using 1 mol% DMAP. Competition experiments and (19)F-NMR studies indicate that the cycloaddition occurs preferentially between the α,β-unsaturated acyl fluoride and the unstabilised azomethine ylide. In addition, an enantioselective variant, using ch...

A mild, efficient and fast method for the oxidation of alcohols and trimethylsilyl and tetrahydropyranyl ethers to their corresponding carbonyl compounds using CrO3 in the presence of sulfonic acid functionalized ordered nanoporous Na+-montmorillonite (SANM) and under solvent-free conditions is reported. All reactions were performed at room temperature in high to excellent...

Zinc chlorochromate nonahydrate is easily prepared from the aqueous solution of chromium trioxide and zinc chloride in quantitative yield. This oxidant, in methylene chloride and at room temperature, oxidizes thiols to their disulfides. Acetals and thioacetals are deprotected to their corresponding carbonyl compounds. Sulfides are selectively converted to ther sulfoxides or sulfones. Arylox...

A comparative study was made of the spectra obtained after gas-liquid chromatography-mass spectrometry of the trimethylsilyl ethers of 1- and 2-monoacyl- and monoalkyl-glycerols. The glycerol derivatives were resolved on the basis of positional substitution and the degree of unsaturation on Silar-5CP (a cyanopropylphenylsiloxane) liquid phase, and the peaks were examined in a Varian MAT CH-5 si...

A simplified method for following the urinary excretion of estriol, pregnanediol, and pregnanoloneduring the course of pregnancy is presented. The procedure has been used successfully in a large hospital laboratory. An important advantage is that the estrogen and progesterone metabolites are measured simultaneously, and separate extraction and gas-liquid chromatographyis not required. The urine...

We used low-resolution gas-chromatography of urinary steroid metabolites, as their trimethylsilyl ethers, in conjunction with the Mahalonobis generalized distance to assess the analyses in terms of a multivariate normal distribution in two populations of women: 18-50 years old and older. We compare the use of this method of interpretation, presenting several cases to illustrate the use of this ...

Novel unsaturated ethers were synthesised in good yields starting from sucrose,using a two-step mild and efficient procedure based on the Gassman method, which consists in forming a vinyl group by the elimination of ethanol from mixed acetals with trimethylsilyl trifluoromethanesulfonate in the presence of alkyl amines. Mixed acetals are readily obtained from the corresponding alcohols and ethy...