José M. Palazón

Stereocontrolled synthesis of cyclic ethers by intramolecular hetero-Michael addition. 4. Enantiomeric synthesis of substituted and fused oxepanes

The use of an intramolecular hetero-Michael addition of enantiomerically enriched 7-alkoxy-4-benzoyloxy-2,3-unsaturated esters for the synthesis of endo-substituted oxepanes is described. The stereochemistry in the cyclization step is governed by the geometry of the double bond in the unsaturated ester and the presence of a Z-double bond in the linear chain is required in order to achieve good yields. The synthesis of the fused oxepane-tetrahydropyran nucleus of marine polyether toxins with absolute control of all the stereocentres is described.

Stereocontrolled synthesis of cyclic ethers by intramolecular hetero-Michael addition. 3. Enantiomeric synthesis of highly functionalized and fused tetrahydropyrans

Abstract A methodology based on intramolecular hetero-Michael addition of properly functionalized alkoxy-γ-benzoyloxy-α,β-unsaturated esters for the synthesis of highly substituted and fused poly-tetrahydropyran nuclei of marine polyether toxins with absolute control of all the stereocentres is described.

Enantiomeric synthesis of polysubstituted Furanes by stereoselective intramolecular bromoetherification

Abstract The stereoselectively controlled synthesis of 2,5 dialkyl,3-substituted furanes by enantioselective construction of chiral alkenols and stereoselective bromocyclization is described.

Enantiomeric syntheses of 6(R), 7(R) and 6(S), 7(S) trans- and cis-laurediol

Abstract The title compounds have been synthesized by using acetylenic coupling procedures, asymmetric epoxidation and stereo- and regio-selective openings of the epoxides.

Stereocontrolled synthesis of chiral nonracemic halotetrahydropyrans

Abstract The stereoselective synthesis of enantiomerically enriched endo-substituted halotetrahydropyrans by an intramolecular Michael addition of a suitable chiral γ=halo-α,β-unsaturated ester is described.

General method to transform chiral 2,3-epoxyalcohols into erythro or threo 1,2-epoxyalcohols with total stereochemical control

Abstract The isomerization of chiral 2,3-epoxyalcohols from E -allylic alcohols to chiral erythro or threo 1,2-epoxyalcohols has been accomplished with good yields, perfect stereochemical control and a very high grade of generality.

Simple and efficient oxidation of sulfides to sulfones using catalytic ruthenium tetroxide

Abstract A procedure for the oxidation of sulfides to sulfones using ruthenium tetroxide as catalyst and periodic acid as stoichiometric oxidant in a biphasic system (CCl 4 , CH 3 CN, H 2 O) is reported.

Enantioselective total synthesis of 6(R), 7(R)-3-cis-9-cis-12-cis, 6-acetoxy-7-chloropentadeca-3,9,12-trien-1-yne and its 3-trans-isomer

Abstract The stereoselective preparation of chemically differentiated diols based on the opening of a conveniently protected 1,2-epoxyalcohol is used in the synthesis of the title compounds.

A new approach to the synthesis of chiral vinyl carbinols from 2,3-epoxy alcohols

Abstract The regioselective opening with benzoic acid of 2,3-epoxy alcohols obtained from the asymmetric epoxidation of 2,3-allylic alcohols, and deoxygenation of the resulting diol benzoales provides an effective, general and simple method to convert chiral 2,3-epoxy alcohols, into vinyl carbinols without the loss of any optical purity.

Comparison of the conformational properties of carbasugars and glycosides: the role of the endocyclic oxygen

A series of carbasugars were prepared and their conformational properties studied by means of NMR spectroscopy. The results were compared to those previously found for O-, S-, and C-β-glycoside analogs. While the rotational populations of the hydroxymethyl group in O-, S-, and C-glycosides are known to depend on the structural nature of their aglycon, in carbasugars it proved to be independent of the pseudo-aglycon. This result confirms that endocyclic oxygen is necessary for the observed relationship between the structure of the aglycon and the rotational populations of the hydroxymethyl group, and indicates that the stereoelectronic exo-anomeric effect is mainly responsible for such conformational dependence.