Synthesis of derivatives of potent antitumor bistramides D and A leading to the first crystal structure of natural bistramide D.

We report a crystalline derivative of bistramide D synthesized from natural bistramide A, and its structure was determined by X-ray analysis.

Short asymmetric synthesis of (-)- and (+)-cis-lauthisan.

The asymmetric synthesis of both enantiomers of cis-lauthisan (3) is achieved in only six steps from diethyl pimelate (4), the key steps being the diastereodivergent reduction of beta-ketosulfoxide 7 and the highly cis-stereoselective Et(3)SiH/TMSOTf-promoted reductive cyclization of enantiopure hydroxy sulfinyl ketones (S)-14 and (R)-14.

Asymmetric synthesis of the tetrahydropyran ring, C32-C38 fragment, of phorboxazoles.

The asymmetric synthesis of a model aldehyde (2R,6R)-2 and the C32-C38 fragment of phorboxazoles, (2R,4R,6R)-1, is described using a sulfoxide as chiral auxiliary. Key advances include the stereoselective reductions of beta-keto- or beta,gamma-diketosulfoxides, the acid-catalyzed cyclization of enantiopure sulfinyl hydroxy ketone precursors to the tetrahydropyran ring, and the Pummerer reaction on the pendant sulfoxide to create the formyl group.

Synthesis and trimethylaluminum additions on gamma-hydroxy-delta-sulfinyl and sulfonyl enoates.

[reaction: see text] The stereoselective synthesis of epimeric (R)- and (S)-gamma-hydroxy-delta-p-tolylsulfinyl (or sulfonyl) enoates is reported. Reaction with AlMe3 occurred exclusively at the ester group allowing a clean and high-yielding access to enantiopure 1,4-diols bearing a tertiary carbinol.

New 2,2'-substituted 4,4'-dimethoxy-6,6'-dimethyl[1,1'-biphenyls], inducing a strong helical twisting power in liquid crystals.

Based on the stabilisation of the molecular motion by the chiral residue, novel optically active biphenylic chiral dopants for nematic liquid crystals were developed. This molecular congestion was obtained by introducing mesogenic residues on the 2,2'-positions of the chiral biphenyl; this led to a novel molecular architecture that was found to be efficient. The synthesised optically active biphenyls were characterised with very short cholesteric pitches when used as chiral dopants in nematic liquid crystals.

Convergent highly stereoselective preparation of the C12-C24 fragment of macrolactin A.

The convergent synthesis of the C12-C24 fragment (lower part) of macrolactin A is described. The adapted strategy allowed building up the lower moiety by the assembly of three key intermediates via organometallic addition. One hydroxylic stereogenic center was introduced by the application of chiral sulfoxides methodology on fragment C19-C24.

Enantioselective access to 2,7-cis-disubstituted oxepanes: formal synthesis of (+)-isolaurepan.

[reaction: see text] The asymmetric synthesis of 2,7-cis-disubstituted oxepanes bearing a sulfoxide is achieved from commercially available precursors in only five steps. The key step is the highly diastereoselective Et3SiH/TMSOTf-promoted reductive cyclization of enantiopure hydroxysulfinyl aryl or alkyl ketones.

Reductive cyclizations of hydroxysulfinyl ketones: enantioselective access to tetrahydropyran and tetrahydrofuran derivatives.

The stereocontrolled formation of cis-2,5-disubstituted tetrahydrofurans and cis-2,6-disubstituted tetrahydropyrans is achieved from enantiopure ketosulfinyl esters by reduction, Weinreb's amide, and ketone formation, followed by the reductive cyclization (Et3SiH/TMSOTf) of the resulting hydroxysulfinyl ketones. The sulfoxide-bearing heterocycles were transformed into two natural products, (-)-centrolobine (1) and both enantiomers of cis-(6-methyltetrahydropyran-2-yl)acetic acid (2).

Reformatsky-type reaction of chiral nonracemic alpha-bromo-alpha'-sulfinyl ketones with aldehydes. Synthesis of enantiomerically pure 2-methyl-1,3-diol moieties.

Chiral nonracemic alpha-bromo-alpha'-sulfinyl ketones were shown to react with aldehydes in the presence of SmI(2) in a Reformatsky-type reaction to give the corresponding adduct with excellent syn diastereoselectivity. Further reduction of the Reformatsky adducts furnished anti- and syn-2-methyl-1,3-diol moieties in excellent yields and diastereoselectivities.

First enantioselective total synthesis of (-)-Centrolobine.

[structure: see text] The first enantioselective total synthesis of (-)-Centrolobine is described. The key reaction is the synthesis of the cis-disubstituted tetrahydropyran framework by intramolecular cyclization of the enantiopure hydroxyketone 3 with Et3SiH and TMSOTf. The stereoselective reduction of the beta-ketosulfoxide 4 is the source of chirality.

First Stereocontrolled Synthesis of the (3S,5R,7R,10R,11R)-C1-C13 Fragment of Nystatin A(1).

A convergent stereoselective synthesis of the (3S,5R,7R,10R,11R)-C1-C13 fragment of Nystatin A(1) is reported in this paper. This fragment contains an all-syn-1,3,5-triol subunit and a syn-1,2-diol moiety. The main features of the synthesis are the enzymatic desymmetrization of a meso diol to obtain an enantiomerically pure syn-4,6-dihydroxy-2-keto-phosphonate, chiral sulfoxide chemistry to prepare an alpha-(R)-hydroxyaldehyde and 2-trimethylsilyl thiazole reagent to synthesize a syn-alpha,beta-(R,S)-dihydroxy aldehyde.

Enantioselective Synthesis of (+)-Isobretonin A.

An enantioselective synthesis of (+)-isobretonin A is described. The chiral glycerol moiety was enantioselectively prepared by reduction of an optically active beta-keto sulfoxide. The all-trans trienic part of the molecule was stereoselectively synthesized via reductive elimination of a 1,6-dibenzoate 2,4-diene with sodium amalgam.