A Convenient and Chemoselective One-Pot Oxidation/Wittig Reaction for the C2-Homologation of Carbohydrate-Derived Glycols

One-Pot O2-Oxidation and the Horner-Wadsworth-Emmons Reaction of Primary Alcohols for the Synthesis of (Z)-α,β-Unsaturated Esters

We developed one-pot oxidation/olefination procedures of primary alcohols giving Z-α,β-unsaturated esters 3. TEMPO-(CuCl or CuBr₂)-(2,2'-bipyridine) (1:1:1) catalyzed O₂ oxidation of primary alcohols in the presence of Z-selective Horner-Wadsworth-Emmons reagent 1b and K₃PO₄ or NaH gave 3 with Z/E = 84:16 to 96:4 in high yields. A stepwise reaction was also developed. After TEMPO-CuBr₂-(2,2'-bipyridine)-K₃PO₄ (1:1:1:1) catalyzed O₂ oxidation of alcohols in MeCN, the resulting mixture was treated with a THF solution of 1b and t-BuOK at -78 °C to 0 °C, giving 3 with higher selectivity (Z/E = 91:9 to 99:1).

One-pot one-base conditions for two shots: organocatalyzed tandem isomerization–olefination of allylic alcohols

Under one-pot one-base conditions, terminal alkenes were synthesized via an organocatalyzed tandem isomerization–olefination of allylic alcohols.

Catalytic, oxidant-free, direct olefination of alcohols using Wittig reagents

Catalytic acceptorless coupling of alcohols with in situ generated phosphonium ylides forms olefins and H₂, with significant stereospecificity.

Aryl alkyl carbene–Pd complex assisted C–Cl bond activation: an unprecedented cross-coupling route to trans-stilbenes

A MW assisted phosphine-free coupling of aryl chlorides with 1-(bromoethyl)benzene, at low Pd concentration for the synthesis oftrans-stilbene derivatives is presented. The reaction is believed to be mediatedviaPd–carbene intermediate.

Preparation and antimalarial activity of semisynthetic lycorenine derivatives

A set of twenty one lycorenine derivatives has been prepared from the alkaloid hippeastrine (1). The modifications performed on hippeastrine included some functional group transformations, structural simplification and preparation of dimers. All alkaloids were tested as potential antimalarial agents, being the hippeastrine dimers the most active compounds.

Novel Stereoselective Synthesis of (Z)-α,β-Unsaturated Esters by Hydrostannylation-Stille Tandem Reaction of Alkynyl Esters with Aryl Iodides

( Z)-α,β-Unsaturated esters can be stereoselectively synthesised in one pot under mild conditions and in good yields, by the hydrostannylation of alkynyl esters followed by Stille cross-coupling with aryl iodides.

Copper-catalyzed tandem oxidation-olefination process

A novel catalytic sequence aerobic oxidation-olefination has been developed. A single and inexpensive copper catalyst provides a large range of olefins from alcohols in good to excellent yields. The reaction exhibits excellent functional group compatibility, and the nonbasic reaction conditions allow the transformation of chiral substrates without racemization.

Synthesis of spacer-containing chlamydial disaccharides as analogues of the alpha-Kdop-(2-->8)-alpha-Kdop-(2-->4)-alpha-Kdop trisaccharide epitope

On the basis of high-resolution crystal structures of the antigen binding fragment of the chlamydia-specific monoclonal antibody S25-2 in complex with the trisaccharide alpha-Kdop-(2-->8)-alpha-Kdop-(2-->4)-alpha-Kdop and part structures thereof, seven modified alpha-Kdop-(2-->8)-alpha-Kdop disaccharide derivatives were synthesized starting from the protected disaccharide allyl ketoside 1. Hydroboration and subsequent oxidation as well as ozonolysis, respectively, followed by Wittig-reaction for chain elongation were used to install a terminal carboxylic group on spacer entities of various chain lengths. Furthermore, addition of methyl 2-thioacetate to the allyl group furnished the corresponding thioether derivative. Standard deprotection gave the target disaccharides as simplified trisaccharide analogues, which will be used to probe the contribution of the proximal carboxylic group in the binding of chlamydia-specific di- and trisaccharide-reactive monoclonal antibodies.