Total Synthesis of (2Z)‐[(4R,5R,6S)‐6‐(β‐D‐Glucopyranosyloxy)‐4,5‐dihydroxycyclohex‐2‐en‐1‐ylidene]ethanenitrile,a Cyanoglucoside from Ilex warburgii

The total synthesis of the noncyanogenic cyanoglucoside 1 , originally isolated from Ilex warburgii, was achieved in nine steps (9% overall yield), starting from an optically pure Diels–Alder adduct ((+)‐ 3 ). The key step of the synthesis, the glycosidation, was carried out under Koenigs–Knorr conditions closely related to those developed for the total syntheses of (?)‐lithospermoside and (?)‐bauhinin. We had to tune the protecting groups used for the two free cis‐configured OH groups of the aglycone, which afforded the desired β‐d‐ glucoside intermediate 15 in very good yield (62%).     

Palladium nano-clusters grown on prestructured HOPG substrates

The growth of Palladium nano-clusters prepared by atomic beam deposition on prestructured highly oriented pyrolytic graphite (HOPG) surfaces has been investigated by means of scanning tunnelling microscopy (STM). Preformed nanosized pits created on the HOPG surfaces are used as localized pinning sites for Pd cluster nucleation and growth at room temperature. We succeeded in obtaining Pd clusters of nanometric size and with rather sharp size distributions. A systematic morphological study conducted by STM reveals a linear dependence between the height and the diameter of the Pd nanostructures. Finally, Pd nano-clusters stabilized on prestructured HOPG surfaces were found to be active catalysts in the Heck cross-coupling reaction.     

Formation of carbon-sulfur and carbon-selenium bonds by palladium-catalyzed decarboxylative cross-couplings of hindered 2,6-dialkoxybenzoic acids

A simple route to diaryl sulfides using a decarboxylative palladium-catalyzed reaction between electron-rich 2,6-dialkoxybenzoic acid derivatives and diaryl disulfides is reported. This coupling proceeds efficiently in the presence of Pd(CF(3)CO(2))(2) and Ag(2)CO(3) in a 65:1 mixture of 1,4-dioxane and tetramethylene sulfoxide (TMSO). We present also the first formation of a carbon-selenium bond via a palladium-catalyzed decarboxylative cross-coupling.     

Synthesis of biaryls via decarboxylative Pd-catalyzed cross-coupling reaction

[reaction: see text] A simple and efficient route to biaryls via Pd-catalyzed decarboxylative cross-couplings of arene carboxylic acids and aryl iodides is reported. The PdCl2/AsPh3 catalytic system in the presence of Ag2CO3 in DMSO was found to be particularly efficient to perform this transformation. This reaction can be extended to the synthesis of various biaryls, including sterically hindered biaryls, with yields ranging from 58% to 90%.     

Selective Formation of β‐D‐Glucosides of Hindered Alcohols

Alternative conditions for the classical glycosidation method of Koenigs‐Knorr allowed us to prepare selectively β‐D ‐glucosides of several hindered alcohols in good yields in a weakly acidic to almost neutral medium. To illustrate the versatility of our conditions, we prepared the β‐D ‐glucoside of an acid‐sensitive aglycone, a key‐intermediate for the total synthesis of a natural cyanoglucoside, bauhinin.     

Highly efficient and reusable supported pd catalysts for Suzuki-Miyaura reactions of aryl chlorides

Syntheses of air- and moisture-stable heterogeneous (tert-butylarylphosphino)polystyrene-supported Pd catalysts and their use for versatile Suzuki-Miyaura reactions of aryl chlorides and arylboronic acids under non-anhydrous conditions are reported. The catalysts are easily recovered by filtration. They can be used many times (more than seven) without showing any loss of activity, and the amount of Pd leached is extremely low (<0.1%).     

Synthesis of (−)-Conduritol C (1L-Cyclohex-5-ene-1,2,3/4-tetrol)

(1R, 2R, 4R)-2-endo-Cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate ((?)-7) has been transformed into the all-cis-configurated 4L -4,5,6/0-trihydroxycyclohex-2-en-1-one derivatives (?)- 12 and (?)- 19 . (?)-Conduritol C ((?)- 3 ) was derived in a stereospecific manner from (?)- 12 .     

Total Syntheses of (−)-Conduritol B ((−)-1L-Cyclohex-5-ene-1,3/2,4-tetrol) and of (+)-Conduritol F((+)-1D-Cyclohex-5-ene-1,2,4/3-tetrol). Determination of the Absolute Configuration of (+)-Leucanthemito

The ‘naked sugar’ (+)-(1R,2R4R)-2-endo-cyano-7-oxabicyclo[2.2.1]hept-5-sn-2-exo-yl acetate ((+)- 4 ) was converted (7 steps, 45% overall) with high stereoselectivity into (?)-(4R,5S,6R)-4,5,6-tris{[(tert-butyl)dimethylsilyl]oxy}cyclohex-2-en-1-one ((?)- 11 ). Reduction of (?)- 1 with NaBH₄- CeCl₃ · 7 H₂O, followed by deprotection of the silyl ether moieties gave (+)-conduritol F ((+)- 1 ; 47%) whose characteristics were identical to those of natural (+)-leucanthemitol. Reduction of (?)- 11 with DIBAH, followed by deprotection of the silyl ether moiety led to (?)-conduritol B ((?)- 3 ; 51 %).