Direct Stereoselective Synthesis of 2-Deoxyglycosides via Visible-Light-Induced Photoacid-Catalyzed Activation of Glycosyl -[1-(-MeO-Phenyl)vinyl]benzoates (PMPVBs) as Donors.

The photoacid-catalyzed synthesis of 2-deoxy glycosides is presented using stable glycosyl -[1-(-MeO-Phenyl)vinyl]benzoate (PMPVB) donors and employing the eosin Y and diphenyl disulfide (PhSSPh) catalytic system in the presence of blue LED lights. The remote activation of the alkene functionality under the photoacid catalysis followed by a 5-- cyclization led to the generation of oxocarbenium ions that were trapped to provide the glycosylated products in excellent yields and decent selectivities under mild conditions. This method is also useful for the photoacid-catalyzed synthesis of -methoxybenzyl-alkyl ethers.

Triple Role of Proton Sponge (DMAN) in the Palladium-Catalyzed Direct Stereoselective Synthesis of -Aryl Glycosides from Glycals.

The triple role of 1,8-bis(dimethylamino)naphthalene (proton sponge) as a reductant, ligand precursor, and organic base in the palladium-catalyzed Heck-type coupling reaction of glycals with aryl iodides affords the rapid and stereoselective synthesis of 2',3'-unsaturated α--aryl glycosides in excellent yields. The role of the proton sponge in reducing palladium(II) to (0) has been studied using cyclic voltammetry, UV-vis, HRMS, and other spectroscopic techniques. This is the first example of a palladium proton sponge complex utilized in coupling reactions.

Exploiting the Strained Ion-Pair Interactions of Sterically Hindered Pyridinium Salts Toward S2 Glycosylation of Glycosyl Trichloroacetimidates.

We demonstrate here that strained and sterically hindered protonated 2,4,6-tri--butylpyridinium (TTBPy) tetrafluoroborate, a crystalline, bench stable salt serves as a mild and efficient organocatalyst for the S2 type displacement of glycosyl trichloroacetimidates toward the stereoselective synthesis of both α- and β-glycosides. The strained ion-pair interactions between the sterically hindered pyridinium cation and the tetrafluoroborate anion infuse unusual reactivity to the ions resulting in the unique anion assisted activation of alcohol. This mild activation of alcohol facilitates the S2 type displacement of glycosyl αtrichloroacetimidates into β-glycosides in a highly diastereoselective manner.

Synthesis of chiral functional polyhydroxylated arenes via Mukaiyama aldol reaction from Perlin aldehydes.

Functionalized aryl polyhydroxylated compounds could be of great synthetic value for natural product synthesis. However, the synthesis of such compounds usually requires multi-step synthesis or the usage of sensitive reagents. We present here a practically simple route for the synthesis of such functionalized arylpolyols from glycal derived α,β-unsaturated 2,3-dideoxy aldehyde as well as α,β-saturated 2,3-dideoxy aldehyde (Perlin aldehydes) via Mukaiyama cross aldol condensation in the presence of silyl enol ether and TiCl It was observed that the nature of the electronic substitution of the silyl enol ether does not play any role in the yield of the desired products.