Palladium-Catalyzed Glycosylation Reaction Research Articles

De novo asymmetric synthesis and biological analysis of the daumone pheromones in Caenorhabditis elegans and in the soybean cyst nematode Heterodera glycines

The de novo asymmetric total syntheses of daumone 1, daumone 3 along with 5 new analogs are described. The key steps of our approach are: the diastereoselective palladium catalyzed glycosylation reaction; the Noyori reduction of 2-acetylfuran and an ynone, which introduce the absolute stereochemistry of the sugar and aglycon portion of daumone; and an Achmatowicz rearrangement, an epoxidation and a ring opening installing the remaining asymmetry of daumone. The synthetic daumones 1 and 3 as well as related analogs were evaluated for dauer activity in Caenorhabditis elegans and for effects on hatching of the related nematode Heterodera glycines. This data provides additional structure activity relationships (SAR) that further inform the study of nematode signaling.

The De Novo Synthesis of Oligosaccharides: Application to the Medicinal Chemistry SAR-Study of Digitoxin

To address the medicinal chemist's need for new synthetic methods for the preparation of unnatural carbohydrates, a new de novo method for carbohydrate synthesis has been developed. These routes use a palladium catalyzed glycosylation reaction to stereoselectively control the anomeric center and subsequent diastereoselective post glycosylation to install the remaining sugar stereocenters. The utility of this method was demonstrated by the syntheses and biological evaluation of several digitoxin oligosaccharide analogues.

De novo approach to 2-deoxy-beta-glycosides: asymmetric syntheses of digoxose and digitoxin.

A highly enantioselective and straightforward route to trisaccharide natural products digoxose and digitoxin has been developed. Key to this approach is the iterative application of the palladium-catalyzed glycosylation reaction, reductive 1,3-transposition, diastereoselective dihydroxylation, and regioselective protection. The first total synthesis of natural product digoxose was accomplished in 19 total steps from achiral 2-acylfuran, and digitoxin was fashioned in 15 steps starting from digitoxigenin 2 and pyranone 8beta. This flexible synthetic strategy also allows for the preparation of mono- and disaccharide analogues of digoxose and digitoxin.

A Stereoselective Synthesis of Digitoxin and Digitoxigen Mono- and Bisdigitoxoside from Digitoxigenin via a Palladium-Catalyzed Glycosylation

A convergent and stereocontrolled route to trisaccharide natural product digitoxin has been developed. The route is amenable to the preparation of both the digitoxigen mono- and bisdigitoxoside. This route featured the iterative application of the palladium-catalyzed glycosylation reaction, reductive 1,3-transposition, diastereoselective dihydroxylation, and regioselective protection. The natural product digitoxin was fashioned in 15 steps starting from digitoxigenin 2 and pyranone 8a or 18 steps from achiral acylfuran.

De Novo Asymmetric Synthesis of Daumone via a Palladium‐Catalyzed Glycosylation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

De Novo Asymmetric Synthesis of Daumone via a Palladium-Catalyzed Glycosylation

The enantioselective syntheses of daumone and two analogues have been achieved in seven to eight steps. This route relies upon a diasteroselective palladium-catalyzed glycosylation reaction for the formation of the anomeric bond. The asymmetry of the sugar and aglycone portion of daumone were introduced by Noyori reduction of an acylfuran and a propargyl ketone. A highly diastereoselective epoxidation and reductive ring opening established the desired C-2 and C-4 stereochemistry of daumone. [reaction: see text]

De novo synthesis of oligosaccharides using a palladium-catalyzed glycosylation reaction.

The natural all d- and/or unnatural all l-1,4- and 1,6-oligosaccharides were synthesized from furan alcohols using a palladium-catalyzed glycosylation reaction. The 1,4- and 1,6-alpha-manno-disaccharides were achieved in seven total steps starting from chiral furan alcohols. Similarly, 1,4- and 1,6-alpha-manno-trisaccharides were also synthesized in nine total steps. Key to the overall efficiency of this process was the use of highly diastereoselective palladium-catalyzed glycosylations, reductions, and dihydroxylations.

A Palladium‐Catalyzed Glycosylation Reaction: The de novo Synthesis of Natural and Unnatural Glycosides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A palladium-catalyzed glycosylation reaction: the de novo synthesis of natural and unnatural glycosides.

A highly stereoselective and sterospecific palladium-catalyzed glycosylation reaction of a variety of alcohols is reported. The reaction selectively converts alpha-2-substituted 6-carboxy-2H-pyran-3(6H)-ones into alpha-2-substituted 6-alkoxy-2H-pyran-3(6H)-ones with complete retention of configuration and similarly converts the pyranones with beta-carboxy groups into pyranones with beta-alkoxy groups. The reaction works equally well with both amino acid- and carbohydrate-based alcohols. To demonstrate the utility of this process for carbohydrate chemistry several of the products were selectively converted into alpha-manno-pyranosides in two additional steps. Because the 2-substituted 6-carboxy-2H-pyran-3(6H)-ones are prepared by asymmetric synthesis, this reaction can be used for the preparation of either d- or l-pyranones.