T1 - A new route toward 2-acetamido-4-O-methyl-2-deoxy-d-mannopyranose from a Ferrier derivative of tri-O-acetyl-d-glucal, which contributes to aldolase-catalyzed synthesis of laninamivir (CS-8958)
Neodysiherbaine A, a neuroexitotoxin occurring in a Micronesian marine sponge , was synthesized from tri--acetyl--glucal with excellent stereocontrol. The method established enables us to obtain gram quantities of neodysiherbaine A and its related compounds.
The use of tri- O -acetyl- d -glucal and - d ..
In a typical reaction procedure, 2,3-unsaturated O-glycosides 3 were prepared, from the reaction of 3,4,6-tri-O-acetyl-D-glucal 1 and alcohols 2 in CH2Cl2 at room temperature in the presence of TCT as catalyst (). Since in this new kind of methodology, there is a great challenge to find new catalysts able to perform the reactions with high activities, we considered TCT as a potential promoter due to its good features for such a transformation. During our investigation, we firstly chose the reaction of 3,4,6-tri-O-acetyl-D-glucal (1mmol) and methanol (1.2mmol) as model reactants and examined the effect of the different amounts of TCT (). When above model reactants were conducted in CH2Cl2 (5mL) in the presence of 0, 0.05, 0.10, 0.15, and 0.20mmol of TCT separately, the best result was obtained using 0.10mmol of catalyst (yield = 90%). Using lower amounts of catalyst resulted in lower yields, while higher amounts of catalyst did not affect the reaction times and yields (, entries 2–5). In the absence of catalyst, the product was not formed (, entry 1). In order to evaluate the effect of the solvent, the reaction of 3,4,6-tri-O-acetyl-D-glucal and methanol in the presence of TCT was performed in various solvents such as CH2Cl2, CH3CN, acetone, THF, and ethyl ether, in which the best result was obtained in CH2Cl2 (, entry 3); thus, we chose it as the solvent for all further reactions (, entries 6–9).
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AB - An intramolecular Diels-Alder approach to the construction of (+)-compactin is described. Alkylation of the lithium enolate of (acetylmethylene)triphenylphosphorane with the tosylate of allenic alcohol 15 affords phosphorane 16, which condenses with aldehyde 6 (prepared from tri-O-acetyl-D-glucal) to afford enone 3. Intramolecular Diels-Alder reaction, reduction with lithium tri-sec-butylborohydride, and acylation with (S)-(+)-2-methylbutyric anhydride yields a chromatographically separable mixture of diastereomers; conversion to compactin was accomplished by acid hydrolysis followed by oxidation.
A highly convergent total synthesis of (+)-compactin
A series of ethyl(phenyl) 6-amino-2,3,6-trideoxy-α-D-glucopyranosides (amino=piperidino (Pip), pyrrolidino (Pyr), azetidino (Az), Bu2N) have been prepared from tri-O-acetyl-D-glucal to obtain catalysts for asymmetric synthesis and the starting compounds for the syntheses of other bidentate ligands.
Thieme E-Journals - Synthesis / Abstract
Cyanuric chloride has been found to be an efficient catalyst for the synthesis of 2,3-unsaturated O-glycosides from the reaction of 3,4,6-tri-O-acetyl-D-glucal and a wide range of alcohols in dichloromethane at room temperature. The experimental procedure is simple, and the products are obtained in high yields.