Conduritol B tetraacetate

Finally for this section, as another asymmetric synthesis of cycliphelitol (1), the synthetic effort of Trost s group will be introduced [52]. Their synthesis was conducted based on the palladium-catalyzed kinetic resolution of racemic conduritol B tetraacetate ( )-94. Since racemic... 

Recently, Trost and Hembre reported a concise asymmetric synthesis of (+)-cyclophellitol based on the Pd-catalyzed kinetic resolution of racemic conduritol B tetraacetate using the chiral ligand (R,R)A. Most syntheses have started with enantiomerically pure natural products, notably carbohydrates. Such a strategy normally entails rather a long route. A pivalate was chosen as the carboxylate nucleophile for the resolution because the resultant allyl pivalate was anticipated to ionize much more slowly than the starting material. The tetraacetate ( )-conduritol was synthesized from benzo-quinone the kinetic resolution was carried out using 0.65 equiv of sodium pivalate with 1 mol % of (i7 -C3H5PdCl)2 and 3 mol % of (R,R)-AA in a two-phase system with tetra-hexylammonium bromide as the phase transfer catalyst. 

Conduritol B Tetraacetate (F). Compound (IV), 30 g, dissolved in 150 ml of trimethyl phosphite, is heated under reflux for 5 hr under nitrogen. The solution is concentrated under reduced pressure to a syrup and triturated with 100 ml of water. The sticky material crystallizes after a few hours. It is recrystallized from 150 ml of methanol/water 3 2. Yield, 18 g m.p., 85°-89°. 

Competitive inhibition, 4 Concanavalin A, 85,368 binding site, 75 Conduritol B, 369 synthesis of, 373 Conduritol B epoxide, 369 active site labeling, 377-380 labeling with, 370 reaction with /3-glucosidases, 369 synthesis of, 371-376 Conduritol B tetraacetate, synthesis of, 373... 

The kinetic resolution of C2-symmetric racemic substrate as shown in Scheme 8E.22 requires differentiation between the starting material and the monoalkylated product 113 in addition to the enantiodiscrimination in the ionization step. With a bulky carboxylic acid as nucleophile, the racemic tetraacetate of conduritol B was efficiently resolved under phase-transfer conditions [68]. Further elaboration of the hydrolytically desymmetrized alcohol resulted in the synthesis of the important glycosidase inhibitor, (+)-cyclophellitol. 

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