D-Glucofuranose, 1,2:5,6-diisopropylidene

Another substance which may be considered to be an acidic orthoester derivative is Ohle s 1,2-isopropylidene-n-glucofuranose monobenzoate. This substance was prepared from 1,2-5,6-diisopropylidene-D-glucofuranose 3-benzoate by the careful removal of the 5,6-isopropyl-idene residue under acidic conditions. A slight alkalinity of the reaction mixture during any stage of the experiment caused the formation of Fischer and Noth s " 6-benzoyl-derivative. The new substance was isolated in sirupy form. Attempted distillation in high vacuum or the addition of one drop of dilute alkali or ammonia to its aqueous solution... 

D-Glucose reacts with acetone in the presence of acid to yield the nonreducing 1,2 5,6-diisopropylidene-D-glucofuranose. Propose a mechanism. 

Three years later, Freudenberg, Burkhart and Braun heated 3-tosyl-l,2 5,6-diisopropylidene-D-glucofuranose with alcoholic ammonia at 170°, thereby replacing the tosyl group by an amino group. Since an ethylene oxide ring could not be formed, no inversion was expected and the compound liberated subsequently by mild acid hydrolysis was believed to be... 

Enantioselective Reductions. NaBH4 has been employed with less success than LiAULt or BH3 in enantioselective ketone reductions. Low to moderate ee values have been obtained in the asymmetric reduction of ketones with chiral phase-transfer catalysts, chiral crown ethers, -cyclodextrin, and bovine serum albumin. On the other hand, good results have been realized in the reduction of propiophenone with NaBH4 in the presence of isobutyric acid and of diisopropylidene-D-glucofuranose (ee = 85%), " or in the reduction of cr-keto esters and -keto esters with NaBHa-L-tartaric acid (ee >86%). ... 

Deoxy-6-chloro-l,2-3,5-diisopropylidene-D-glucofuranose refluxed 2 days in anhydrous hydrazine crude 6-deoxy-6-hydrazino-l,2-3,5-diisopropylidene-D-glucofuranose (Y 93%) dissolved in ethanol and hydrogenated 2 days with Raney-Ni crude 6-deoxy-6-amino-l,2-3,5-diisopropylidene-D-glucofuranose (Y 94%). E. Hardegger, G. Zanetti, and K. Steiner, Helv. 46, 282 (1963). 

The 5,6-anhydro derivatives of D-sorbitol and D-mannitol41 69 behave in like manner to the 5,6-anhydro-l,2-isopropylidene-D-glucofuranose of Freudenberg and coworkers.70 Thus, 5,6-anhydro-l,3 2,4-diethyli-dene-D-sorbitol (LXXXV) readily suffers ring scission with ammonia to give 6-amino 6-desoxy-l,3 2,4-diethylidene-D-sorbitol (LXXXVI)69 or with sodium methoxide to form 6-methyl-l,3 2,4-diethylidene-D-sorbitol.42 l,2 3,4-Diisopropylidene-5,6-anhydro-D-mannitol gives rise... 

A series of cyanoacetic acid derivatives 96 (94TA1435, 95TA255) was used for the introduction of a chiral moiety into position 3 of a pyran ring Oppolzer s sultam (a), (—)-menthol (b), (IS)-endo-(-)-borneol (c), ethyl (S)-(—)-lactate (d), diisopropylidene-o-glucofuranose (e). Both Methods 1 and... 

Hydrolytic removal of acetals can be selective, as in the well-known production of 1,2-isopropylidene ot-D-glucofuranose from mild acid-catalysed hydrolysis of l,2 5,6-diisopropylidene ot-D-glucofuranose. °° The difference in reactivity of the two isopropylidene derivatives lies in the differing stabilities of the oxocarbenium ion intermediates. Under acid-catalysed conditions, a cyclic ketal with different electron demand at the alcohol sites will first open to give the most stable oxocarbenium ion leaving group ability is not an issue... 

Diisopropylidene-5-thio-a-D-allofuranose, T-54 1,2 5,6-Di-0 -isopropylidene-3-thio-a-D-glucofuranose, T-72... 

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