Selective Oxidation of the Primary Hydroxyl Group

The direct oxidation of hydroxyls on inulin allows the potential introduction of carbonyl and carboxyl groups, altering the properties of the polysaccharide and opening additional commercial applications (Bragd et al., 2004). The primary hydroxyl in the C-6 position on the fructofuranoside subunits can be selectively oxidized using 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO). This forms a stable radical that can be oxidized by hypobromite, or similar reagent, to give a nitrosonium 

Biology and Chemistry of Jerusalem Artichoke Helianthus tuberosus L. 

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Useful syntheses of D- and L-lyxose from 1,3-O-benzylidene-D- and L-arabinitol have been achieved through the highly selective oxidation of the primary hydroxyl groups by dimethyl sulfoxide-dicyclohexylcarbodiimide.463 Oxidation of but one of the two (equivalent) hydroxyl groups in 1,3,4,6-tetra-O-benzyl-D-mannitol464 and l,6-di-0-benzyl-2,5-0-methylene-D-mannitol465 was possible with dimethyl sulfoxide-acetic anhydride. 

In contrast to the oxidation of acyclic polyhydric alcohols in benzene,508 treatment of 1,2-O-isopropylidene-a-D-glucofuranose with silver carbonate-on-Celite in boiling methanol led to selective oxidation of the primary hydroxyl group, with the formation of the al-duronic acid derivative in 68% yield.517... 

The synthesis of glycosiduronic acids includes two main approaches one involves selective oxidation of the primary hydroxyl group of a neutral glycoside, and the other, condensation of the agly-con with an appropriately protected alduronic acid derivative. The present Section is concerned mainly with the synthetic methods leading to glycosiduronic acids. An attempt has been made to collate information on the reactions of glycosiduronic acids, and to illustrate some of the physical methods that have contributed to the characterization of these compounds. 

Selective oxidation of a primary alcohol. The final step in a recent synthesis of strophanthidin required selective oxidation of the primary hydroxyl group of stro-phanthidol (1) to an aldehyde group. Oxidations with chromic acid, N-haloamides,... 

Theoretically, selective oxidation of the primary hydroxyl group of G9 to carboxyl would then lead to the bactobolin skeleton. However, this goal remained elusive under a variety of experimental conditions. The only isolable products were the diene Gil and the vinylogous lactone G13, logical intermediates for which are the hemiacetals GIO and G12. 

Partially protected carbohydrates can be selectively oxidized at the primary hydroxy group to uronic acids at the nickel hydroxide electrode. At the same electrode, in polyhydroxy steroids, a preferential oxidation of the sterically better accessible hydroxyl groups is achieved [142]. By way of the mediator, TEMPO, carbohydrates that are only protected at the anomeric hydroxyl group are selectively oxidized at the primary hydroxyl group (Fig. 27) [143-145]. 

The same sequence of reactions was accomplished on the bicyclic iodide 16-R (Scheme 10), the reaction of which with tetrabutylammonium azide in toluene at 60 °C afforded the azide 33-R in 76% yield. Selective deprotection of the primary hydroxyl group of compound 33-R and Jones oxidation, finally afforded compound 35-R as masked glyco-aminoacid. The azido group was maintained in these compounds as protected equivalent of the amino group. 

Selective oxidation of a primary hydroxyl group. The first synthesis of the secoiridoid 4 has been achieved from the tetraacetate (1) of secologanin, the biological precursor of secoiridoids. Dihydroxylation of 1 with Os04 and potassium... 

The required donor for the total synthesis of bulgecin C (3) was prepared from 3,4,6-tri-O-acetyl-D-glucal by conversion into 2-azido glucoside 21 (Scheme 3). Benzylation with benzyl bromide followed by acid hydrolysis and subsequent selective benzylation of the primary hydroxyl group using bis(tributyltin)oxide and benzyl bromide produced... 

Alternatively, compound 14 was oxidized with sodium periodate, followed by reduction with sodium borohydride in ethanol to afford 18 (Scheme 3). Hydrolysis of the isopropy-lidene group in 18 with 50% aqueous trifluoroacetic acid followed by hydrogenation of the azide group and then intramolecular reductive amination and protection of the imine group afforded 19. Selective mesylation of the primary hydroxyl group in 19 followed by silylation and subsequent removal of the benzyloxycarbonyl group and then cyclization with sodium acetate afforded 20. Deprotection of 20 led to me50-quinuclidine-3,5-diol (3). 

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