Oxidation/reduction protocol

Historically, the oxidation-reduction protocol was the only reliable method to prepare the y0-m<2w 6>-glycoside until the insoluble silver salt method was established. In 1972, Ekborg et al. reported the use of the 2-(9-benzoylated glucosyl bromide 51 for this purpose [83] (O Scheme 28). Glycosylation with diacetone galactose and selective deprotection of the 2 -position followed by DMSO oxidation afforded the 2-uroside which was reduced by hydrogenation over Pt. The use of the 1,2-0-orthoester for the same purpose was also reported [84]. 

In combination with the oxidation-reduction protocol, the glycal-based oligosaccharide assembling strategy [89] which has been extensively developed by Danishefsky gives an expedient... 

Fraser-Reid et al. have reported the utilization of the -pentenyl orthobenzoate for the synthesis of octa-y6-l,2-mannan through the repetition of -selective glucosylation followed by the oxidation-reduction protocol [91]. 

The allylic alcohol was subjected to an Eschenmoser-Claisen rearrangement with dimethylacetamide dimethylacetal to introduce the C14 substituent in a stereoselective manner. Reduction of the amide to the corresponding aldehyde with phenyl silane in the presence of Ti(0/Pr)4 was followed by an acid-promoted closure of the C-ring of codeine. In order to prevent N-oxidation, the amine was converted to the corresponding tosylamide, via debenzylation and treatment with tosyl chloride, before the allylic alcohol was introduced by the reaction of the alkene with selenium dioxide (65). The stereochemistry of the C6 hydroxy functionality was corrected by applying the well-known oxidation/reduction protocol [46, 60] before the benzylic double bond was reductively removed under Birch conditions. Codeine (2) was obtained in 17 steps with an overall yield of approximately 0.6%. 

Appendino G, Jakupovic J, Cravotto G, Enriu R, Varese M, Bombardelli E (1995) Synthesis of Modified Baccatins via an Oxidation-Reduction Protocol. Tetrahedron Lett 36 3233... 

Orientalol F is a natural product isolated from a traditional Chinese medicinal herb, the rhizome of Alisma orientalis, and is stmcturaUy related to englerin A. The same group synthesized the antipode of natural orientalol F in three steps from 298 (Scheme 18.63) [52]. The stereochemistry of the hydroxyl group in 298 was inverted by an oxidation-reduction protocol, as the a-face was the less hindered. Finally, catalytic hydrogenation chemoselectively reduced... 

Epimerization of carbohydrate stractures to the corresponding epi-hydroxy stereoisomers is an efficient means to generate compounds with inverse coirfiguration that may otherwise be cumbersome to prepare. Several different synthetic methods have been developed, including protocols based on the Mitsunobu reaction,sequential oxidation/reduction... 

Periodate Oxidation/Reductive Amination Conjugation Protocols... 

MW protocols for oxidation-reduction reactions using immobilized reagents on solid supports have been extensively explored. The oxidation of sulfides to sulfoxides and sulfones was also developed under MW irradiation with good... 

Polymer-supported sodium cyanoborohydride (PSCBH), now available commercially, has become more widely used. It is stable and effective even in the presence of oxidants, such as manganese dioxide, shown in this one pot oxidation-reduction amination protocol (eq 38). ... 

Williams and coworkers [42] utilized a similar palladium(II)-mediated oxidative cyclization/w situ reduction protocol in the total synthesis of (+)-paraherquamide B (101, Scheme 9.14). Indole 99 was treated with 1.2 equiv of PdC and 2 equiv of AgBp4 to presumably form an alkylpalladium species, which was reduced with NaBH4 to ultimately provide 100 in good yield. This compound was further transformed to paraherquamide B in six steps. Williams et al. [43] later described the total synthesis of paraherquamide A utilizing the palladium(II)-mediated cyclization on a structurally similar compound. 

Later, Shimada et al. reported a novel tandem oxidation-reduction reaction with a combination of two fnndamentally distinct Ru catalysts [13], By means of this strategy, the racemic secondary benzylic alcohols could be transformed efficiently into (R)-enantiomers (Scheme 9.10). This catalytic system, containing two different chiral ruthenium catalysts, provides an alternative to chiral secondary alcohol synthesis beyond direct raJuction or addition protocols. 

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