Benzyl <i>N</i>-Phenyl-2,2,2-trifluoroacetimidate: A New and Stable Reagent for O-Benzylation

Okada, Yasunori; Ohtsu, M.; Bando, Masafumi; Yamada, Hidetoshi

doi:10.1246/cl.2007.992

Cited by 24 publications

(4 citation statements)

References 13 publications

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“…Typically, the benzyl protection has been carried out by treating alcohols with a benzyl halide in the presence of a stoichiometric base, such as potassium hydroxide and sodium hydride . The benzyl protection of alcohols without a base has been achieved by using benzyl trichloroacetimidate or other O -benzyl imidates , in the presence of an acid promoter. Benzyl diphenylphosphinite and 2-benzyloxy-1-methylpyridinium triflate are known as effective benzylating agents of hydroxy groups under neutral conditions.…”

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confidence: 99%

Benzyl Protection of Phenols under Neutral Conditions: Palladium-Catalyzed Benzylations of Phenols

Kuwano

Kusano

2008

Org. Lett.

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Benzyl protection of phenols under neutral conditions was achieved by using a Pd(eta3-C3H5)Cp-DPEphos catalyst. The palladium catalyst efficiently converted aryl benzyl carbonates into benzyl-protected phenols through the decarboxylative etherification. Alternatively, the nucleophilic substitution of benzyl methyl carbonates with phenols proceeded in the presence of the catalyst, yielding aryl benzyl ethers.

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confidence: 99%

Benzyl Protection of Phenols under Neutral Conditions: Palladium-Catalyzed Benzylations of Phenols

Kuwano

Kusano

2008

Org. Lett.

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“…To prepare for these two glycosylations, the protective groups were manipulated in the following three steps. The C6-alcohol of 6-α was protected as the acid-resistant benzyl ether of 38 using N -phenyl-2,2,2-trifluoroacetimidate and catalytic TfOH . Chemoselective removal of the acid-labile acetonides of 38 was realized by application of the reagent combination of BF 3 ·OEt 2 and 1,3-propane dithiol in MeCN without affecting the potentially reactive C1-acetal or benzyl ether .…”

Section: Resultsmentioning

confidence: 99%

Convergent Total Synthesis of Hikizimycin Enabled by Intermolecular Radical Addition to Aldehyde

et al. 2020

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Hikizimycin (1), which exhibits powerful anthelmintic activity, has the most densely functionalized structure among nucleoside antibiotics. A central 4-amino-4-deoxyundecose of 1 possesses 10 contiguous stereocenters on a C1–C11 linear chain and is decorated with a cytosine base at C1 and a 3-amino-3-deoxyglucose at C6-OH. These distinctive structural features of 1 make it an extremely challenging target for de novo construction. Herein, we report a convergent total synthesis of 1 from four known components: 3-azide-3-deoxyglucose derivative 4, bis-TMS-cytosine 5, d-mannose 9, and d-galactose derivative 10. We first designed and devised a novel radical coupling reaction between multiply hydroxylated aldehydes and α-alkoxyacyl tellurides. The generality and efficiency of this process was demonstrated by the coupling of 7c and 8, which were readily accessible from two hexoses, 9 and 10, respectively. Et3B and O2 rapidly induced decarbonylative radical formation from α-alkoxyacyl telluride 8, and intermolecular addition of the generated α-alkoxy radical to aldehyde 7c yielded 4-amino-4-deoxyundecose 6-α with installation of the desired C5,6-stereocenters. Subsequent attachments of the cytosine with 5 and of the 3-azide-3-deoxyglucose with 4 were realized through selective activation of the C1-acetal and selective deprotection of the C6-hydroxy group. Finally, the 3 amino and 10 hydroxy groups were liberated in a single step to deliver the target 1. Thus, the combination of the newly developed radical-coupling and protective-group strategies minimized the functional group manipulations and thereby enabled the synthesis of 1 from 10 in only 17 steps. The present total synthesis demonstrates the versatility of intermolecular radical addition to aldehyde for the first time and offers a new strategic design for multistep target-oriented syntheses of various nucleoside antibiotics and other bioactive natural products.

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“…Most pleasingly, the yield of 28 was significantly improved up to 67% when this reaction proceeded in 1,4‐dioxane with benzyl 2,2,2‐trifluoro‐ N ‐phenylacetimidate (BnOPTFAI) and a catalytic amount of TfOH. [ 57 ] Finally, removal of allyl group at rhamnosyl…”

Section: Background and Originality Contentmentioning

confidence: 99%

Chemical Synthesis of an Octasaccharide Derivative Related to Group B StreptococcusCell‐Wall Polysaccharide

et al. 2022

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Comprehensive Summary Group B Streptococcus (GBS) is the major pathogen that causes invasive infectious diseases in neonates and infants. The development of preventive and therapeutic strategies against GBS infection has been becoming the most pressing subject worldwide. Group B carbohydrate (GBC), the group B‐specific polysaccharide that distinguishes GBS with other streptococci species, has been identified as an attractive antigen for diagnosis and vaccine development because of its highly conservative tetra‐antennary structure. In this paper, a highly convergent [3 + 5] glycosylation strategy for efficient synthesis of an octasaccharide derivative related to GBC oligosaccharide unit II has been developed. In this synthesis, each glycosylation reaction was efficiently constructed with glycosyl imidates, especially trifluoroacetimidate, as donors, and each glycosidic bond was stereoselectively controlled via the neighboring group participation effect of acyl group on the 2‐O‐position of imidate donors or the solvent effect of Et2O. Furthermore, the aminoethylphosphate group was smoothly installed on the 6‐O‐position of d‐glucitol residue using the phosphoramidite method. After global deprotection, the target octasaccharide was successfully obtained from d‐glucitol in 29 steps with an overall yield of 1.37%. The free amino group installed on the aminoethylphosphate spacer of the target molecule enables its modification with functionalized biomolecules for further biological studies.

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Benzyl N-Phenyl-2,2,2-trifluoroacetimidate: A New and Stable Reagent for O-Benzylation

Cited by 24 publications

References 13 publications

Benzyl Protection of Phenols under Neutral Conditions: Palladium-Catalyzed Benzylations of Phenols

Benzyl Protection of Phenols under Neutral Conditions: Palladium-Catalyzed Benzylations of Phenols

Convergent Total Synthesis of Hikizimycin Enabled by Intermolecular Radical Addition to Aldehyde

Chemical Synthesis of an Octasaccharide Derivative Related to Group B StreptococcusCell‐Wall Polysaccharide

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