Scavenging Byproducts in the Sulfoxide Glycosylation Reaction:  Application to the Synthesis of Ciclamycin 0

Gildersleeve, Jeffrey C.; Smith, Alastair; Sakurai, Kaori; Raghavan, Subharekha; Kahne, Daniel

doi:10.1021/ja990690a

Cited by 92 publications

(55 citation statements)

References 17 publications

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“…13 With the glycosyl acceptor 5 , itself a thioglycoside, the sulfenyl trap 1-octene was added to the reaction mixture before it was allowed to warm to room temperature to prevent premature activation of the disaccharyl thioglycoside. 7a,14 As anticipated, 11 these reactions were highly β-selective with only a single anomer being isolated in each case. Acidolysis of the reactive trans -fused acetonide in 4 and 5 was then followed by benzoylation to give 6 and 7 , which, on treatment with sodium cyanoborohydride and HCl 15 underwent reductive cleavage of the benzylidene acetal units to give the corresponding 6′- O -benzyl ethers retaining hydroxyl groups at the 4′-position, 8 and 9 (Scheme 1).…”

Section: Resultssupporting

confidence: 64%

Synthesis and Structural Verification of the Xylomannan Antifreeze Substance from the Freeze-Tolerant Alaskan Beetle Upis ceramboides

Crich

Rahaman

2011

J. Org. Chem.

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Tetra-, hexa-, and octasaccharide subunits of the [→4)-β-D-Manp-(1→4)-β-D-Xylp-(1→]n xylomannan motif proposed as the structure of a novel non-protein, thermal hysteresis-producing antifreeze substance from the freeze-tolerant Alaskan beetle Upis ceramboides have been accessed by total chemical synthesis. Comparison of their NMR spectral data with data of the isolate lends strong support to the proposed structure. Synthetic tetrasaccharides representing various linkage isomers considered (α- rather than β-manno, and linkage through mannose O3 rather than O4) show more significant chemical shift differences with the isolate and are therefore excluded from further consideration.

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Section: Resultssupporting

confidence: 64%

Synthesis and Structural Verification of the Xylomannan Antifreeze Substance from the Freeze-Tolerant Alaskan Beetle Upis ceramboides

Crich

Rahaman

2011

J. Org. Chem.

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“…Sulfenyl group transfer to substrate-based nucleophiles has been observed previously and can typically be suppressed by working in the presence of a sacrificial alkene. 62,126 However, even working in the presence of multiple equivalents of 1-octene or the highly reactive β-pinene 127–128 we were unable to obtain a satisfactory yield of 32 (Chart 1, Table 1, entry 4). This observation, coupled with the relative paucity of such side reactions in the mannose series (Table 1, entries 1–3), suggests an intramolecular process and caused us to abandon the use of the gluco-configured sulfoxide 21 in clock reactions.…”

Section: Resultsmentioning

confidence: 98%

Cation Clock Reactions for the Determination of Relative Reaction Kinetics in Glycosylation Reactions: Applications to Gluco- and Mannopyranosyl Sulfoxide and Trichloroacetimidate Type Donors

et al. 2015

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The development of a cation clock method based on the intramolecular Sakurai reaction for probing the concentration dependence of the nucleophile in glycosylation reactions is described. The method is developed for the sulfoxide and trichloroacetimidate glycosylation protocols. The method reveals that O-glycosylation reactions have stronger concentration dependencies than C-glycosylation reactions consistent with a more associative, SN2-like character. For the 4,6-O-benzylidene-directed mannosylation reaction a significant difference in concentration dependence is found for the formation of the β- and α-anomers suggesting a difference in mechanism and a rationale for the optimization of selectivity regardless of the type of donor employed. In the mannose series the cyclization reaction employed as clock results in the formation of cis and trans-fused oxabicyclo[4,4,0]decanes as products with the latter being strongly indicative of the involvement of a conformationally mobile transient glycosyl oxocarbenium ion. With identical protecting group arrays cyclization in the glucopyranose series is more rapid than in the mannopyranose manifold. The potential application of related clock reactions in other carbenium ion-based branches of organic synthesis is considered.

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“…Employing this method, Kahne et al completed the total synthesis of ciclamycin 0(86) in 1999, which is an anthracycline antibiotic isolated from Streptomyces capoamus (Scheme 20) 121. Thus, the condensation of the intact aglycone 88 with trisaccharide sulfoxide 87 was performed in the presence of Tf 2 O (3 equiv.…”

mentioning

confidence: 99%

O-Glycosylation methods in the total synthesis of complex natural glycosides

2015

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The total syntheses of 33 complex natural O-glycosides, such as the glycosides of macrocyclic lactones/lactams, enediynes, angucyclines, and anthracyclines, are highlighted, with a major focus being placed on the O-glycosylation reactions which connect the saccharides and the aglycones. These successful O-glycosylation reactions employ such donors as glycosyl bromides, fluorides, iodides, trichloroacetimidates, N-phenyl trifluoroacetimidates, thioglycosides, sulfoxides, heteroaryl thioglycosides, 1-hydroxyl sugars, 1-O-acetates, and ortho-alkynylbenzoates. Each synthesis is depicted starting from the O-glycosylation of the aglycone (or its precursor); the glycosylation conditions and outcomes (yields and stereoselectivities) are discussed, and the subsequent transformations toward the final target, including the elongation of the glycan, the elaboration of the aglycone, and the protecting group manipulations are also given in detail.

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Scavenging Byproducts in the Sulfoxide Glycosylation Reaction: Application to the Synthesis of Ciclamycin 0

Cited by 92 publications

References 17 publications

Synthesis and Structural Verification of the Xylomannan Antifreeze Substance from the Freeze-Tolerant Alaskan Beetle Upis ceramboides

Synthesis and Structural Verification of the Xylomannan Antifreeze Substance from the Freeze-Tolerant Alaskan Beetle Upis ceramboides

Cation Clock Reactions for the Determination of Relative Reaction Kinetics in Glycosylation Reactions: Applications to Gluco- and Mannopyranosyl Sulfoxide and Trichloroacetimidate Type Donors

O-Glycosylation methods in the total synthesis of complex natural glycosides

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