Further studies on cation clock reactions in glycosylation: observation of a configuration specific intramolecular sulfenyl transfer and isolation and characterization of a tricyclic acetal

• Published in: Carbohydrate research Vol. 427; pp. 21 - 28
• Main Authors: Huang, Min, Furukawa, Takayuki, Retailleau, Pascal, Crich, David, Bohé, Luis
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 02.06.2016; Elsevier
• Subjects: Acetals - chemical synthesis; Acetals - chemistry; Biochemistry & Molecular Biology; Carbohydrate Conformation; Cation clock; Cations - chemistry; Chemistry; Chemistry, Applied; Chemistry, Organic; Crystallography, X-Ray; Cyclization; Glycosylation; Life Sciences & Biomedicine; Models, Molecular; Physical Sciences; Science & Technology; Sulfenyl transfer; Sulfoxide donor; Sulfoxides - chemistry; Tricyclic acetal; Sulfoxide donor; Glycosylation; Sulfenyl transfer; Tricyclic acetal; Cation clock; SERIES; SULFOXIDE; C-GLYCOSYLATION; DONORS; MECHANISMS; GLUCO; GLYCOSIDE REACTIVITY; NEIGHBORING-GROUP PARTICIPATION; CHEMISTRY; CHEMICAL GLYCOSYLATION
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2016.03.028

•Design of cation clocks.•Intramolecular sulfenyl group transfer in glucosylation using sulfoxide donors.•Exploratory use of hydroxylated groups as internal nucleophiles for cation clocks. [Display omitted] The use of the 2-O-(2-trimethylsilylmethallyl) group as intramolecular nucleophile and cation clock reaction in the glucopyranose series depends on the nature of the glycosyl donor. As previously reported, with trichloroacetimidates the anticipated intramolecular Sakurai reaction proceeds efficiently and is an effective clock, whereas with sulfoxides complications arise. The source of these complications is now shown to be an intramolecular sulfenyl transfer reaction between the tethered allylsilane and the activated sulfoxide. These results illustrate how a different unimolecular clock reaction may be required for a given cation when it is generated from different donors in order to avoid side reactions. The synthesis and cyclization of a 2-O-(3-hydroxypropyl) glucopyranosyl sulfoxide leading on activation to the formation of a trans-fused acetal is also described. The formation of this crystallographically-established trans-fused acetal is discussed in terms of the high effective concentration of the intramolecular nucleophile which leads to a high degree of a SN2 character in the displacement of the α-glucosyl triflate or at the level of the corresponding α-CIP. The possible use of such intramolecular alcohols as clock reactions and their limitations is discussed.