Reactions with and in Anydrous Hydrogen Fluoride, 13. A Convenient One-Pot Synthesis of Glucofurano[2,1-d]oxazolines with an Additional 3,5,6-Orthoester Function
✍ Scribed by Miethchen, Ralf ;Klein, Holger ;Pedersen, Christian
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- English
- Weight
- 358 KB
- Volume
- 1994
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
The reactions of dioxolanylium and oxazolinium ions, formed in anhydrous HF from N‐acylated 2‐amino‐2‐deoxy‐D‐glucoses and one equivalent of carboxylic acid anhydride or chloride, were investigated by treatment of their HF solutions with triethylamine/alkane or triethylamine/ether systems. Thus, the 2‐acylamido‐2‐deoxy‐D‐glucoses 1 and 2 react with acetic anhydride, dodecanoic anhydride or pivaloyl chloride in anhydrous HF at −30°C to give 5,6‐dioxolanylium ions. On treatment with formic acid at room temperature they undergo further reaction to yield the thermodynamically favored 3,6‐anhydro derivatives. The glucofurano‐oxazolines 3–5, containing an orthoester substructure, as well as the 3,6‐anhydro‐D‐glucofuranose derivatives 6 and 7 can be isolated after treatment of the HF solutions with triethylamine. The oxazoline derivative 4 was used as glycosyl donor for methanol giving the methyl glycoside 8 without cleavage of the orthoester moiety.