REACTIONS WITH AND IN ANHYDROUS HYDROGEN FLUORIDE .13. A CONVENIENT ONE-POT SYNTHESIS OF GLUCOFURANO[2,1,-D]OXAZOLINES WITH AN ADDITIONAL 3,5,6-ORTHOESTER FUNCTION

The reactions of dioxolanylium and oxazolinium ions, formed in anhydro us 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/ethe r systems, Thus, the 2-acylamido-2-deoxy-D-glucoses 1 and 2 react with acetic anhydride, dodecanoic anhydride or pivaloyl chloride in anhydr ous HF at -30 degrees C to give 5,6-dioxolanylium ions. On treatment w ith formic acid at room temperature they undergo further reaction to y ield the thermodynamically favored 3,6-anhydro derivatives. The glucof urano-oxazolines 3-5, containing an orthoester substructure, as well a s 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.