In May 1991 I was working on my degree thesis in organic chemistry and I was stuck in the synthesis of the molecule 9, when I get the molecule 10 thanks to serendipity.
This research earned me a coffee and thirty years of article citations.
These authors have shown, for the first time, that the addition of Grignard reagents to N-benzyl and N-alkyl glycosylamines derived from perbenzylated pentofuranoses or hexopyranoses followed by a simple cyclization procedure afforded a short and convenient approach to imino-C-glycosides in the pyrrolidine and piperidine series [43,44]. The procedure is illustrated in Scheme 2 (see compounds 1–6) from a d-arabinofuranosylamine, using octylmagnesium bromide, and from a d-glucopyranosylamine using allylmagnesium bromide, and cyclization promoted by reacting the intermediate amino alditol with triflic anhydride.
A first application of this reaction to the synthesis of azasugars was described in 1993 by the same authors, which opened the route to a new and efficient synthetic procedure towards this type of compounds.
This observation opened the way to an easy formation of azasugars following the sequence of a ) glycosylamine formation, b) Grignard reaction.
and c ) cyclization with Tf2O. This procedure is easily extended to include pyranose rings.