Modulating Glycosylation Approach for Participating Thioglycosyl Donors
Mong, Kwok-Kong Tony;* Lin, Yu Hsien
National Chiao-Tung University, Ta Hsueh Rd, Hsinchu City, 30010, Taiwan, R.O.C.
Recently DMF-modulating glycosylation method has been developed for
non-participating glycosyl donors. This method employs the nucleophilic property of
DMF to entrap glycosyl oxacarbenium ion as glycosyl imidate. Along this line, it is
a reasonable projection to apply such modulation concept for glycosyl donors bearing
participating function at C2. This work hypothesizes that activation of participating
glycosyl donor would generate a glycosyl dioxalenium ion through NPG effect. As the
dioxalenium ion is electrophilic and the -face of which is blocked by the
dioxalenium function, it should react with the DMF to produce either -glycosyl
imidate or imidoyl orthoester (see Figure). Given the dioxalenium ion and/or imidoyl
orthoester is more than the -glycosyl imidate and thus it reacted an acceptor to
furnish 1,2-transglycosylation product. Further NMR studies detect for the first time
the -glycosyl imidate. In the symposium, the latest development of the DMF
modulating glycosylation is updated including the application of the modulating
glycosylation for iterative 1,2-trans -glycosidic bond formation, NMR
detection/characterization of -glycosyl imidate, and synthesis of -mannan using
the present glycosylation method.
 Lu, S.-R.; Lai, Y.-H.; Chen, J.-H.; Liu, C.-Y.; Mong, K.-K. T. Angew. Chem., Int. Ed. 2011, 50, 7315–7320.
 Lin, Yu Hsien; Mong, K.-K. T. manuscript in preparation