β-Selective Glycosylation by Using O-Aryl-Protected Glycosyl Donors
Yuji Otsuka1,2, Toshihiro Yamamoto1,2, Koichi Fukase1
1Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka Prefecture, 560-0043, Japan.
Abstract:
New glycosyl donors have been developed that contained several para-substituted O-aryl protecting groups and their stereoselectivity for the glycosylation reaction was evaluated. A highly β-selective glycosylation reaction was achieved by using thioglycosides that were protected by 4-nitrophenyl (NP) groups, which were introduced by using the corresponding diaryliodonium triflate. Analysis of the stereoselectivities of several glycosyl donors indicated that the β-glycosides were obtained through an SN 2-type displacement from the corresponding α-glycosyl triflate. The NP group could be removed by reduction of the nitro group and acylation, followed by oxidation with ceric ammonium nitrate (CAN).
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