- β-1,4-Galactosyltransferase-catalyzed synthesis of the branched tetrasaccharide repeating unit of Streptococcus pneumoniae Type 14
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A chemoenzymatic approach is described towards the branched tetrasaccharide repeating unit, β-d-Galp-(14)-β-d-Glcp-(16)-[β-d-Galp-(14)]-β-d-GlcpNAc, of Streptococcus pneumoniae type 14 in a form suitable for conjugation. The linear trisaccharide acceptor,
- Niggemann, Jutta,Kamerling, Johannis P.,Vliegenthart, Johannes F. G.
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- Regio/Stereoselective Glycosylation of Diol and Polyol Acceptors in Efficient Synthesis of Neu5Ac-α-2,3-LacNPhth Trisaccharide
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A concise approach to a Neu5Ac-α-2,3-LacNPhth trisaccharide derivative was developed. First, the regio/stereoselective glycosylation between glycoside donors and glucoNPhth diol acceptors was investigated. It was found that the regioselectivity depends not only on the steric hindrance of the C2-NPhth group and the C6-OH protecting group of the glucosamine acceptors, but also on the leaving group and protecting group of the glycoside donors. Under optimized conditions, LacNPhth derivatives were synthesized in up to 92 % yield through a regio/stereoselective glycosylation between peracetylated-α-galactopyranosyl trichloroacetimidate and p-methoxyphenyl 6-O-tert-butyldiphenylsilyl-2-deoxy-2-phthalimido-β-d-glucopyranoside, avoiding the formation of glycosylated orthoesters and anomeric aglycon transfer. Then, the LacNPhth derivative was deacylated and then protected on the primary position by TBDPS to form a LacNPhth polyol acceptor. Finally, the Neu5Ac-α-2,3-LacNPhth derivative was synthesized in 48 % yield through the regio/stereoselective glycosylation between the LacNPhth polyol acceptor and a sialyl phosphite donor. Starting from d-glucosamine hydrochloride, the target Neu5Ac-α-2,3-LacNPhth derivative was synthesized in a total yield of 18.5 % over only 10 steps.
- Zhang, Ying,Zhao, Fu-Long,Luo, Tao,Pei, Zhichao,Dong, Hai
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p. 223 - 234
(2018/12/05)
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