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Synthesis of the Pentasaccharide Moiety of Thornasterside A
Author(s) -
Xiong Junlong,
Lu Zhichao,
Ding Ning,
Ren Sumei,
Li Yingxia
Publication year - 2013
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201300575
Subject(s) - chemistry , moiety , glycosidic bond , trisaccharide , stereochemistry , glycosylation , stereoselectivity , starfish , yield (engineering) , disaccharide , glycosyl , organic chemistry , catalysis , biochemistry , ecology , materials science , metallurgy , biology , enzyme
The synthesis of the pentasaccharide moiety of thornasteroside A, the first asterosaponin isolated from starfish in 1978 has been achieved for the first time. Initially, a [3+2] convergent strategy was attempted, but the β(1→4) glycosidic linkage between galactopyranose (sugar IV) and xylopyranose (sugar II) was formed with a low stereoselectivity and in low yield. Subsequently, a [3+1+1] strategy was adopted. A galactopyranosyl donor ( 18 ) equipped with a neighboring participating Lev (levulinoyl) group at the 2‐position was first coupled with a trisaccharide acceptor to construct the β(1→4) glycosidic bond. Then the Lev group was selectively removed, and subsequent glycosylation with a perbenzoylated D ‐fucopyranosyl Schmidt donor efficiently gave the desired pentasaccharide.