title: 5-N,4-O-carbonyl-7,8,9-tri-O-chloroacetyl-protected sialyl donor for the stereoselective synthesis of alpha-(2-->9)-tetrasialic acid.
abstract: An efficient stereoselective synthesis of alpha-(2-->9)-tetrasialic acid was achieved using tri-O-chloroacetyl-derivatized sialyl donor and a triol sialyl acceptor. Both the acceptor and the donor were also protected with a cyclic 5-N-4-O-carbonyl protecting group. The donor is highly reactive and enabled alpha-selective sialylation with various primary, secondary, and tertiary acceptors under in situ activation conditions (NIS/TfOH, -78 degrees C, acetonitrile/dichloromethane). The trans-fused oxazolidinone ring and O-chloroacetyl protecting groups were easily removed under mild reaction conditions to provide the fully deprotected alpha(2-->9)-tetrasialic acid.
authors.affiliation: Department of Chemistry, National Tsing Hua University, 101, Sec. 2, Kuang Fu Rd, Hsinchu 30013, Taiwan.
authors.forename: Chang-Ching
authors.initials: CC
authors.lastname: Lin
authors.forename: Nai-Pin
authors.initials: NP
authors.lastname: Lin
authors.forename: L Sk
authors.initials: LS
authors.lastname: Sahabuddin
authors.forename: Vijaya Raghava
authors.initials: VR
authors.lastname: Reddy
authors.forename: Li-De
authors.initials: LD
authors.lastname: Huang
authors.forename: Kuo Chu
authors.initials: KC
authors.lastname: Hwang
authors.forename: Chun-Cheng
authors.initials: CC
authors.lastname: Lin