title: Total Synthesis of Sialylgalactosylgloboside: Stage-Specific Embryonic Antigen 4.
abstract: A versatile total synthesis of sialylgalactosylgloboside (SGG, 1), carrying the stage-specific embryonic antigen 4 (SSEA-4) is reported, illustrating a more general strategy for the synthesis of complex globo-series glycosphingolipids. Starting from readily available building blocks 7, 8, and 10, two different approaches to the synthesis of the key tetrasaccharide 6 have been developed in a highly convergent manner. Further glycosylations with galactosyl trichloroacetimidate (5) and sialyl phosphite (2) donors successively afforded the penta- and hexasaccharides 3 and 11. The latter was finally converted into the target molecule (SGG, 1) with the help of a azidosphingosine glycosylation procedure, favored in this case by the stereocontrolling properties of the 2a-O-pivaloyl protecting group. Valuable intermediates 6 and 3, having the oligosaccharidic skeletons of Gb(4) and Gb(5) (SSEA-3), respectively, were obtained in the course of the synthesis.
authors.affiliation: Fakultät für Chemie, Universität Konstanz, Postfach 5560 M 725, D-78434 Konstanz, Germany.
authors.forename: José M.
authors.initials: JM
authors.lastname: Lassaletta
authors.forename: Karin
authors.initials: K
authors.lastname: Carlsson
authors.forename: Per J.
authors.initials: PJ
authors.lastname: Garegg
authors.forename: Richard R.
authors.initials: RR
authors.lastname: Schmidt