A Convenient Synthesis of 2-Deoxy-β-D-glucopyranosides

Total Synthesis of Apoptolidin

“…In preparation for a b-selective glycosylation, an auxiliary SPh substituent was introduced at C2 of the doleandrose building block. [11] …”

Special Problems in Glycosylation Reactions: 2‐Deoxy Sugars

“…The 2'-deoxy-2'-iodo-Pdisaccharides (57) were obtained in high yield and with a stereoselectivity often higher than 9: 1. The high levels of stereochemical control in glycosylations with either a-iodoacetates (46) or P-iodoacetates (55) are undoubtedly due to the fact that corresponding iodonium ions of type 4 or 5 respectively are configurationally stable under the glycosylation conditions (TMSOTf, low temperatures); no equilibration of these ions occurs.…”

“…Addition of phenylsulfenyl chloride, PhSCl, to 3,4,6-tetra-O-benzyl-D-glucal29 was first performed by Schmidt [46]. The adduct arising from a below-plane addition was hydrolyzed with Na2C03 (80% overall yield), then converted into an w-trichloroacetimidate which in the presence of BF,.OEt2 and alcohols delivered mainly 2-deoxy-2-(phenylthio)-~-~-glucopyranosides.…”

“…This subject is still a matter of high controversy [53]. Desulfurization is achieved with Raney-nickel in refluxing ethanol or tetrahydrofuran at room temperature [46], or Bu3SnH-AIBN in toluene at 100°C [49].…”

Totalsynthese von Apoptolidin

“…Dazu wurde 14 zunächst mit PhSCl und dann mit Ag 2 CO 3 , CH 3 CN/H 2 O in ein a-anomeres Halbacetal über-führt, das anschließend in den Trichloracetimidat-Glycosyldonor 15 umgewandelt wurde. Die Verknüpfung von 11 und 15 erfolgte über die Aktivierung des Imidats durch TMSOTf [11] und führte mit ausgezeichneter b-Selektivität (> 95 %) zum Disaccharid 16. Nach einem Tosyl-Iod-Austausch wurden die Iod-und die Thiophenyl-Gruppe mit Bu 3 SnH entfernt, und man erhielt den geschützten Baustein 17.…”