Stereospecific entry to [4.5]spiroketal glycosides using alkylidenecarbene C-H insertion.

Duncan J Wardrop, Wenming Zhang, Joseph Fritz

Index: Org. Lett. 4 , 489-92, (2002)

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Abstract

[reaction: see text] A novel method for the stereospecific preparation of [4.5]spiroketal glycosides utilizing the 1,5 C-H bond insertion of alkylidenecarbenes is described. Treatment of 2-oxopropyl beta-pyranosides A with lithium (trimethylsilyl)diazomethane in THF at -78 degrees C afforded 1,6-dioxaspiro[4,5]decenes B in good yield. Submission of the corresponding alpha-glycosides C to the same reagent gave the isomeric insertion products D in moderate to high yield.