Results and Problems of <i>O</i>‐Glycoside Synthesis

Abstract

Abstract Considerable problems attend the synthesis of biologically important natural products whose carbohydrate components display a greater or lesser degree of complexity. The present progress report surveys recent developments in the formation of O ‐glycosidic bonds starting from 1‐halo sugars and from sugar 1,2‐orthoesters. Particular emphasis is placed on attempts to reach a better understanding of the steric course of glycosylation reactions on the basis of mechanistic considerations. Studies on the silver‐salt dependence of the Koenigs‐Knorr synthesis led to improvements in preparative applications and to new concepts concerning the reaction course. The introduction of sugar 1,2‐orthoesters as glycosylation components has greatly enriched our preparative armoury for the synthesis of trans glycosides. Remarkable progress has also been made in the synthesis of cis glycosides, in part by exploiting novel neighbouring group effects.