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[摘要]：Carbohydrates are an omnipresent class of highly oxygenated natural products. Due to their wide spectra of biol. activities, they have been in the center of synthetic org. chem. for more than 130 years. During the past 50 years non-natural carbohydrates attracted the interest of various chemists in the fields of org., biol., and medical chem. Esp. desoxygenated sugars proved to be an important class of compds. Up to date, most non-natural analogs are synthesized starting from natural, enantiomerically pure carbohydrates in multistep synthesis. In this report, a synthetic strategy that allows the selective modular synthesis of natural and non-natural carbohydrates within five synthetic steps starting from readily available starting materials is reported. Due to a sequential introduction of O- or N-functionalities, a regioselective protection of each new functional group is possible. The key step in the carbohydrate synthesis is a RuO4-catalyzed oxidative cyclization via a pH-dependent dehydrogenation-dihydroxylation-cyclization or an oxidative fragmentation-cyclization, leading to highly substituted new carbohydrates, in which each functional group is orthogonally protected and accessible for further synthetic operations. |
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