Synthesis Of D-manno-heptulose And Studies On The Construction Of Seven-carbon Sugar Backbones

Heptoses are rare higher-carbon sugars which are widely found in higher plants,algae,fungi and bacteria.Usually,they have a variety of biological activities.D-manno-Heptulose is a naturally occurring seven-carbon sugar first isolated from avocado,which exhibited promising diabetogenic effects through suppression of the glucose metabolism and insulin secretion via competitive inhibition of the glucokinase pathway.Accordingly,it was considered to be a potential therapeutic agent for hypoglycemia.Therefore,the study of its synthesis is of great significance.So far,there are two kinds of synthetic methods for the synthesis of heptoses,especially D-manno-heptulose,which are mainly constructed by the rearrangement reaction and the carbon chain extension reaction mainly based on "6+1" and "5+2".The aim of this study is to develop "4+3" Aldol condensation reaction to achieve the extension of the carbon chain.Firstly,the synthesis of the C4 aldehyde commenced with commercially available D-lyxose.Then the cascade aldol/hemiketalization reaction of a C4 aldehyde with a C3 ketone provided the differentially protected ketoheptose building block,which was finally converted into the target D-manno-heptulose.The reported differentially protected ketoheptose building blocks may find further application in the preparation of structurally diverse D-manno-heptulose derivatives.