Synthesis and Reactivity of Sugars with Two Branches at C-3

The reaction of dialdehydes obtained by periodate oxidation of glycosides with active methylene compounds using soft bases (piperidine or potassium fluoride) as catalysts is a versatile method for the synthesis of sugars bearing two functional groups at C-3. The reaction shows a good stereoselectivity, and the products obtained can be transformed easily into a variety of 3-deoxy sugars. 1. Introduction 2. General Considerations: Dialdehydes, Active Methylene Compounds, and Reaction Conditions Used 3. Reactions with Symmetric Active Methylene Compounds 3.1. Reactions with Malononitrile 3.2. Reactions with 2,4-Pentanedione 4. Reactons with Non-Symmetric Active Methylene Compounds 4.1. Reactions with Cyano Esters (Ethyl and tert-Butyl Cyanoacetate) 4.1.1. Synthesis of 3-Cyano-alk-2-eno- and -3-enopyranose and -thiopyranose Derivatives 4.1.2. First Approaches to the Synthesis of Branched-Chain Sugars with Aminomethyl and Hydroxymethyl Groups at C-3 4.2. Reactions with Cyanoacetamide 4.2.1. Synthesis of 3-Amino-3-deoxy Sugars Branched at C-3 4.3. Reactions with Nitro Derivatives Using Potassium Fluoride, as Catalyst 5. Synthesis of Methyl 3-Deoxyheptoseptanosides 6. Synthesis of 3-Deoxy-5-thiopentopyranosides Branched at C-3 7. Conclusions