Stereoselective Aldol Additions of Glycolic Acid and Its Derivatives

Abstract

This review gives a comprehensive overview of aldol additions of glycolic acid derivatives to achiral aldehydes and acetals affording α,β-dihydroxycarboxylic acids or derivatives thereof. The focus is on simple diastereoselectivity. A selection of related aldol additions is also presented: aldol additions of glycolic acid derivatives to ketones with two different substituents and aldol additions of α-substituted glycolic acid derivatives. 1 Introduction 1.1 Organization of this Review 1.2 Outside the Scope of this Review: Aldol Additions Giving α,β-Dihydroxyaldehydes and α,β-Dihydroxyketones Diastereoselectively 1.3 Non-Aldol Routes to Diastereomerically Pure α,β-Dihydroxycarboxylic Acid Derivatives 2 Aldol Additions of Glycolic Acid (Derivative) Enolates to Aldehydes 2.1 Aldol Additions of Glycolate Enolates (‘Glycolic Acid Dianions’) 2.2 Aldol Additions of Glycolic Ester Enolates 2.3 Aldol Additions of Glycolic Thioester Enolates 2.4 Aldol Additions of Glycolimide Enolates 2.5 Aldol Additions of Glycolamide Enolates 2.6 Mukaiyama Aldol Additions of Silyl Ketene Acetals of Glycolic Esters\xad and Thioesters 2.7 Aldol Additions of Glycoloyl Chlorides via Acyl Ammonium Enolates 3 Aldol-Providing Substitutions of Glycolimide Enolates in Acetals 4 Additions Related to Aldol Additions of Glycolic Acid Derivative Enolates to Aldehydes 4.1 Selected Simply Diastereoselective Aldol Additions of Enolates of Glycolic Acid Derivatives to Ketones with Two Different Substituents 4.2 Simply Diastereoselective Aldol Additions of Enolates of Glycolic Acid Derivatives with a Methyl Substituent at C-α (Lactic Acid Derivatives) 5 Conclusion