A full paper on the use of sequentially linked columns, whereby solid-phase reagents and catalysts are packed into individual columns, for the synthesis of ß-lactams has appeared (Hafez A M et al, J Amer Chem Soc 2001, 123, 10853). In column 1, a solid phase base is used for the generation of a ketene and in column 2 its asymmetric cycloaddition to an imine is carried out using a solid phase catalyst. Finally a purification step using a solid phase scavenger is required. Simple analogues of bases such as Hunig's base cannot be used to generate ketenes in column 1 and it was eventually found that the highly basic resin BEMP, which contains a triaminophosphoramide imine group was successful, although there was some batch to batch variation depending on supplier and lot number. The advantages of the solid phase system are:

• Ease of recovery of reagents and catalysts
• Simple work up and purification.