Polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS, Figure 1) is a versatile method for studying the hydrolysis of long-chain lipids at the air/water interface and the influence of phase separations on the activity of proteins. [1, 2] Our investigations using this method were performed on phospholipase A 2 (PLA 2 ). PLA 2 cleaves selectively the sn-2 ester linkage of phospholipids, leading to a fatty acid and a lysophospholipid. PLA 2 plays an important role in the arachidonyl cascade, since arachidonyl is the main group found in the 2-position at the glycerol of the phospholipids in mammal cells. PLA 2 is an interfacially active enzyme, whose activity is strongly dependent on the physical-chemical structure of the substrate, which makes it very difficult to develop inhibitors. The investigations at the air/water inter-synthesize a,b-unsaturated esters and amides with total E stereoselectivity from the easily available 2-halo-3-hydroxyesters or amides.
Experimental Section
A solution of SmI 2 (1 mmol) in THF (12 mL) was very slowly added dropwise, under a nitrogen atmosphere, to a stirred solution of halohydroxyester 1 (0.4 mmol) in THF (2 mL) at room temperature, until the reaction mixture turned permanently blue. The reaction mixture was quenched with aqueous HCl (1m, 5 mL). Standard work-up and filtration through a pad of Celite provided pure a,b-unsaturated esters 2 (> 98 %).