A solution of (4-benzylthio-2-oxoazetidin-1-yl)acetamide (0.63 g, 2.52 mmol) in dry THF (15 ml) was added to a suspension of sodium hyride (60% in oil, 0.10 g, 2.5 mmol) in dry THF at -10° C. under a nitrogen atmosphere. The reaction was stirred at -10° C. for 10 minutes and was then treated with a solution of 6-phenylhexanoyl chloride (0.58 g, 2.75 mmol) in dry THF (5 ml) dropwise over 2 minutes maintaining the temperature at -10° C. The cooling bath was removed an after stirring for 60 minutes the reaction was treated with sodium hydride (50 mg, 1.25 mmol) and 6-phenylhexanoyl chloride (0.29 g, 1.38 mmol) in dry THF (2 ml). The reaction was stirred for 60 minutes, poured into ice/brine (100 ml), extracted with ethyl acetate (2×50 ml). The organic extracts were combined, washed with aq. sat. NaHCO3 solution, brine, dried (MgSO4) and evaporated under reduced pressure to an orange oil. Purification by repeated column chromatography eluted with hexane:ethyl acetate (3:1 to 1:1) gave the product as a colourless oil (0.22 g, 21% yield, contains 10% 6-phenylhexanoic acid) 1H nmr δ (CDCl3) 1.3-1.7 (6H, m, 3×CH2), 2.44 (2H, t, J=7.4 Hz, NHCOCH2), 2.62 (2H, t, J=7.6 Hz, PhCH2), 2.96, 3.02 (1H, dd, J=2.4, 15.3 Hz, H3), 3.39, 3.45 (1H, dd, J=5.1, 15.3 Hz, H3), 3.61, 4.32 (each 1H, d, J=18.8 Hz, NCH2CO), 3.76 (2H, m, SCH2), 4.9 (1H, m, H4), 7.1-7.3 (10H, m, 2×Ph--H), 8.17 (1H, m, NH)
