A protocol for achiral GC-MS analysis of ISY reactions was adapted from procedures published previously (11, 25). Reactions were conducted in a total volume of 50 μl of buffer C containing 0.5 mg/ml nickel affinity-purified enzyme, 0.8 mm NADPH, and 0.6 mm 8-oxogeranial. After 30 min at 30 °C, products were extracted with 100 μl of ethyl acetate in a 400-μl flat-bottom glass insert (Agilent, 5181-3377) in a GC-MS vial closed with a polytetrafluoroethylene septum. Phase separation was improved by centrifugation of the glass insert in a 2-ml plastic tube at 2000 × g for 2 min. A volume of 3 μl of the clear supernatant was injected in splitless mode on a Hewlett Packard 6890 GC-MS equipped with an Agilent HP-5MS 5% phenylmethylsiloxane column (30 m × 250 μm, 0.25-μm film thickness), a 5973 mass selective detector, and an Agilent 7683B series injector and autosampler. The front inlet temperature was set to 220 °C. After an initial hold at 60 °C for 5 min, a thermal gradient was run from 60° to 150 °C at 20 K/min, from 150 °C to 280 °C at 45 K/min, with a final hold of 4 min at a helium flow rate of 37 cm/s and 1 ml/min. After a solvent delay of 5 min, electron impact fragmentation spectra from 50–300 m/z were collected at a fragmentation energy of 70 eV.