Catalytic Asymmetric Synthesis of Epoxides from Aldehydes Using Sulfur Ylides with In Situ Generation of Diazocompounds We thank the EPSRC (K.M.L., M.J.P., J.R.S.), Avecia for the support of a studentship (M.P.), the EU for a Marie Curie Fellowship (E.A.; HPMF-CT-1999-00076), and Sheffield University for financial support. We thank Dr. J. Blacker (Avecia), Dr. R. V. H. Jones (Zeneca Agrochemicals), and Dr. R. Fieldhouse (Zeneca Agrochemicals) for their interest in this work.