Abstract: The intramolecular cyclization of “hydroxamate” 2 using Mitsunobu conditions was inefficient for the formation and isolation of the C-4 dimethyl monobactam 3. However, chemospecific 0-sulfonation of 2 and subsequent cyclization with base provides a useful method for &lactam synthesis from a sterically hindered B-hydroxy amino acid. Competitive rearrangement of 2 also occurs during cyclization providing isomeric j3-lactam 5.
