We were unable to find suitable conditions to prepare urazole-containing peptides (14) on solid support, prompting the development of an alternative and selective strategy. First, we optimized conditions to access deprotected semicarbazide-peptides (13b) following steps i., ii, and iii.' (Figure ). We found the cyclization of semicarbazide-peptides 13b using alkaline conditions (step iv.' K2CO3, EtOH, reflux) in solution to provide general access to urazole-peptides (14) in good overall yields while avoiding hydantoin-peptide (15) formation. Over 20 urazole-peptides ( ) have been prepared using this strategy, including those that bear acyclic residues at position-2 (e.g., Xaa2 = Ala2) (see the Supplementary Information).