Thioesters, thiocarbamates, thiocarbazates, semithiocarbazates, peptides, aza-amino acid conjugates, and azapeptides; and a chemoselective and site-specific functionalization protocol of protected thiocarbazates and semithiocarbazates are described. The protocol features the use of Mitsunobu reaction to alkylate specifically the nitrogen atom close to the acylthiol moiety with alcohols to produce protected mono-substituted thiocarbazates that can be stored for months, activated under mild conditions at low temperature using halonium reagents and integrated orthogonally to make substituted semicarbazides that can be used, e.g., as synthons in synthesis of aza-amino acid conjugates, azapeptides and other peptidomimetics. Methods for preparing and using ureases, carbazides, semicarbazides, beta-peptides, azapeptides, and other peptidomimetics and azapeptide conjugates, and uses of ureases, carbazides, semicarbazides, beta-peptides, azapeptides in drug discovery, diagnosis, inhibition, prevention and treatment of diseases are also described.