The invention provides methods and compositions useful for making synthetic peptide conjugates. In one embodiment, the invention provides compositions comprising the structure: ##STR00001## wherein R is selected from lower substituted or unsubstituted alkyl, O, NH and S and P is an amine protection group. In more particular embodiments, the compositions comprise .alpha.-amine protected 4,5-dehydroleucine or .alpha.-amine protected (2S)-aminolevulinic acid and/or P is F-moc. These compounds may be incorporated into peptides, for example, peptides comprising a substituted or unsubstituted (2S)-aminolevulinic acid residue, such as (2S)-aminolevulinic acid residue is substituted with an O- or N-linked glycoconjugate, or a detectable label.