The present invention provides a process for preparing a peptide of formula (I): Sub-[L]-[NH-A-C(O)].sub.n+m--OH (I) comprising: (a) reacting an immobilized compound of formula (II): Sub-(L)-[NH-A-C(O)].sub.n--OH (II) with an amino acid ester or peptide derivative of formula (III): H--[NH-A-C(O)].sub.m--O(tBu) (III) in the presence of a coupling agent to yield a peptide compound of general formula (IV): Sub-[L]-[NH-A-C(O)].sub.n+m--O(tBu); (IV) (b) removing the tBu (t-butyl) group to produce a solid-support bound carboxylic acid or peptide derivative of general formula (I); wherein n is a positive integer, e.g., 1-10, preferably 1-5; m is a positive integer.