2-Hydroxy-4-methoxybenzyl, acid-labile carboxamide protecting group used for the reversible backbone modification of peptides. Incorporation of Fmoc-Hmb amino acids  or dipeptides (Fmoc-Xaa-HmbYaa-OH) during Fmoc-SPPS prevents aggregation and thus facilitates the elongation of the peptide. Facilitation of cyclization reactions and prevention of aspartimide formation are further applications of Hmb backbone protection. See also Dmb.