4-(Hydroxymethyl)phenoxyacetic acid (also named as HMP Linker) is typically used as linker (linkage agent) in solid-phase peptide synthesis (SPPS).

 Acid-labile resin linkage agents for use in solid phase peptide synthesis. [1]

 Improving the performance of an acid-labile 4-hydroxymethyl phenoxyacetic acid (HMP) linker on resin and SynPhase grafted solid-supports. [2]

 References:

[1] R.C.Sheppard, et al, Int. J. Pept. Protein Res., 1982, 20(5), pp 451-454.

[2] C.T.Bui, et al, J. Pept. Sci., 2000, 6(10), pp 534-538.