Spacers which can be incorporated during Fmoc-SPPS:

• Fmoc-εAhx-OH, Fmoc-8-aminooctanoic acid (Fmoc-8-Aoc-OH) (both non-polar)
• Fmoc-AEEAc-OH (polar)

For Boc-SPPS:

• Boc-εAhx-OH, 11-(Boc-amino)-undecanoic acid
• N-terminal FITC requires a spacer.